Numerical Study of Compressible Turbulence Flow in Pipe Enlargements by Using a Novel Pressure Based Algorithm

By using the mass flux definition of AUSM+-up (Advection Upstream Splitting Method), a pressure correction equation on the discrete level is derived. The numerical algorithm does not require any time derivative preconditioning. The algorithm is computationally more efficient than conventional density-based methods using preconditioning. The pressure correction method is employed to compare theturbulent compressible and incompressible flows through pipe abrupt enlargements. It is found that the reattachment length is an increasing function of the expansion ratio. For compressible flows, the pressure is minimum and constant through the distance from theexpanding section to the axial position of recirculation center. By increasing the expansion ratio, the minimum pressure of the flow and the distance at which the pressure is constant increases. Temperature increases slightly along this distance. Following this region,density reaches a local maximum value. The fluid is heated by the expansion process and the outlet temperature in 5-7 percent greater than the inlet temperature for M=0.6.

Keywords:

pressure based , turbulent , pipe enlargement , reattachment , compressible flow