Flow-Induced Pulsations in Gas Transport Systems: prediction, prevention and influence on volume flow measurements (ESF.5645)

The project is aimed at the quantitative prediction of unsteady shedding of vortices in confined flows and of the interaction of these vortices with acoustic waves. This topic has a very wide field of application, ranging from the support of diagnostics of human voice pathology to the prediction of pulsations in solid propellant rocket engines. In the present project we focus on the prediction of self-sustained flow instabilities in high-pressure gas transport systems and on the impact of such instabilities on volume-flow measurement. While this problem has significant direct applications, supporting and developing the aero-acoustical expertise in the Netherlands is the long term goal of this project. Aero-acoustics, the study of the flow-acoustic interaction, is a field in which quantitative prediction depends on a careful balance between experimental, numerical and analytical work. Specific approximations have to be used, which are not available in commercial methods an which depend strongly on the application considered. Such a project is therefore only possible in collaboration with a group developing numerical methods such as our partners at the University of Twente. More specifically we will firstly study the interaction between spontaneous flow instabilities driven by vortex shedding occurring at closed side branches and flow pulsations generated by a second independent sound source such as a compressor. The aim of this part of the project is to develop models predicting lock-in phenomena. In particular we are interested in the recently discovered phenomenon of cavity-flow stabilisation by high frequency forcing. These models should be implemented within the PULSIM code of TNO which can be used as a test environment. PULSIM is presently used to predict the response of complex pipe systems to compressor induced pulsations but cannot yet predict quantitatively self-sustained flow instabilities. An original application of such models has been proposed by TNO: deduce from pressure or vibration level measurements, the velocity fluctuations at the position of flow meters. The second part of the project is, therefore, a study of the interaction of flow meters with pulsating flows. Velocity fluctuations can induce systematic errors which is a problem of strategic importance for Gasunie. Our aim is to obtain correction formulas to account for unsteady flow effects. We will focus on turbine meters and on vortex flow meters which are common in industry.

More information can be found on the websites of the reserach group:

• Project 1: Aero-acoustical behaviour of turbine flowmeters
• Project 2: Aero-acoustics of shear layers

Seven companies are involved in htis project.