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Non-Tax-Deductible Donation

If you like Aero Troll and/or would like to see it developed further, please make a non-tax-deductible donation. Developing a CFD codes takes time and money. A new workstation, at the moment, is about $7000 and has a half life of about 2 yrs. A workstation costs about $50 a month to run 24/7. And that does not even cover my time (and a lot of it has been dedicated to this effort) or other costs such as web site, papers/articles, books, fees, or coffee! The donated amount, regardless of the size, will be appreciated.

Updates

Notifications will be made on this web page and on twitter when updates become available. The twitter account is used mostly for posting availablity of software and example page updates. So don't expect much tweeting!Aero Troll

Aero Troll (v0.3.0b) is a software tool with a graphical user 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 still has a way to go before this goal is fully realized. The tool supports education, academic aerodynamic analysis, the flight simulator community, and verification and validation efforts. Currently the code interfaces with the higher order panel method PANAIR (A502) and a 2D Reynolds Averaged Navier-Stokes (RANS) solver. Work is underway to extend Aero Troll further.

Aero Troll is available for Linux (32 and 64-bit) and Windows. Aero Troll was developed and extensively tested under Linux and Windows XP. Aero Troll requires the PANAIR (A502) code which is now included with Aero Troll courtesy of Public Domain Aeronautical Software. Aero Troll requires Java 1.5 or later. Aero Troll also requires the publicly available JOGL, Jython, JavaPlot, CGNS, and gnuplot libraries and executables which are included in the Aero Troll distribution.

Manuals:

Version 0.3.0b Supplement Manual

Version 0.2.0b Manual

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. The key creation system is fully automatic and I personally do not take part in the process. The key system is in place to reduce the impact of web crawlers and such things.

Generate an Aero Troll Download Key

Download Aero Troll

The development of the CFD portion of Aero Troll, otherwise known as Aero Troll CFD (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 Aero Troll 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)

4) Freestream

5) Freestream Characteristics

6) Zero Gradient

7) Axis

8) Periodic

9) Symmetry

What AT CFD Is Not

-Time accurate. (Dual time stepping is required.)

-Higher order.

-Multigrid.

-Machine distributable. (Doesn't run distributed over multiple machines.)

-Set up with low-Mach number preconditioning.

-Capable of LES/DES.

Wish List

-Dual time stepping.

-2nd order time marching.

-Higher order spatial stencil.

-Wilcox k-omega and/or Menter k-omega SST.

-Multigrid.

-GPU enabled.

-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.

-Dissipation matrix.

-LU-SGS.

References

1) | Slooff, J. W, and Schmidt, W., "Computational Aerodynamics Based on the Euler Equations," AGARD-AG-325, AGARD, Sept. 1984. |

2) | Pulliam, T. H., and Chaussee, D. S., "A Diagonal Form of an Implicit Approximate-Factorization Algorithm," J. Comput. Phys. 39, 347-363 (1981). |

3) | Pulliam, T. H., "Solution Methods In Computational Fluid Dynamics," http://people.nas.nasa.gov/~pulliam/mypapers/vki_notes/vki_notes.html |

4) | Vinokur, M., "An Analysis of Finite-Difference and Finite-Volume Formulations of Conservation Laws," NASA CR-177416, NASA, June 1986. |

5) | Tannehill, J. C., Anderson, D. A., and Pletcher, R. H., "Computational Fluid Mechanics and Heat Transfer," Taylor & Francis, 1997. |

6) | A. Rizzi, "Numerical Implementation of Solid-Body Boundary Conditions for the Euler Equations," ZAMM. Vol. S8, pp. 301-304, 1978. |

7) | P. R. Spalart and S. R. Allmaras, "A One-Equation Turbulence Model for Aerodynamic Flows," AIAA-92-0439, 1992. |

8) | B. A. Payne and A. W. Toga, "Distance Field Manipulation of Surface Models," IEEE Computer Graphics and Applications, January 1992, pp 65- 71. |

9) | http://www.cfd-online.com/Wiki/Favre_averaging |

10) | http://turbmodels.larc.nasa.gov |

11) | http://www.grc.nasa.gov/WWW/winddocs/utilities/b4wind_guide/trilinear.html |