|
发表于 2006-12-24 06:30:09
|
显示全部楼层
关于空气动力学中的一个问题
If an object flies at supersonic speed, it creates a shock wave in fornt of the object. If you follow a coordinate system fixed to the object, then the object is considered "stationary" and the flow is "supersonic". The "supersonic" flow region is ahead of the shock wave. But if you view the problem from a fixed observer, the object is flying together with the shock wave, the region ahead of the shock wave is actually stationary!
Bakc to the moving coordiante system, the flow behind the shock wave near the object is SUBSONIC!, so in this area, the potential flow applies. It remains subsonic untill a set of expansion wave accelerate the flow to supersonic again.
What this is saying is that the consideration of "supersonic flow" is only required across the shock wave and the expansion waves, where the constant entropy conditions apply and shock wave "jump condition" determines the flow field ahead and behind the waves. These are the only areas where potential flow is not valid, requiring other mathematical treatments. In all other regions, potential flow is still valid.
I hope this answers your question. |
|