shock tube
 

hi every one.......i modeled a shock tube problem in cfx v12.1 but its results have many fluctuation.......should i give 0 [atm] for refrence pressure?
problem:
air ideal gas.....high pressure:300kpa low pressure:150kpa
high pressure length:0.5m low pressure length:1.5m total time:0.001
RMS Courant Number:0.01 max Courant Number:0.04
do this value for max Courant Number is Logical?? do you can explain it?
thanks

No. You should define the reference pressure as the base pressure in the model. Search the forum for further details, this question has been asked a lot.

Do a time step sensitivity check to establish the best time step size.

My PhD thesis has a discussion about things to consider when trying to get accurate shock wave modelling, see http://hdl.handle.net/2100/248

thanks a lot for replay....
You should define the reference pressure as the base pressure in the model. Search the forum for further details, this question has been asked a lot.

do u can explain it for me....i solved my problem with a 0 atm refrence pressure and my results were logical when i use 1atm refrence pressure it didnt give a normal solve......what should i use for my problem as i say above



Do a time step sensitivity check to establish the best time step size?
how do i do it?

Both of these questions have been asked many times on the forum. Do a search to find them.