
[Sponsors] 
April 10, 2006, 23:30 
mass flow inlet boundary condition

#1 
Guest
Posts: n/a

Sponsored Links


Sponsored Links 
April 11, 2006, 02:04 
Re: mass flow inlet boundary condition

#2 
Guest
Posts: n/a

Hi vivian As we know P total= P static+0.5*rho*v^2 where v can be obtained from mass flow rate. by using mass flow rate= rho*Area*v Moreover, please be informed that static pressure is specified at the mass flow inlet only when flow is supersonic. Otherwise it is only for specifying intial guess if u r initialising the solution from mass flow inlet. hope this answers ur question


April 11, 2006, 04:32 
Re: mass flow inlet boundary condition

#3 
Guest
Posts: n/a

Hi, Rags Thanks for your useful information! Does the Rho in the equation P total= P static+0.5*rho*v^2 need extrapolate? In my problem, the variety Rho is not constant. And another question, the gas dynamics equation Ptotal=Pstatic*(1+(k1)*Ma*Ma/2.) can be used for this problem? (k is the adiabatic index 1.4, Ma is Mach number, Ma*Ma=u*u/(Rc*T*k)) Thanks a lot!


April 11, 2006, 08:13 
Re: mass flow inlet boundary condition

#4 
Guest
Posts: n/a

Hi Vivian The 2 equations P total= P static+0.5*rho*v^2 Ptotal=Pstatic*(1+(k1)*Ma*Ma/2.) are one and same. U will come to know of it if u see the derivation of second equation. If Rho is not constant, Ptotal will also vary accordingly.In my opinion, you are trying to get the value of Ptotal at the inlet by hand calculation. If it is so, u can get the rho value at the temperature and pressure specified at the inlet.(I assume that u are using Ideal gas law for rho variation) Let me know if you have any probs..


April 11, 2006, 23:04 
Re: mass flow inlet boundary condition

#5 
Guest
Posts: n/a

Hi, Rags I have understood how to set the mass flow inlet boundary condition. Thanks for your help! I have another problem.
I am writing a finite volume code for unsteady 2D laminar flow. It uses for numerical simulations of resonant oscillations in a tube which has one inflow and three walls (no outflow). It is like fluid entering a closed end box. The tube is filled with air under normal circumstances initially (T0=291.789, p0=101325pa). I don't know how to set the boundary conditions. In my problem, I think the inlet velocity and inlet pressure can not be given simultaneously. Which boundary condition can be used, inlet velocity or inlet pressure? The boundary conditions I use now is prescribed velocity u=u0*sin(wt) at the inlet. And the pressure at the boundary is extrapolated. But I find if I use this inlet velocity boundary condition, I don't know how to get the absolute pressure. My code follows the pressure correction schemes for transient predictions and for compressible flow. The density need to be calculated through the equation of state Rho=P/(Rc*T). So I enquire for the mass flow boundary condition, hoping for the absolute pressure can be calculated through the inlet velocity. Or the pressure boundary condition should be used for this problem? Can you give me some advice? Thank you! 

April 21, 2006, 06:23 
Re: mass flow inlet boundary condition *NM*

#6 
Guest
Posts: n/a



Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Problem with assigned inlet velocity profile as a boundary condition  Ozgur_  FLUENT  5  August 25, 2015 04:58 
velocity calculations in mass flow inlet boundary condition  montazer1012  FLUENT  1  October 18, 2010 03:11 
Mass flow boundary condition  Renato.  Main CFD Forum  0  July 21, 2006 22:07 
Mass Flow Inlet  Pravir Kumar Rai  FLUENT  0  February 19, 2003 15:03 
mass flow inlet  Denis Tschumperle  FLUENT  7  August 9, 2000 02:19 
Sponsored Links 