Direct Numerical Simulation of Heated Cryogenic Channel Flow at Supercritical Pressure

摘要

Predicting heat transfer characteristics in regenerative cooling channels at supercritical pressure is crucial to thermal designs of liquid rocket engines. Past numerical studies indicated that current Reynolds-Averaged Navier-Stokes (RANS) simulations have poor accuracy in predicting heat transfer characteristics of transcritical flow with deteriorated heat transfer. For the discussion of the poor accuracy in current RANS, comparison between Direct Numerical Simulation (DNS) is an attractive approach. However, there are two large problems in conducting DNS of deteriorated heat transfer flowfields. Firstly, it is not clear if the deteriorated heat transfer can be observed even at low Reynolds number flowfields. Secondly, conventional constant heat flux conditions may cause large temperature fluctuation on the channel wall. To investigate those two problems, RANS and DNS simulations of heated cryogenic channel flow at supercritical pressure are conducted. RANS clarified that deteriorated heat transfer can be observed even at low-Reynolds number flowfields. A comparison between RANS and DNS shows that turbulent heat flux in DNS is larger than RANS. The large heat flux is caused by temperature fluctuation on the wall and the fluctuation is due to a constant instantaneous heat flux condition. This DNS result indicates that constant heat flux wall conditions without temperature fluctuation have to be imposed in DNS of the deteriorated heat transfer flowfields.