Learning Forum

[kds_ansys]

Hello, 

I am new to both UDF and Ansys and am currently using the following UDF code for my simulation. While the code compiles without any errors, when I try to initialize the model, I encounter an error and the simulation closes automatically.

Node 6: process 13572: received signal sigsegv.

Node 7: process 110688: received signal sigsegv.

99999: mpt_accept: error : accept failed: No error

99999: mpt_accept: error : accept failed: No error

99999: mpt_accept: error : accept failed: No error

99999: mpt_accept: error : accept failed: No error

Bad termination of one of your application processes 

Rank 0 PID 99524 Running at xxx

Exit status: -1 (ffffffff) 

---------------------------------------------

Here is my code

 

 

/*************************************************/

/*************************************************/ 

/*************************************************/ 

#include "udf.h" 

#include "sg.h" 

real m_sum=0; 

real ar_sum=0; 

real m_max=0; /*mass flux at the corner of meniscus: used for thin film region*/ 

real h_ar_int=0; 

real h_avg=0; 

 

DEFINE_ADJUST(Get_q_V, d) 

{ 

Thread *t; // thread pointer

Domain *domain;    // domain pointer   

cell_t c,c0;  // define cell

face_t f,f2,f_face_l; //define face

Thread *tf, *tf2; 

int n,n2; // define n and n2

real S=0; 

int liquid_id=7; // the liquid zone's thread ID the domain ID

/*real p, ps, Ts, hfg, M_bar, R_bar, M_air, p_l_sat;*/   

//water properties

real ps=3167.739; 

real Ts= 298; 

real hfg= 2270e3; 

real M_bar=18.01; 

real R_bar=8314.47; 

real p_l_sat=0; 

real cp = 4181.3;

   

int liquid_inter_id1=12; // the liquid interface at the liquid/vapor interface

real count=0; 

 

real dr0[ND_ND];   // the vector that connects the centroid of cell c0 to the face centroid

real dr1[ND_ND];   // the vector that connects the centroid of cell c1 to the face centroid

real A[ND_ND];   // the area normal vector

real es[ND_ND];  //the unit normal vector in the direction from cell c0 to c1

    

real T;  // define the temperature

  

real temp2;  // define the mass flow rate

real cent1[3],cent2[3]; // the centroid of cell

    

real ar; /* area of the face of the cell*/  

real q, temp;    

real q_conv;  

real qd=0;         

 

real ds, A_by_es;     // the value A.A/A.es

    

 

real AA, B;    

 

m_sum=0;   

ar_sum=0;  

m_max=0;  

h_ar_int=0; 

 

domain = Get_Domain(7);  // get the domain selected, put the liquid domain id inside 

tf= Lookup_Thread(domain, liquid_inter_id1);   /* look up the face thread of the domain 

liquid_inter_id1 which is the liquid vapor interface */

begin_f_loop (f, tf)  

{   

c=F_C0(f,tf); // macros to identify adjacent faces  

t=F_C0_THREAD(f,tf);        // macros to identify adjacent faces thread

 

T=F_T(f,tf);   //get the temperature at the face

F_AREA(A,f,tf);   // can be used to return the real face area vector

ar=NV_MAG(A);    // get the area 

 

p_l_sat=ps*exp((1/Ts-1/T)*hfg*M_bar/R_bar) ;   

temp2 = .03*sqrt(M_bar/(2*3.1415*R_bar))*(p_l_sat/sqrt(T) - ps/sqrt(Ts)); /*evap mass flux from the face */   

qd = temp2*ar*hfg;   

F_UDMI(f,tf,1)= temp2;              

 

S=qd/C_VOLUME(c,t); /*S is like energy source term*/ 

 

if (S/hfg > m_max)      

{            

m_max=S/hfg; /*highest mass source term for any cell*/      

}

            

C_UDMI(c, t, 0) = S;     // store or access the value of mass source

C_UDMI(c, t, 1) = qd/(hfg*ar);

            

F_UDMI(f,tf,2) = temp2*hfg/(T-298);      

C_UDMI(c,t,2) = temp2*hfg/(T-298);      

h_ar_int = h_ar_int + F_UDMI(f,tf,2)*ar; 

        

m_sum=m_sum+qd/hfg; /*total mass evaporated in Kg/s*/      

ar_sum=ar_sum+ar;      

count=count+1;  

}  

end_f_loop(f,tf)  

 

h_avg = h_ar_int/ar_sum;  

    

Message ("Total area of interface: %g\n", ar_sum);     

Message ("Total mass evaporated (kg/s): %g\n", m_sum);     

Message ("h integral on interface: %g\n", h_ar_int);     

Message ("h Average on interface: %g\n", h_avg);     

Message ("Total faces on the interface: %g\n", count);     

Message("Highest mass source term for any cell: %g\n", m_max); } 

 

 

 DEFINE_SOURCE(Mass_liquid, c, t, dS, eqn) 

{     

Thread *c_thread;   

face_t f;  

Thread *tf;  

int n;  

real S=0;  

//methanol  

real hfg=2270e3;  

//water 

// real hfg = 2270e3;  

real ar;    

 

int liquid_id=7; /*liquid zone 's thread ID*/  

int liquid_inter_id1=12; // the interface of the domain/ liquid vapor interface

 

c_face_loop(c, t, n)  

{   

f = C_FACE(c,t,n);   // the face of the liquid

tf = C_FACE_THREAD(c,t,n);   // the face thread of the liquid 

/* looping through the face */   

if(THREAD_ID(tf)==liquid_inter_id1 )         

{     

S=-1*C_UDMI(c,t,0)/hfg;   // store or access the value of mass source

}  

}  

return S; 

}  

 

DEFINE_PROFILE(h_interface, thread, position)  

{  

face_t f;  

  

real T_room=298;  

real T;  /*wall temperature*/  

real dT;/*dT=T-T_room*/  

real k=0.68; 

real Nu,h;  

real hfg=2270e3;  

  

begin_f_loop (f, thread)  

{       

T=F_T(f,thread);   

dT=fabs(T-T_room);   

h = F_UDMI(f, thread, 1)*hfg/dT; 

     

F_PROFILE(f,thread,position)=h; 

   

}  

end_f_loop (f, thread)

    

Message("dT: %g\n",dT);  

Message("T :%g\n", T);   

Message("h :%g\n", h);  

} 

 

[Rob]

I'm not going to debug the code, but common issues include data being used that's not available and insufficient UDMs being assigned in Fluent (you do this manually). 

As a more general comment, use indents to make blocks easier to read and be careful when assigning number types:

real whatever = 0 ; 

isn't great, 

real whatever = 0.0 ; 

is more appropriate. 

[kds_ansys]

Thank you Rob for the reply. I have assigned UDM manually in Fluent. To make sure I wouldn't assign a small UDM number, I assigned a big number (100). However, I am still seeing the same error. 

 

[Rob]

OK. Break the code down. If you don't use the source & profile what happens? Note, some single/few letter variables can clash with Fluent's built in functions: it's always best to use more descriptive variables. 100 UDMs may be a little excessive, I don't think it'll cause a problem but may result in data files that are a lot bigger than they need to be. 

[kds_ansys]

Thanks Rob. It is actually working now. I divided the file into two rather than one, and it worked.