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-   -   How can apply mass flow rate boundary condition? (http://www.cfd-online.com/Forums/phoenics/52209-how-can-apply-mass-flow-rate-boundary-condition.html)

Sima November 25, 2007 04:04

How can apply mass flow rate boundary condition?
 
Hi I am trying to simulate a compressible flow and I have mass flow rate at inlet boundary. I don't have any information about density and velocity, so how can I apply "mass flow rate" boundary condition at inlet? I have seen only "volume flow rate" boundary in PHOENICS.

Regards.

patti December 1, 2007 19:55

Re: How can apply mass flow rate boundary conditio
 
Encyclopedia, under INLET:

INLET ----- Command; group 13 -------------- -

This command is used to declare inlets, ie fixed-mass-inflow boundaries. Used in conjunction with VALUE it does no more than can be done via PATCH and COVAL, but is slightly more compact and conceptually easier to deal with.

As well as the mass-flow rate per unit area, non-zero values of velocity and scalar quantities convected in by the mass flow can be specified by the VALUE command. See the entry on VALUE for more information.

The syntax is : INLET(NAME,TYPE,IXF,IXL,IYF,IYL,IZF,IZL,ITF,ITL)

NAME is a unique identifier for the INLET, up to 8 characters in length. TYPE can be NORTH,SOUTH,EAST,WEST,HIGH or LOW, and specifies which cell face areas will be used to multiply the mass-flow set. IXF ... ITL specify the limits in space and time over which the mass source is to be active. Thus :

REAL(WIN,RHOIN); WIN=3; RHOIN=1.0 INLET(INL1,LOW,1,NX,1,NY,1,1,1,LSTEP) VALUE(INL1,P1,RHOIN*WIN) ; VALUE(INL1,W1,WIN)

specifies an INLET extending from IX = 1 to NX, IY = 1 to NY at IZ = 1, active over all time steps, in which mass is entering the LOW faces of the cell at a rate of RHOIN*WIN/unit area.

The function of the command is to generate a PATCH with the NAME and TYPE specified over the set limits. COVALs are also generated for all solved variables, with ONLYMS,0.0 for the COefficient and VALue, except for P1 (and P2 if .NOT.ONEPHS) which has COefficient FIXFLU, VALue 0.0.


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