Papers by prashanth hanmaiahgari
Turbulent Flow Characteristics in Interior and Wake Region of Emergent and Sparse Vegetation Patch
Sustainable Civil Infrastructures, 2018
Vegetation in the flow field affects flow hydrodynamics. For example, emergent vegetation patch i... more Vegetation in the flow field affects flow hydrodynamics. For example, emergent vegetation patch in the flow field produces changes in river morphology, changes in flow velocity and turbulence. Therefore, investigation of flow characteristics in and around the emergent vegetation patch is a topic of importance. The main aim of this study is to investigate the self-similarity and scaling of profiles of streamwise and lateral velocities, turbulence intensities, Reynolds shear stress and kinetic energy in the interior and the wake region of the vegetation patch. A Nortek Vectrinoplus Acoustic Doppler Velocimeter (ADV) was used to measure the point velocity data throughout the depth along the centerline of the vegetation patch in the streamwise direction. Seventy numbers of acrylic cylinders were used to make the emergent vegetation array in the middle of a laboratory flume. In this study, flows with two different Reynolds numbers and two different aspect ratios were investigated. The results demonstrate self-similarity of streamwise velocity profiles normalized by depth averaged velocity in the outer region in the interior and wake region of the emergent and sparse vegetation patch irrespective of Reynolds number and aspect ratio of flow. Similarly, wall wake similarity was observed in the Reynolds shear stress distribution.
Time Variation of Scour at Downstream Pier for Two Piers in Tandem Arrangement
A semi-empirical model is presented to estimate the time variation of scour depth at downstream o... more A semi-empirical model is presented to estimate the time variation of scour depth at downstream of pier when two piers are arranged in tandem arrangement under clear water scour condition with uniform sediments. The methodology developed for computing the time variation of scour depth is based on the concept of the conservation of mass of sediment, considering the primary horseshoe vortex system to be the main agent of scouring and assuming a layer-by-layer scouring process. The proposed model agrees closely with the reported experimental data of time variation of scour depth at downstream piers in tandem pier arrangements under clear water condition with uniform sediments.
Scaling of Open Channel Flow Velocities in Emergent, Sparse and Rigid Vegetation Patch with Rough Bed Interior of the Patch
Experimental analysis of turbulent open channel flow in the near-wake region of a surface-mounted horizontal circular cylinder
Mathematical Modeling of Solar Energy based Thermal Energy Storage for House Heating in Winter
Journal of Energy Storage, 2021
Abstract A novel solar thermal energy storage (TES) system for house heating purposes is modeled ... more Abstract A novel solar thermal energy storage (TES) system for house heating purposes is modeled in the present study. The solar parabolic collector acts as a heat source to charge the TES using compressed CO2. The thermal energy in terms of sensible heat is stored in mild steel (MS) block wrapped in the thermal insulation material and buried in the ground at a certain depth. The stored energy will be used for house heating in the winter season. A mathematical model is developed to calculate the quantity of stored energy, consumption, and loss from TES along with the optimal storage volume of the block to fulfill the energy demand for house heating. Computational analysis of the 3D model is executed by adopting stipulated boundary conditions. Quantitative and qualitative studies of numerical results have been investigated for two cases: Initial charging and year-round performance. Numerical results revealed that the initial charging of the block takes in 55.2 days with maximum block temperature and stored energy as 324.2 °C and 2604 MJ, respectively. The average exergy efficiency and exergetic effectiveness of TES are observed as 49.9 % and 0.50, respectively. The partial charging of the block continued to compensate the heat losses after initial charging. The year-round performance of TES exhibits the reduction of stored energy by 71.6% at the end of January due to increased heating demand. Meanwhile, during a cyclic year, the average exergy efficiency and exergetic effectiveness of TES are noticed as 56.12 % and 0.76 respectively. The proposed TES has enough potential for year-round house heating since 28.4 % of net stored energy exists with the least block temperature of 106 °C. The rational economic study endorsed the proposed system 42.5% less expensive than the traditional heating methods for 50 years of utilization in addition to mitigating the average CO2 production of 5.655 Tons/year.
Effects of Reynolds Number and Aspect Ratio on the Turbulence Characteristics in Developing and Fully Developed Flow Over a Rough Bed
Sustainable Civil Infrastructures, 2019
In order to enhance the physical understanding of the turbulent structures, the streamwise evolut... more In order to enhance the physical understanding of the turbulent structures, the streamwise evolution of the turbulent flow in narrow open channel over a fixed continuous rough bed has been investigated experimentally. The experiments were conducted to investigate the effects of Reynolds number and aspect ratio on turbulence characteristics in developing and fully developed narrow open channel flows. Instantaneous 3-D velocities were acquired using a Nortek VectrinoPlus down looking acoustic Doppler velocimeter at streamwise intervals of 0.5 m along the centerline of the flume. The time mean velocities with inner scaling for different aspect ratio flows demonstrate the self-similarity of fully developed flow. The effects of Reynolds number and aspect ratio on the normalized turbulence intensities, Reynolds shear stress and turbulent kinetic energy were found significant in the outer region of both the developing and fully developed narrow open channel flow.
Sādhanā, 2019
In the past, many researchers have carried out water-hammer pressure analysis using Joukowsky equ... more In the past, many researchers have carried out water-hammer pressure analysis using Joukowsky equation. However, it has been observed that the computed pressure surge is no longer applicable based on the equation. The Joukowsky equation cannot be used even within the reflection time of the long pipeline. In such cases, the actual pressure rise due to the sudden closure of a quick acting valve will be several times more than that of the sudden increase in pressure as calculated by the Joukowsky equation. The phenomenon of rising pressure at the upstream of an instantaneously closed valve with the passage of time caused by the pipe friction is commonly called as linepacking. In this paper, various parameters affecting the linepack pressure have been thoroughly investigated. As the relative roughness increases, the resulting non-dimensional linepack pressure P LP =P o ð Þsignificantly increases and the proportionality constant was equal to 1.5. The linepack pressure was determined to be decreasing with increasing valve closure time. The dominant parameter that influences the linepack pressure is found to be the Reynolds number as compared to the Mach number, and the relative roughness. Furthermore, the linepack pressure is found to be proportional to frictional head loss h L =D ð Þ, and inversely proportional to inlet pressure P o = cL o ð Þ ð Þ. Finally, a linear regression equation was developed in terms of non-dimensional variables to estimate the linepack pressure using hand calculations without undergoing numerical modeling procedures. The proposed equation was validated for sudden valve closure pressure histories available in the literature. The proposed method is applicable to long distance water supply pipelines where the linepack pressures are significant.
Sādhanā, 2017
A methodology to identify the partial blockages in a simple pipeline using genetic algorithms for... more A methodology to identify the partial blockages in a simple pipeline using genetic algorithms for non-harmonic flows is presented in this paper. A sinusoidal flow generated by the periodic on-and-off operation of a valve at the outlet is investigated in the time domain and it is observed that pressure variation at the valve is influenced by the opening size of blockage and its location. In this technique, the unsteady (steady oscillatory) pressure time series at only one location is required to identify two blockages. In the proposed methodology, the solution of the governing hyperbolic PDEs of pipe flow is obtained using the method of characteristics. For any piping system similar to the hypothetical pipe system used in the simulations, generalized best amplitude and best frequency of the valve operation are determined, which give maximum deviation in pressure responses for a specific blockage at different locations for a given constant-head reservoir. The generalized best amplitude and best frequency of the valve operation are also obtained for two blockages. Accuracy of the proposed methodology in identifying blockages in a hypothetical simple pipe system with increased noise in the simulated measurements is studied. A non-dimensional variable is proposed to determine whether the proposed methodology is applicable to isolate partial blockages in a piping system. Finally, the proposed methodology is experimentally validated on a laboratory piping system for a single blockage and two blockages.
Novel thermal treatment model to decontaminate airborne SARS Cov‐2 virus for residential and commercial buildings
Heat Transfer
In the COVID-19 pandemic, control of airborne virus transmission is exceptionally challenging as ... more In the COVID-19 pandemic, control of airborne virus transmission is exceptionally challenging as it is attached to suspended particles in the air and stays for an extended time. Air contaminated with airborne viruses holds a substantial risk for household transmission. In this study, a novel thermal treatment system is modeled based on porous heating for the decontamination of airborne SARS-Cov-2. The model includes an air heating domain, insulated chamber, buffer tank and heat exchanger. The airborne SARS-Cov-2 is decontaminated when passing through a porous heat pipe and the insulated chamber for an anticipated dwelling period of more than 5 min at 105°C and further stored in a buffer tank for natural cooling. The obligatory decontaminated air is allowed in the residential space under ambient conditions passing through a heat exchanger. The numerical investigation of the porous pipe model at different L/D ratios with altered porosities aims to establish the best-performing porous domain. Besides this, the buffer tank is intended to maintain buffer storage of the treated air and significant natural cooling before passing to the heat exchanger. A solar PV module is proposed to meet the prerequisite energy requirements of the equipped devices.
Fluids
This research article analyzed the self-preserving behaviour of wall-wake region of a circular pi... more This research article analyzed the self-preserving behaviour of wall-wake region of a circular pipe mounted horizontally over a flat rigid sand bed in a shallow flow in terms of mean velocity, RSS, and turbulence intensities. The study aims to investigate self-preservation using appropriate length and velocity scales.in addition to that wall-normal distributions of the third-order correlations along the streamwise direction in the wake region are analyzed. An ADV probe was used to record the three-dimensional instantaneous velocities for four different hydraulic and physical conditions corresponding to four cylinder Reynolds numbers. The results revealed that the streamwise velocity deficits, RSS deficits, and turbulence intensities deficits distributions displayed good collapse on a narrow band when they were non-dimensionalized by their respective maximum deficits. The wall-normal distance was non-dimensionalized by the half velocity profile width for velocity distributions, while...
Fluids, 2022
This paper reviews existing studies relating to the assessment of sediment concentration profiles... more This paper reviews existing studies relating to the assessment of sediment concentration profiles within various flow conditions due to their importance in representing pollutant propagation. The effects of sediment particle size, flow depth, and velocity were considered, as well as the eddy viscosity and Rouse number influence on the drag of the particle. It is also widely considered that there is a minimum threshold velocity required to increase sediment concentration within a flow above the washload. The bursting effect has also been investigated within this review, in which it presents the mechanism for sediment to be entrained within the flow at low average velocities. A review of the existing state-of-the-art literature has shown there are many variables to consider, i.e., particle density, flow velocity, and turbulence, when assessing the suspended sediment characteristics within flow; this outcome further evidences the complexity of suspended sediment transport modelling.
Water Science and Technology Library, 2017
Important turbulent characteristics are compared between upstream, interior and downstream of a s... more Important turbulent characteristics are compared between upstream, interior and downstream of a sparse and emergent vegetation patch along the centerline in an open-channel flow. The emergent vegetation patch is made up of seventy uniform rigid acrylic cylindrical rods with regular spacing between two cylinders along streamwise and lateral directions. Along the centerline from upstream to downstream through the interior of the vegetation patch, time-averaged streamwise and lateral velocities are decreasing whereas vertical velocities are increasing. The profiles of streamwise lateral and vertical normal stresses, and turbulent kinetic energy increase in downstream direction through the vegetation patch along the centerline but slightly decrease in the wake region immediate downstream of the trailing edge as compared the values in the middle region of the vegetation patch. The dominant Reynolds shear stress Àu 0 w 0 profiles show decreasing trend in the downstream direction inside the vegetation patch and in the wake region downstream of trailing edge. The vertical distribution of Àu 0 v 0 shows negative values at the leading edge of the vegetation patch, but positive at interior and immediate downstream of the vegetation patch, which demonstrates increased lateral momentum transfer in downstream direction along the vegetation patch.
Comparison of Turbulent Hydrodynamics with and without Emergent and Sparse Vegetation Patch in Free Surface Flow
Water Science and Technology Library, 2017
In the present study, we have compared the turbulent hydrodynamics in open turbulent flow with an... more In the present study, we have compared the turbulent hydrodynamics in open turbulent flow with and without an emergent and sparse vegetation patch. The rigid patch, located at the middle cross-sectional region, was made by acrylic cylindrical rods with regular spacing between them along streamwise and transverse directions. The measurements of flow velocity components were taken by a Nortek Vectrino Plus acoustic Doppler velocimeter, and experimental data were collected along cross section for vegetation-free fully developed flow and along the cross section which is located at the middle of the streamwise length of the vegetation patch. Inside the vegetation patch, we have observed decreased value of time-averaged streamwise velocity in comparison with those of the vegetation-free fully developed flow. The time-averaged values of transverse and vertical velocities show increased magnitude with respect to the corresponding values in the vegetation-free fully developed flow. Inside the vegetation patch, with increasing transverse length from right-hand sidewall to left-hand sidewall, the magnitudes of normal stresses gradually increase and exceed the corresponding magnitudes of normal stresses in the vegetation-free fully developed flow. Along the cross section inside the patch, the magnitudes of governing Reynolds shear stress are smaller than the corresponding values of Reynolds shear stress without the vegetation. Along the cross section inside the patch, the vectors of secondary current follow are directed towards the left-hand sidewall together with zigzag pattern in vertical direction. In the interior of the vegetation, the strength of anticlockwise vortex in terms of the magnitude of moment of momentum is greater than that of the vegetation-free fully developed flow.
Lateral Variation of Turbulent Features in Developing and Developed Narrow Open-Channel Flow
In the present study, a detailed experimental investigation of lateral variation of turbulent cha... more In the present study, a detailed experimental investigation of lateral variation of turbulent characteristics is carried out in developing and fully developed flow over a fixed rough bed. Experiments are conducted in a rectangular flume of aspect ratio \((b/h = 3.05)\) and bed roughness \(d_{50} = 2.5\,{\text{mm}}\). Instantaneous three-dimensional velocities were measured using a Nortek Vectrino plus downlooking ADV. The characteristics of normalized flow velocity, turbulent intensities, Reynolds shear stresses and TKE distribution have been investigated. Raw velocity data have been filtered as prescribed in the recent literature. From the experimental data, it is observed that boundary-layer thickness increases along the streamwise distance in the developing flow region and reaches maximum in fully developed flow. On the contrary, boundary-layer thickness decreases in the lateral direction from the centreline of the channel towards sidewalls in both developing flow and fully devel...
Water, 2021
Here, recent developments in the key numerical approaches to water hammer modelling are summarize... more Here, recent developments in the key numerical approaches to water hammer modelling are summarized and critiqued. This paper summarizes one-dimensional modelling using the finite difference method (FDM), the method of characteristics (MOC), and especially the more recent finite volume method (FVM). The discussion is briefly extended to two-dimensional modelling, as well as to computational fluid dynamics (CFD) approaches. Finite volume methods are of particular note, since they approximate the governing partial differential equations (PDEs) in a volume integral form, thus intrinsically conserving mass and momentum fluxes. Accuracy in transient modelling is particularly important in certain (typically more nuanced) applications, including fault (leakage and blockage) detection. The FVM, first advanced using Godunov’s scheme, is preferred in cases where wave celerity evolves over time (e.g., due to the release of air) or due to spatial changes (e.g., due to changes in wall thickness)....
Turbulent hydrodynamics through cross-sections at upstream, interior and downstream of sparse vegetation patch in open channel flow
Comparison of turbulent features through upstream, interior and downstream of sparsely vegetated open channel turbulent flow
Fluids, 2021
Building roofs represents a critical pathway for sediment mixing with rainwater. This study aims ... more Building roofs represents a critical pathway for sediment mixing with rainwater. This study aims to explore the correlation between roof-top deposited sediment matter in the different areas of the Ikorodu Local Government Area in Lagos, Nigeria. The deposition rate on the roof was studied for 34 weeks in total (i.e., 17 weekly analyses in the rainy season and 17 weekly analyses in the dry season). The total deposition was collected by a 10 inch funnel and directed into a 5 L container, which was partially filled with sterilised water. The roof-top deposition in four different areas was inspected and analysed. The four areas were selected based on the levels of sanitation and vegetation. The experimental results showed that the enumerated total depositions in different areas were higher in the dry season than the rainy season, with the highest deposition occurring in the Harmattan period. The data obtained from this study have evidenced that the contamination from roof-harvested rain...
Water, 2021
During flooding, the suspended sediment transport usually experiences a wide-range of dilute to h... more During flooding, the suspended sediment transport usually experiences a wide-range of dilute to hyper-concentrated suspended sediment transport depending on the local flow and ground conditions. This paper assesses the distribution of sediment for a variety of hyper-concentrated and dilute flows. Due to the differences between hyper-concentrated and dilute flows, a linear-power coupled model is proposed to integrate these considerations. A parameterised method combining the sediment size, Rouse number, mean concentration, and flow depth parameters has been used for modelling the sediment profile. The accuracy of the proposed model has been verified against the reported laboratory measurements and comparison with other published analytical methods. The proposed method has been shown to effectively compute the concentration profile for a wide range of suspended sediment conditions from hyper-concentrated to dilute flows. Detailed comparisons reveal that the proposed model calculates t...
Journal of Hydroinformatics, 2020
The proposed study investigated the applicability of the finite volume method (FVM) based on the ... more The proposed study investigated the applicability of the finite volume method (FVM) based on the Godunov scheme to transient water hammer with shock front simulation, in which intermediate fluxes were computed using either first-order or second-order Riemann solvers. Finite volume (FV) schemes are known to conserve mass and momentum and produce the efficient and accurate realization of shock waves. The second-order solution of the Godunov scheme requires an efficient slope or a flux limiter for error minimization and time optimization. The study examined a range of limiters and found that the MINMOD limiter is the best for modeling water hammer in terms of computational time and accuracy. The first- and second-order FVMs were compared with the method of characteristics (MOCs) and experimental water hammer measurements available in the literature. Both the FV methods accurately predicted the numerical and experimental results. Parallelization of the second-order FVM reduced the compu...
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Papers by prashanth hanmaiahgari