Advanced Fluid Machinery Systems Laboratory

Complex Flow Research Division

Advanced Fluid Machinery Systems Laboratory

Concurrent Professor
Taku
Ohara
Associate Professor
Yuka
Iga

In this laboratory, complex flow phenomenon associated with high-speed gas-liquid mixture flows, especially about cavitation, is studied by using supercomputing and experiment. Additionally, advancement of fluid machinery systems with the mixture flows is investigated.

Cavitation Instabilities in Liquid Propellant Turbopump

In an axial-flow pump which is called inducer in liquid-propellant rocket turbopump, undesirable oscillation phenomenon is caused by cavitation. It is called cavitation instabilities; rotating cavitation causes asynchronous axial vibration of the turbopump and cavitation surge brings pulsation of working fluid. When the cavitation instabilities occur in the inducer, efficiency of the turbopump declines and launch failure of the rocket was rarely reported. Especially, super-synchronous rotating cavitation has opposite characteristics of propagation direction to the general rotating instabilities in any other rotating machinery. The occurrence mechanism has not been clarified, so that, it is very interesting phenomenon. In this laboratory, prediction of the oscillation characteristics, development of new control/suppression technique and clarification of occurrence mechanism are attempted by using supercomputing.

Advancement of Cavitation Model in CFD

Cavitation is complex flow phenomenon including various fluid and flow factors; bubble coalescence/splitting, evaporation/condensation, phase non-equilibrium, micro jet, counter jet, slip velocity, dynamic contact angle of solid-liquid-gas, surface instability, separation, vortex, turbulence, re-entrant jet, and so on. In these days, several cavitation models and the numerical method have been developed and several commercial CFD software has been put on a market. But the prediction accuracy is not so high, for example, time averaged lift of a single foil is unable even to predict in transient cavitation condition in higher angle of attack condition. Therefore, the advancement of prediction accuracy of cavitation is a remaining problem in the research field of CFD, and also in this laboratory, the cavitation model is attempt to be modified.

Advanced Fluid Machinery Systems Laboratory