Thank you for the information, sir. I would like to ask something. By increasing the air density many times to reach the Reynolds number in the cryogenic tunnel, wouldn't it be altering the actual atmospheric conditions of the flight? Is the cold, dry air in the higher altitude less dense than the hot, humid air in the lower altitude? The air really ceased to exist and became rare, or the nitrogen that goes up to 1000km occupied the spaces and left the air at a higher density, but without oxygen for us to breathe and perform combustion in the engine? Thank you!
Thanks. The main purpose is to achieve the high Reynolds number, which is only related to density and the kinematic viscosity, both would be the function of temperature. Whether we are using nitrogen or air, it matters only when comes to the density and viscosity. If these are right, then the modelling would be correct.
@@ScienceofFluids Thank you sir for the answer. In fact, I think it's very strange that the air is less dense as it rises. After all, moist air is less dense than dry air. The inferior mirage of the sun and the moon itself, on a daily basis, could indicate the denser air over the less dense air. But thank you very much again.
@@ScienceofFluids It is very contradictory for the tunnel to decrease the air temperature, as it actually is up there, to be able to increase the density, but we are told that the super cold air up there is less dense. Thanks.
It is informative. Thanks for sharing.
So useful thanks sir
Thank you for the information, sir. I would like to ask something.
By increasing the air density many times to reach the Reynolds number in the cryogenic tunnel, wouldn't it be altering the actual atmospheric conditions of the flight?
Is the cold, dry air in the higher altitude less dense than the hot, humid air in the lower altitude? The air really ceased to exist and became rare, or the nitrogen that goes up to 1000km occupied the spaces and left the air at a higher density, but without oxygen for us to breathe and perform combustion in the engine?
Thank you!
Thanks. The main purpose is to achieve the high Reynolds number, which is only related to density and the kinematic viscosity, both would be the function of temperature. Whether we are using nitrogen or air, it matters only when comes to the density and viscosity. If these are right, then the modelling would be correct.
@@ScienceofFluids Thank you sir for the answer. In fact, I think it's very strange that the air is less dense as it rises. After all, moist air is less dense than dry air. The inferior mirage of the sun and the moon itself, on a daily basis, could indicate the denser air over the less dense air. But thank you very much again.
@@ScienceofFluids It is very contradictory for the tunnel to decrease the air temperature, as it actually is up there, to be able to increase the density, but we are told that the super cold air up there is less dense.
Thanks.