# Why isn't there shock wave in this case !

1. May 19, 2007

### havythoai

Hi everybody !

I have used FLUENT to do the following simulation ( it's 1.5 cm, not 1,5)

I set 500 for "Number of Iterations". After running Fluent, I saw CL and Cd have convergenced, then I turn off the interation process. And here are my result

Are my results right ? Are the shock waves in my result right ?

Here's my grid resolution ? Is it smooth enough to capture the shock wave ?

Last edited: May 19, 2007
2. Jun 20, 2007

### havythoai

Everybody ? :(

Is there shock wave in My result ? :(

3. Jun 20, 2007

### caslav.ilic

If the flow were inviscid, the best show of shock would be by plotting the total pressure. It would appear all red before the shock, and flow-parallel rainbow stripes after the shock.

Given that your example is viscous, plus at not too high Reynolds number and with a blunt tail, total pressure will not be that revealing (it will dissipate by the viscous effects as well as shock), but give it a try.

--
Chusslove Illich (Часлав Илић)

4. Jun 21, 2007

### cliff

It appears that the shock is about 2/3rds the way up the wedge surface, and is standing 90* in relation to the free stream flow before the wedge. At Mach 1 this is right on the money.
You didn't say at what altitude the simulation was run at, but if your trying to show the Mach shock better, lowering the altitude (keeping everything else the same) will increase the shocks density and visibility. Also of course, increasing the resolution will to, if you have the extra time.

5. Jun 21, 2007

### minger

Well the first thing I would do is compare this to an exact solution. I don't have my notes on my now, but I'm pretty sure there is a similarity solution to flow over wedges. I remember it being very very clever. Anyways, like said before it may be a good idea to plot total or stagnation pressure. You know that through a shock there will be a jump (jump being however well your grid can resolve the shock) in stagnation quantities.

6. Jun 28, 2007

### jaap de vries

Where does the asymmetry come from in your Mach number plot? Also, judging from your contour plot the Mach number on the left seems to be less then 0.8, what kind of grid did you use?

7. Jun 30, 2007

Thank you !