City Research Online

Abstract

The linear homogeneous boundary condition, currently applied to flow calculations, to represent perforated windtunnel walls, is known to be inadequate. An improved boundary condition, which takes account of viscous effects in the flow near such walls, is proposed here. This boundary condition requires data relating to the flow through the particular type of wall of interest, and experiments have been carried out to generate data for this cross-flow, for a wall with an open area ratio of 6 percent and 60 degree inclined perforations. The results from these experiments yield the wall crossflow characteristic. When used in conjunction with a boundary layer prediction method, also developed during this research, it is possible to generate the required boundary condition, for application to inviscid flow calculations.

It is demonstrated that the new boundary condition is capable of modelling the viscous flows, near and through the perforated wall with some success, for a range of high subsonic Mach number flows through the windtunnel, wall crossflow angles being simulated with a standard deviation of discrepancy of 0.11 degree about the experimental values.

A potential flow method has been developed, for calculating the subsonic flow of air through a windtunnel with solid and porous regions of wall, with a lifting aerofoil mounted in the working section. This method operates successfully, and when incorporating the proposed boundary condition, gives results which agree favourably with experiment.

Although calculations carried out using the proposed boundary condition are certainly more accurate than those using conventional linear boundary conditions, it is considered that still further improvement is required. This improvement is likely to be achieved using the present method, if experiments are performed more accurately and some changes are made to present computer programs

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology T Technology > TL Motor vehicles. Aeronautics. Astronautics
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

Export

Downloads