大家有没有这个程序Compressible Flow of an Ideal Gas

uakron

[这个贴子最后由uakron在 2007/03/09 09:40pm 第 1 次编辑]

本人做作业，需要的，看大家是否可以提供些信息或者代码的。
多谢大家的
Flow through a Converging-diverging nozzle
A converging-diverging nozzle is an important tool in aerodynamics. Also called a de Laval nozzle, it is an essential element of a supersonic wind tunnel. In this application the nozzle draws air from a reservoir which is at atmospheric conditions or contains compressed air. Back pressure at the end of the diverging section is such that air reaches sonic conditions at throat. This flow is then led through the diverging section. As we have seen before the flow Mach Number increases in this section. Area ratio and the back pressure are such that required Mach Number is obtained at the end of the diverging section, where the test section is located. Different area ratios give different Mach Numbers.
We study here the effect of Back Pressure on the flow through a given converging-diverging nozzle. The flow is somewhat more complicated than that for a converging nozzle. Flow configurations for various back pressures and the corresponding pressure and Mach Number distributions are given in Fig. 3.2. Let us discuss now the events for various back pressures, a,b,c,....
(a) Back Pressure is equal to the reservoir pressure, pb= p0. There is no flow through the nozzle.
(b) Back Pressure slightly reduced,pb< p0 . A flow is initiated in the nozzle, but the condition at throat is still subsonic. The flow is subsonic and isentropic through out.
(c) The Back Pressure is reduced sufficiently to make the flow reach sonic conditions at the throat,pb = pc . The flow in the diverging section is
still subsonic as the back pressure is still high. The nozzle has reached choking conditions. As the Back Pressure is further reduced, flow in the converging section remains unchanged.
We now change the order deliberately to facilitate an easy understanding of the figure 3.2.
(i) We can now think of a back Pressure, pb = pi , which is small enough to render the flow in the diverging section supersonic. For this Back
Pressure, the flow is everywhere isentropic and shock-free.
(d) When the Back Pressure is pd , the flow follows the supersonic path. But the Back Pressure is higher than pi . Consequently, the flow meets
the Back Pressure through a shock in the diverging section. The location and strength of the shock depends upon the Back Pressure. Decreasing the Back Pressure moves the shock downstream.


Figure 3.2: Pressure and Mach Number Distribution for the Flow through a Converging-Diverging Nozzle.
(e) One can think of a Back Pressure pf, when the shock formed is found at the exit plane. pf / p0  is the smallest pressure ratio required for the operation of this nozzle.
(f) A further reduction in Back Pressure results in the shocks being formed outside of the nozzle. These are not Normal Shocks. They are Oblique Shocks. Implication is that the flow has reduced the pressure to low values. Additional shocks are required to compress the flow further. Such a nozzle is termed Overexpanded.
(g) The other interesting situation is where the Back Pressure is less than pi . Even now the flow adjustment takes place outside of the nozzle, not through shocks, but through Expansion Waves. Here the implication is that the flow could not expand to reach the back Pressure. It required further expansion to finish the job. Such a nozzle is termed Underexpanded.

流星客

采用二维可以解决问题，具体看看ANDERSON的计算流体力学基础，好像有一个这样的算例吧，主要是研究格式的稳定性和激波分辨率，呵呵