Reverse thrust characteristics of water jet with different geometry nozzles

Abstract

This paper is to investigate the effects of nozzle geometry on the reverse thrust characteristics under various nozzle dimensions, inlet and outlet conditions. The reverse thrust formula is deduced based on the elementary momentum theory through the theoretical analysis. CFD simulations are conducted to acquire the pressure and velocity distributions on the outlet cross-section of nozzles. The pressure and velocity distributions are substituted into the reverse thrust formula and therefore the computational results of the reverse thrust are calculated. The experiments are also carried out in comparison with the computational results. The results indicate that the water jets issuing from the streamline nozzle produce considerably larger reverse thrust compared to the other two geometries. The reverse thrust reaches the maximum when the aspect ratio (length to diameter ratio) <i style="mso-bidi-font-style:normal">l</i>/<i style="mso-bidi-font-style:normal">d</i>=1. Under the same flow-rate and aspect ratio, at the bigger diameter the reverse thrust is smaller. The reverse thrust shows linear and<b> </b><span style="mso-font-kerning:18.0pt;mso-bidi-font-weight:bold">quadratic growth with increasing inlet pressure and flow-rate, respectively. The outlet pressure exerts little effect on the reverse thrust. The computational results are found in good agreement with the experimental results.

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