Effect of Development-Zone Restrictions on the Turbulent Characteristics of Impinging Jet Flow

This study is to examine the turbulent characteristics of an axisymmetric impinging jet flow in the stagnation region. The flow measurement is carried out using a standard PIV technique. The changes of the turbulent characteristics of the jet with various levels of the development-zone restriction are examined. The restrictions are imposed by putting an annular, concentric, solid block around the jet, and then varying its inner diameter. The PIV measurement of the flow field is carried out for each case. The height of the block is kept constant for all the cases, with the Reynolds number of 5000, which falls well within the turbulent range. The instantaneous velocity data obtained from the PIV measurement is used to calculate the turbulent statistics. The results are compared for all of the cases. In consequence, it is found that the turbulent statistics do not change much for the block’s inner diameter larger than a critical value, which is found to be three times the inlet diameter of the jet. However, if it is smaller, the turbulent statistics vary significantly, as the inner wall of the block damages the development of the potential core of the jet.