Design and calibration of a wind tunnel with a two dimensional contraction

A low speed, open circuit, laboratory wind tunnel has been redesigned for use in turbine blade cooling experiments. The two dimensional contraction was designed using a sixth order polynomial. This paper outlines the process of design optimisation, using Computational Fluid Dynamics (CFD) to model the contraction. The parameters that were varied were the location of the point of inflection and the curvature at the contraction inlet. The optimisation was based on flow uniformity at the working section midplane, prevention of separation in the contraction and minimising the boundary layer thickness at entrance to the working section. Calibration of the wind tunnel after construction has demonstrated the value of the design process and validated the CFD predictions.