[vasava]

I am writing a UDF for calculating Oscillatory Shear Index (OSI).

The definition of OSI can be found here (right side bottom of 2nd page)
http://utopia.duth.gr/~soulis/Public...0of%20Non-.pdf

Any hint or help about this?

[Mailto]

I'm trying to do the same actually

[djing]

hi dear colleague, to calculate the shear oscillation index in FLUENT I found these two links:

http://www.cfd-online.com/Forums/flu...ng-fluent.html
http://cape-forum.com/index.php/topic,1074.0.html

but in the second link the colleague "infocfd" is about a UDF attached, but I can’t download it ... if you can download the UDF or help me to understand the principle of calculated OSI on FLUENT please answer me ... thank you for your cooperation.

[vasava]

Sorry but I cant download it either. Anyways I calculated OSI with matlab however visualization of the calculated is still an issue for us.

[khuti]

Hello Guys,

I did some work in this field awhile ago, you can use the attached UDF I wrote for my uses back then.

Hope it helps, and yeah I know this one is an oldie...

Regards.

[vasava]

I will give it a try. Thanks Khuti!

[dhplsy]

Thank you, Khuti.
I want to clarify if the OSI values are area-averaged.

[khuti]

Hi Dhplsy,

Sorry for the delayed response.

The values that are being used in the calculation are taken from the Fluent raw data storage, so they are per cell face and averaged by the relevant cell face area.

Also please note, that you might want to delete some of the code related to the names of the UDM:

DEFINE_EXECUTE_ON_LOADING(nameinit, libudf)
{
Set_User_Memory_Name(0, "uWSS");
Set_User_Memory_Name(1, "uWSSx");
Set_User_Memory_Name(2, "uWSSy");
Set_User_Memory_Name(3, "uWSSz");
Set_User_Memory_Name(4, "OSI");
}

( as I remember it caused some problems, hadn't the chance to figure out what was the problem)

Enjoy!

[andrea impiombato]

Hello,
I've been used the UDF above. I don't understand why the WSS values are not in good agreement as those automatically calculated by Fluent. Consequently, the calculation of OSI is not consistent ... Has anyone solved this problem?


Thanks

[ATT]

Originally Posted by khuti

Hello Guys,

I did some work in this field awhile ago, you can use the attached UDF I wrote for my uses back then.

Hope it helps, and yeah I know this one is an oldie...

Regards.

Can you give me?Thank you

[aerosuraj1]

hello KHUTI,
I am confused, i interpret the UDF you had provided and run the simulation but after solution is complete, where did the result of OSI has been saved?
please suggest the correct way

thank you

[AlexanderZ]

go to contours
-> contours of
-> user -defined memory
-> select "OSI" (also it could be udm-4)

[aerosuraj1]

Originally Posted by AlexanderZ

go to contours
-> contours of
-> user -defined memory
-> select "OSI" (also it could be udm-4)

thank you Alexander Z

[aerosuraj1]

Originally Posted by AlexanderZ

go to contours
-> contours of
-> user -defined memory
-> select "OSI" (also it could be udm-4)

Dear Alexander sir,
could you please explain it in detail. because I have tried it by interpreting the UDF in Fluent. then in contours drobox I didn't found any user-defined option.
please help
thank you

[pakk]

You have to make a new contour first.

[amscosta]

Hi All,
For using the code :
DEFINE_EXECUTE_AT_END(OSI)
{
Domain *domain;
real area;
face_t f;
real A[ND_ND];
cell_t c, c0;
Thread *t,*t0, *c_thread;
real wallshear [ND_ND];

domain = Get_Domain(domain_ID);
t = Lookup_Thread(domain,zone_ID);

begin_f_loop(f, t)
{
F_AREA(A,f,t);
area = NV_MAG(A);
NV_V(wallshear,=,F_STORAGE_R_N3V(f,t, SV_WALL_SHEAR));
c0 = F_C0(f,t);
t0 = THREAD_T0(t);
C_UDMI(c0,t0,0) += NV_MAG(wallshear)/area;
C_UDMI(c0,t0,1) += -wallshear[0]/area;
C_UDMI(c0,t0,2) += -wallshear[1]/area;
C_UDMI(c0,t0,3) += -wallshear[2]/area;
C_UDMI(c0,t0,4) = (1.-sqrt(C_UDMI(c0,t0,1)*C_UDMI(c0,t0,1) + C_UDMI(c0,t0,2)*C_UDMI(c0,t0,2) + C_UDMI(c0,t0,3)*C_UDMI(c0,t0,3))/C_UDMI(c0,t0,0))/2;
}
end_f_loop(f,t)
}


In Fluent must be enabled Data Sampling for Time Statistics and defined CFFs = UDM(0),...(4) ? In this way unsteady statistics(such time averaged) results are available for the UDMs ?

[sara9310]

Originally Posted by AlexanderZ

go to contours
-> contours of
-> user -defined memory
-> select "OSI" (also it could be udm-4)

Hello Alexander
I try to calculate "osi" and i compiled this udf
After finished run, i go to contours and select OSI but any thing is showing!!
What's the problem??
Thank you

[AlexanderZ]

in case you could select OSI inside contours menu everything is OK.
may be you are using wrong settings for contours

if you still have problems, show your code, compilation log, whats fluent version you are using, explain how you are making contours

[sara9310]

Originally Posted by AlexanderZ

in case you could select OSI inside contours menu everything is OK.
may be you are using wrong settings for contours

if you still have problems, show your code, compilation log, whats fluent version you are using, explain how you are making contours

Code:/************************************************** ****
Oscillatory shear index
************************************************** ****/

#include "udf.h"
#include "math.h"
#include "storage.h"
#include "sg_udms.h"

#define domain_ID 1
#define zone_ID 7

/* Define Names for the WSS UDMI and its components */
DEFINE_EXECUTE_ON_LOADING(nameinit, libudf)
{
Set_User_Memory_Name(0, "uWSS");
Set_User_Memory_Name(1, "uWSSx");
Set_User_Memory_Name(2, "uWSSy");
Set_User_Memory_Name(3, "uWSSz");
Set_User_Memory_Name(4, "OSI");
}


/* Initialize the UDM value to zero in complete domain */
DEFINE_INIT(meminit,domain)
{
Thread *c_thread;
cell_t c;

thread_loop_c(c_thread,domain)
{
begin_c_loop(c, c_thread)
{
C_UDMI(c,c_thread,0)= 0;
C_UDMI(c,c_thread,1)= 0;
C_UDMI(c,c_thread,2)= 0;
C_UDMI(c,c_thread,3)= 0;
C_UDMI(c,c_thread,4)= 0;
}
end_c_loop(c, c_thread)
}
}

/* Calculate wall shear stress and store them in UDM */
DEFINE_EXECUTE_AT_END(OSI)
{
Domain *domain;
real area;
face_t f;
real A[ND_ND];
cell_t c, c0;
Thread *t,*t0, *c_thread;
real wallshear [ND_ND];

domain = Get_Domain(domain_ID);
t = Lookup_Thread(domain,zone_ID);

begin_f_loop(f, t)
{
F_AREA(A,f,t);
area = NV_MAG(A);
NV_V(wallshear,=,F_STORAGE_R_N3V(f,t, SV_WALL_SHEAR));
c0 = F_C0(f,t);
t0 = THREAD_T0(t);
C_UDMI(c0,t0,0) += NV_MAG(wallshear)/area;
C_UDMI(c0,t0,1) += -wallshear[0]/area;
C_UDMI(c0,t0,2) += -wallshear[1]/area;
C_UDMI(c0,t0,3) += -wallshear[2]/area;
C_UDMI(c0,t0,4) = (1.-sqrt(C_UDMI(c0,t0,1)*C_UDMI(c0,t0,1) + C_UDMI(c0,t0,2)*C_UDMI(c0,t0,2) + C_UDMI(c0,t0,3)*C_UDMI(c0,t0,3))/C_UDMI(c0,t0,0))/2;
}
end_f_loop(f,t)
}

I compiled udf with visual studio 2010
Fluent version: 19R3
I go to contours>>new contour
Location:wall body
Variable:OSI>>apply
But range of osi display is 0.0-0.0

[AlexanderZ]

code seems to be correct
did you hook functions in fluent GUI?
user-defined - > function hooks