A primitive variable, strongly implicit calculation procedure for two and three-dimensional unsteady viscous flows: applications to compressible and incompressible flows including flows with free surfaces

A coupled solution procedure is described for solving the time-dependent Navier-Stokes equations in body-fitted nonorthogonal curvilinear coordinates for both compressible and incompressible flows in two and three dimensions;For the two-dimensional compressible form of equations, this approach employs the strong conservation law form of the governing equations but uses primitive variables (u, v, p, T) rather than the more traditional conservative variables ([rho], [rho]u, [rho][upsilon], E[subscript]t) as unknowns. A coupled modified strongly implicit procedure (CMSIP) is used to efficiently solve the Newton-linearized algebraic equations. It appears that this procedure is effective for Mach numbers ranging from the incompressible limit (M[subscript][infinity]~ 0.01) to supersonic. Generally, smoothing was not needed to control spatial oscillations in pressure for subsonic flows despite the use of central differences. Dual time stepping was found to further accelerate convergence for steady flows. Sample calculations, including steady and unsteady low Mach number internal and external flows and a steady shock-boundary layer interaction flow, illustrate the capability of the present solution algorithm;For three-dimensional incompressible liquid flows with the presence of free surfaces, this approach, coupled with the artificial compressibility method, is used to solve the Newton-linearized algebraic equations for the primitive variables (u, [upsilon], w, p). A true unsteady three-dimensional flow simulation has been obtained for liquid sloshing flow in a partially filled spherical container undergoing a general motion characteristic of that experienced by a spin-stabilized satellite. It appears that this unified approach can handle compressible and incompressible flows very effectively

Approaches to the determination of parallelism in computer programs

Approaches to the determination of parallelism in computer program

A numerical investigation of magnetic fields in laser-produced plasmas

Imperial Users onl

Circuit simulation using distributed waveform relaxation techniques

Simulation plays an important role in the design of integrated circuits. Due to high costs and large delays involved in their fabrication, simulation is commonly used to verify functionality and to predict performance before fabrication. This thesis describes analysis, implementation and performance evaluation of a distributed memory parallel waveform relaxation technique for the electrical circuit simulation of MOS VLSI circuits. The waveform relaxation technique exhibits inherent parallelism due to the partitioning of a circuit into a number of sub-circuits. These subcircuits can be concurrently simulated on parallel processors. Different forms of parallelism in the direct method and the waveform relaxation technique are studied. An analysis of single queue and distributed queue approaches to implement parallel waveform relaxation on distributed memory machines is performed and their performance implications are studied. The distributed queue approach selected for exploiting the coarse grain parallelism across sub-circuits is described. Parallel waveform relaxation programs based on Gauss-Seidel and Gauss-Jacobi techniques are implemented using a network of eight Transputers. Static and dynamic load balancing strategies are studied. A dynamic load balancing algorithm is developed and implemented. Results of parallel implementation are analyzed to identify sources of bottlenecks. This thesis has demonstrated the applicability of a low cost distributed memory multi-computer system for simulation of MOS VLSI circuits. Speed-up measurements prove that a five times improvement in the speed of calculations can be achieved using a full window parallel Gauss-Jacobi waveform relaxation algorithm. Analysis of overheads shows that load imbalance is the major source of overhead and that the fraction of the computation which must be performed sequentially is very low. Communication overhead depends on the nature of the parallel architecture and the design of communication mechanisms. The run-time environment (parallel processing framework) developed in this research exploits features of the Transputer architecture to reduce the effect of the communication overhead by effectively overlapping computation with communications, and running communications processes at a higher priority. This research will contribute to the development of low cost, high performance workstations for computer-aided design and analysis of VLSI circuits

A Metaphysical and linguistic approach to type design and typography

Significant changes have taken place in the type design as a result of what has often been termed the desktop revolution. With the popularization and increased availability to the average person of typographic tools formerly available only to professionals type is slowly moving into the realm of personal communication. This move has sparked significant controversy among the various schools of typographic thought, but little consensus exists. As well, technological developments are contributing to a widening of the definition of what constitutes a typeface. This study, then, will examine the current views of type design as an art form and the reaches of the technological developments in progress in light of linguistics and metaphysical thought

Solution of partial differential equations on vector and parallel computers

The present status of numerical methods for partial differential equations on vector and parallel computers was reviewed. The relevant aspects of these computers are discussed and a brief review of their development is included, with particular attention paid to those characteristics that influence algorithm selection. Both direct and iterative methods are given for elliptic equations as well as explicit and implicit methods for initial boundary value problems. The intent is to point out attractive methods as well as areas where this class of computer architecture cannot be fully utilized because of either hardware restrictions or the lack of adequate algorithms. Application areas utilizing these computers are briefly discussed

The Sixth Copper Mountain Conference on Multigrid Methods, part 2

The Sixth Copper Mountain Conference on Multigrid Methods was held on April 4-9, 1993, at Copper Mountain, Colorado. This book is a collection of many of the papers presented at the conference and so represents the conference proceedings. NASA Langley graciously provided printing of this document so that all of the papers could be presented in a single forum. Each paper was reviewed by a member of the conference organizing committee under the coordination of the editors. The multigrid discipline continues to expand and mature, as is evident from these proceedings. The vibrancy in this field is amply expressed in these important papers, and the collection clearly shows its rapid trend to further diversity and depth