[mali28]

Hi

Does any one know what is the UDF macro to get the relative humidity of air (%) in a certain cell?

Thnak you.

[m zahid]

hi, have you find the answer ? if yes please share the answer.i am modeling a spray in the air using Fluent . I want to get the relative humidity at a various points at different temperature within the domain. if u know the UDF or any other way please share your experience.

thanks

[Jaskull]

Hi,
there is a macro to get RH in cell:
relative_humidity(cell, thread)

I found it by checking the fluent files one by one.

[m zahid]

thanks Jaskull, i will try it and reply you as soon as possible.
thanks

[jacek]

How to use it, and where did you find some description?

Originally Posted by Jaskull

Hi,
there is a macro to get RH in cell:
relative_humidity(cell, thread)

I found it by checking the fluent files one by one.

[Jaskull]

I didn't find any description. I fount it in one of the fluent files. To use it you need to find the particle cell and thread:
cell_t cc = P_CELL(p);
Thread *t0 = P_CELL_THREAD(p);

then you can find RH in cell where the particle is e.q.:
humidity = relative_humidity(cc, t0);

I'm using it in calculation of equilibrium moisture content of drying particles and it works well.

[jacek]

That is not all indispensable to run this macro.
Ii is yet necessary to declare a suitable file in the header:

#include "udf.h"
#include " ???"

What a file one should include?

[Jaskull]

Im using this function in macro:
DEFINE_DPM_HEAT_MASS(multivap,p,Cp,hgas,hvap,cvap_ surf,Z,dydt,dzdt)
and read those files:
#include "udf.h"
#include "math.h"

In my opinion "math" is not necessary.

[jacek]

I tried using it as a trial in EXECUTE_ON_DEMAND macro whith:

#include "udf.h"
#include "math.h" // not neccessary in this case
#include "species.h" // I foundin this file a string ".. real relative_humidity..."

But I receive a compilation error "...unresolved external symbol RELATIVE_HUMIDITY... "

I think you are more lucky whith this issue...

[jacek]

#include "udf.h"
#include "species.h"

// your code, for instance:

DEFINE_ON_DEMAND(NaZadanie)
{
Domain *dom = Get_Domain(Dzie);
Thread *th_flu = Lookup_Thread(dom, ID_flu); //
cell_t ce_flu;

relative_humidity(ce_flu, th_flu) // lower case only !!! uppercase - you get error!

}

[jacek]

relative_humidity() works on node values, so if your calculation is cell-based be carefull...