Flow resistance

3 Abstract: The Republic of Kazakhstan has about 39,000 rivers, including 15 large rivers and 40 medium. The rest, i.e. more than 90% of the rivers, can be referred to as small rivers with shallow depths. To date, all the methods of average flow rate calculation have been designed for medium and large rivers and cannot be used for small streams. Therefore this article offers the formula for determination of the average rate in small rivers of Kazakhstan. But currently, the most widely used formulas for finding the average rate on a speed vertical are based on the approximate method of dividing the rate curve into the equal parts. This approach reduces the accuracy of the average rate estimation at finding the water flow rate. Therefore, the aim of the study was to develop a better method for calculation of the water flow rate which would allow measurements at shallow depths using a mathematical expression that would describe the distribution of the longitudinal rate at different dep...

for an Invited Paper for the MAR06 Meeting of the American Physical Society Subcritical shear-induced instabilities and turbulence of visco-elastic fluids WIM VAN SAARLOOS, Leiden University While instabilities in normal Newtonian fluids are usually due to inertial effects, most visco-elastic instabilities are noninertial, i.e. happen at small Reynolds numbers. In polymeric fluids the viscoelastic instabilities and turbulence are due to shearinduced anisotropic elastic forces: when the so-called Weissenberg number is larger than about 1, a polymer fluid is very non-Newtonian: in this regime the fluid is anisotropic and elastic, and relaxation effects are important. After reviewing some recent experiments, I will discuss the recent progress on understanding the viscoelastic instabilities in parallel shear flows (planar Couette and Poiseuille flow). Contrary to common belief that such flows are absolutely stable in the small Reynolds number limit, our recent nonlinear amplitude analysis predicts that the transitions are subcritical. The critical Weissenberg number our analysis predicts is close to the values where in practice such flows are found to exhibit instabilities. The scenario suggested by these results shows strong resemblance to the transition to (weak) turbulence scenario in Newtonian shear flows. A. N. Morozov and W. van Saarloos, Subcritical finite-amplitude solutions in plane Couette flow of visco-elastic fluids, Phys.

A PV pumped, solar domestic hot water system for a shower building installed at a state park is described. The system is "drain freeze protected". A system overview, description of the monitoring instruments and results for a for total domestic hot water use, solar collector efficiency, and performance relative to solar collector area, storage size and type are presented.

The removal of bed material from active river channels usually affects the bed profile of the streambed, causing progressive degradation upstream and downstream of the extraction site. These effects can extend for kilometers affecting hydraulic structures located in the vicinity of the river reach. In this paper, the geomorphic effects of gravel mining are reviewed and summarized. Some cases in Venezuelan streams are presented to illustrate the problem. To describe the processes of erosion and sedimentation in a gravel extraction pit, a recent developed mathematical model for the simulation of flow and sediment transport in gravel-cobble bed streams is applied to a hypothetical case of gravel mining in a river channel. A simple rectangular dredge pit is imposed as initial condition in the channel bed, and changes in bed elevations and grain size distribution of bed material are calculated by using the numerical model. The process of deposition within the pit, and the downstream and upstream migration of the erosion wave are well simulated by the model and closely resemble the phenomena observed in laboratory experiments. The response of the friction coefficient to the changes in flow and bed elevations shows the importance in modeling adequately flow resistance and sediment transport in gravel-cobble bed streams.

Flood flows have the potential to cause substantial damage to infrastructure, mankind, livestock and agricultural land which all stacks up to greatly affect the financial condition of the region. During 2010 Pakistan floods, more than two million houses were damaged partly or totally [1]. To minimize these types of destructions, inland vegetation can be considered a natural barrier to dissipate the energy of flood flow and limits widespread inundation. This study involves volume of fluid (VOF) modelling approach to figure out the role of vegetation of finite width in energy reduction of flood flow, in front of houses, against: vegetation of varying Aspect Ratio (A/R width-length ratio) and distance between vegetation & houses (Lr). Channel domain was built in ANSYS workbench toolkit and meshing was done in meshing building toolkit. For the postprocessing and simulation, FLUENT was used. Various contour plots & profiles of cross stream-wise velocities and water level measurements are presented in this paper. The simulation results of cross stream-wise velocities and water level measurements were identical with experimental data. At vegetation upstream and downstream, velocity reduction observed in higher A/R (2.40) compared to vegetation of A/R-1. Whereas, outside the vegetation and near the walls of channel domain flow velocities were high. The water level was raised on the upstream side of the vegetation due to resistance offered by vegetation. On the upstream side of vegetation, the rise in backwater depth increased by increasing A/R. Contrarily, on the downstream side of vegetation, an undular hydraulic jump was observed in between vegetation and a house. By increasing A/R, the energy loss increases under constant vegetation conditions (G/d = 0.24, Fro = 0.70; G = spacing of each cylinder in cross-stream direction and d= diameter of cylinder and Fro = initial Froude number) and increase in house distance from 1W to 2W, the energy reduction increased from 2.40% to 3.15% which was further increased to 5.04% for another 5W increase in house distance, where W is the vegetation width. Simulation results also shown that with increasing Froude no from 0.60 to 0.70 water level depth has also an incremental pattern which ultimately results in increase in energy dissipation along the varying building distance (1W, 2W & 5W). Thus, to minimize the structural damage, a structure must be located at a safe distance away from the vegetation where flow becomes sub-critical.

Local scour at the piers is one of the main reasons of bridge foundation undermining. Earlier research studies focused mainly on the scour at a single bridge pier; nevertheless, modern designs of the bridges comprise wide-span and thus group of piers rather than a single pier are usually used to support the superstructure. The flow and scour pattern around group of piers is different from the case of a single pier due to the interaction effect. Reviewing the literature of local scour around bridge piers group revealed that the local scour around bridge piers group founded in cohesive soil bed was not investigated, and most of the scour studies were related to scour in cohesionless soils. The objective of the present study is to investigate the effect of the interaction between two in-line (tandem) circular bridge piers of variable spacings founded in cohesive soil on the local scour. A set of laboratory flume experiments were conducted under the clear-water scour condition to investigate this effect. This study is the first that investigates experimentally the scour around group of bridge piers in cohesive bed. It was found that the maximum scour depth at the upstream pier of the two in-line piers occurred at a spacing of two times the diameter of the pier, scour at the downstream pier was reduced due to a sheltering effect, the interference effect will be reduced for pier spacings larger than three times of the pier diameter. A recent pier scour equation was used to estimate the scour depths at the two in-line piers in cohesive soil and compare the estimated value with the measured scour depths in the laboratory. The comparison indicated that the proposed scour equation overestimates the scour depths at both the upstream and the downstream pier.

In natural rivers, vegetation grows on floodplains, generating complex velocity field within the compound channel. The efficient modelling of the flow hydraulics in a compound channel with vegetated floodplains is necessary to understand and determine the natural processes in rivers and streams. As the three dimensional (3D) flow features are difficult to capture through experimental investigation; therefore, the present numerical study was carried out to investigate the complex 3D flow structures with the vertically layered vegetation placed over the floodplains in a symmetric trapezoidal compound channel. The simulations were conducted using a Computational Fluid Dynamics (CFD) code FLUENT, whereas a Reynolds Averaged Navier-Stokes (RANS) technique based on Reynolds stress model (RSM) was implemented for turbulence closure. The numerical model successfully replicated the flow behavior and showed a good agreement with the experimental data. The present study concluded the presence of quite-S shaped velocity profile in the layered vegetated floodplains when the short vegetation was submerged during high flows or floods, whereas the velocity profile was uniform or almost logarithmic during low floods or when both short and tall vegetation remained emergent. The lateral exchange of mass and momentum was promoted due to the flow separation and instability along the junction of the floodplains and main channel. The flow velocities were significantly reduced in the floodplains due to resistance offered by the vegetation, which consequently resulted in an increased percentage i.e. 67-73%, of passing discharge through the main channel. In general, the spatial distribution of mean flow and turbulence characteristics was considerably affected near the floodplain and main channel interfaces. Moreover, this study indicated a positive flow response for the sediment deposition as well as for the nourishment of the aquatic organisms in the riparian environment.

Polymer flooding is a commercial enhanced oil recovery (EOR) method used to increase the sweep efficiency of water floods. Hydrolyzed polyacrylamide (HPAM), a synthetic commercial polymer, is widely used in commercial polymer floods and it is also used for mobility control of chemical floods using surfactants such as surfactant-polymer flooding and alkaline-surfactant-polymer flooding. The increase in the degree of hydrolysis of HPAM at elevated temperature or pH with time affects the polymer solution viscosity and its adsorption on rock surfaces. A polymer hydrolysis model based on published laboratory data was implemented in UTCHEM, a chemical EOR simulator, in order to assess the effect of hydrolysis on reservoir performance. Both 1D and 3D simulations were performed to validate the implementation of the model. The simulation results are consistent with the laboratory observations that show an increase in polymer solution viscosity as hydrolysis progresses. The numerical results ...

The stream power is one of the important river variables which is used in morphological analysis. Therefore, the stream power determines both erosion and deposition. This research examines the stream power, instability and morphometric changes of the channel using the annual geomorphic energy (AGE) in Haji Arab River in Buin Zahra (Qazvin Province). The AGE is calculated by integrating the relationship between the excess specific stream power and discharge using a flow duration curve. The AGE values for each reach should be either positive or negative. Therefore, according to the differentials in AGE values, depositional and erosional reach are determined. In this paper, the results of the AGE method were compared with the rapid geomorphic assessments (RGA), including the channel stability indicators (CSI) model and OSEPI index. Also, the RHS method based on the field works was used to identify depositional and erosional geomorphic landforms. Comparing the results of the AGE with rapid RGA indices, shows that results of the OSEPI are more consistent with the erosional and depositional status of the reaches, based on the AGE. Spatial variations in lithology and structure, when combined with the course of the Haji Arab River indicate that channel morphometry locally reflects geological factors that have caused slope differences in different reaches. The calculated AGE values at different cross-sections have significant variability, reflecting characteristic local variation in bed slope, cross-section geometry and bed-sediment composition.

This work deals with the experimental design of hybrid absorbers for broadband noise control in ducts. The followed strategy is the control of input impedance of the multilayer system over a large frequency bandwidth, combining both passive and active technologies. Control of medium and high frequencies is afforded by a porous material backed with an air gap, while low frequencies are reduced with active control. Three active techniques are investigated: pressure-release in the back face of the porous layer, impedance-matching and zero -reflection condition. First experimental results of the developed prototype are shown.

This work introduces and validates the Comin Formula for friction factor estimation. Limitations: The Comin Formula is valid for Reynolds numbers between 8,000 and 1,000,000 and for relative roughness ε/D < 0.005, typical of PVC and PEAD pipelines. Outside these ranges, the accuracy decreases and conventional equations (e.g., Colebrook-White) are recommended.

This paper presents an evaluation and analysis of resistance parameters: friction slope, friction velocity and Manning coefficient in unsteady flow. The methodology to enhance the evaluation of resistance by relations derived from flow equations is proposed. The main points of the methodology are (1) to choose a resistance relation with regard to a shape of a channel and (2) type of wave, (3) to choose an appropriate method to evaluate slope of water depth, and (4) to assess the uncertainty of result. In addition to a critical analysis of existing methods, new approaches are presented: formulae for resistance parameters for a trapezoidal channel, and a translation method instead of Jones' formula to evaluate the gradient of flow depth. Measurements obtained from artificial dam-break flood waves in a small lowland watercourse have made it possible to apply the method and to analyse to what extent resistance parameters vary in unsteady flow. The study demonstrates that results of friction slope and friction velocity are more sensitive to applying simplified formulae than the Manning coefficient (n). n is adequate as a flood routing parameter but may be misleading when information on trend of resistance with flow rate is crucial. Then friction slope or friction velocity seems to be better choice.

The motion of two red blood cells in a stenosed microvessel was simulated using dissipative particle dynamics. The effects of intercellular interaction, red blood cell deformability and the initial cell orientation on the deformation and aggregation of the RBCs and on the flow resistance were investigated. The red blood cell membrane was treated as a three-dimensional coarse-grained network model and the intercellular interaction was modeled by the Morse potential based on a depletion-mediated assumption. It is shown that the flow resistance increases dramatically when the red blood cells enter into the stenosis and decreases rapidly as RBCs move away from the stenosis. Particularly, for a pair of stiffer red blood cells with the initial inclination angle of 90°, the maximum value of the flow resistance is larger; while a higher flow resistance can also come from a stronger aggregation. For a pair of stiffer red blood cells moving parallel to the main flow, when their positions are ...

A critical mechanical system in advanced hypersonic engines is the panel-edge seal system that seals gaps between the articulating horizontal engine panels and the adjacent engine splitter walls. Significant advancements in seal technology are required to meet the extreme demands placed on the seals, including the simultaneous requirements of low leakage, conformable, high temperature, high pressure, sliding operation. In this investigation, the seal concept design and development of two new seal classes tha!t show promise of meeting these demands will be presented. These seals include the ceramic wafer seal and the bralded ceramic rope seal. The paper presents key elements of leakage flow models for each of these seal types.: Flow models such as these help designers to predict performance-robbing parasitic losses past the seals, and estimate purge coolant flow rates. Comparisons are made between measured and predicted leakage rates over a wide range of engine simulated temperatures and pressures, showing good agreement.

Combined cycle ramjet/scramjet engines being designed for advanced hypersonic vehicles, including the National Aerospace Plane (NASP), require innovative high temperature dynamic seals to seal the sliding interfaces of the articulating engine panels. New seals are required that will operate hot (1200-2000 °F), seal pressures ranging from 0-100 psi, remain flexible to accommodate significant sidewall distortions, and resist abrasion over the engine's operational life. This report reviews the recent high temperature durability screening assessments of a new braided rope seal concept, braided of emerging high temperature materials, that shows promise of meeting many of the seal demands of hypersonic engines. The paper presents durability data for: (a) the fundamental seal building-blocks--a range of candidate ceramic fiber tows; and for (b) braided rope seal subelements scrubbed under engine simulated sliding, temperature and preload conditions. Seal material/architecture attributes and limitations are identified through the investigations performed. The paper summarizes the current seal technology development status and presents areas in which future work will be performed.

Riparian vegetation is an important feature in rivers and essential in hydraulic engineering including flood management and river restoration. Deforestation activities have been pointed out as a contributing factor to the severity of flood damages. This shows that the importance of riparian vegetation in river restoration schemes in order to lessen the issues of flood risk and flood protection. The riparian vegetation creates additional resistance to flood flow which resulted in velocity reduction, increasing of flow depth and transportation of sediment in rivers. The hydraulics of flood flows in vegetated floodplain of mobile bed straight channel was experimented in the Hydraulics Laboratory, Faculty of Civil Engineering, Universiti Teknologi Malaysia. Two-lined steel rods with tandem and staggered arrays to simulate as rigid emergent vegetation were placed along the riparian zone of an asymmetrical channel. The flow resistance including Manning's n, Darcy's f and drag force, FD were studied. The findings showed that the riparian vegetation had increased the Manning's n by 20%. Meanwhile, staggered arrangement of vegetation was found to generate the highest Darcy's f of about 16% as compared to tandem arrangement. The presence of riparian vegetation also found to induce 20% more drag force compared to the main channel roughness effect. The dramatically changes of bed morphology also led to the increase of the flow resistance in the channel.

Pressure oscillations applied to human airways can help patients to evacuate bronchial mucus, a highly non-Newtonian gel. To explore the fluid mechanics aspects of these therapies, we perform numerical simulations of pulsated non-Newtonian fluids in two dimensional channels. The fluid rheology is modeled by the Herschel-Bulkley law, reproducing two essential non-linear mechanical properties of the mucus, namely the yield-stress and shear-thinning/thickening properties. The flow dynamics is simulated using the lattice-Boltzmann method over large ranges of the three main non-dimensional parameters, i.e. the pulsation rate or Womersley number α, the flow index n quantifying the shear-thinning/thickening effect and the Bingham number controlling the yield stress. The ratio between the fluctuating and average parts of the oscillatory forcing is examined through three typical cases: a purely oscillating flow, a weakly oscillating flow and a strongly oscillating flow. For each configuration, specific sets of parameters are found to have a drastic effect on the dynamics of mucus plugs, which suggests new therapeutic strategies for patients suffering from bronchial obstructions.

The flow resistance of the existing modules in the bio-ecological drainage system (BIOECODS) is high and may lead to flood instead of its mitigation. As part of efforts to enhance the performance of the system, the river engineering and urban drainage research center (REDAC) module was developed. This study modelled the hydrodynamics of flow through this module using FLOW-3D and laboratory experiments for two cases of free flow without module (FFWM) and flow with a module (FWM) to understand and visualize the effects of the module. With less than 5% error between the numerical and experimental results, REDAC module altered the flow pattern and created resistance by increasing the Manning’s roughness coefficient at the upstream, depth-averaged flow velocity (43.50 cm/s to about 46.50 cm/s) at the downstream and decreasing water depth (7.75–6.50 cm). These variations can be attributed to the complex nature of the module pattern with further increase across the porous openings. Therefo...

The analysis of flow resistance due vegetation remains an issue in the hydraulic industry, although it has been systematically studied for several decades, accurate prediction of the resistance is still a challenge. This is because most of previous studies used synthetic vegetation to model flow -vegetation interactions. This paper presents the applications of artificial neural network (ANN) and gene expression programming (GEP) as advanced tools, to predict the flow resistance (n) of natural vegetation using a grassed swale and laboratory channel, irrespective of the grass height with relative to flow depth. To achieve this, hourly discharges and water depths were measured in the grassed swale for different rainfall events using electromagnetic current meter. Experiments were performed in the laboratory channel using the same grass, in order to get additional data. From the results obtained regression equation was developed for predicting the flow resistance through the use of dimensional analysis. The regression equation obtained was compared with the established models of ANN and GEP. The results show that ANN and GEP models gave a better prediction of n-values, based on performance indices. However, the GEP model would be preferred as it produced a physical equation that can be used in engineering practice.

Geometric frustration emerges when local interaction energies in an ordered lattice structure cannot be simultaneously minimized, resulting in a large number of degenerate states. The numerous degenerate configurations may lead to practical applications in microelectronics [1], such as data storage, memory and logic [2]. However, it is difficult to achieve extensive degeneracy, especially in a two-dimensional system [3,4]. Here, we showcase in-situ controllable geometric frustration with massive degeneracy in a twodimensional flux quantum system. We create this in a superconducting thin film placed underneath a reconfigurable artificial-spin-ice structure [5]. The tunable magnetic charges in the artificial-spin-ice strongly interact with the flux quanta in the superconductor, enabling the switching between frustrated and crystallized flux quanta states. The different states have measurable effects on the superconducting critical current profile, which can be Nature Nanotechnology 13, 560 (2018)

A flow apparatus for the study of Ziegler polymerization was constructed. The design and instrumentation of this apparatus has proved quite satisfactory. The work was aimed at studying the reaction of various monomer systems on the same catalyst surface. Difficulties were encountered in preliminary experiments regarding the removal of polymer formed from the catalyst bed, and maintaining the catalytic efficiency of the bed. The resistance to flow exerted by the catalyst bed was found to be a sensitive measure of deposition of polymer, which may be useful in future theoretical investigations.

This study investigates the frequency-dependence of fluid flow in heterogeneous porous media using the theory of dynamic penneability and a finite-difference method. Given a penneability distribution, the dynamic penneability is applied locally to calculate the frequency-dependence of fluid flow at each local point. An iterative Alternating Direction Implicit finite-difference technique is applied to calculate the flow field in the frequency domain. We compare the flow through a 2-D heterogeneous porous medium and that through an equivalent homogeneous medium and find that the two media do not behave equivalently as a function of frequency. At very low-frequencies, the heterogeneous medium is less conductive than the homogeneous medium, However, in the transition region from quasi-static to dynamic regimes, the fonner medium becomes more conductive than the latter medium, with the ratio of the fonner flow over the latter flow reaching a maximum in this region. The larger the scale, or the higher the degree of the heterogeneity, the higher this maximum is. This finding is important for studying the interaction of a borehole stoneley wave with a heterogeneous porous fonnation. The finite-difference technique is also applied to simulate frequency-dependent flow through a single fracture with rough surfaces. It is shown that the fiow exhibits strong frequency-dependence even for small fractures with contacting surfaces. The amount of flow through the fracture is reduced by the surface roughness .

In this study, a material removal model for surface finishing (MR) using a small polishing head with a permanent magnet is proposed. The small ball tip magnetorheological (MR) polishing process using a permanent magnet is applied in the machining of products with complex contour impurities with small defects or convex surfaces with small curvature radii. In this process, the magnitude of the magnetic field of the ball tip and the cutting application of the MR material act on the perfect surface, creating a shadow effect. This stu dy presents and simulates the research and experiment of the polishing tool design process combining the grinding solution (MoS2/Fe3O4)@rGO+SiC to create polishing action. In this study, a 3D nanocomposite (MoS2/Fe3O4)@rGO with the ability to absorb the magnetic field generated by the moving magnetic polishing head significantly was synthesized through the hydrothermal method and chemical cabinet finishing. The fusion of Fe3O4 from the calculation with rGO and MoS2 helps to optimize the parameters. In addition, to improve the polishing performance for this process, Silicon Carbide material. Process design and implementation simulations were performed to evaluate the surface finish and mat erial removal performance. Simulation results and experimental data showed that high surface roughness was achieved without damaging or aff ecting the surface. The underlying mechanism of the material removal process was also studied and discussed.

The unsteady (oscillatory) Stokes resistance is numerically computed for finite-length, circular cylinders using a first-kind, boundary integral formulation for low and moderate dimensionless frequencies. Translational oscillations parallel and perpendicular to the cylinder axis (axial and transverse oscillations) are considered. For arbitrarily oriented cylinders with length-to-width ratios in the range: l/lO<a/b<lO, a simple, previously proposed, expression accurately ( f 5%) describes the oscillatory Stokes resistance at all frequencies in terms of steady Stokes and inviscid flow resistance parameters. Numerical calculations for spheroids agree with previous results; the results for cylinders and transverse oscillations of oblate spheroids are new.

Enhanced red blood cell (RBC) aggregation has an adverse effect on microcirculatory blood flow and tissue oxygenation. It has been previously shown that obesity is associated with increased RBC aggregation. The objectives of the present study were to further characterize obesity-related RBC aggregation and to examine whether the enhanced aggregation is a plasma-or cellular-dependent process. METHODS: Obese (body mass index (BMI) ¼ 4076.3 kg/m 2 , n ¼ 22) and nonobese (BMI ¼ 2473.4 kg/m 2 , n ¼ 18) individuals were evaluated for inflammation markers and aggregation parameters. Aggregation parameters were derived from the distribution of RBC population into aggregate sizes, and from the variation of the distribution as a function of flow-derived shear stress, using a cell flow properties analyzer. To differentiate plasmatic from cellular factors, we determined the aggregation in the presence of autologous plasma or dextran-500kDa and calculated the plasma factor (PF) in the obese group. PF ranges from 0 to 1. When the PF ¼ 1, the aggregation is all due to plasmatic factors, when PF ¼ 0, the altered aggregation depends entirely on cellular factors, whereas 0oPFo1 reflects the joint contribution of cellular and plasmatic factors. RESULTS: Obese subjects had relatively larger aggregates that were more resistant to dispersion by flow. The calculated PF in the obese group was 0.9, indicating a pronounced contribution of plasma to RBC aggregation in obesity. DISCUSSION: Our results suggest that obese individuals present pathological plasma-dependent RBC aggregation, which is probably triggered by plasma macromolecules associated with the inflammatory response. These findings impact the future attempts to develop strategies aimed at attenuation of the enhanced RBC aggregation in obese individuals.

The structure of turbulence overlying impermeable and permeable rough walls T. KIM, G. BLOIS, J. BEST, Univ. of Illinois, K.T. CHRIS-TENSEN, Univ. of Notre Dame -Turbulent flow overlying complex topographies, both impermeable and permeable, occur across a broad range of scales in both natural and engineering environments. Permeability of the wall introduces a higher degree of both structural and conceptual complexity, with previous studies suggesting that interactions between the turbulent free flow and pore flow occur along the permeable interface and play a defining role in momentum exchange across the interface. Here we employ a Refractive-Index-Matching (RIM) technique in order to access the flow across the permeable interface with the particle image velocimetry (PIV) method, resulting in unimpeded optical access to the fluid flow at and within a permeable bed. Cubic-packed hemispheres are studied in both impermeable and permeable configurations, with models cast by an acrylic resin whose refractive index matched that of the working fluid (aqueous sodium iodide). The statistical and structural features of the flow in the near-wall region of the impermeable case and the interfacial region of the permeable case are compared to understand the role of permeability in driving momentum exchange processes as a function of Reynolds number. Comparisons to recent numerical simulations are also made.

BACKGROUND: In a traditional endotracheal tube (ETT), there is a linear outward pull through its attachment to the ventilator tubing that leads to risk of accidental dislodgement. This study was conducted to assess the ETT flow characteristics and to evaluate providers' intubation experience using two ETT's in a simulated setting. METHODS: Respiratory pressure-volume dynamics for the 2 ETTs were studied in a simulation laboratory by using 3 different flow settings and 2 different test lungs. The time taken for successful intubation on a mannikin was compared by direct observation of 33 separate intubation attempts by 11 different providers. Comfort with intubation by using both tubes was assessed with a Likert scale-based survey. The potential increase in physical and cognitive work load of nurses and respiratory therapists was assessed by the NASA task load index. RESULTS: There were slightly lower average tidal volumes delivered with SecureTube compared with the standard tube at different peak inspiratory pressures. Similarly, the same tidal volume delivered with a different flow and bag compliance required slightly higher peak inspiratory pressure compared with the standard ETT. Among providers, there was no difference in the average time to intubate when using either tube. All survey respondents (N ‫؍‬ 11) rated intubation attempts with the SecureTube to be very easy compared with the standard tube. The NASA task load index (N ‫؍‬ 26) showed very low task loads on all the tasks. CONCLUSIONS: There was minimal impact on flow resistance on pressure or volume with the SecureTube compared with the standard tube. Most providers felt comfortable intubating with the SecureTube and took a comparable amount of time to intubate in a simulated setting. We observed low task load scores for securement, maintenance, and manipulation per nurses and respiratory therapists.

Vertical and temporal variations in hydrodynamics were investigated within and above a salt marsh canopy and the adjacent mudflat through a vertical profiling method, where profiles represent flow velocity throughout the water column. Hydrodynamics were quantified using resolved horizontal velocity, turbulence intensities, turbulent kinetic energy, and 2D and 3D Reynolds stresses. The impacts of vegetation were assessed through comparative analysis of in-canopy and mudflat profiles, with in-canopy profiles showing a marked reduction in flow velocity and turbulent kinetic energy. Accelerated flow zones identified above the mudflat surface showed general correlation with the location of higher flow velocities within the vegetated canopy, suggesting that incoming tidal energy had a direct impact on in-canopy profiles, as large-scale circulation patterns influence flow within the marsh system. Vegetation effectively acts to control flow velocity and turbulence on the surface of a salt m...

We investigated relationships between geomorphic and hydraulic factors and invertebrate drift in high-gradient streams. We measured drift density of a highly mobile mayfly (Baetis bicaudatus) into and out of 12 stream reaches in western Colorado, as well as benthic density and abiotic variables within those reaches, during a time of moderate discharge. Multiple regression analysis indicated that drift propensity (drift density/benthic density), a measure of drift standardized by the benthic density of the source population, was significantly related to Reynolds number, a dimensionless ratio of fluid inertial forces to viscous forces, and Shields number, a dimensionless ratio of shear stress to submerged particle weight that quantifies flow competence. Drift propensity was positively correlated with Reynolds number, but counter to our hypothesis that stronger hydraulic forces would be associated with higher drift, mayflies in reaches with greater flow competence (Shields number) showed lower propensities to drift. Further, immigration ratio (drift in/drift out of each reach) increased significantly with Shields number, indicating that more individuals drifted into than out of reaches with higher flow competence. Although we hypothesized that more hydraulically rough stream reaches (i.e. those with greater flow resistance) would be more favourable to benthic invertebrates and would thus have lower drift, neither drift propensity nor immigration ratio were related to flow resistance. In high-gradient streams at discharges below the range of incipient motion of bed particles, mayfly drift behaviour may be influenced by hydraulic forces, but the relationships we observed are not indicative of passive, abiotically driven drift.

Objective." To investigate the flow-resistance of a new generation of Heat Moisture Exchanging Filters (HME filters) during 24 h of clinical use. Design: Before-after trial. Setting." A general Intensive Care Unit of a university hospital. Patients." A consecutive series of 96 patients undergoing mechanical ventilation for respiratory insufficiency of various etiology and severity. The characteristics of the secretions collected by tracheal suctioning and the pressure/flow relationship of the HMEs before and after 24 h of clinical use were analyzed. The resistance of the HMEs when dry was 2 hPa/1, s, and it increased to a maximum of I hPa/1, s in 83 ~ of the patients after 24 hours; in four patients with particularly heavy secretions HME resistance was 4-5 hPa/1, s. There were no significant modifications of the secretions within the investigation period, excluding, in particular, an increase in density with consequent tracheal tube obstruction. The gas conditioning efficiency and design performance of the tested HMEs did not create a significant obstacle to airflow medium term mechanical ventilation; however, these devices should be cautiously used in patients with heavy bronchial secretions.

Advancements in tracheostomy tube design now provide clinicians with a range of options to facilitate communication for individuals receiving ventilator assistance through a cuffed tube. Little is known about the impact of these modern design features on resistance to air flow. We undertook a bench model test to measure pressure-flow characteristics and resistance of a range of tubes of similar outer diameter, including those enabling subglottic suction and speech. A constant inspiratory ± expiratory air flow was generated at increasing flows up to 150 L/min through each tube (with or without optional, mandatory, or interchangeable inner cannula). Driving pressures were measured, and resistance was calculated (cm H2O/L/s). Pressures changed with increasing flow (P &lt; .001) and tube type (P &lt; .001), with differing patterns of pressure change according to the type of tube (P &lt; .001) and direction of air flow. The single-lumen reference tube encountered the lowest inspiratory a...

The reach-average impacts of frictional forces, which retard flows in man-made channels and natural streams, are basically taken into account by flow resistance coefficients. These coefficients have been commonly treated as either a constant or a variable parameter, while the latter is only feasible through a tedious calibration process considering different flow and channel-boundary conditions. When neither historical records are available nor flow measurement is possible, applying a fixed-value roughness coefficient is practically inevitable. Although variation of Manning's coefficient (n) with flow characteristics has been established in the literature, it has not been systematically implemented into hydraulic flow routing models, particularly because of the absence of a flow-dependent bed roughness predictor (BRP) suitable for numerical applications. In this study, a new grain roughness predictor, which provides derivations of n in respect with discharge and stage, is proposed. This grain roughness estimator, which enables to consider flow-dependent variation of n, is implemented in casting of governing equations of onedimensional hydraulic flow routing method. In the numerical experiments designed to assess this implementation, three scenarios for n were considered: (1) constant n, (2) variable n computed using the new roughness predictor, and (3) variable n calculated based on the observed data. The third scenario, which requires a significant amount of field measurements, was considered as the benchmark solution. The obtained results showed that applying the proposed BRP to the hydraulic flow routing improved estimated outflows more than 40% based on the mean absolute relative error. The achieved improvement obviously demonstrates that considering variable resistance coefficient, like the one suggested in this study, may considerably improve the results of the flow-related numerical modeling.

Determination of flow resistance in open channel flows is not only important for practical engineering applications but also challenging because of multiple factors involved. The literature review reveals that despite of various data-driven formulas and schemes, only classic Manning's resistance equation and Keulegan's formula have been utilized in practice. It also indicates that sole application of Artificial Intelligence (AI) models facilitates roughness estimation while they have not been used within a systematic roughness estimator scheme. In this study, a new eight-step scheme is developed to predict grain and total Manning's coefficients when grain and form roughness are the major sources of friction, respectively. The new scheme not only uses a new explicit equation for computing hydraulic radius related to bed for estimating grain roughness coefficient but also utilizes AI models named artificial neural network and genetic programming in the seventh step for estimating form roughness coefficient. It improves R 2 for estimating Manning's grain coefficient and RMSE for estimating discharge by 21% and 64% comparing with that of one of common formulas available in the literature, respectively. Moreover, the new scheme incorporating AI models significantly enhances the accuracy of estimation results for predicting roughness coefficient and discharge comparing with the new scheme using new developed empirical formula based on RMSE, MARE and R 2 criteria. The obtained improvement demonstrates that application of AI models as a part of a data-based roughness estimator scheme, like the one suggested, may considerably improve the precision of prediction results of flow resistance and discharge.

Perforated plates find many practical applications in industry--as flow control devices in particular, to control the flow emerging from a wide-angle diffuser, with applications to electrostatic precipitator design. Thus, an objective of the present investigation is to add to the existing body of knowledge concerning the mechanisms of screen flow and the associated flow resistance. Experimental data describe the behaviour of the flow emerging from the perforated plates in relation to the measuring locations and geometry of the perforated plates. The main results of investigations are (1) static pressures, (2) velocity distributions and (3) flow angles at the rear side of the perforated plates where jets occur. al,2

This paper presents a numerical study of the cake formation and growth in sedimentation or filtration in which the flow of discrete particles is three-dimensional and the flow of continuous liquid one-dimensional. The motion of particles is controlled by various forces, including particle-particle interactions due to collision and the van der Waals forces between particles, and particlefluid interactions such as buoyancy, drag and lift forces. The validity of the method is tested by comparing the simulated and measured results. It is shown this simulation technique can generate detailed information at both microscopic and macroscopic levels. The cake thickness, average cake solidosity, filtrate volume, filtrate flow rate (for constant pressure filtration) or pressure drop across the filter unit (for constant rate filtration) as a function of filtrate time have been quantified under different flow and operational conditions. The effects of variables such as particle size, Hamaker constant, fluid density and fluid viscosity on cake properties are examined through a series of controlled numerical experiments.

This study presents a methodology for improving the efficiency of Baptist and Stone and Shen models in predicting the global water flow resistance of a reclamation channel partly vegetated by rigid and emergent riparian plants. The results of the two resistance models are compared with the measurements collected during an experimental campaign conducted in a reclamation channel colonized by Common reed (Phragmites australis (Cav.) Trin. ex Steud.). Experimental vegetative Chézy’s flow resistance coefficients have been retrieved from the analysis of instantaneous flow velocity measurements, acquired by means of a downlooking 3-component acoustic Doppler velocimeter (ADV) located at the channel upstream cross section, and by water level measurements obtained through four piezometers distributed along the reclamation channel. The main morphometrical vegetation features (i.e., stem diameters and heights, and bed surface density) have been measured at six cross sections of the vegetated ...

Understanding of the role of turbulence in controlling transport processes is of paramount importance for the preservation and protection of aquatic ecosystems, the minimisation of deleterious consequences of anthropogenic activity, and the successful sustainable development of river and maritime areas. In this context, the present Special Issue collects 15 papers which provide a representation of the present understanding of turbulent processes and their effects in river and maritime environments. The presented collection of papers is not exhaustive but it allows for highlighting key priority areas and knowledge gaps in this field of research.

The growth of aquatic mosses attached to cobbles as a bed material in riffles was confirmed in a river in Japan. Covering bed material with aquatic mosses reduces the biomass of attached algae that is a source of energy for commercial fish. We sought to understand how aquatic mosses maintain coverage on the river bed in riffles from the viewpoint of response to flood disturbance. Resistance to disturbances due to water flow and sediment impingement on mosses was investigated with a laboratory experiment. We observed that intermediate impact seems to remove silt in the biofilm but that the majority of mosses maintain coverage. Based on visual inspection of moss cover following the experiment, we found that remaining moss consists of short fresh stems. In general, mosses seem well adapted to the high-speed flow environment typical in riffles.

The study of the effect of leukocyte adhesion on blood flow in small vessels is of primary interest to understand the resistance changes in venular microcirculation. Available computational fluid dynamic studies provide information on the effect of leukocyte adhesion when blood is considered as a homogeneous Newtonian fluid. In the present work we aim to understand the effect of leukocyte adhesion on the non-Newtonian Casson fluid flow of blood in small venules; the Casson model represents the effect of red blood cell aggregation. In our model the blood vessel is considered as a circular cylinder and the leukocyte is considered as a truncated spherical protrusion in the inner side of the blood vessel. The cases of single leukocyte adhesion and leukocyte pairs in positions aligned along the same side, and opposite sides of the vessel wall are considered. The Casson fluid parameters are chosen for cat blood and human blood and comparisons are made for the effects of leukocyte adhesion in both species. Numerical simulations demonstrated that for a Casson fluid with hematocrit of 0.4 and flow rate Q = 0.072 nl/s, a single leukocyte increases flow resistance by 5% in a 32 microns diameter and 100 microns long vessel. For a smaller vessel of 18 microns, the flow resistance increases by 15%.

The study of the effect of leukocyte adhesion on blood flow in small vessels is of primary interest to understand the resistance changes in venular microcirculation. Available computational fluid dynamic studies provide information on the effect of leukocyte adhesion when blood is considered as a homogeneous Newtonian fluid. In the present work we aim to understand the effect of leukocyte adhesion on the non-Newtonian Casson fluid flow of blood in small venules; the Casson model represents the effect of red blood cell aggregation. In our model the blood vessel is considered as a circular cylinder and the leukocyte is considered as a truncated spherical protrusion in the inner side of the blood vessel. The cases of single leukocyte adhesion and leukocyte pairs in positions aligned along the same side, and opposite sides of the vessel wall are considered. The Casson fluid parameters are chosen for cat blood and human blood and comparisons are made for the effects of leukocyte adhesion...

In the present study, a numerical investigation is carried out using ANSYS CFD to observe the heat transfer and heat dissipation, the method is by forced convection heat transfer, with a modern and innovative heat sink. In the study, a configuration of six vertical central fins of equal size and three small fins horizontally is observed. With the lower surface heated, this simulates the heat rejection of electronic devices such as video cards in CPUs. The Navier-Stokes equations for fluid dynamics and the Kappa-Epsilon turbulence model based on RNG (Renormalization) are established for this study. The temperature in the air surrounding the heat sink increases by 0.62 to 0.79 °C, for the base temperature of 80 °C and 100 °C, respectively. This means that at a higher air flow speed, 20 m/s, the air has the capacity to heat up more since its heat exchange is stronger, therefore, the heat sink reduces its temperature. 1

Introduction: Sulfur, F, Cl and a range of metals (Zn, Ga, Cu, Pb, Ni and other elements) are found coating glass beads in basaltic pyroclastic deposits from Apollo 17 (orange glass) and Apollo 15 (green glass) [1, 2]. The coatings are believed to have deposited from a volcanic gas during decompression and cooling of the eruptive plume [1, 3]. Using volatile element (H, C, Cl, S, F) concentrations measured in Apollo 17 orange glass beads [4, 5] and assuming an oxygen fugacity two log units below the iron-wüstite buffer (IW-2), we have derived a model for the composition of a lunar volcanic gas (mole%: H=31.8, O=15.4, C=15.9, Cl=0.2, S=34.6, F=2). Adding 0.001 mole% (arbitrarily set far below saturation) of the metals Zn, Ni, Pb, Ga, Cu and Fe, we have calculated the speciation of the bulk composition at pressures from 10 to 10 bar and from 500 to 1500 °C using a Gibbs Free energy minimization approach. Here we present a new model linking the thermochemical evolution of the lunar vol...

The objective of this study was to investigate the parameters that affect the drying process of wood chips at low air flow conditions. This objective was determined by measuring the air pressure resistance being produced by wood chips by examining different variables such as: air flow rate, air velocity, wood chip size, bulk density, bulk height and porosity. The air flow resistance was measured inside a 3 meter high cylindrical air duct constructed at University of Hohenheim. Physical properties of two different Spruce wood chip fractions were analyzed and their characteristics were considered on fitting the model expression. The analysed model expresses the physical behaviour of air flow resistance. Statistical analyses show high correlation of air speed versus air flow resistance. The model could be used for determination of drying conditions with low air mass flow. The height of bulk density according air mass flow generated or the necessary air mass flow needed for transporting...

Catalytic wire gauzes were used for years for ammonia oxidation. At present, various gauzes with a catalyst deposited on them have been receiving a great deal of attention as reactors fillers used for oxidation other than ammonia compounds. The flow and transfer properties of staked gauzes have been sufficiently examined yet. The study presents an experimental programme of pressure drop for stacked wire gauzes (woven and knitted) which allowed to generate a representative database. The theoretically derived mathematical model of flow through wire gauzes basing on Ergun's approach has been forward and tested on the collected database. The model does not include any empirical constants based on experimental data. The model prediction reasonably agree with the experimental results. The model provides a tool for the approximate classification of wire gauzes for the application as reactor fillers.

Based on experimental results of gas flow resistance through two metal foams, NC 2733 and Ni 2733, a modeling is performed to adjudicate governing flow mechanism. Two essential models are considered: developing laminar flow within short capillary channel (i.e., foam pore) and flow around solid body (foam strut modeled as cylinder or sphere), each of them of some variants. Foam geometry was studied using computer microtomography. The model of flow around a sphere (diameter equal to strut thickness) gives the best conformity with experiments.

The study deals with the flow resistance and heat transport properties of woven and knitted wire gauzes stacked in a tubular apparatus. The experimental programme included flow resistance and heat transfer experiments performed for air flow (Re = 2-300) using three woven gauzes and one knitted gauze. During the heat transfer experiments, the gauzes were heated by electric current flowing directly through them. The models describing the flow resistance and the heat transfer were put forward. Both the models base on the concept of the laminar flow developing in a short capillary channel (i.e. the gauze mesh). The model describing the flow resistance does not contain the experimentally derived parameters thus it may describe a number of wire gauzes offered on the market. The heat transfer results might be described using single empirical equation for all the gauzes studied if the concept of developing laminar flow is applied. The number of the gauze sheets stacked influences neither flow resistance (per single gauze sheet) nor the heat transfer coefficient.

Based on experimental results of gas flow resistance through two metal foams, NC 2733 and Ni 2733, a modeling is performed to adjudicate governing flow mechanism. Two essential models are considered: developing laminar flow within short capillary channel (i.e., foam pore) and flow around solid body (foam strut modeled as cylinder or sphere), each of them of some variants. Foam geometry was studied using computer microtomography. The model of flow around a sphere (diameter equal to strut thickness) gives the best conformity with experiments. © 2017 American Institute of Chemical Engineers AIChE J, 63: 1799–1803, 2017