Study of time accuracy of flow variables across discontinuous boundaries
Abstract
The Chimera grid scheme, a multiple overset mesh technique, was coupled with an implicit Euler flow solver (ARC3D) and was successfully applied to a number of steady and unsteady aerodynamics problems. Errors were identified when an overset mesh is moved with respect to a stationary global mesh. Several methods were developed to try to reduce the errors across the moving boundary: (1) solving the Euler equations with a relaxation scheme; (2) solving the Euler equations with a predictorcorrector scheme; (3) improving the interpolation sequence to reflect the motion of the moving grid; and (4) reducing the errors using gridbased studies. The time lag error is found to be quite small; the resulting error is found to be largely due to spatial interpolation. Accuracy across an interface is improved for a given time step using a relaxation scheme, and this scheme was successfully applied to a more realistic threedimensional problem designed to take full advantage of the scheme. A predictorcorrector method developed for the onedimensional and threedimensional Euler equations proved promising but has a stability limitation. A change in the interpolation procedure to include the time metrics gives a small improvement for the accuracy in the test cases. Removing the onesided differencing for the metric terms on the updated outer boundary, and selecting a suitable grid size also give minor improvements for accuracy.
 Publication:

Ph.D. Thesis
 Pub Date:
 1990
 Bibcode:
 1990PhDT........51K
 Keywords:

 Computational Grids;
 Discontinuity;
 Euler Equations Of Motion;
 Fluid Boundaries;
 Grid Generation (Mathematics);
 PredictorCorrector Methods;
 Steady Flow;
 Unsteady Aerodynamics;
 Computational Fluid Dynamics;
 Error Analysis;
 Finite Difference Theory;
 Interpolation;
 Relaxation Method (Mathematics);
 Time Lag;
 Fluid Mechanics and Heat Transfer