Numerical Solutions of Oscillatory Lift Interference. Part I Oscillatory Lift Interference in Low-Speed Rectangular Tunnels with Porous-Slotted Roof and Floor. Part II Oscillatory Lift Interference in Subsonic Compressible Flow

Abstract

Part I. A solution of lift interference in oscillatory incompressible flow is described. Both steady and unsteady interference parameters are determined from a complete solution of the complex velocity potential, which is achieved by treating the real and imaginary parts separately throughout the tunnel, except at the tunnel walls where the two parts are linked through the boundary conditions. Both parts satisfy the Laplace equation which is solved using dynamic relaxation. Results over a range of frequency are given for a square and a rectangular tunnel with different boundary conditions; the most involved being the porous-slotted boundary. Part II. This report describes a method of calculating the oscillatory lift-interference parameters in subsonic compressible flow for ventilated wind tunnels. Results are obtained by solving the finite-difference form of the governing equations using the dynamic-relaxation method. Detailed results are obtained at M = 0.7 for square tunnels with closed side walls and with a variety of conditions on the roof and floor. As the frequency of the oscillations is increased different trends are noted between the present compressible flow parameters and earlier incompressible results.