Tomiko Ishiguro

A method for computing flow fields around moving bodies

Abstract A new method for computing flow fields with arbitrarily moving boundaries is proposed. Under the concept of Lie derivatives the field equations in general moving coordinates are derived, which consist of several kinds of equations, for example, one written in Viviands conservative form. According to our formulation, it is natural and reasonable to consider that the computational coordinates fitted to the body move in space, contrary to the usual computational procedures. The two-dimensional incompressible Navier-Stokes equations in gemeral moving coordinates are solved by a finite difference method. The present calculations are made for (a) the blood flow in human ventricle, and (b) the dynamic stall process on oscillating airfoil. Consequently it is shown that the flows generated by moving bodies can easily be analyzed by the present method.

ON THE RECENT DIFFERENCE SCHEMES FOR THE THREE-DIMENSIONAL EULER EQUATIONS

Numerical estimations of TVD schemes(YeeHartens TVD and Chakravarthy-Oshers TVD) in three-dimensional general coordinate system are performed by solving the Euler equations around the ONERA M6 wing. It is known their TVD schemes do not give good solutions in curvilinear coordinate system, and several modifications with regard to treatment of metrics are carried out. Comparing with the solution of Beam-Warming scheme, our modified TVD schemes yield excellent solutions with very few numerical oscillations for strong shock waves and high ability of capturing the leading edge expansion. Further it is shown the solutions of both the TVD schemes almost perfectly coincide with each other in case of the computations using an adaptive grid.

Turbulence models for 3D transonic viscous flows

Computation of 3D transonic viscous flows around the ONERA-M6 wing is performed by using the Harten-Yee TVD scheme with modification of geometrical treatment in order to seek better turbulence models. The models used here are the Jones--Launder (k-E )-model and the subgrid-scale model in the large eddy simulation (US), and for comparison the Baldwin-Lomax model. The diagonalization of flow equation system including a two-equation model necessary to perform the TVD scheme and the improvement accompanied by extending the LES to compressible flow problems are presented, and then the utilities of both models in compressible flow problems with shock waves have been j nvestigated. The (kE )-model and the LES work well in the large reverse flow problem by adjusting the coefficients compared with the Baldwin-Lomax model.

A Fully Implicit High-Resolution Scheme for Chemically Reacting Compressible Flows

The eigenvalues and eigenvectors are analytically derived for general real gas dynamic equations in three-dimensional generalized curvilinear coordinates. In our diagonalizing formulation, the total mass conservation equation is taken into account, and arbitrary nonequilibrium effects, such as chemical reactions or vibrational nonequilibrium, can be treated in the same fashion. Making use of this diagonalization, we construct a fully implicit and high resolution scheme for chemically reacting real gases. Numerical results of two-dimensional shock-induced combustion problem show the efficiency and high resolution of our scheme.