[longamon]

Hi

I'm trying to use groovybc to specify an inflow condition, however i'm kinda stuck with it. my c++ knowledge is very limited.

the velocity profile i'm trying to implement is

U=min(y,kln(y)+B) , 0 , 0

where k and B are constants, y is the y coordinate of the point. Velocity is only streamwise, the other 2 components at the inlet are 0.

I can create yp=y and kln=k*log(yp)+B, however I don't how to choose the minimum of these two.

I'm using OF 1.7

thanks for any help

[gschaider]

Originally Posted by longamon

Hi

I'm trying to use groovybc to specify an inflow condition, however i'm kinda stuck with it. my c++ knowledge is very limited.

the velocity profile i'm trying to implement is

U=min(y,kln(y)+B) , 0 , 0

where k and B are constants, y is the y coordinate of the point. Velocity is only streamwise, the other 2 components at the inlet are 0.

I can create yp=y and kln=k*log(yp)+B, however I don't how to choose the minimum of these two.

I'm using OF 1.7

thanks for any help

The min-function in groovyBC takes the minimum of a field and therefore only takes one argument.

The minimum of two fields a and b can be taken with the ?:-notation: (a < b ? a : b)

[longamon]

thanks gschaider, that worked like a charm. kudos on the groovyBC app, great tool.

[longamon]

Hi, its me again. Upgraded to OF 2.0 and installed swak4foam, however the notations has changed a bit. This is the entry for the boundary "Entrada"

   Entrada
      {
        type            groovyBC;
	valueExpression "vector(ret*nu*v/1.5,0,0);";
        variables       "ret{Entrada}=590;nu{Entrada}=0.000138217;y1{Entrada}=pos().y;ymax{Entrada}=max(y1);y2{Entrada}=ymax-pos().y;yi{Entrada}=(y1<y2?y1:y2);yp{Entrada}=ret*yi/1.5;klny=2.5*log(yp+0.000001)+5;v{Entrada}=(yp<klny?yp:klny);";
        value           uniform (1 0 0);
      }

and it throws this error:

--> FOAM FATAL ERROR: 
 Parser Error at "1.5-6" :"field y1 not existing or of wrong type"
"max(y1)"
"     ^^"

Appreciate your help

David

[gschaider]

Originally Posted by longamon

Hi, its me again. Upgraded to OF 2.0 and installed swak4foam, however the notations has changed a bit. This is the entry for the boundary "Entrada"

   Entrada
      {
        type            groovyBC;
	valueExpression "vector(ret*nu*v/1.5,0,0);";
        variables       "ret{Entrada}=590;nu{Entrada}=0.000138217;y1{Entrada}=pos().y;ymax{Entrada}=max(y1);y2{Entrada}=ymax-pos().y;yi{Entrada}=(y1<y2?y1:y2);yp{Entrada}=ret*yi/1.5;klny=2.5*log(yp+0.000001)+5;v{Entrada}=(yp<klny?yp:klny);";
        value           uniform (1 0 0);
      }

and it throws this error:

--> FOAM FATAL ERROR: 
 Parser Error at "1.5-6" :"field y1 not existing or of wrong type"
"max(y1)"
"     ^^"

Appreciate your help

David

Hmm. At first: You're working on the patch Entrada anyway, so there's no need to write the variables like this "ret{Entrada}=590" ("ret=590" is sufficient).

In my opinion this should not be the cause of your problem, but could you try it anyway? BTW: Using the external-variables syntax might lead to strange results if used on the "same" patch as external variables always get only one value (which is used for all faces).

[longamon]

That was it, y1{Entrada}=pos().y was supposed to be a vector and it wasn't

thanks

[RygeltheXVI]

Hail all,
My c++ skill is quite low. Much like the original post I wish to compare to vector fields and get the minimum.
Basically I want:
U=(min(1,pos()z),0,0)

I was wondering how I would go about generating a field of uniform values 1. At the moment my work around is to use field2=(pos().z/pos().z). And seeing as this produces the result I want I'm not exactly complaining as much as I wish to know the 'correct' way to do it in the future.

And so i use:
variables "d=pos().z/pos().z;e=pos().z;profile=(e < d ? e : d)*vector(1,0,0);";
valueExpression "profile";

Its probably something really obvious or implied that I'm not aware of,
Striving for elegance, and Cheers

[gschaider]

Originally Posted by RygeltheXVI

Hail all,
My c++ skill is quite low. Much like the original post I wish to compare to vector fields and get the minimum.
Basically I want:
U=(min(1,pos()z),0,0)

I was wondering how I would go about generating a field of uniform values 1. At the moment my work around is to use field2=(pos().z/pos().z). And seeing as this produces the result I want I'm not exactly complaining as much as I wish to know the 'correct' way to do it in the future.

And so i use:
variables "d=pos().z/pos().z;e=pos().z;profile=(e < d ? e : d)*vector(1,0,0);";
valueExpression "profile";

Its probably something really obvious or implied that I'm not aware of,
Striving for elegance, and Cheers

Since the release that has the date 2011-07-26 (check the README) there is a binary min/max in the parser. So basically

vector(min(pos().z,1),0,0)

should work