CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   Main CFD Forum (http://www.cfd-online.com/Forums/main/)
-   -   1D Euler Boundary Conditions using Riemann Variables?? (http://www.cfd-online.com/Forums/main/82811-1d-euler-boundary-conditions-using-riemann-variables.html)

Ozzy December 6, 2010 15:33

1D Euler Boundary Conditions using Riemann Variables??
 
Hello all,

I am at the moment writing a code for a uni project using a second order Lax-Wendroff scheme to model unsteady flow.

I am trying to implement boundary conditions using characteristics but am struggling....the method described by Benson for a 'closed' boundary does not produce reflections but results in big oscillations in my program:

1) Do I not need to set the temperature at the boundary to be a constant?

2) Will the homoentropic method at the boundary suffice?

I would really appreciate any help :confused:

Thanks,

Ozzy

ignat December 11, 2010 17:44

Quote:

Originally Posted by Ozzy (Post 286245)
:

1) Do I not need to set the temperature at the boundary to be a constant?

It depends on flow type at the boundary.

if it's subsonic INflow (M<1) then 2 constant values should be specified, usually total Entalpy and entropy

Entalpy = \frac{\gamma p}{(\gamma-1)\rho}+u^2/2 \

Entropy=\frac{p}{\rho^\gamma}

and 1 parameter should be determined by closest cell inside the domain, ususlly velocity u.

if bounday is subsonic OUTflow then 1 constant parameter
is specified - ambient pressure and 2 others are dtermined by closest cell inside the domain.


All times are GMT -4. The time now is 18:42.