CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Phoenics

Inlet Profile (Please, I really need some help...)

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   April 12, 2006, 18:14
Default Inlet Profile (Please, I really need some help...)
  #1
Bernardo Santos Aflalo
Guest
 
Posts: n/a
Hi!

I am a last year Mechanical Engineering student and I am working on a simulation of a flow over a backward step, and Im having problems in the non unifom inlet profile.

I created a user defined object, a patch of this object and a in form of it. My group 13 of the q1 file looks like this:

************************************************** ********* Group 13. Boundary & Special Sources

PATCH (TESTE1 ,EAST ,1,0,0,0,5,20,1,1)

WALLCO = GRND3 ************************************************** ********* Echo InForm settings for Group 13 inform13begin (SOURCE OF U1 AT INLET1 IS ZG^2 WITH IMAT<100) inform13end ************************************************** *********

and in the objetcs list:

> OBJ, NAME, INLET1
: OBJ, POSITION, 4.000000E-01, 0.000000E+00, 8.000000E-02
: OBJ, SIZE, 0.000000E+00, 1.000000E-01, 1.900000E-02
: OBJ, CLIPART, default
: OBJ, ROTATION24, 1
: OBJ, TYPE, USER_DEFINED

Am I doing the right procedures? Please, I dont know what more can I do! What´s wrong in this code???

Best Regards,

Bernardo Aflalo
  Reply With Quote

Old   April 13, 2006, 06:01
Default Re: Inlet Profile (Please, I really need some help
  #2
Mike
Guest
 
Posts: n/a
There is no mass injected at this inlet. You need a source for p1 equal to density*uin). Below is an INFORM example for two-user-defined inlets to represent the wind profile of an atmospheric boundary layer. Your case is much simpler, but this should give you the idea of how to do it.

************************************************** ********** Group 13. Boundary & Special Sources

INLET (BLINL ,LOW ,3,0,0,0,0,0,1,1) VALUE (BLINL ,P1 , 0.000000E+00) VALUE (BLINL ,U1 , 0.000000E+00) VALUE (BLINL ,V1 , 0.000000E+00) VALUE (BLINL ,W1 , 0.000000E+00) VALUE (BLINL ,KE , 0.000000E+00) VALUE (BLINL ,EP , 0.000000E+00)

INLET (BLINW ,WEST ,5,0,0,0,0,0,1,1) VALUE (BLINW ,P1 , 0.000000E+00) VALUE (BLINW ,U1 , 0.000000E+00) VALUE (BLINW ,V1 , 0.000000E+00) VALUE (BLINW ,W1 , 0.000000E+00) VALUE (BLINW ,KE , 0.000000E+00) VALUE (BLINW ,EP , 0.000000E+00)

WALLA = 2.000000E-02 ;WALLB = 0.000000E+00 EGWF = T WALLCO = GRND5 ************************************************** **********

inform13begin REAL(VREF,REFHEIGHT,RHIN,ROUGHH,AKAP,ZRFDRH) REAL(VTAU,VTAUX,VTAUZ) REAL(VELX,VELZ,IN_ANG,PI) ** constants AKAP=0.41;PI=3.1415926 ** wind speed, reference height, roughness height VREF=1.5;REFHEIGHT=10.0;ROUGHH=0.022 ** wind incidence angle IN_ANG=30.0*PI/180.

VELZ=VREF*COS(IN_ANG) VELZ

VELX=VREF*SIN(IN_ANG) VELX

ZRFDRH=REFHEIGHT/ROUGHH

VTAU=VREF*AKAP/LOG(ZRFDRH) VTAU

VTAUX=VELX*AKAP/LOG(ZRFDRH) VTAUX

VTAUZ=VELZ*AKAP/LOG(ZRFDRH) VTAUZ

RHIN=1.189 CHAR(FORM1,FORMX,FORMZ,FORMK,FORME)

FORM1=VTAU/AKAP FORMX=VTAUX/AKAP FORMZ=VTAUZ/AKAP

FORMK=VTAU^2/0.3 FORME=VTAU^3/AKAP

(SOURCE OF P1 AT BLINL IS RHIN*(:FORMZ:*LOGE(YG/:ROUGHH) WITH IMA$ T<100) (SOURCE OF U1 AT BLINL IS RHIN*(:FORMZ:*LOGE(YG/:ROUGHH)*:FORMX:*$ LOGE(YG/:ROUGHH WITH IMAT<100) (SOURCE OF W1 AT BLINL IS RHIN*(:FORMZ:*LOGE(YG/:ROUGHH)*:FORMZ:*$ LOGE(YG/:ROUGHH WITH IMAT<100) (SOURCE OF KE AT BLINL IS RHIN*(:FORMZ:*LOGE(YG/:ROUGHH)*:FORMK: $ WITH IMAT<100) (SOURCE OF EP AT BLINL IS RHIN*(:FORMZ:*LOGE(YG/:ROUGHH)*:FORME:/$ YG WITH IMAT<100)

(SOURCE OF P1 AT BLINW IS RHIN*(:FORMX:*LOGE(YG/:ROUGHH) WITH IMA$ T<100) (SOURCE OF U1 AT BLINW IS RHIN*(:FORMX:*LOGE(YG/:ROUGHH)*:FORMX:*$ LOGE(YG/:ROUGHH WITH IMAT<100) (SOURCE OF W1 AT BLINW IS RHIN*(:FORMX:*LOGE(YG/:ROUGHH)*:FORMZ:*$ LOGE(YG/:ROUGHH WITH IMAT<100) (SOURCE OF KE AT BLINW IS RHIN*(:FORMX:*LOGE(YG/:ROUGHH)*:FORMK: $ WITH IMAT<100) (SOURCE OF EP AT BLINW IS RHIN*(:FORMX:*LOGE(YG/:ROUGHH)*:FORME:/$ YG WITH IMAT<100)

inform13end
  Reply With Quote

Old   April 13, 2006, 16:57
Default Re: Inlet Profile (Please, I really need some help
  #3
Bernardo Santos Aflalo
Guest
 
Posts: n/a
Thanks for the answer, Mike! It helps me a lot...but I still have some questions:

a) Why I have to define this pressure source if my inlet have a well defined velocity profile?

b) In my case, which is indeed much simpler, I have to do a pressure source of uin * density too?

c) Why the velocity source is density * uin^2? The source in my simulation is just the formula for the uin...is this incorrect?

Thanks again!

Aflalo
  Reply With Quote

Old   April 18, 2006, 06:43
Default Re: Inlet Profile (Please, I really need some help
  #4
Mike
Guest
 
Posts: n/a
In PHOENICS, the P1 variable in the COVAL function denotes the continuity equation; and U1, V1, and W1 are the variables for the momentum equation.

It is necessary to specify the boundary condition for the continuity equation,

ie mass inflow rate = density*velocity*area

which is in kg/s.

It is also necessary to specify the corresponding momentum source, which is

mass inflow rate*velocity

and has units of Newtons.

If you specify the source just as velocity*area, then the units are incorrect, ie m^3/s.

  Reply With Quote

Old   April 18, 2006, 11:38
Default Re: Inlet Profile (Please, I really need some help
  #5
Bernardo Santos Aflalo
Guest
 
Posts: n/a
Now I got it! Thank you so much , Mike!
  Reply With Quote

Old   July 1, 2006, 13:37
Default Re: Inlet Profile (Please, I really need some help
  #6
PattiMichelle
Guest
 
Posts: n/a
Thank you for the code snippets, Mike, they were fun to practice reading.

Patti
  Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Inlet Profile with CFX-Pre Fadi Ishak CFX 1 June 10, 2008 07:12
k-w inlet profile Hicham CFX 0 July 12, 2007 12:10
unsteady inlet profile Justin Main CFD Forum 0 July 4, 2007 13:58
Lig-law inlet profile Vinod FLUENT 0 July 14, 2005 13:13
using profile to specify inlet VOF and velocity yf FLUENT 8 June 2, 2005 05:40


All times are GMT -4. The time now is 13:04.