BC problem

November 19, 2003, 03:41

Hi Experts, I am solving a problem involving convergent divergent nozzle. I am employing pressure BC at both ends. Now I have two problems. 1. After post processing I am seeing the Pstat greater (around double) than what I have applied as BC at inlet as well as at outlet. 2. I want to apply only presure at outlet and temperature to be calculated by code. But StarCd wants temperature also at pressure BC. How to do this? Help. -

November 20, 2003, 23:58

Answer No.1 question. The pressure in STAR-CD is relative pressure. If the environment(or inlet) pressure is 1atm, then you have to set the referance pressure 1atm and in inlet BC set 0atm.

November 21, 2003, 13:22

Answer to Question 2:

True, you have to specify temperature at pressure boundaries. But this temperature is only used if the flow at the boundary is INTO the domain. If the flow is out of the domain, the temperature is extrapolated from the interior, in the same was as on outlet boundaries.

Same goes for other scalar quantities at pressure boundaries, like TE and ED.

November 24, 2003, 03:14

If scalar quantities are extrapolated from the interior by default, what means switch ZERO GRAD for scalar quantities TE,ED,T?

November 19, 2003, 03:41	BC problem	#1
newone Guest Posts: n/a	Hi Experts, I am solving a problem involving convergent divergent nozzle. I am employing pressure BC at both ends. Now I have two problems. 1. After post processing I am seeing the Pstat greater (around double) than what I have applied as BC at inlet as well as at outlet. 2. I want to apply only presure at outlet and temperature to be calculated by code. But StarCd wants temperature also at pressure BC. How to do this? Help. -

November 20, 2003, 23:58	Re: BC problem	#2
Nyquist Guest Posts: n/a	Answer No.1 question. The pressure in STAR-CD is relative pressure. If the environment(or inlet) pressure is 1atm, then you have to set the referance pressure 1atm and in inlet BC set 0atm.

November 21, 2003, 13:22	Re: BC problem	#3
Brian Guest Posts: n/a	Answer to Question 2: True, you have to specify temperature at pressure boundaries. But this temperature is only used if the flow at the boundary is INTO the domain. If the flow is out of the domain, the temperature is extrapolated from the interior, in the same was as on outlet boundaries. Same goes for other scalar quantities at pressure boundaries, like TE and ED.

November 24, 2003, 03:14	Re: BC problem	#4
Daria Guest Posts: n/a	If scalar quantities are extrapolated from the interior by default, what means switch ZERO GRAD for scalar quantities TE,ED,T?

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