Aero Troll is a prototype graphical interface for academic aerodynamic analysis. The goal of Aero Troll is to allow a user to describe and analyze simplified geometries with a set of aerodynamic analysis methods. The tool supports education, academic aerodynamic analysis, the flight simulator community, and verification and validation efforts. The software was created to broaden my knowledge of software development and aerodynamic modeling. It is hoped that the tool can serve others in a similar manner. Currently the code interfaces with the higher order panel method PANAIR (A502) and work is underway to include other methods.
Aero Troll is available for Linux (32 and 64-bit), Windows XP, and Mac (Intel). Aero Troll was developed and extensively tested under Linux and Windows XP. Aero Troll was ported over to the Mac using a friend's machine. The Mac version has had limited testing. Aero Troll requires the PANAIR (A502) code. PANAIR can be obtained from Public Domain Aeronautical Software. Aero Troll requires Java 1.5 or later. Aero Troll also requires the publicly available JOGL java library which is included in the Aero Troll distribution.
Downloading Aero Troll requires a "key". To create the key follow the "Generate an Aero Troll Download Key" link below. Once you receive the key you can download Aero Troll by following the "Download Aero Troll" link. The key will be sent to you by email.
Generate an Aero Troll Download Key
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NOTE: Aero Troll allows for the specification of a ground plane with PANAIR. To use this feature, version 14 of PANAIR must be installed and patched with this panair_v14_gp.patch.
Aero Troll CFD
Currently Aero Troll CFD, otherwise known as AT CFD, is under development. At some point AT CFD will be included in Aero Troll. The driving force for the development of AT CFD is to give me a better understanding of how a CFD code works under the hood. I also wanted the resulting code to be quick and easy to run on multiple operating systems for solving aerodynamics about basic geometries.
The development of AT CFD is totally in debt to the work of those who pioneered and advanced CFD. By presenting this code I do not claim to have invented something. I went though the literature and reconstructed what was presented. It amazes me how some of the ideas and procedures which form the foundation of CFD materialized. Maybe in hindsight it is somewhat obvious, but in foresight? I would like to thank those who paved the way. But, truthfully, I am ignorant of all the shoulders this work stands upon and of who originated what. So, instead of listing the names of those who I think contributed to the field, I would like to just give a big Thank You to all those who made this possible.
Listed below are some things that AT CFD is and is not, along with some references. I hope this provides a good understanding of what AT CFD is.
What AT CFD Is
-A solver for the compressible Euler and Reynolds Averaged Navier-Stokes (RANS (Favre)) equations in conservation law form for a calorically perfect gas.
-A 2nd order central finite difference method.
-A solver for 1st order time marching.
-A solver for steady state. (Local and global time stepping)
-A solver for a multiple structured grids (Chimera (trilinear interpolation)).
-A turbulent viscous flow solver (Spalart-Allmaras (SA-noft2)).
-A multi thread/multi processor (however, not multi machine) enabled code.
-A Beam-Warming Alternating Direction Implicit method (ADI).
-A Pulliam-Chaussee Diagonalized Implicit Approximate Factorization method (DIAF/DADI).
-A method which adds nonlinear mixed second and fourth order artificial dissipation to both the right hand side and the DIAF/ADI method.
-A method with the following possible boundary conditions:
1) Inviscid Wall (dp/dn = 0.0, 1st order pressure extrapolation)
2) Inviscid Wall (momentum, Rizzi)
3) Viscous Wall (dp/dn = 0.0, 1st order pressure extrapolation)
5) Freestream Characteristics
6) Zero Gradient
What AT CFD Is Not
-Time accurate. (Dual time stepping is required.)
-Machine distributable. (Doesn't run distributed over multiple machines.)
-Set up with low-Mach number preconditioning.
-Capable of LES/DES.
-Dual time stepping.
-2nd order time marching.
-Higher order spatial stencil.
-Wilcox k-omega and/or Menter k-omega SST.
-Improve momentum boundary by coupling neighboring surface points.
-Include derivatives of dissipation switch and spectral radius in LHS for better convergence.
-Include derivatives of B.C.s in LHS for better convergence. (Done for ADI)
-Capability to integrate loads on overlapping surface grids. (Along lines of MIXSUR, USURP, or POLYMIXSUR)
-Improve hole cutting. Currently hole boundary may get too close to surface.
-Include methodology for determining interpolation weights in regions close to overlapping surfaces.
-Check for intersection of grid cell edges, surfaces, and volumes with boundary surfaces for iblanking. Currently only interior points are iblanked.
|1)||Jameson, A., Schmidt, W., and Turkel, E., "Numerical Solution of the Euler Equations by Finite Volume Methods using Runge-Kutta Time-Stepping Schemes," AIAA Paper 81-1259, June 1981.|
|2)||Slooff, J. W, and Schmidt, W., "Computational Aerodynamics Based on the Euler Equations," AGARD-AG-325, AGARD, Sept. 1984.|
|3)||Pulliam, T. H., and Chaussee, D. S., "A Diagonal Form of an Implicit Approximate-Factorization Algorithm," J. Comput. Phys. 39, 347-363 (1981).|
|4)||Pulliam, T. H., "Solution Methods In Computational Fluid Dynamics," http://people.nas.nasa.gov/~pulliam/mypapers/vki_notes/vki_notes.html|
|5)||Vinokur, M., "An Analysis of Finite-Difference and Finite-Volume Formulations of Conservation Laws," NASA CR-177416, NASA, June 1986.|
|6)||Tannehill, J. C., Anderson, D. A., and Pletcher, R. H., "Computational Fluid Mechanics and Heat Transfer," Taylor & Francis, 1997.|
|7)||A. Rizzi, "Numerical Implementation of Solid-Body Boundary Conditions for the Euler Equations," ZAMM. Vol. S8, pp. 301-304, 1978.|
|8)||P. R. Spalart and S. R. Allmaras, "A One-Equation Turbulence Model for Aerodynamic Flows," AIAA-92-0439, 1992.|
|9)||B. A. Payne and A. W. Toga, "Distance Field Manipulation of Surface Models," IEEE Computer Graphics and Applications, January 1992, pp 65- 71.|