GRID GENERATION

An indirect boundary integral method is used to solve transient nonlinear ship wave problems. A resulting mixed boundary value problem is solved at each time-step using a mixed Eulerian} Lagrangian time integration technique. Two dynamic node allocation techniques, which basically distribute nodes on an ever changing body surface, are presented. Both two-sided hyperbolic tangent and variational grid generation algorithms are developed and compared on station curves. A ship hull form is generated in parametric space using a B-spline surface representation. Two-sided hyperbolic tangent and variational adaptive curve grid-generation methods are then applied on the hull station curves to generate e!ective node placement. The numerical algorithm, in the "rst method, used two stretching parameters. In the second method, a conservative form of the parametric variational Euler}Lagrange equations is used the perform an adaptive gridding on each station. The resulting unsymmetrical in#uence coe$cient matrix is solved using both a restarted version of GMRES based on the modi"ed Gram}Schmidt procedure and a line Jacobi method based on LU decomposition. The convergence rates of both matrix iteration techniques are improved with specially devised preconditioners. Numerical examples of node placements on typical hull cross-sections using both techniques are discussed and fully nonlinear ship wave patterns and wave resistance computations are presented. 2000 Academic Press

The requirement for significantly higher electricity network investment in the UK seems certain as the capacity of distributed generation and large scale renewables increases on the system. In this paper, which forms a chapter in the forthcoming Book “Delivering a Low Carbon Electricity System: Technologies, Economics and Policy”2, the authors make a number of significant suggestions for improvement to the current system of network regulation. First, they suggest that the RPI-X system needs to be overhauled in favour of a simpler yardstick based system and which allows for more merchant transmission investments. Second, future regulation should involve more negotiated regulation involving agreements between network owners and purchasers of network services. This would be particularly advantageous for decisions on new network investments. Third, more extensive use needs to be made of locational pricing within the transmission and distribution system in order to facilitate the least c...

providing details and we will investigate your claim. Download date: 18. Sep. 2024 1. Characterize the rheology of a given polymer melt. 2. Conduct computations to verify the conditions that yield the fountain flow instability. 3. Subject the polymer melt to the injection molding process. Here, the process is mimicked by a cell with two continuously-rotating conveyor belts.

Electron-beam lithography is capable of high-resolution lithographic pattern generation (down to 10 nm or below). However, for conventional e-beam lithography, pattern-placement accuracy is inferior to resolution. Despite significant efforts to improve pattern placement, a limit is being approached. The placement capability of conventional e-beam tools is insufficient to fabricate narrow-band optical filters and lasers, which require sub-micrometer-pitch gratings with a high degree of spatial coherence. Moreover, it is widely recognized that placement accuracy will not be sufficient for future semiconductor device generations, with minimum feature sizes below 100 nm. In electron-beam lithography, an electromagnetic deflection system is used in conjunction with a laser-interferometer-controlled stage to generate high-resolution patterns over large areas. Placement errors arise because the laser interferometer monitors the stage position, but the e-beam can independently drift relative to the stage. Moreover, the laser interferometer can itself drift during exposure. To overcome this fundamental limitation, the method of spatial phase-locked electron-beam lithography has been proposed. The beam position is referenced to a high-fidelity grid, exposed by interference lithography, on the substrate surface. In this method, pattern-placement performance depends upon the accuracy of the reference grid and the precision with which patterns can be locked to the grid. The grid must be well characterized to serve as a reliable fiducial. This document describes work done to characterize grids generated by interference lithography. A theoretical model was developed to describe the spatial-phase progression of interferometric gratings and grids. The accuracy of the interference lithography apparatus was found to be limited by substrate mounting errors and uncertainty in setting the geometrical parameters that determine the angle of interference. Experimental measurements were performed, which agreed well with the theoretical predictions. A segmented-grid spatial-phase locking system was implemented on a vector-scan e-beam tool to correct field placement errors, in order to fabricate high-quality Bragg reflectors for optical filters and distributed-feedback lasers. Before this work, Bragg reflectors of adequate fidelity had not been fabricated by e-beam lithography. The phase coherence of the gratings fabricated with the segmented-grid method was characterized by measuring the displacement between adjacent fields. From these measurements, field-placement errors of -20 nm (mean + 3 sigma) were estimated. The segmented grid method was used to pattern Bragg gratings, which were used in the fabrication of integrated optical filters. The devices demonstrated excellent performance.

Optimized Schwarz methods form a class of domain decomposition methods for the solution of partial differential equations. Optimized Schwarz methods employ a first or higher order boundary condition along the artificial interface to accelerate its convergence. In the literature, analysis of optimized Schwarz methods rely on Fourier analysis and so the domains are restricted to be regular (rectangle or disk). By expressing the interface operator in terms of Poincare-Steklov operators, we are able to derive upper bounds of the spectral radius of the operator for Poisson-like problems for two essentially arbitrary subdomains. For a first order (Robin) boundary operator, an optimal choice of the parameter in the boundary operator leads to an upper bound of 1 -O(h 1/2 ) of the spectral radius, where h is the discretization parameter. For a certain higher order boundary operator, a clever choice of the two parameters in the boundary operator leads to an upper bound of 1 -O(h 1/4 ) of the spectral radius. These agree with the predicted rates for rectangular subdomains available in the literature and are also the observed rates in numerical simulations. This contribution summarizes the author's work in . Let Ω be a bounded domain in I R N with a smooth boundary. Suppose Ω is composed of two nonoverlapping open subdomains, that is, ) and is a smooth curve. We shall always assume that ∂Ω i \ Γ is non-trivial for both i = 1, 2. Recall the trace space with dual H -1/2 (Γ ). For i = 1, 2, let

This paper investigates a fundamental question related to the massive railway infrastructure development in China. What is the impact of high-speed rail (HSR) on regional economic disparity? The question is investigated from three perspectives. First, the influence of HSR on regional economic disparity is discussed theoretically from the perspective of New Economic Geography. Second, the variation in economic disparity at both the national and regional levels is investigated using three indexes: the weighted coefficient of variation, the Theil index and the Gini index. Third, the linkages between regional economic growth and HSR is measured empirically from a quantitative and qualitative perspective using an endogenous growth modelling framework with a panel data covering the period 2000-2014. The rail network density is adopted as a proxy to reflect the quantity change in rail investment. Three accessibility indicators (weighted average travel time, potential accessibility and daily accessibility) are introduced to capture the improvement of HSR transport quality. Our findings confirm that regional economic disparity has been decreased since the development of HSR. HSR has promoted regional economic convergence in China. Specifically, the positive effect of rail network density on regional economic growth is found to be significant in the East and North, whereas the positive effect of accessibility change is found to be more significant in the Middle Reaches of Yangtze River, the Southwest and the South China.

In this paper the hydrodynamics and shell side mass transfer of laminar flow across in-line tube arrays is studied numerically. The hydrodynamics of a five-tube array were described by the two-dimensional Navier-Stokes equations, employing the stream function-vorticity method. After a converged solution for the hydrodynamics had been found, a transport equation for the concentration was solved. The numerical grid of the investigated geometries consists of a number of basic cells, which are generated with a domain decomposition method combined with orthogonal grid generation. The hydrodynamics and mass transfer were analysed for Reynolds = 2-200, Péclet = 10-300 and pitch-to-diameter ratios of 1.5, 1.85 and 2.0. It is shown that the strength of the recirculation occurring between the adjacent tubes increases with increasing Reynolds number, and with decreasing pitch-todiameter ratio. Cartesian coordinates A tube radius C concentration c dimensionless concentration D diffusivity f distortion function h η , h ξ scalar factor Pe Péclet number Re Reynolds number Sc Schmidt number Sh Sherwood number U ∞ bulk velocity Greek symbols ψ stream function ω vorticity ξ, η computational coordinates λ pitch-to-diameter ratio ν kinematic viscosity Subscripts avg.

Two new quasi-linear elliptic systems of partial differential equations to automatically generate two-dimensional boundary conforming structured grids are formulated. One of the new systems generates grids with near-uniform cell areas. The other produces meshes with near-uniform coordinate line spacings. In both cases, the resulting grids conform to complex boundaries with severe singularities without self-overlapping. In contrast with other elliptic generators, the control functions are held as dependent variables. They obey Poisson-type equations with appropriate forcing. Grid quality analysis reveals the advantage in terms of smoothness and cell area uniformity of the new grids compared with other structured grids. An efficient procedure to combine the novel elliptic grids with algebraic grids for large domains is devised.

A new approach to generate structured grids for two-dimensional multiply connected regions with several holes is proposed. The bounding curves may include corners or cusps. The new algorithm constitutes an extension of the Branch Cut Grid Line Control (BCGC) technique introduced byVillamizar et al. [V. Villamizar, O. Rojas, J. Mabey, Generation of curvilinear coordinates on multiply connected regions with boundary-singularities, J. Comput. Phys. 223 (2007) 571-588] to domains with a finite number of holes. Regions with multiple holes are reduced to several contiguous single hole subregions. Then, the BCGC algorithm is applied to each single hole subregion producing a smooth grid with line control. Finally, the subregions with their respective grids are joined and their interfaces are smoothed resulting a globally smooth grid. The advantages of the novel grids are revealed by employing them to numerically solve acoustic scattering problems in the presence of multiple complexly shaped obstacles.

A grid of bars towed through a sample of He II produces both superfluid turbulence and classical hydrodynamic turbulence. The two velocity fields-in the normal fluid and in the superfluid-have been observed to have the same energy spectral density over a large range of scales. Here, we introduce a characteristic scale l q ϭ2(/ 3 ) Ϫ1/4 , where is the rate of turbulent energy dissipation per unit volume, and note that the energy spectrum in superfluid turbulence depends also on the quantum of circulation , for wave numbers k Ͼk q ϵ2/l q . We propose that the spectral density in this range is of the form (k)ϭC Ϫ1 k Ϫ3 , where C is the three-dimensional Kolmogorov constant in classical turbulence. This form is consistent with recent experiments in the temperature range 1.2 KϽTϽ2 K on the temporal decay of the vortex line density in the grid-generated He II turbulence.

The subject of mesh generation and optimization is very important in many scientific applications. In this paper, we investigate the issue of mesh optimization via the construction of Centroidal Voronoi Tessellations. Given some initial Delaunay meshes with only average quality, it is shown that the CVT based mesh optimization generates a robust, high quality mesh which does not rely critically on the choice of the initial mesh. In comparison, other smoothing techniques, such as the classical Laplacian smoothing, tend to be more sensitive to the initial distributions of vertices. Thus, the CVT based optimization may be advocated as a prefered choice for mesh optimization and smoothing.

Approximate nonlinear inviscid theoretical techniques for predicting aerodynamic characteristics and surface pressures for relatively slender vehicles at supersonic and moderate hypersonic speeds were developed. Emphasis was placed on approaches that would be responsive to conceptual configuration design level of effort. Second order small disturbance and full potential theory was utilized to meet this objective. Numerical codes were developed for relatively general three dimensional geometries to evaluate the capability of the approximate equations of motion considered. Results from the computations indicate good agreement with experimental results for a variety of wing, body, and wing-body shapes.

The VAIDAK medical imaging and model reconstruction toolkit manipulates medical image volume data and constructs accurate surface and solid models of skeletal and soft tissue structures. It takes CT (Computed tomography), MRl (magnetic resonance imaging), or laser surface imaging data as input and incoporates both heuristic and exact methods for contouring of image data, active thresholding, tiling and polygon reconstruction. It also incorporates a scanner to view image data and interactively pick threshold values, a browser feature to modify the contours, an editor for the boundary polygons of a reconstructed solid object and a render window to change lighting and display modes.

In the present study, a method is developed to incorporate neural network models for material response into nonlinear elastic truss analysis. Different feedforward network configurations are developed to assess the accuracy of neural network modeling of nonlinear material response. In addition to this, a scheme based upon linear interpolation for material data, is also implemented for comparison purposes. It is found that the neural network approach can yield very accurate results if used with care. For the type of problems under consideration, it offers a viable alternative to other material modeling methods. 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION

The aim of this work is the development of an automatic, adaptive mesh refinement strategy for solving hyperbolic conservation laws in two dimensions. There are two main difficulties in doing this. The first problem is due to the presence of discontinuities in the solution and the effect on them of discontinuities in the mesh. The second problem is how to organize the algorithm to minimize memory and CPU overhead. This is an important consideration and will continue to be important as more sophisticated algorithms that use data structures other than arrays are developed for use on vector and parallel computers. b? 1989 Academic Press, Inc.

In the present work, robust and efficient adaptive finite element techique has been proposed for solving singularly perturbed parabolic equation in one-dimension. Quasilinearization technique has been considered to tackle with the nonlinearity arising in the problem. Implicit Euler method has been used for temporal semi-discretization. Exponentially fitted splines have been used for spatial discretization on piecewise uniform Shishkin mesh. Streamline upwind/Petrov-Galerkin (SUPG) stabilization technique has been taken into the consideration for the considered problem. The proposed adaptive numerical scheme has been shown absolute stable. In the end, numerical tests have been performed and it has been shown that the proposed adaptive technique is quite efficient in capturing sharp boundary layers as singular perturbation parameter becomes sufficiently small.

This paper deals with the use of the Conjugate Gradient Method of function estimation with Adjoint Problem for the simultaneous identification of two boundary conditions in natural convection inverse problems in two-dimensional irregular cavities. The unknown boundary conditions are estimated with no a priori information about their functional forms. Irregular geometries in the physical domain are transformed into regular geometries in the computational domain by using an elliptic scheme of numerical grid generation. Therefore, the proposed formulation can be applied to the solution of inverse problems in different geometries. The methodology is applied to cases involving an annular cavity, where the position-and time-dependent heat fluxes are unknown at the inner and outer surfaces. The effects of the number and position of temperature sensors on the inverse problem solution are also addressed in the paper.

Images in this presentation are taken from Wikipedia 2 Definition -Electric Power Systems (EPS) refer to the infrastructure involved in the generation, transmission, distribution, and utilization of electric power. Electric Power Systems Introduction 3 Key Components: -Generation: Power plants (renewable and non-renewable sources). -Transmission: High-voltage lines to transport electricity over long distances. -Distribution: Low-voltage lines that deliver power to homes and businesses. -Utilization: End-user consumption, such as industrial, residential, and commercial use.

Results from an outdoor hover test of a full-scale Lynx tail rotor are presented. The investigation was designed to further the understanding of the acoustic8 of an isolated tail rotor hovering out-of-ground effect in atmospheric turbulence, without the effects of the main rotor wake or other helicopter components. Measurements include simuitaoeons rotor performance, ooise, inflow, and far-field atmospheric turbulence. Results with grid-generated inflow turbulence are also presented. The effects of atmospheric turbulence ingestion on rotor noise are quantified. In contradiction to current linear theories, increasing rotor inflow and rotor thrust were found to increase turbulence ingestion noise.

The two-point flux-approximation (TPFA) scheme is robust in the sense that it generally gives a linear system that has a solution regardless of the variations in K and the geometrical and topological complexity of the grid. The resulting solutions will also be monotone, but the scheme is only consistent for certain combinations of grids and permeability tensors K. This implies that a TPFA solution will not necessarily approach the true solution when we increase the grid resolution. It also means that the scheme may produce different solutions depending upon how the grid is oriented relative to the main flow directions; we will discuss this in more detail in Chapter 10. In this chapter, we first explain the lack of consistency for TPFA, before we introduce a few consistent schemes implemented in MRST. If you have only limited interest in discretizations, my advice is that you read Sections 6.1 and 6.3 before continuing to Chapter 7.

The error of the numeric approximation of the semiconductor device equations particularly depends on the grid used for the discretization. Since the most interesting regions of the device are generally straightforward to identify, the method of choice is to use structurally aligned grids. Here we present an algorithm for generating structurally aligned grids including anisotropy and for producing grids whose resolution varies over several orders of magnitude. Furthermore the areas with increased resolution and the corresponding resolutions can be defined in a flexible manner and criteria on grid quality can be enforced. The grid generation algorithm was applied to sample structures which highlight the features of this method. Furthermore we generated grids for the simulation of a high voltage trench gate MOSFET. In order to resolve the junction regions accurately, four regions were defined where the grid was grown in several directions with varying resolutions. Finally device simulations performed by MINIMOS NT show current voltage characteristics and the threshold voltage.

Earth Science (ES) is an all-encompassing term for sciences related to the planet Earth like seismology, geology, hydrology, and meteorology. DEGREE is a Specific Support Action (SSA) project that aims to promote Grid technologies throughout the large and diverse Earth Science community as a platform for e-collaboration in academic and industrial organizations.

This thesis focuses on developing algorithm to calculate best length line
segments in (u) and (w) directions. By of tool paths for free form surfaces based on the required accuracy of the manufactured part, which is represented by mathematical curves and surfaces. Bezier method was used to apply the proposed algorithms. The proposed algorithms consist of two parts; the first part is to calculate the better length line segment in (u) direction between cutter contact points (CC), the second part is to calculate the better line segment in (w) direction depending on the type of surface, cutter radius, tolerance and height scallop being given. The algorithms are applied in production field such as design of extrusion
dies using three types of curve interpolation such as approximation cubic Bezier, interpolator Bezier and compound-CRHS profile die. In this paper, the manufactured parts are machined using a 3-axis CNC milling machine. The machining operations are simulated using SURFCAM software depending on the different interpolation techniques mentioned. An evaluation test is applied to the three interpolation methods based on Finite Element Method (FEM) using ANSYS 9.0 software to expect the strain and force required to extrude billet through the dies which are designed using the three mentioned interpolation methods. The G-code programs have been implemented on 5-axis CNC machine (Okuma VH-40-HS dynamic machine), the sample material is (cibatool) and the machining process is achieved without a lubricant at the Protoshop Oy in Helsinki/Finland.

In this paper we study the transient heat conduction in a piston of a diesel engine, subjected to a periodic boundary condition on the surface in contact with the combustion gases. An elliptic scheme of numerical grid generation was used, so that the irregular shaped piston in the physical domain was transformed into a cylinder in a computational domain. The timewise variations of the temperature of several points in the piston are examined for different piston materials, as well as for motored and fired engines.

A combination algebraic/elliptic technique is presented for the generation of three dimensional grids about turbomachinery blade rows for both axial and radial flow machinery. The technique is built around use of an advanced engineering workstation to construct several two dimensional grids interactivley on predetermined blade-to-blade surfaces. A three dimensional grid is generated by interpolating these surface grids onto an axisymmetric grid. On each blade-to-blade surface, a grid is created using algebraic techniques near the blade to control orthogonality within the boundary layer region and elliptic techniques in the mid-passage to achieve smoothness. The interactive definition of bezier curves as internal boundaries is the key to simple construction. This procedure lends itself well to zonal grid construction, an important example being the tip clearance region. Calculations done to date include a space shuttle main engine turbopump blade, a radial inflow turbine blade, and the first stator of the United Technologies Research Center large scale rotating rig. A finite volume Navier Stokes solver was used in each case.

Numerical simulations of the flow field generated by a six-bladed paddle impeller in a closed unbaffled mixing vessel are presented. Computations were performed using the CFD software package FLUENT using grids generated from the pre-processor software package Gambit. The Rotating Frame Model was used in the solution process. Investigations were carried out over a range of Reynolds numbers covering laminar, transitional and turbulent flow regimes, while varying the axial dimension of the blade. Predicted flow field results have compared reasonably well with data from previous studies. It was found that increases in blade width (Wb) have resulted in corresponding increases in flow number (Nq), power number (Np) and pumping efficiency (λ p ), at least for the range of blade widths covered here. For all Wb's considered here, Np was highest in the laminar region and lowest in the turbulent region, whereas Nq was highest in the transitional regime. Pumping effectiveness (η e ) was found to maintain constant values of 0.215 in the transitional and 0.24 in the turbulent regions for all the blade widths; however, it exhibited some sensitivity to variation of blade width in the laminar region. C impeller off-bottom clearance (m) D impeller diameter (m) n number of blades N rotational speed (s -1 ) Np Power number = P/(N 3 D 5 ρ ) Nq flow or pumping number = Qp/ND 3 p pressure (Pa) P impeller power input (w) Qp pumping flow rate (m 3 s -1 ) r radial coordinate (m) Re Reynolds number = (ρND 2 )/ µ RRF rotating reference frame model MRF multiple reference frame model s represents source terms T tank diameter (m) T torque (Nm) u velocity (m/s) Wb blade width (m) ρ liquid density (kg/m 3 ) µ dynamic viscosity (kg/ms) η e pumping effectiveness = Nq/Np λ pumping efficiency= Nq/(Np) 1/3 p τ stress tensor Ω angular velocity of the frame (rad s -1

Numerical simulations of the flow field generated by a six-bladed paddle impeller in a closed unbaffled mixing vessel are presented. Computations were performed using the CFD software package FLUENT using grids generated from the pre-processor software package Gambit. The Rotating Frame Model was used in the solution process. Investigations were carried out over a range of Reynolds numbers covering laminar, transitional and turbulent flow regimes, while varying the axial dimension of the blade. Predicted flow field results have compared reasonably well with data from previous studies. It was found that increases in blade width (Wb) have resulted in corresponding increases in flow number (Nq), power number (Np) and pumping efficiency (λ p ), at least for the range of blade widths covered here. For all Wb's considered here, Np was highest in the laminar region and lowest in the turbulent region, whereas Nq was highest in the transitional regime. Pumping effectiveness (η e ) was found to maintain constant values of 0.215 in the transitional and 0.24 in the turbulent regions for all the blade widths; however, it exhibited some sensitivity to variation of blade width in the laminar region. C impeller off-bottom clearance (m) D impeller diameter (m) n number of blades N rotational speed (s -1 ) Np Power number = P/(N 3 D 5 ρ ) Nq flow or pumping number = Qp/ND 3 p pressure (Pa) P impeller power input (w) Qp pumping flow rate (m 3 s -1 ) r radial coordinate (m) Re Reynolds number = (ρND 2 )/ µ RRF rotating reference frame model MRF multiple reference frame model s represents source terms T tank diameter (m) T torque (Nm) u velocity (m/s) Wb blade width (m) ρ liquid density (kg/m 3 ) µ dynamic viscosity (kg/ms) η e pumping effectiveness = Nq/Np λ pumping efficiency= Nq/(Np) 1/3 p τ stress tensor Ω angular velocity of the frame (rad s -1

An Arbitrary Curvilinear Coordinate PIC Method CHRIS FICHTL, JOHN FINN, Los Alamos National Lab, KEITH CARTWRIGHT, AFRL -We demonstrate the feasibility of a new approach to the PIC method in which a grid generation strategy is coupled to a generalization of the PIC algorithm on the logical domain. Our grid generation strategy conforms to objects of arbitrary shape, eliminating such problems as stair-stepping along curved boundaries, and thus allows us to simulate complicated physical structures very accurately. We then use the mappings from the physical to the logical domain to run our PIC code. We have developed a semi-implicit particle mover for based on a generalization of the leapfrog method to arbitrary (including nonorthogonal) grids. We show our mover is symplectic and thus preserves phase-space area exactly. Extensive testing has shown that it also conserves energy to high accuracy. The electrostatic fields are solved on the logical domain using a preconditioned conjugate gradient method. We show test case results for several standard physics examples on multiple physical domains.

A second-order finite-volume (FV) method has been developed to solve the time-domain (TD) Maxwell equations, which govern the dynamics of electromagnetic waves. The computational electromagnetic (CEM) solver is capable of handling arbitrary grids, including structured, unstructured, and adaptive Cartesian grids, which are topologically arbitrary. It is argued in this paper that the adaptive Cartesian grid is better than a tetrahedral grid for complex geometries considering both efficiency and accuracy. A cell-wise linear reconstruction scheme is employed to achieve second-order spatial accuracy. Second-order time accuracy is obtained through a two-step Runge-Kutta scheme. Issues on automatic adaptive Cartesian grid generation such as cell-cutting and cell-merging are discussed. A multi-dimensional characteristic absorbing boundary condition (MDC-ABC) is developed at the truncated far-field boundary to reduce reflected waves from this artificial boundary. The CEM solver is demonstrated with several test cases with analytical solutions.

The greedy triangulation of a finite planar point set is obtained by repeatedly inserting a shortest diagonal that does not cross those already in the plane. The Delaunay triangulation, which is the straight-line dual of the Voronoi diagram, can be produced in O(n log n) worst-case time, and often even faster, by several practical algorithms. In this paper we show that for any planar point set S, if the Delaunay triangulation of S is given, then the greedy triangulation of S can be computed in linear worst-case time (and linear space).

Current, sea level and bed load transport are investigated in the Great Bay Estuary, New Hampshire, U.S.A.-a well-mixed system with low freshwater flow and having main channel tidal currents over 2 m/sec. Current and sea level forced by the Mi-Mi-Ma tide at the estuary mouth are simulated by a vertically averaged, nonlinear, time-stepping, finite-element model. The hydrodynamic model uses a fixed boundary computation domain and accounts for flooding-dewatering over tidal flats by making use of a groundwater component. Inertia terms are neglected in comparison with pressure gradient and bottom friction terms, which is consistent with the observed principal dynamic balance for this system. The accuracy of the hydrodynamic predictions is demonstrated by comparison with 5 tidal elevation stations and 2 cross-sectional ly averaged current measurements. Simulated current and bottom stress are then used to model bed load transport in the vicinity of a rapidly growing shoal located in the main channel of the lower system. Consisting of coarse sand and gravel, the shoal must be dredged every 5-8 years. Two approaches are taken-an Eulerian parametric method in which nodal bed load flux vectors are calculated at each time step and a Lagrangian particle tracking approach in which a finite number of sediment particles are released and tracked. Both methods yield pathways and accumulations in agreement with the observed shoal formation and the long-term rate of sediment accumulation in the shoal area.

Realistic lunar tides of the Great Bay Estuarine System have been simulated using a fixed boundary finite element numerical model as described by Ip et al. [1998]. It is a two-dimensional, nonlinear, time-stepping model with a groundwater component coupled to a kinematic force balance to facilitate the realistic drainage and filling of elements during ebb and flood, respectively. The numerical model reproduces the observed M 2 tides as described by Swift and Brown [1983], and it successfully captures qualitatively correct residual currents and transports, realistic massconserving flooding and dewatering of the tidal flats, and current asymmetry between flood and ebb. The simulation results were sensitive to local bathymetry and the implemented friction law. The accuracy of the model is demonstrated by comparison with the 1975 Great Bay study [Swift and Brown, 1983] in terms of tidal elevations at 14 tidal stations and 4 cross-sectionally averaged current measurements in the estuary. Quantitatively, the model results show good agreement with observations, displaying correlation coefficients of !0.96 in surface elevation and !0.95 in averaged current, with average RMS errors of 0.12 m and 0.26 m s À1 , respectively. In addition, tidal flat hydrodynamics, characteristic distributions of residual current, sediment bed load transport, and influence of topography on the overall circulation in the region are also discussed.

Current, sea level and bed load transport are investigated in the Great Bay Estuary, New Hampshire, U.S.A.-a well-mixed system with low freshwater flow and having main channel tidal currents over 2 m/sec. Current and sea level forced by the Mi-Mi-Ma tide at the estuary mouth are simulated by a vertically averaged, nonlinear, time-stepping, finite-element model. The hydrodynamic model uses a fixed boundary computation domain and accounts for flooding-dewatering over tidal flats by making use of a groundwater component. Inertia terms are neglected in comparison with pressure gradient and bottom friction terms, which is consistent with the observed principal dynamic balance for this system. The accuracy of the hydrodynamic predictions is demonstrated by comparison with 5 tidal elevation stations and 2 cross-sectional ly averaged current measurements. Simulated current and bottom stress are then used to model bed load transport in the vicinity of a rapidly growing shoal located in the main channel of the lower system. Consisting of coarse sand and gravel, the shoal must be dredged every 5-8 years. Two approaches are taken-an Eulerian parametric method in which nodal bed load flux vectors are calculated at each time step and a Lagrangian particle tracking approach in which a finite number of sediment particles are released and tracked. Both methods yield pathways and accumulations in agreement with the observed shoal formation and the long-term rate of sediment accumulation in the shoal area.

The dispersions of smoke or hazardous materials during accidental releases are of concern in many practical applications. A technique combining saltwater modeling and Particle Image Velocimetry (PIV) is developed to study the dispersion of a buoyant plume in a complex configuration. Saltwater modeling based on the analogy between saltwater flow and fire induced flow has proven to be a successful method for the qualitative analysis of fire induced plumes. With the use of nonintrusive laser diagnostics such as the PIV, detailed measurements of the velocity field can be taken for quantitative analysis of the plume behavior. The technique is first validated for a canonical unconfined plume scenario by comparing the results with theory and previous experimental data, and subsequently extended to qualitatively and quantitatively analyze plume dispersion in a crossflow with the construction of a crossflow generation system for the saltwater modeling facility. Lastly, plume dispersion in a crossflow near a building is analyzed.

The TOUGH2 simulator and its parallel version TOUGH2-MP continue to be the industry standards for the development of numerical models of geothermal systems. Increasing processing power enables us to simulate larger, more complex systems, while improved data collection and remote sensing techniques provide an ever greater suite of observations against which to calibrate the model. As a consequence, the raw text input files that control the simulations grow increasingly cumbersome to construct, while post-processing of model output becomes more challenging. We use the Python scripting language and the PyTOUGH library to interact with TOUGH2 in a number of novel ways to control simulation tasks accurately and efficiently. In this paper several examples of the use of PyTOUGH are described. A new method for automatically generating geothermal production wells is described that allows well information to be stored in concise, readable and easily updatable files. Examples are given of sequential modification of model geometries to represent effects such as eruptions and excavation. The generation of atmosphere blocks that vary in space and time due to changes in lake levels and extreme altitude are presented. Methods for controlling sequential simulations with both TOUGH2 and TOUGH2-MP are described including techniques for dealing with numerical nonconvergence. Finally, PyTOUGH's ability to combine and post-process results from multiple simulations and different types of output files is discussed.

In this present work the development, the implementation and the results interpretation of an Immersed Boundary Method, in a bi-dimensional Cartesian grid are shown. Three interpolations for the Immersed boundary correction were implemented and tested in a cavity flow with analytical solution. The second order of convergence from the FV discretization was obtained with a polynomial regression using material points and neighbor fluid cells based on the Least Square Method. The verification of the model was performed by comparison of the obtained results with computational data from the literature in steady laminar flows. Both qualitative and quantitative features of the flow were considered and showed considerable resemblance with the literature. In the moving boundary chapter verification was achieved by comparison with both experimental and computational data. The developed code allowed applications for computational modeling of moving boundaries immersed in fluid flows, accurately representing the behaviour of the fluid and the interactions between the fluid and the body's structure. The study of a portion from a winding Eucalyptus peel tube, one of the most common reasons for the propagation of forest wild fires, is performed and the aerodynamic drag force is shown. The comparison of the results with both empiric and computational data confirmed that the method is reliable to solve problems of immersed boundaries and that the computational cost can be decreased for this type of calculations.

Abstract: A study was conducted in 2002 with the aim of defining and analysing, both spatially and temporally, meteorological, topographic, socio-demographic and vegetation conditions which might be linked to the occurrence of forest fires caused by humans in Catalonia in Spain, ...

vocal fold vibrations. In the past, the simplified symmetric straight geometric models were commonly employed for experimental and computational studies. The shape of larynx lumen and vocal folds are highly three-dimensional indeed and the complex realistic geometry produces profound impacts on both glottal flow and vocal fold vibrations. To elucidate the effect of geometric complexity on voice production and improve the fundamental understanding of human phonation, a full flow-structure interaction simulation is carried out on a patient-specific larynx model. To the best of our knowledge, this is the first patient-specific flow-structure interaction study of human phonation. The simulation results are well compared to the established human data. The effects of realistic geometry on glottal flow and vocal fold dynamics are investigated. It is found that both glottal flow and vocal fold dynamics present a high level of difference from the previous simplified model. This study also paved the important step toward the development of computer model for voice disease diagnosis and surgical planning.

The helicopter manufacturers face a great challenge by extending the limit of the flight envelop for adapting their rotorcrafts to changing customer needs. For supporting further developments, the recent progress in Computational Fluid Dynamics (CFD) enable a better understanding of the flow physics especially in the case of complex geometries like the Fenestron®. This paper proposes a first Large Eddy Simulation (LES) performed on a full scale Dauphin Fenestron®. The objective is to better understand the turbulent flows especially for high blade pitch angle where the rotor blade can encounter massive boundary-layer separations. A comparison between a steady state RANS and a LES is achieved to characterize the effect of turbulence modeling on the flow predictions. Both approaches are compared with experimental data to evaluate the capability of the numerical simulations to estimate both global performance (thrust and power) and local flows (static pressure at the shroud and radial p...

In this paper we present a framework for determining the intersection of geometric objects based on the 9-Intersection model used in qualitative spatial reasoning. Triangle-triangle intersection is the computational basis for interaction between 2D/3D objects; hence a fast, robust intersection detection algorithm is beneficial. Additionally, we present efficient predicates for classification of the intersections. This work is applicable for most region connection calculi, particularly, VRCC-3D+, which detects intersections in 3D as well as projections in 2D for occlusion detection.