sponsored by the American Institute of Aeronautics and Astronautics Orlando, Florida, July 6-9, 1993https://ntrs.nasa.gov/search.jsp?R=19940012655 2019-04-27T11:28:58+00:00ZAIA.A93-3368 ON SOLVING THE COMPRESSIBLE NAVIER-STOKES EQUATIONS FOR UNSTEADY FLOWS AT VERY LOW MACH NUMBERS R.H.Pletcher Institute forCompmational Mechamics in Prolmlsion ABSTRACTThe properties of a preconditioned, coupled, stronglyimplicit finite-difference scheme for solving the compressible Navier-Stokes equations in primitive variables are investigated for two unsteady flows at low speeds, namely the impulsively started driven _vity .and the start.up of pipe flow. For the shear-driven rarity now, me computanonal eslort was observed to be nearly independent of Mach number, especially at the low end of the range considered. This Much number independence was also observed for steady pipe flow calculations; however, rather different conclusions were drawn for the unsteady calculations. In the pressure-driven pipe startup problem, the compressibility of the fluid_began to significantly influence the physics of the flow develolmumt at quite low Mach numbers. "t_e present scheme w_ ouserved to produce the expected _ties of completely incompressible flow when the Macn numtx:r was set at very low values. Good agreement with incompressible results available in the literature was observed.

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