Introduction
The CFDToolkit is intended to be a collaborative and integrative grid computing environment to address challenging multi-scale, multi-physics interdisciplinary fluid dynamics problems. To achieve such a goal, various numerical discretization techniques as well as algorithms for governing equations of fluid flow phenomena (Navier-Stokes equations) will be implemented using the cactus framework .Motivations for the development of such a framework are:

• A collaborative grid computing environment for challenging fluid dynamics problems

• A benchmark for the peta-scale computing platforms

• An integrative interdisciplinary tool that utilizes the available expertise at the center in a pragmatic fashion

Description of CFD Toolkit arrangement
The following arrangements and thorns: cactusCFD, CFDIO, CFDMesh, CFDBCs, CFDdrivers, CFDbase and CFDEvolvers are already committed to CVS (more information is available on the CactusCFD wiki). The centered finite difference weights for 2nd, 4th and 6th order accuracy for the first and second spatial derivatives have been written for collocated meshes as well as regular staggered meshes. Documentation of the thorns in this arrangement will be under constant development. An implementation of lid-driven cavity is provided in CFDExamples.These simple applications will also aid in teaching numerical methods, CFD as well computational frameworks. Also, these cases serve as the benchmark for numerical validation/verification (V&V). With IGERT on multi-scale CFD funded, it is expected that there will be graduate students working on interdisciplinary CFD projects. The CFD Toolkit could potentially serve as their common “language”.

Major components of the toolkit include

• CFDBase: Description of primitive variables or conserved fluxes. It will be extended to work with CGNS (CFD general notation system, refer wiki).

• CFDEvolvers: Various pressure-velocity coupling algorithms. It will be generalized to both implicit as well as explicit time integrations.

• CFDdrivers: Defines the application and selects the appropriate thorns for the specified algorithm.

• CFDMesh: Creates a logically Cartesian mesh or reads a computational mesh. It will be extended for both unstructured as well as multi-block meshes.

• CFDBCs: Specifically tailored to use CFD nomenclature for the Bcs and will be extended to introduce user-specified perturbations at inlets.

As the first step, CFD Toolkit contains an implementation of the fractional step algorithm to solve unsteady incompressible Navier-Stokes equations. The driven cavity driver will serve as a CFDToy example.The main driver must call:

• Grid setup: creating single block cartesian meshes or importing from a grid generator

• Initialization: reading default values in the dependent variables

• Predictor step: calculation of various terms with fixed set of coefficients that will be generalized later

• Poisson solve: calculation of pressure field) Corrector step (project the velocity field using the pressure gradients

• Boundary conditions: Dirichlet and Neumann conditions

The CFD Toolkit intends to support FDM, FVM, FEM or any hybrid application of these discretizations. A plethora of solution algorithms such as artificial compressiblity, SIMPLE, fractional step (projection) method etc. for incompressible flows, LDFSS for the compressible flows will be developed as the user base for CFD Toolkit grows. A variety of numerical solvers (PETSc, Trilinos) already interface with cactus and can be used to exploit the advantages and avoid the limitations of any specific numerical solver.

Development Team:
Mayank Tyagi
Yaakoub El Khamra
Jason Ventrella
Jung-Han Kimn

Collaborators:
Soon-Heum Ko

Students:
Razvan Carbunescu
Andrew Davidson
Prasad Kalghatgi

Publications and Presentations:

• CFDToolkit presentation CCT-KISTI meeting May 15th 2006
• CFDToolkit Driven Cavity Animation
• CFDToolkit Driven Cavity Animation (zipped file)
• CFDToolkit Infrastructure
• MOAB Presentation
  

Download:
The CFDToolkit is now available via anonymous CVS access from CCT's CVS server (cvs.cct.lsu.edu) using the username: "cvs_anon" and "anon" as a password. The main repository is "Arrangements/CactusCFD". For internal reports about the CFDToolkit please checkout CFDDocs from cvs.cct.lsu.edu:/Frameworks using the same username and password.