Mapping of Hydraulic Model Dynamics Using Transient Operating Conditions

This paper reviews the issue of making unsteady measurements involving cavitating flow in traditional test loops. Transients were applied to a model turbine, including both ramping in time of wicket gate movement and time dependent variations of model test loop system pressure. These actions allowed a continuous change of parameters such as reduced flow rate and cavitation index as a function of time. By the use of Joint Time Frequency Analysis (JTFA) techniques mappings of the dynamics of stationary hydrofoils and rotating machinery can be compared. The objective of this study to investigate whether transient operation would allow a rapid mapping of dynamic for different operation points. Special attention was given to the requirements for controlling the machinery in a manner that allows such experiments to be possible. This paper reports results of so-called ramping tests and compares the results with data obtained by traditional means.