Nonuniform Grid

An analytical calculation of the magnetic field of a cylindrical permanent magnet linear generator is presented. The generator utilises a discrete Halbach permanent magnet array as magnetic field source. The array is constructed of permanent magnets that have a non-uniform length. To solve the governing equations, a direct solution method is used. The flux distributions in the air gap, inside the permanent magnet and in the shaft are calculated. Solutions that are derived using this method are compared with that obtained from the finite element analysis simulation method. Another method is also used in the field calculation, and the result is presented for comparison.

Ray tracing on GPUs is an area of ongoing research. GPUs are well suited for this parallel rendering algorithm. GPU computing devices typically have characteristics which make them quite different from CPUs: increased data parallelism, increased memory bandwidth, smaller caches, lower memory capacity. Presently it is difficult to visualize large scenes with tens of millions of triangles in these memory constrained platforms. In this paper we present a compressed grid data structure, capable of state of the art rendering performance, using up to 6× less memory than conventional grid storage schemes. The compressed grid is built and traversed on the GPU.

Ray tracing is an inherently parallel visualization algorithm. However to achieve good performance, at interactive frame rates, an acceleration structure to decrease the number of per ray primitive intersections is required. Grid acceleration structures have some of the fastest build times, with O (N) complexity, but traditionally achieved this at a high memory cost. Recent research has reduced the memory footprint by employing compression for one-level grids. Render time performance can be improved using multi-level grids. We ...

Ray tracing on GPUs is an area of ongoing research. GPUs are well suited for this parallel rendering algorithm. GPU computing devices typically have characteristics which make them quite different from CPUs: increased data parallelism, increased memory bandwidth, smaller caches, lower memory capacity. Presently it is difficult to visualize large scenes with tens of millions of triangles in these memory constrained platforms. In this paper we present a compressed grid data structure, capable of state of the art rendering performance, using up to 6× less memory than conventional grid storage schemes. The compressed grid is built and traversed on the GPU.

Ray tracing is an inherently parallel visualization algorithm. However to achieve good performance, at interactive frame rates, an acceleration structure to decrease the number of per ray primitive intersections is required. Grid acceleration structures have some of the fastest build times, with O (N) complexity, but traditionally achieved this at a high memory cost. Recent research has reduced the memory footprint by employing compression for one-level grids. Render time performance can be improved using multi-level grids. We ...

Grids have some of the lowest ray tracing acceleration structure build times. This is because acceleration structure construction is analogous to a sorting algorithm. The ideal behavior for a sorting algorithm is to have O (N) time complexity regarding the number of elements. Grids also have O (N) construction time complexity regarding the number of primitives unlike other commonly used acceleration structures, such as kd-trees or bounding volume hierarchies, which have an O (N log N) lower bound. This trait makes grid ray ...

Commonly used hierarchical data structures such as bounding volume hierarchies and kd-trees have rather high build times, which can be a bottleneck for applications rebuilding or updating the acceleration structure required by data changes. On the other hand uniform grids can be built almost instantly in linear time, however, they can suffer from severe performance penalty, in particular in scenes with non-uniformly populated geometry. We improve on performance using a two-step approach that combines both approaches: first we build a uniform grid and test its performance. Second, using an estimate on the number of rays to be queried we either continue using the grid or build a hierarchical data structure instead. This way we select a more efficient data structure given a particular implementation of the algorithms which yields with high probability an overall smaller computational time. We evaluate the properties of this method for a set of 28 scenes.

Ray tracing is an inherently parallel visualization algorithm. However to achieve good performance, at interactive frame rates, an acceleration structure to decrease the number of per ray primitive intersections is required. Grid acceleration structures have some of the fastest build times, with O (N) complexity, but traditionally achieved this at a high memory cost. Recent research has reduced the memory footprint by employing compression for one-level grids. Render time performance can be improved using multi-level grids. We ...

Grids have some of the lowest ray tracing acceleration structure build times. This is because acceleration structure construction is analogous to a sorting algorithm. The ideal behavior for a sorting algorithm is to have O (N) time complexity regarding the number of elements. Grids also have O (N) construction time complexity regarding the number of primitives unlike other commonly used acceleration structures, such as kd-trees or bounding volume hierarchies, which have an O (N log N) lower bound. This trait makes grid ray ...

Grids have some of the lowest ray tracing acceleration structure build times. This is because acceleration structure construction is analogous to a sorting algorithm. The ideal behavior for a sorting algorithm is to have O (N) time complexity regarding the number of elements. Grids also have O (N) construction time complexity regarding the number of primitives unlike other commonly used acceleration structures, such as kd-trees or bounding volume hierarchies, which have an O (N log N) lower bound. This trait makes grid ray ...

A computer code has been developed for regular geometry. SIMPLE algorithm based on finite volume method on staggered grid has been used. Deferred QUICK scheme have been implemented for all calculations. A standard code is used for lid driven cavity. This code can be used for mean flow solution of the problem i.e. U and V can be obtained after modifying the code for boundary condition at the left wall for the given problem. The computational results for lid driven cavity problem are compared with benchmark solution for Re = 100, 400, 1000, 3200, 5000 and Pr = 0.71. The results are very good agreement with benchmark solution.

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Wireless Sensor Networks (WSNs) became essential in developing many applications, including smart cities and Internet of Things (IoT) applications. WSN has been used in many critical applications such as healthcare, military, and transportation. Such applications depend mainly on the performance of the deployed sensor nodes. Therefore, the deployment process has to be perfectly arranged. However, the deployment process for a WSN is challenging due to many of the constraints to be taken into consideration. For instance, mobile nodes are already utilized in many applications, and their localization needs to be considered during the deployment process. Besides, heterogeneous nodes are employed in many recent applications due to their efficiency and cost-effectiveness. Moreover, the development areas might have different properties due to their importance. Those parameters increase the deployment complexity and make it hard to reach the best deployment scheme. This work, therefore, seek...

Ray tracing on GPUs is an area of ongoing research. GPUs are well suited for this parallel rendering algorithm. GPU computing devices typically have characteristics which make them quite different from CPUs: increased data parallelism, increased memory bandwidth, smaller caches, lower memory capacity. Presently it is difficult to visualize large scenes with tens of millions of triangles in these memory constrained platforms. In this paper we present a compressed grid data structure, capable of state of the art rendering performance, using up to 6× less memory than conventional grid storage schemes. The compressed grid is built and traversed on the GPU.

Ray tracing is an inherently parallel visualization algorithm. However to achieve good performance, at interactive frame rates, an acceleration structure to decrease the number of per ray primitive intersections is required. Grid acceleration structures have some of the fastest build times, with O (N) complexity, but traditionally achieved this at a high memory cost. Recent research has reduced the memory footprint by employing compression for one-level grids. Render time performance can be improved using multi-level grids. We ...

Grids have some of the lowest ray tracing acceleration structure build times. This is because acceleration structure construction is analogous to a sorting algorithm. The ideal behavior for a sorting algorithm is to have O (N) time complexity regarding the number of elements. Grids also have O (N) construction time complexity regarding the number of primitives unlike other commonly used acceleration structures, such as kd-trees or bounding volume hierarchies, which have an O (N log N) lower bound. This trait makes grid ray ...

The vorticity-stream function formulation of the two-dimensional incompressible Navier-Stokes equations is used to study the effectiveness of the coupled strongly implicit multigrid (CSI-MG) method in the determination of high-Re fine-mesh flow solutions. The driven flow in a square cavity is used as the model problem. Solutions are obtained for configurations with Reynolds number as high as 10.000 and meshes consisting of as many as 257 x 257 points. For Re = 1000, the (129 x 129) grid solution required 1.5 minutes of CPU time on the AMDAHL 470 V/6 computer. Because of the appearance of one or more secondary vortices in the flow field, uniform mesh refinement was preferred to the use of one-dimensional gridclustering coordinate transformations.

Doktoritöös käsitletakse lineaarsete Fredholmi teist liiki integraalvõrrandite ligikaudse lahendamisega seotud probleeme situatsioonis, kus võrrandi tuum võib argumentide kokkulangemise korral olla iseärane (nõrgalt singulaarne). Tuuma iseärasus toob reeglina kaasa integraalvõrrandi lahendi iseärase käitumise integreerimispiirkonna raja lähedal ning raskused kiirete lahendusmeetodite konstrueerimisel niisuguste võrrandite jaoks. Töö põhitulemuseks on kiirete ja kvaasikiirete meetodite väljatöötamine nimetatud võrrandite korral. Kiire meetod tähendab siin meetodit võrrandi lähislahendite leidmiseks, mis antud ülesannete klassi korral annab lähislahenditele optimaalset järku täpsuse võimalikult väikese aritmeetiliste tehete arvu korral. Vajalikud veahinnangud on saadud lähteülesande periodiseerimise kaudu, mille puhul integraalvõrrandi lähislahendite leidmine taandub perioodiliste funktsioonide aproksimeerimisele trigonomeetriliste polünoomide abil.In the present thesis the bounds of ...

Because of the presence of corner eddies that change in number and pattern the lid-driven cavity problem has been found suitable to study various aspects of the performance of solution algorithms for incompressible viscous flows. It retains all the difficult flow physics and is characterized by a large primary eddy at the centre and secondary eddies located near the cavity corners. In this work, lid-driven cavity flow is simulated by lattice Boltzmann method with single-relaxation-time and it is compared with those by lattice Boltzmann method with multi-relaxation-time and finite difference method. The effects of the Reynolds number on the size, centre position and number of vortices are studied in detail together with the flow pattern in the cavity. The close agreement of the results bears testimony to the validity of this relatively new approach. However lattice Boltzmann method with multi-relaxation-time model is seen to remove the difficulties faces by the lattice Boltzmann method with single-relaxation-time at higher Reynolds numbers.

This work is concerned with the computation of two-and four-sided lid-driven square cavity flows and also two-sided rectangular cavity flows with parallel wall motion by the Lattice Boltzmann Method (LBM) to obtain multiple stable solutions. In the two-sided square cavity two of the adjacent walls move with equal velocity and in the four-sided square cavity all the four walls move in such a way that parallel walls move in opposite directions with the same velocity; in the two-sided rectangular lid-driven cavity flow the longer facing walls move in the same direction with equal velocity. Conventional numerical solutions show that the symmetric solutions exist for all Reynolds numbers for all the geometries, whereas multiplicity of stable states exist only above certain critical Reynolds numbers. Here we demonstrate that Lattice Boltzmann method can be effectively used to capture multiple steady solutions for all the aforesaid geometries. The strategy employed to obtain these solutions is also described.

The purpose of this work is to develop an innovative procedure for reconstructing the pressure field from PIV velocity measurements of unsteady, incompressible flows. The proposed technique is based on a generalization of the Glowinski-Pironneau method for the uncoupled solution of the incompressible Navier-Stokes equations written in primitive variables and exploits a finite element discretization of the measurement grid. By virtue of the underlying mathematical formulation, the method is stable and more accurate than the other techniques proposed so far in the literature. The method is first applied to an exact solution of the Navier-Stokes equations, showing second order convergence of the L ∞ error for the pressure variable. The robustness of the method with respect to stochastic perturbations in the velocity field is then tested and the results compared with other techniques proposed in the literature. Finally, the proposed technique is applied to both phase-averaged and time-resolved PIV velocity measurements of the flow around a pitching airfoil employed to investigate the dynamic stall. The reconstructed pressure is compared with direct pressure measurements, showing very encouraging results.

Piecewise polynomial collocation methods on special nonuniform grids are efficient methods for solving weakly singular Fredholm and Volterra integral equations but there is a widespread belief that those methods are numerically unstable in the case of large values of the nonuniformity parameter r. We show that this method by itself is stable and discuss some implementation problems that may lead to unstable behavior of numerical results.

A popular class of methods for solving weakly singular integral equations is the class of piecewise polynomial collocation methods. In order to implement those methods one has to compute exactly certain integrals that determine the linear system to be solved. Unfortunately those integrals usually cannot be computed exactly and even when analytic formulas exist, their straightforward application may cause unacceptable roundoff errors resulting in apparent instability of those methods in the case of highly nonuniform grids. In this paper fully discrete analogs of the collocation methods, where integrals are replaced by quadrature formulas, are considered, corresponding error estimates are derived.

Article history: Received 9 August 2017 Received in revised form 20 November 2017 Accepted 30 November 2017 In this paper, accurate and efficient calculations of the flow inside different types of cavities are presented. The incompressible Navier-Stokes equations are expressed in generalized curvilinear coordinates using artificial compressibility method. The governing equation in conservative form is solved numerically using an upwind compact finite difference scheme. The solution algorithm for solving the resulting linear system of equation is approximate factorization based ADI scheme. The computed results are compared with the results in the literature and the agreement is good. Also the presence of multiple solution and critical value of aspect ratio and Reynolds number for two sided cavity calculated and compared.

Article history: Received 9 August 2017 Received in revised form 20 November 2017 Accepted 30 November 2017 In this paper, accurate and efficient calculations of the flow inside different types of cavities are presented. The incompressible Navier-Stokes equations are expressed in generalized curvilinear coordinates using artificial compressibility method. The governing equation in conservative form is solved numerically using an upwind compact finite difference scheme. The solution algorithm for solving the resulting linear system of equation is approximate factorization based ADI scheme. The computed results are compared with the results in the literature and the agreement is good. Also the presence of multiple solution and critical value of aspect ratio and Reynolds number for two sided cavity calculated and compared.

Finite volume methods based on pressure-velocity coupling in incompressible flow has been evolved as the basic guideline and is successfully implemented in numerous industrial and aerospace fields. In our studies, we use this class of techniques for analysing flow inside the lid driven cavity. Our simulation analysis is based on the finite-volume method using non-uniform staggered mesh. An issue of storing and coupling pressure-velocity in finite volume method is solved by using SIMPLE algorithm are reviewed. Current works aim to study the formation of vortex for varied Reynolds numbers based on numerical simulations and its influence over mid-plane velocities as extending the length of the cavity. The simulation results are represented in terms of contours of streamlines and velocity plot.

An essential component of a finite volume method (FVM) is the advection scheme that estimates values on the cell faces based on the calculated values on the nodes or cell centers. The most widely used advection schemes are upwind schemes. These schemes have been developed in FVM on different kinds of structured and unstructured grids. In this research, the physical influence scheme (PIS) is developed for a cell-centered FVM that uses an implicit coupled solver. Results are compared with the exponential differencing scheme (EDS) and the skew upwind differencing scheme (SUDS). Accuracy of these schemes is evaluated for a lid-driven cavity flow at Re = 1000, 3200, and 5000 and a backward-facing step flow at Re = 800. Simulations show considerable differences between the results of EDS scheme with benchmarks, especially for the lid-driven cavity flow at high Reynolds numbers. These differences occur due to false diffusion. Comparing SUDS and PIS schemes shows relatively close results fo...

Article history: Received 9 August 2017 Received in revised form 20 November 2017 Accepted 30 November 2017 In this paper, accurate and efficient calculations of the flow inside different types of cavities are presented. The incompressible Navier-Stokes equations are expressed in generalized curvilinear coordinates using artificial compressibility method. The governing equation in conservative form is solved numerically using an upwind compact finite difference scheme. The solution algorithm for solving the resulting linear system of equation is approximate factorization based ADI scheme. The computed results are compared with the results in the literature and the agreement is good. Also the presence of multiple solution and critical value of aspect ratio and Reynolds number for two sided cavity calculated and compared.

This paper describes how the Solver tool in Microsoft Excel can be used to solve nonlinear systems of equations resulting from finite difference discretization of the governing equations for fluid dynamics and heat transfer. Students learning computational fluid dynamics and heat transfer for the first time typically spend an inordinate amount of time struggling with algorithm development and programming issues. The use of the visual presentation and automated solution capabilities of Excel can help bolster the student's understanding of basic discretization issues unencumbered by programming details. Cell formatting can be used to visualize the geometry and how the grid variables interact with one another, a feature that is particularly helpful when dealing with irregular geometries or staggered grids. Results can be easily shown on contour or x-y plots. Although the number of grid points and thus accuracy is limited by the number of equations that the Solver tool can handle, a spreadsheet model is nevertheless valuable for giving students an intuitive feel for discretization before going on to write code. Two applications are described. The first is a twodimensional conduction problem that is introduced to show how Solver can be used to solve systems of finite difference equations. The second demonstrates the solution of the incompressible Navier-Stokes equations using the staggered grid formulation. The conduction problem is one that is easily incorporated into an undergraduate heat transfer class, while the flow problem is appropriate for a graduate level course.

The vorticity-stream function formulation of the two-dimensional incompressible Navier-Stokes equations is used to study the effectiveness of the coupled strongly implicit multigrid (CSI-MG) method in the determination of high-Re fine-mesh flow solutions. The driven flow in a square cavity is used as the model problem. Solutions are obtained for configurations with Reynolds number as high as 10.000 and meshes consisting of as many as 257 x 257 points. For Re = 1000, the (129 x 129) grid solution required 1.5 minutes of CPU time on the AMDAHL 470 V/6 computer. Because of the appearance of one or more secondary vortices in the flow field, uniform mesh refinement was preferred to the use of one-dimensional gridclustering coordinate transformations.

by Lina Baroudi Adviser: Professor Taehun Lee A numerical study has been performed using a lattice Boltzmann method (LBM) for an incompressible binary fluid based on the Cahn-Hilliard diffuse interface approach to investigate the early-time coalescence dynamics of two liquid drops. The two drops approach each other at a very low Weber number (We) and the coalescence process is driven by surface tension. When the two drops come into contact, the curvature diverges and causes infinitely large surface tension forces, leading to the formation of a rapidly growing liquid bridge. Depending on the forces that govern the widening of the liquid bridge, the coalescence dynamics can be classified into viscous regime, where the viscous forces govern the coalescence and inertial regime, where the inertial forces govern the coalescence. For the coalescence in the inertial regime, where the liquid bridge radius r grows as r(t) ∝ √ t, the effect of the initial separation between the drops on the gr...

Finite volume methods based on pressure-velocity coupling in incompressible flow has been evolved as the basic guideline and is successfully implemented in numerous industrial and aerospace fields. In our studies, we use this class of techniques for analysing flow inside the lid driven cavity. Our simulation analysis is based on the finite-volume method using non-uniform staggered mesh. An issue of storing and coupling pressure-velocity in finite volume method is solved by using SIMPLE algorithm are reviewed. Current works aim to study the formation of vortex for varied Reynolds numbers based on numerical simulations and its influence over mid-plane velocities as extending the length of the cavity. The simulation results are represented in terms of contours of streamlines and velocity plot.

Kajian ini meneroka amalan kepimpinan instruksional pensyarah sebagai pemimpin pengajaran dan pembelajaran di Kolej Kemahiran Tinggi MARA Sri Gading, Kolej Kemahiran Tinggi MARA Ledang dan Kolej Kemahiran Tinggi Masjid Tanah. Pensyarah yang dipilih sebagai kepimpinan instruksional adalah terdiri daripada Timbalan Pengarah HEA, Ketua Jabatan, Ketua Program, Ketua Unit dan Penyelaras Kursus yang berasaskan empat amalan pengurusan instruksional iaitu merangka matlamat pengajaran dan pembelajaran, pemantauan kurikulum dengan pengajaran dan pembelajaran, mengekalkan pemantauan kurikulum dengan pengajaran dan pembelajaran, dan berdasarkan sokongan pembelajaran dengan pengajaran dan pembelajaran. Kajian deskriptif ini dijalankan secara tinjauan keatas 108 responden dari tiga lokasi kajian dengan menggunakan borang soal selidik. Pengumpulan data secara mengedarkan soal selidik mengandungi bahagian demografi dan 4 bahagian mengandungi 24 item kajian kepada semua responden. Analisis data bera...

An analytical calculation of the magnetic field of a cylindrical permanent magnet linear generator is presented. The generator utilises a discrete Halbach permanent magnet array as magnetic field source. The array is constructed of permanent magnets that have a non-uniform length. To solve the governing equations, a direct solution method is used. The flux distributions in the air gap, inside the permanent magnet and in the shaft are calculated. Solutions that are derived using this method are compared with that obtained from the finite element analysis simulation method. Another method is also used in the field calculation, and the result is presented for comparison.

CFD tools have an important benchmark problem, and the lid-driven cavity is one of the most outstanding tools. This paper presents the benchmark tool for CFD simulation of a lid-driven cavity, examining the particular case of top-and-bottom moving boundary conditions. The governing equation that is used is an unsteady Navier-Stokes equation in a primitive variable formulation. The solution method is implicit finite difference with staggered grid. The result is a symmetrical vortex with half top and lower part. The Reynolds number was varied between 100, 500,1000, 4000 and 10000. In this paper we also present the secondary vortex in some circumstances. The velocity profile in a quarter, half and three-fourth full x and y axis is also presented.

CFD tools have an important benchmark problem, and the lid-driven cavity is one of the most outstanding tools. This paper presents the benchmark tool for CFD simulation of a lid-driven cavity, examining the particular case of top-and-bottom moving boundary conditions. The governing equation that is used is an unsteady Navier-Stokes equation in a primitive variable formulation. The solution method is implicit finite difference with staggered grid. The result is a symmetrical vortex with half top and lower part. The Reynolds number was varied between 100, 500,1000, 4000 and 10000. In this paper we also present the secondary vortex in some circumstances. The velocity profile in a quarter, half and three-fourth full x and y axis is also presented.

Grids have some of the lowest ray tracing acceleration structure build times. This is because acceleration structure construction is analogous to a sorting algorithm. The ideal behavior for a sorting algorithm is to have O(N) time complexity regarding the number of elements. Grids also have O(N) construction time complexity regarding the number of primitives unlike other commonly used acceleration structures, such as kd-trees or bounding volume hierarchies, which have an O(N log N) lower bound. This trait makes grid ray tracing interesting for many applications including animation. Recent algorithmic developments have also made it possible to achieve one-level grid construction, with low memory requirements, by compressing empty grid cells. Unfortunately one-level grids achieve lower render time performance than recursive structures such as multi-level grids. We present a method for rapidly building a grid with similarly good render time performance and using less memory than classic multi-level grids. We demonstrate that this method is a remarkably effective solution for interactive ray tracing of large scanned models.

Ray tracing is an inherently parallel visualization algorithm. However to achieve good performance, at interactive frame rates, an acceleration structure to decrease the number of per ray primitive intersections is required. Grid acceleration structures have some of the fastest build times, with O (N) complexity, but traditionally achieved this at a high memory cost. Recent research has reduced the memory footprint by employing compression for one-level grids. Render time performance can be improved using multi-level grids. We ...

Grids have some of the lowest ray tracing acceleration structure build times. This is because acceleration structure construction is analogous to a sorting algorithm. The ideal behavior for a sorting algorithm is to have O (N) time complexity regarding the number of elements. Grids also have O (N) construction time complexity regarding the number of primitives unlike other commonly used acceleration structures, such as kd-trees or bounding volume hierarchies, which have an O (N log N) lower bound. This trait makes grid ray ...

Grid is one of the first data structure introduced at the very beginning of computer graphics. Grids are used in several applications of computer graphics, especially in rendering algorithms. Lately, in ray tracing dynamic scenes, grid has received attention for its appealing linear time building time. In this paper, we aim to survey several aspects behind the use of grids in ray tracing. In particular we investigate grid traversal algorithms, building techniques and several approaches for hierarchical grids.

Grid is one of the first data structure introduced at the very beginning of computer graphics. Grids are used in several applications of computer graphics, especially in rendering algorithms. Lately, in ray tracing dynamic scenes, grid has received attention for its appealing linear time building time. In this paper, we aim to survey several aspects behind the use of grids in ray tracing. In particular we investigate grid traversal algorithms, building techniques and several approaches for hierarchical grids.

Finite volume methods based on pressure-velocity coupling in incompressible flow has been evolved as the basic guideline and is successfully implemented in numerous industrial and aerospace fields. In our studies, we use this class of techniques for analysing flow inside the lid driven cavity. Our simulation analysis is based on the finite-volume method using non-uniform staggered mesh. An issue of storing and coupling pressure-velocity in finite volume method is solved by using SIMPLE algorithm are reviewed. Current works aim to study the formation of vortex for varied Reynolds numbers based on numerical simulations and its influence over mid-plane velocities as extending the length of the cavity. The simulation results are represented in terms of contours of streamlines and velocity plot.

by Lina Baroudi Adviser: Professor Taehun Lee A numerical study has been performed using a lattice Boltzmann method (LBM) for an incompressible binary fluid based on the Cahn-Hilliard diffuse interface approach to investigate the early-time coalescence dynamics of two liquid drops. The two drops approach each other at a very low Weber number (We) and the coalescence process is driven by surface tension. When the two drops come into contact, the curvature diverges and causes infinitely large surface tension forces, leading to the formation of a rapidly growing liquid bridge. Depending on the forces that govern the widening of the liquid bridge, the coalescence dynamics can be classified into viscous regime, where the viscous forces govern the coalescence and inertial regime, where the inertial forces govern the coalescence. For the coalescence in the inertial regime, where the liquid bridge radius r grows as r(t) ∝ √ t, the effect of the initial separation between the drops on the gr...

Recent advances in integrated electronic devices motivated the use of Wireless Sensor Networks (WSNs) in many applications including target surveillance and tracking. A number of sensor nodes are scattered within a sensitive region to detect the presence of intruders and forward subsequent events to the analysis center(s). Obviously, the sensor deployment should guarantee an optimal event detection rate. This paper proposes a tracking framework based on Voronoi tessellations. Two mobility models are proposed to control the coverage degree according to target presence. The objective is to set a non-uniform coverage within the monitored zone to allow detecting the target(s) by multiple sensor nodes. We show how the proposed algorithm adapts to the situation where multiple targets move in the monitored zone. Moreover, we introduce an algorithm to discover redundant nodes (which do not provide additional information about target position). This algorithm is shown to be effective in reducing the energy consumption using an activity scheduling approach. Simulations are carried out to underline the efficiency of the proposed models.

Article history: Received 9 August 2017 Received in revised form 20 November 2017 Accepted 30 November 2017 In this paper, accurate and efficient calculations of the flow inside different types of cavities are presented. The incompressible Navier-Stokes equations are expressed in generalized curvilinear coordinates using artificial compressibility method. The governing equation in conservative form is solved numerically using an upwind compact finite difference scheme. The solution algorithm for solving the resulting linear system of equation is approximate factorization based ADI scheme. The computed results are compared with the results in the literature and the agreement is good. Also the presence of multiple solution and critical value of aspect ratio and Reynolds number for two sided cavity calculated and compared.

Lid-driven cavity flows have been widely investigated and accurate results have been achieved as benchmarks for testing the accuracy of computational methods. This paper verifies the accuracy of a mesh refinement method numerically using two-dimensional steady incompressible lid-driven flows and finer meshes. The accuracy is shown by comparing the coordinates of centres of vortices located by the mesh refinement method with the corresponding benchmark results. The accuracy verification shows tha ...

In recent years OpenFOAM solvers have attracted great attention of the academia and industrial practitioners. Principal potentialities of this software are full access to the code, easy solver generation, modification and a huge and open users community among others. The isothermal flow patterns in liddriven cavity for three different geometric configurations of the cavity are obtained using OpenFOAM solvers. These configurations include the square cavity, skewed cavity and trapezoidal cavity. The steady flow patterns obtained by OpenFOAM for different Reynolds numbers (Re) ranging from 100 to 3200 are compared with the benchmark published results of Ghia et al. The isothermal flow in all the three cavities are discussed in detail for varying Reynolds numbers.

This work investigates the efficiency of the Multigrid numerical method when applied to solve the temperature field in a tank filled with a porous substrate. The numerical method includes finite volume discretization with the flux blended deferred correction scheme on structure orthogonal regular meshes. The correction storage (CS). Multigrid algorithm performance is compared for different values of porosity and permeability. Up to four grid for both Wand V-cycles are considered. Results indicate that also for flow in porous media there are advantages in using more than one computational grid when numerically solving the governing equations.