Curvature Effects in the Curved Duct for the Compressible Viscous Flow With Heat Transfer

In this paper, non-reflecting boundary conditions based on the NSCBC method for three-dimensional compressible viscous flows, especially outlet boundary conditions, are examined and numerical tests for a curved duct flow are made. Using the subsonic non-reflecting outflow boundary conditions, curvature effects for compressible flow are investigated. First, numerical flows in a straight duct was tested for the stability of the solution and the efficiency of the subsonic non-reflecting outflow conditions extended to 3D problems. Numerical tests show that the non-reflecting NSCBC method provides accurate results for very low Reynolds number flow with isothermal no-slip walls. Second, the unsteady Navier-Stokes equations in cylindrical coordinates were numerically solved using the non-reflecting outflow conditions for a curved duct flow with isothermal no-slip walls. The numerical results show the consistency of the solution. Finally, analyzing the curved duct flow results, effects of the duct curvature were studied. A comparison of the numerical results between two curved ducts, the curvature is 10² times larger than smaller one, shows that the maximum intensity of secondary flow appeared at the outlet section of the more curved duct is about 10² times larger.