Unsteady flow rate simulations methodology for identification of the dynamic transfer function of a cavitating venturi
Résumé
The development of new rocket turbopumps makes it necessary to study different phenomena occurring during cavitation, such as auto-oscillations that can cause the POGO effect and damage the rocket structure if they occur at the structural eigenfrequency. This is why an experimental facility is currently being developed in the Cremhyg laboratory in Grenoble, France in order to perform dynamic characterization of different cavitating devices to define the general identification methodology. The work presented in this paper serves the purpose to test this methodology on a simulation case of the cavitating Venturi computed with the IZ code. The principle of the IZ code is presented in the second paragraph. The first step of the methodology consists of evaluating pressures and mass flow rates at the inlet and the outlet of the cavitating profile and the next steps aims at estimating the dynamic transfer function of the cavitating Venturi. For this purpose, the Kinetic Differential Pressure method was chosen and introduced and its robustness towards evaluation uncertainties is evaluated in the third paragraph. Next, the numerical simulation with the IZ code gives the empirical transfer function results from the precise inlet and outlet pressure data which is later compared with the transfer matrix coefficients obtained with the Kinetic Differential Pressure method using the standard identification procedures such as the Empirical transfer function evaluation and the user-made Auto-Regressive Moving Average eXogenous algorithm.
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