Abstract:

Low speed time-derivative preconditioning schemes are implemented in the compressible Navier-Stokes code to deal with the low Mach number flows, which makes the methods have unified accuracy and efficiency for computing incompressible and compressible flows. The subsonic hovering flow fields of Caradonna-Tung rotor are simulated by this way, in which the equations are solved on rotating coordinates and the meshes are constructed using overlap grids. The results show that the convergence speed is improved markedly by virtue of low speed preconditioning technique and flow details such as down washing are highlighted.In addition,the preconditioning methods make all the eigenvalues of equations be on the same level,thus avoiding amplifying the numerical dissipation in case of eigenvalue discrepancy,and as a result the accuracy of numerical computation is enhanced.

Key words: low , speed , preconditioning,  , rotating , coordinate,  , hover,  , Caradonna-Tung , rotor,  , N-S , equaion