Liquid velocity determination using thermal anemometry in two-phase flows: new developments

This article is intended to give an overview of novel approaches to apply thermal anemometry measuring technique for the determination of gas and liquid velocities in two-phase flows, which are currently being pursued at Helmholtz-Zentrum Dresden-Rossendorf. Thermal anemometers are commonly used for determination of local fluid velocities within single phase flows. Because of their high temporal resolution they are also capable of determining velocity fluctuations, as they are common in highly turbulent flows in technical applications and devices. These experimental data are, amongst others, required for validation and development of CFD codes. However, since turbulent two-phase flows (e.g. bubbly flows) are predominant in technical applications, the application of thermal anemometers is highly desired there as well. But, interpretation of those measurement signals is rather complex, since they contain information of both phases, e.g. liquid and gas respectively. To overcome these difficulties, application-oriented adoptions of this measurement technique have to be made. The here presented approaches comprise sophisticated design modifications of the probe itself as well as a novel operation mode. It is intended to utilize such a probe especially for the velocity measurement of the liquid phase in two-phase flows within complex geometries at high temporal resolution.