Comparison of Measured and Computed Boundary Layers at the Tail-End of an Axisymmetric Body in an Air-Jet.

摘要

The limited range of Reynolds numbers achievable in low speed wind tunnels frequently prevents direct simulation of full scale flow fields. This problem is accentuated if it is required to model the flow over an underwater vehicle because of the widely differing kinematic viscosities of air and water. A tool is therefore required to predict the characteristics of air flows over models so that similarity with the full scale situation can be assessed. The aim of this experimental study was to validate a theoretical model, developed earlier at AMTE Teddington, which predicts the potential flow and boundary layer development on an axisymmetric body placed in an open jet emerging from a nozzle. The report describes the measurement of boundary layer velocity profiles at the tail-end of an axisymmetric body in an air jet, and compares the results with the predictions of the computer program. Good agreement is obtained in most cases, although for extreme positions of the body in the duct the calculated boundary layer thickness is smaller than the measured value by almost 15%.