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Introduction
Object-Oriented Implementation of a Computational Fluid Dynamics Method
Stephen McMahon
Introduction
Hypersonic aircraft and spacecraft
The role of Computational Fluid Dynamics, CFD
Outline of the current work
Basic Principles
Fluid dynamics
Conservation of mass
Navier-Stokes equation
Conservation of energy
Equation of state
Current numerical methods
Discretising the model equations
Control volume approach to discretisation
Method of Characteristics
Godunov type methods
Particle-in-Cell, PIC
Fluid-in-Cell, FLIC
The difference equations
Boundary conditions
Stability and accuracy
The Free Piston Shock Tunnel
Shock tunnel development
The free piston shock tunnel
Test time limitation
A particular driver gas contamination problem
Expected boundary layer thickness
Milthorpe's Algorithm
Overview
Conservation algorithm
Phase 1 - Diffusion
Phase 2 - Pressure gradient effects
Upwinding factor
Phase 3 - Convection
Calculation of dependent flow variables
Stability limits
Boundary conditions
Upstream boundary
Symmetric boundary
Freestream boundary
Comparison with FLIC
Pressure gradient effects
Transport effects
Implementation in C++
Overview
Object-oriented programming
Procedural programming
Modular programming
Data abstraction
Objects
The design of
CONVECT
The object classes
Domain
Region
Cell
Species
Diffuser
Convector
Squeezer
Transport
Implementation differences between Milthorpe's method and
CONVECT
Dynamic memory allocation
De-referencing
Momentum and velocity as cell properties
Timestep adjustments
Inputs file
Calcinit.pl - calculation of initial conditions
Cross platform features
Stability
Artificial viscosity
The tuning algorithm
Parallel implementation
Overview
Implementation points
Message Passing Interface (MPI)
Data structures
Output file processing
Results
Tuning and development
Object-oriented development times and issues
Tuning results
Flat plate calculations
Early
CONVECT
results
Parallel
CONVECT
results
Timings
Comparison with previous results
Artificial viscosity study
Comparison to General Aerodynamic Simulation Program, GASP
Discussion
The implementation
Development time issues
Tuning
Artificial viscosity study
Comparison with GASP
Driver gas contamination
Conclusions
Bibliography
Files that make up the
CONVECT
computer program
An example inputs file
Calcinit.pl
About this document ...
Mr Stephen McMahon 2002-02-04
