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Inlet Profile (Please, I really need some help...) |
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April 12, 2006, 19:14 |
Inlet Profile (Please, I really need some help...)
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#1 |
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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 |
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April 13, 2006, 07:01 |
Re: Inlet Profile (Please, I really need some help
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#2 |
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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 |
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April 13, 2006, 17:57 |
Re: Inlet Profile (Please, I really need some help
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#3 |
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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 |
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April 18, 2006, 07:43 |
Re: Inlet Profile (Please, I really need some help
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#4 |
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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. |
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April 18, 2006, 12:38 |
Re: Inlet Profile (Please, I really need some help
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#5 |
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Now I got it! Thank you so much , Mike!
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July 1, 2006, 14:37 |
Re: Inlet Profile (Please, I really need some help
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#6 |
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Thank you for the code snippets, Mike, they were fun to practice reading.
Patti |
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