Horizontal Buoyancy Effects on the Pressure Distribution of an Axisymmetric Body Operating in a Cylindrical Duct.

摘要

It is well known that the static pressure coefficient values obtained from tests of axisymmetric bodies in, for example, a large water tunnel indicate the existence of tunnel wall interference. This interference is due to blockage experienced by the body operating within the boundaries of the test section walls, and to the skin friction on both the tunnel walls and the surface of the body, which in turn causes finite thickness boundary layers to develop. These factors result in a decrease in static pressure along the test section which leads to a spurious horizontal buoyancy on the body. Potential flow calculations can only account for solid blockage effects. A control volume analysis has thus been carried out from which pressure coefficient correction terms due to horizontal buoyancy have been obtained. They may be directly applied to any inviscid pressure distribution calculated for any given body operating a given tunnel. These correction factors are computed for a large, streamlined body operating over a range of velocities. They are applied to a theoretically-determined potential flow, in-tunnel body pressure distribution to obtain the viscous flow pressure distributions which are compared to those determined experimentally.