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-   -   DPM - UDF for fluctuating bubble size (http://www.cfd-online.com/Forums/fluent/40630-dpm-udf-fluctuating-bubble-size.html)

 Jaroslav Kotara April 18, 2006 11:06

DPM - UDF for fluctuating bubble size

I am concerning with DPM model for the gas bubble tracking in viscous liquid. I use UDF to simulate fluctuating bubble diameter with respect to the temperature and pressure of the continuum. I have an empirical formula for the bubble diameter but probably have problem to set this in the DEFINE_DPM_LAW(name, p, ci).

My UDF causes fatal error and doesn't work.

DEFINE_DPM_LAW(bubble_size,p,ci) {

cell_t c;

real A;

real T = C_T(c,t);

real ro = C_R(c,t);

real eta = C_MU_L(c,t);

/* compute variable A*/

A = 0.382 * 8.31434 * T * pow(9.81,(1/3)) * pow(ro,(1/3)) * pow(eta,(1/3));

/* compute new particle diameter */

P_DIAM(p) = P_DIAM0(p) + A/101325/44*(1.4e-9 - 1.04e-14 * 101325) * P_TIME(p);

}

Does anyone know where is the problem? This UDF doesn't work yet and causes fatal error while DPM is beeing calculated in the 10th flow iteration.

 nicholas April 19, 2006 09:02

Re: DPM - UDF for fluctuating bubble size

you should define the varialbe in the same line ,may be this is problem, fluent documentation said if you don't do like this ,it may some problem. I suggest you ,first,only calculate A,if there is no problem ,then calculate P_DIAM(p)=P_TIME(p) or P_DIAM(p)=A/101325/44*(1.4e-9 - 1.04e-14 * 101325) * P_TIME(p),last ,assume P_DIAM0(p) is a constant ,then try, you will find the problem.

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