The circulation growth of non-impulsive starting jet

Abstract

An analytical model that can be used to predict the circulation growth process for non-impulsive starting jets has been developed by extending the over-pressure correction model for impulsive starting jets. Only the jet velocity function U0(t) is needed to obtain the circulation growth process of non-impulsive starting jet. The non-impulsive starting jets generated by nozzle and orifice configurations are performed numerically with two acceleration schemes (represented by two kinds of velocity functions) and different acceleration stage stroke ratios LaD (modifying the acceleration time ta in each velocity function to obtain LaD=0.05:0.2:1.25) to verify the accuracy of the proposed analytical model. The influence of radial velocity distribution in the jet inflow boundary is ignored in the process of constructing this model, but this has been proven to be reasonable. The time-averaged relative error with the growth process of the total circulation predicted by this model is about 11% to 26%, which is smaller than the 44% to 88% obtained by the classical slug model. For the range of LaD from 0.05 to 1.25, the relative error with the prediction of the total circulation at the end of the acceleration stage is from 4% to 28%, as compared to the 39% to 96% for the slug model.