Gas-kinetic methods for 3-d inviscid and viscous flow solutions on unstructured/hybrid grids

Ilgaz, Murat
In this thesis, gas-kinetic methods for inviscid and viscous flow simulations are developed. Initially, the finite volume gas-kinetic methods are investigated for 1-D flows as a preliminary study and are discussed in detail from theoretical and numerical points of view. The preliminary results show that the gas-kinetic methods do not produce any unphysical flow phenomena. Especially the Gas-Kinetic BGK method, which takes into account the particle collisions, predicts compressible flows accurately. The Gas-Kinetic BGK method is then extended for the solution of 2-D and 3-D inviscid and viscous flows on unstructured/hybrid grids. The computations are performed in parallel. Various inviscid and viscous test cases are considered and it is shown that the Gas-Kinetic BGK method predicts both inviscid and viscous flow fields accurately. The implementation of hybrid grids for viscous flows reduces the overall number of grid cells while enabling the resolution of boundary layers. The parallel computations significantly improve the computation time of the Gas-Kinetic BGK method which, in turn, enable the method for the computation of practical aerodynamic flow problems.


Evaluation of a new turbulence model for boundary layer flows with pressure gradient
Marangoz, Alp; Çıray, Cahit; Department of Aerospace Engineering (2005)
In this thesis, a new turbulence model developed previously for channel and flat plate flows is evaluated for flat plate flows with pressure gradient. For this purpose a flow solver, which uses boundary layer equations as the governing equations and Von Karman momentum integral equation for the calculation of skin friction, is developed. It is shown that the error of the new turbulence model, in predicting the velocity profile, is less than 5 % for the flat plate flows without pressure gradient and less tha...
Two dimensional finite volume weighted essentially non-oscillatory euler schemes with different flux algorithms
Aktürk, Ali; Akmandor, İbrahim Sinan; Department of Aerospace Engineering (2005)
The purpose of this thesis is to implement Finite Volume Weighted Essentially Non-Oscillatory (FV-WENO) scheme to solution of one and two-dimensional discretised Euler equations with different flux algorithms. The effects of the different fluxes on the solution have been tested and discussed. Beside, the effect of the grid on these fluxes has been investigated. Weighted Essentially Non-Oscillatory (WENO) schemes are high order accurate schemes designed for problems with piecewise smooth solutions that invol...
Fluid structure coupled analysis of an aerodynamic surface
Sümer, Bülent; Akgün, Mehmet A.; Department of Aerospace Engineering (2004)
In this thesis a 3-D Euler flow solver is coupled with a finite element program in order to solve static aeroelastic problems involving aircraft wings. A loosely coupled solution approach based on an iterative solution procedure is used to solve the coupled field problem. Because of the deformation of the underlying surface over which the flow is solved, Computational Fluid Dynamics mesh has to move at each computational aeroelastic iteration in order to comform to the new shape of the aerodynamic surface. ...
Parallel navier stokes solutions of low aspect ratio rectangular flat wings in compressible flow
Durmuş, Gökhan; Eyi, Sinan; Department of Aeronautical Engineering (2004)
The objective of this thesis is to accomplish the three dimensional parallel thin-layer Navier-Stokes solutions for low aspect ratio rectangular flat wings in compressible flow. Two block parallel Navier Stokes solutions of an aspect ratio 1.0 flat plate with sharp edges are obtained at different Mach numbers and angles of attack. Reynolds numbers are of the order of 1.0E5-3.0E5. Two different grid configurations, the coarse and the fine grids, are applied in order to speed up convergence. In coarse grid co...
Implementation of turbulence models on 2d hybrid grids using an explicit/implicit multigrid algorithm
Yılmaz, Ali Emre; Tuncer, İsmail Hakkı; Department of Aerospace Engineering (2011)
In this thesis study, implementation, numerical stability and convergence rate issues of turbulence modeling are explored. For this purpose, a one equation turbulence model, Spalart-Allmaras, and a two-equation turbulence model, SST k-w, are adapted to an explicit, cell centered, finite volume method based, structured / hybrid multi grid flow solver, SENSE2D, developed at TUBITAK-SAGE. Governing equations for both the flow and the turbulence are solved in a loosely coupled manner, however, each set of equat...
Citation Formats
M. Ilgaz, “Gas-kinetic methods for 3-d inviscid and viscous flow solutions on unstructured/hybrid grids,” Ph.D. - Doctoral Program, Middle East Technical University, 2007.