[Jack0210Jack]

Hi,

I am new to udf and c programming. Currently I am working on a project to simulate ammonia absorption into water droplets using two-film theory and DPM. I have read the udf manuals and researching online for examples to come up with codes below:

#include "udf.h"

DEFINE_DPM_HEAT_MASS(nh3absorption, tp, Cp, hgas, hvap, cvap_surf, Z, dydt, dzdt)
{
	int is;
	int nc = TP_N_COMPONENTS(tp); /*number of particle components*/
	real gas_index;
	printf("\n######");
	for (is = 0; is < nc; is++)
	{
		int gas_index = TP_COMPONENT_INDEX_I(tp, is); /* index of vaporizing component in the gas phase */
		printf(" gas_index=%d is=%d TP_COMPONENT_I=%e ", gas_index, is, TP_COMPONENT_I(tp, is));
	}
	printf("#######$\n");
	Thread* t0 = P_CELL_THREAD(tp); /*thread where the particle is in*/
	Material* gas_mix = THREAD_MATERIAL(DPM_THREAD(t0, tp)); /*gas mixture material*/
	Material* cond_mix = P_MATERIAL(tp); /*particle mixture material*/
	cphase_state_t** c0 = &(tp->cphase); /*cell information of particle location*/

	real yi_NH3_l; /*mass fraction of ammonia in particle*/
	for (yi_NH3_l = 0; yi_NH3_l < 1; ++TP_COMPONENT_I(tp, is))
	{
		Domain* d; /* Get domain pointer */
		real T; /*Temperature*//*[K]*/
		real yi_NH3_g;
		real den_g;
		Thread* t;
		cell_t c;
		int i;
		d = Get_Domain(1);
		/* Loop over all cell threads in domain */
		thread_loop_c(t, d)
		{
			/* Loop over all cells */
			begin_c_loop(c, t)
			{
				{
					T = C_T(c, t);
					yi_NH3_g = C_YI(c, gas_index, 4); /*mass fraction of ammonia in air*/
					den_g = C_R(c, gas_index); /*density of air*/
				}
			}
			end_c_loop(c, t);
		}

		real MW_NH3 = 17.031e-3; /*Molecular mass of ammonia*//*[kg/mol]*/

		real C_g = yi_NH3_g * den_g / MW_NH3; /*molar concentration of NH3 in air*//*[mol/m3]*/
		real P_g = C_g * 8.314 * T; /*partial pressure of ammonia in air*/

		real den_l = P_RHO(tp); /*density of particle*/
		real C_l = yi_NH3_l * den_l / MW_NH3; /*molar concentration of ammonia in water droplet*//*[mol/m3]*/

		real H = 0.59 * exp(4200 * ((1 / T) - 1 / (298.15)));	/*Henry Constant*//*[mol/(m3*Pa)]*/

		real mp = P_MASS(tp); /* particle mass */
		real Dp = DPM_DIAM_FROM_VOL(mp / P_RHO(tp)); /* particle diameter */
		real Ap = DPM_AREA(Dp); /*particle surface area*/
		real v = NV_MAG(P_VEL(tp)); /*water droplet velocity*/
		real vg = 15.69e-6;	/*kinematic viscosity of air*//*[m2/s]*/
		real Re = Dp * v / vg;

		real D = 1.64e-7; /*molecular diffusivity coefficient*//*[m/s]*/
		real Sc = vg / D;

		real ky = 2.0 + 0.6 * sqrt(Re) * pow(Sc, 1. / 3.); /*mass transfer coefficient in liquid phase*/

		real NA = ky * (P_g - H * C_l); /*Mass transfer flux of ammonia*/
		dydt[2] = NA;
	}
	return;
}

After compiling it in Fluent, 2 error messages pop up:

..\..\src\nh3absorption.c(39): error C2223: left of '->storage' must point to struct/union
..\..\src\nh3absorption.c(40): error C2223: left of '->storage' must point to struct/union

Does anyone know how should I fix it? Thanks.

The idea of this project is to simulate the ammonia absorption into water droplet. Water droplet will be injected via DPM and ammonia absorption will be added via udf. When the ammonia mass fraction in water droplet is less than 1, the ammonia will be absorbed into the water droplet and the mass transfer rate is based on the mass fraction of ammonia in water droplet.

[pakk]

You added a loop over all cells. But you use only info from the last cell, which is chosen by fluent. It makes no sense.

Go back to your old udf, replace c by c0, and you will use the gas density at the location of the particle.
If you want the gas density somewhere else (why would you?) explain what you want.

[Jack0210Jack]

Thanks. I think I have more understanding on this. Initially I assumed c0 is where the cell that has particle and the particle = cell. Now if I'm not wrong, c0
is the cell that holds the particle and the spaces surrounding the particle.

So based on your suggestions, I changed it to

real T = C_T(c0, t0); /*Temperature*//*[K]*/
real yi_NH3_g = C_YI(c0, t0, 4); /*mass fraction of ammonia in air*/
real den_g = C_R(c0, t0); /*density of air*/

and removed the Get_Domain functions.

However, here comes new errors

error C2107: illegal index, indirection not allowed

for these 3 lines.

btw, I have changed this line

cphase_state_t** c0 = &(tp->cphase); /*cell information of particle location*/

into

cphase_state_t* c0 = &(tp->cphase); /*cell information of particle location*/

as suggested even though I'm receiving this warning

warning C4047: 'initializing': 'cphase_state_t *' differs in levels of indirection from 'cphase_state_t **'

Hopefully the warning can be ignored.

Thanks.

[pakk]

You first had

cell_t c0 = P_CELL(tp); /*cell where the particle is in*/

As definition for c0. What's wrong with that? Why change it?

[Jack0210Jack]

Oh gawd, no more error now.

At first due to that misunderstanding I thought that line was useless and I changed "cphase_state_t** c" into "cphase_state_t** c0" since I wanted to use "c" variable in Get_Domain below. Thanks for reminding me those lines have been modified when I rearrange the codes.

Now only left this error to be solved which I think it is related to Environment Variables

LINK : fatal error LNK1104: cannot open file 'kernel32.lib'

Your help is very much appreciated. Thank you.

[pakk]

Hmm, that one is probably Fluent installation/configuration. Don't know much about that, sorry...

[Jack0210Jack]

No worries. You and others have helped me a lot. Hopefully I can get the results I want from this udf.

Thank you.

[Jack0210Jack]

Hi, I need helps again.

So after all those editing, the file shows no error after I "build". But when I want to load the codes, it shows

LINK : fatal error LNK1104: cannot open file 'kernel32.lib'

Some people said it is related to SDKs path or compability or environmental variables. I then checked a few solutions and decided to install VS 2012 (that time I was using VS 2019). Which means I had 2 VS at that time.

By installing VS 2012, the LINK error has been solved. But it came up another error:

the udf library you are trying to load (libudf) is not compiled for parallel use

I then try anything I could think of and find, like using series instead of parallel, etc. But after I uninstalled both VS and reinstalled VS 2012 only, suddenly errors appears:

error C2275: 'Thread' : illegal use of this type as an expression
error C2065: 't0' : undeclared identifier

error C2275: 'cell_t' : illegal use of this type as an expression
error C2146: syntax error : missing ';' before identifier 'c0'
error C2065: 'c0' : undeclared identifier

error C2275: 'Material' : illegal use of this type as an expression
error C2065: 'gas_mix' : undeclared identifier
error C2065: 't0' : undeclared identifier
error C2223: left of '->sub_threads' must point to struct/union
fatal error C1903: unable to recover from previous error(s); stopping compilation

which refer to lines below

Thread* t0 = P_CELL_THREAD(tp); /*thread where the particle is in*/

cell_t c0 = P_CELL(tp); /*cell where the particle is in*/

Material* gas_mix = THREAD_MATERIAL(DPM_THREAD(t0, tp)); /*gas mixture material*/

I have not change anything in the udf and I saw some people mention they have this issue when they use diff VS, so I reinstalled VS 2019 too, but the errors still persist. Besides, the last error (fatal error C1903) seems like telling me the compiler cannot compile lines after line 16.

I have tried with another code which I copied from udf manual and this code shows no errors like the the above mentioned (Thread, LINK, ...not compiled for parallel use)

#include "udf.h"
DEFINE_ADJUST(my_adjust, d)
{
	Thread* t;
	/* Integrate dissipation. */
	real sum_diss = 0.;
	cell_t c;
	thread_loop_c(t, d)
	{
		begin_c_loop(c, t)
			sum_diss += C_D(c, t) *
			C_VOLUME(c, t);
		end_c_loop(c, t)
	}
	printf("Volume integral of turbulent dissipation: %g\n", sum_diss);
}

If you may, please guide me once again. Thank you.

[Jack0210Jack]

UPDATE

I think the issue lies within the compiler. So I tried with Ansys 2020 R2 and it doesn't show any errors I mentioned above now.

Once again, thank you.

[hanzain]

Hi guys, I am just wondering with this udf what species transport model and multiphase model has been used? Do we define any reactions with it. Thank you