Cavitation dynamics and thermodynamic effects at elevated temperatures in a small Venturi channel

The effects of temperature on hydraulic cavitation dynamics are investigated under various operating conditions, in a close loop cavitation tunnel with a small-scale venturi type section. A systematic study is performed with temperatures varying between 24 degrees C and 85 degrees C, using a high-speed visualization system to observe the cavitating flow. The image processing methods provided in the paper present a quantitative comparison of the cavitation dynamics and structure development. The results show that the increase of the fluid temperature induces the growth of the cavitation volume up to about 55 degrees C, thereafter an additional increase in temperature has the opposite effect. This evolution is interpreted as a competition between a Reynolds effect and the well-known thermal effect. Cavitation is more closely investigated within the temperature range 50 degrees C - 65 degrees C, to analyze the changes in the structure and the cavitation dynamics. For the prediction of thermal suppression head, the thermal effect parameter Sigma which can be used empirically, is derived at the maximum cavitation length. This fluid thermodynamic parameter Sigma(T-tra(ns)) at the transition peak can be referred to to avoid the maximum cavitation aggressiveness induced vibration or erosion for thermos-fluids around the thermal transition temperature. Finally, the factors influencing cavitation length and shedding frequency are presented and analyzed. (C) 2021 Elsevier Ltd. All rights reserved.