On numerical simulation of cavitating flows under thermal regime
Résumé
In this work, we investigate closure laws for the description of interfacial mass transfer in cavitating flows
under thermal regime. In a first part, we show that, if bubble resident time in the low pressure area of the
flow is larger than the inertial/thermal regime transition time, bubble expansion are no longer monitored
by Rayleigh equation, but by heat transfer in the liquid phase at bubbles surfaces. The modelling of inter-
facial heat transfer depends thus on a Nusselt number that is a function of the Jakob number and of the
bubble thermal Péclet number. This original approach has the advantage to include the kinetic of phase
change in the description of cavitating flow and thus to link interfacial heat flux to interfacial mass flux
during vapour production. The behaviour of such a model is evaluated for the case of inviscid cavitating
flow in expansion tubes for water and refrigerant R114 using a four equations mixture model. Compared
with inertial regime (Rayleigh equation), results obtained considering thermal regime seem to predict
lower local gas volume fraction maxima as well as lower gradients of velocity and gas volume fraction.
It is observed that global vapour production is closely monitored by volumetric interfacial area (bubble
size and gas volume fraction) and mainly by the Jakob number variations. It is found that, in contrast with
phase change occurring in common boiling flow, Jakob number variation is influenced by phasic temper-
ature difference but also by density ratio variation with pressure and temperature.
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