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- Title
- Checkpointing schemes for high-performance parallel applications in networks of workstations.
- Creator
- He, Fusen., Florida Atlantic University, Wu, Jie
- Abstract/Description
-
In this thesis, a low interprocessor communication overhead and high performance data parallelism parallel application model in a network of workstations (NOWs) is proposed. Checkpointing and rollback technologies are used in this model for performance enhancement purpose. The proposed model is analyzed both theoretically and numerically. The simulation results show that a high performance of the parallel application model is expected. As a case study, the proposed model is used to the...
Show moreIn this thesis, a low interprocessor communication overhead and high performance data parallelism parallel application model in a network of workstations (NOWs) is proposed. Checkpointing and rollback technologies are used in this model for performance enhancement purpose. The proposed model is analyzed both theoretically and numerically. The simulation results show that a high performance of the parallel application model is expected. As a case study, the proposed model is used to the parallel Everglades Landscape Fire Model (ELFM) code which was developed by South Florida Water Management District (SFWMD). The parallel programming environment is Message-Passing Interface (MPI). A synchronous checkpointing and rollback mechanism is used to handle the spread of fire which is a dynamic and irregular component of the model. Results show that the performance of the parallel ELFM using MPI is significantly enhanced by the application of checkpointing and rollback.
Show less - Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/15597
- Subject Headings
- Computer networks, Electronic data processing--Distributed processing, Fault-tolerant computing
- Format
- Document (PDF)
- Title
- A numerical study of bluff body aerodynamics by vortex method.
- Creator
- He, Fusen., Florida Atlantic University, Su, Tsung-Chow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Vortex methods are grid-free; therefore, their use avoids a number of shortcomings of Eulerian, grid-based numerical methods for solving high Reynolds number flow problems. These include such problems as poor resolution and numerical diffusion. In vortex methods, the continuous vorticity field is discretized into a collection of Lagrangian elements, known as vortex elements. Vortex elements are free to move in the flow field which they create. The velocity field induced by these vortex...
Show moreVortex methods are grid-free; therefore, their use avoids a number of shortcomings of Eulerian, grid-based numerical methods for solving high Reynolds number flow problems. These include such problems as poor resolution and numerical diffusion. In vortex methods, the continuous vorticity field is discretized into a collection of Lagrangian elements, known as vortex elements. Vortex elements are free to move in the flow field which they create. The velocity field induced by these vortex elements is a solution to the Navier-Stokes equation, and in principle the method is suitable for high Reynolds number flows. In this dissertation, viscous vortex element methods are studied. Some modifications are developed. Discrete vortex element methods have been used to solve the Navier-Stokes equations in high Reynolds number flows. Globally satisfactory results have been obtained. However, computed pressure fields are often inaccurate due to the significant errors in the surface vorticity distribution. In addition, different ad hoc assumptions are often used in different proposed algorithms. In the present study, improvements are made to better represent the near-wall vorticity when obtaining numerical solutions for the Navier-Stokes equations. In particular, we split the boundary vortex sheet into two parts at each time step. One part remains a vortex sheet lying on the boundary of the solid body, and the other enters into the flow field as a free vortex element with a uniformly distributed vorticity. A set of kinematic relationships are used to determine the two appropriate portions of the split, and the position of the vortex element to be freed at the time of release. Another improvement is to include the nonlinear acceleration terms in the governing equations near the solid boundary when evaluating the surface pressure distribution. The aerodynamic force coefficients can then be obtained by summing up the pressure forces. By comparing the computed surface vorticities, surface pressures and aerodynamics force coefficients with existing numerical/experimental data in the cases of viscous flow around a circular cylinder, an aerofoil, and a bridge deck section, it is shown that the present approach is more accurate in modelling the flow features and force coefficients without making different ad hoc assumptions for different geometries. The computation is efficient. It can be useful in the study of the unsteady fluid flow phenomenon in practical engineering problems.
Show less - Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/12574
- Subject Headings
- Vortex-motion, Fluid mechanics, Viscous flow
- Format
- Document (PDF)