http://pc.freeshell.org/ 2009-11-21T10:05:40+00:00 http://pc.freeshell.org/ http://pc.freeshell.org/lib/images/favicon.ico text/html 2008-10-24T10:58:52+00:00 http://pc.freeshell.org/research/adjopt?rev=1224845932 We have developed an adjoint solver for the CFD code nuwtun which is used to perform drag minimization of RAE2822 airfoil under lift constraint. The initial and optimized pressure contours are shown in figures below. The shape was parameterized using 10 uniformly distributed Hicks-Henne functions on the upper and lower surfaces (20 parameters in total). The optimizer was the conmin_mfd from DAKOTA. Note that the shock has disappeared as a result of optimization. text/html 2008-08-19T16:48:33+00:00 http://pc.freeshell.org/research/cfd?rev=1219164513 The following codes are developed by me and my collaborators. If you have any comments or suggestions, then please email me. Codes * euler2d: 2-D inviscid flow/adjoint solver: euler2d is a 2-D inviscid flow and adjoint solver which uses finite volume method on triangular grids. * flo2d: A 2-D inviscid and viscous solver which is under development during my spare time. It is a continuation of euler2d. * Nuwtun: A 2D/3D flow solver on multi-block structured grids. Adjoint solver is under … text/html 2008-07-23T09:14:17+00:00 http://pc.freeshell.org/research/codes?rev=1216804457 Flow solvers Channelflow Website: <http://www.cns.gatech.edu/channelflow/> Channelflow is a software system for numerical analysis of the incompressible Navier-Stokes flow in rectangular geometries, written in C++. The core engine of channelflow is a spectral CFD algorithm for integrating the Navier-Stokes equations. This engine drives a number of higher-level algorithms that (for example) compute equilibria, traveling waves, and periodic orbits of Navier-Stokes. Channelflow provides these al… text/html 2007-01-14T21:26:41+00:00 http://pc.freeshell.org/research/euler2d?rev=1168810001 euler2d is a 2-dimensional inviscid flow and adjoint solver. It solves the Euler equations of gas dynamics on unstructured triangular grids using a vertex-centroid scheme which is second order accurate. The adjoint solver is developed using the automatic differentiation tool Tapenade. Both the flow and adjoint solvers are accelerated using matrix-free LUSGS scheme. text/html 2007-01-17T19:42:52+00:00 http://pc.freeshell.org/research/fitted?rev=1169062972 Philippe Caupennet Theoretical Aerodynamic Department of DEA On that Friday evening, the viewing room was almost full. As usual for the week-end, it was time for the “Team” to get into the most dangerous numerical practices. But everybody could feel, on that particular evening, the charged intensity that always characterized a big premiere. text/html 2007-01-17T19:40:17+00:00 http://pc.freeshell.org/research/future?rev=1169062817 by Robert Coopersmith January, 2096 Lockheed Aeronautical Systems Company We all know of the importance of computers in today’s aerospace engineering environment. The latest advances in cryogenically cooled semi-superconductor technology and microscopic germanium sub-wafer assembly has made desktop 100 MINS (Millions of Navier-Stokes solutions) machines commonplace in engineering use. text/html 2007-01-04T20:44:04+00:00 http://pc.freeshell.org/research/fvm?rev=1167943444 Finite volume methods (FVM) are commonly used for numerical solution of conservation laws. Most of the laws of nature can be written in conservation form like conservation of mass, momentum, energy and charge. A conservation law for a conserved quantity u can be simply stated as: text/html 2007-01-17T19:44:44+00:00 http://pc.freeshell.org/research/history?rev=1169063084 by Naomi Tsafnat May 17, 1999. text/html 2006-11-17T16:16:31+00:00 http://pc.freeshell.org/research/ideas?rev=1163780191 Shepard interpolation for VC FVM Currently, people use inverse-distance or area averaging for interpolating the value at vertices in vertex-centroid schemes. This does not even have linear consistency. An alternative is the so-called Laplace averaging where the weights are determined to preserve linear consistency. However there is problem of loss of positivity of weights and the interpolated value may not be bounded between minimum and maximum. This is especially true on highly stretched grids… text/html 2007-03-05T13:38:24+00:00 http://pc.freeshell.org/research/links?rev=1173101904 CFD-related links * CFD WWW home-pages list Optimization * Optimization software guide * Virginia Torczon's homepage * Optimization papers collection Open source codes * NSC2KE: NSC2KE is a Finite-Volume Galerkin program computing 2D and axisymmetric flows on unstructured meshes. To solve the Euler part of the equations, a Roe, an Osher and a Kinetic solvers are available. To compute turbulent flows a k-epsilon model is available. Near-wall turbulence is computed either by wall-la… text/html 2007-04-26T16:05:02+00:00 http://pc.freeshell.org/research/mds?rev=1177603502 Torczon’s multi-directional search is a simplex method which does not require derivatives. I optimized the RAE2822 airfoil for drag reduction keeping the lift constant. The cost function is J = Cd/Cd0 + 10e4 * max(0, 1-Cl/Cl0) where Cd0=0.00917209414, Cl0=0.854904661 are the drag and lift for the RAE2822 airfoil. The shape deformation is parametrized by 20 Hicks-Henne functions, 10 on lower and 10 on upper surface. For the optimized airfoil the drag and lift are Cd=0.00353457467 and Cl=0.85… text/html 2008-04-08T08:56:03+00:00 http://pc.freeshell.org/research/pso?rev=1207644963 PSO is modeled on the behaviour of a swarm of animals when they hunt for food or avoid predators~\cite{miller2007}. In nature a swarm of animals is found to exhibit very complex behaviour and capable of solving difficult problems like finding the shortest distance to a food source. However the rules that govern the behaviour of each animal are thought to be simple. Animals are known to communicate the information they have discovered to their neighbours and then act upon that individually. The i… text/html 2007-01-17T20:04:54+00:00 http://pc.freeshell.org/research/view?rev=1169064294 P. L. Roe, Royal Aircraft Establishment Bedford, England. R. LeVeque, University of California, Los Angeles B. van Leer, Delft University of Technology, Delft, The Netherlands Abstract: A critical study is made of the tricks of the upwinding trade. Five lines, it would seem, can describe any scheme of the class that the authors surveyed. text/html 2007-01-17T19:51:18+00:00 http://pc.freeshell.org/research/wine?rev=1169063478 GODUNOV: Produced from vines of great antiquity, this full-bodied vintage has an immediate impact guaranteed to satisfy the most demanding palate. Although modern viniculture is able to deliver most of its features at substantially reduced cost, Godunov is always worth serving on rarefied occasions.