凝结相变对低温风洞雷诺数试验的影响

In order to investigate the condensation effect on Reynold number test for the cryogenic wind tunnel, a two-phase condensing flow model was established based on the Fluent software. The classic nucleation theory considering the non-isothermal effect and Gyarmathy droplet growth theory were employed for the prediction of spontaneous condensation. Under varying inflow pressures and testing Reynold numbers, the numerical simulations of nitrogen flowing around the NACA 0012 airfoil were carried out. The simulation results showed that the decrease of incoming flow temperature resulted in rapid expansion and the gas supercooled state at region near the airfoil surface. With further reduction of the incoming flow temperature, significant change of local flow fields affected by condensation was observed at a macroscopic level. The release of latent heat heated up the nitrogen flow and thus resulted in a deceleration of Mach number and a deviation of pressure coefficient in comparison with the case without condensation. Without destroying the airfoil aerodynamic performance test, it was feasible to make full use of gas supercooling for reducing the incoming flow pressure, which also meant few cost of driving power and liquid nitrogen injection. Alternatively, keeping the incoming flow pressure constant increased the testing Reynold number of the cryogenic wind tunnel.