[Shoh]

Hello. I would really appreciate it, if you can provide an answer.

In the domain, I have two faces obtained from 'mesh modify-zones slit-face-zone' at the same location.
I imposed a mass-flow-outlet boundary condition at one face (face 1) and a velocity-inlet boundary condition at the other surface (face 2).

Here, I would like to match the velocity profile of the face 2 with that of the face 1, using DEFINE_PROFILE. So, I wrote a code for the velocity profile of the face 2 as follows (ID of the face 1 is 4):

#include "udf.h"

DEFINE_PROFILE(sync,t,i)
{
Domain *d = Get_Domain(1);
face_t f;

int nid=4; /* ID of face 1 */
Thread *tf = Lookup_Thread(d,nid);

begin_f_loop(f,t)
{
F_PROFILE(f,t,i) = F_U(f,tf);
}
end_f_loop(f,t)
}

However, the velocity contours on two faces are different. How can I overcome this problem??

[AlexanderZ]

do you think that velocity along X direction is the only characteristic of flow? may be this is a problem

why do you use this approach with inlet and outlet on slit faces? you may use contact instead with coupled boundary condition

[Shoh]

Dear AlexanderZ,

Thank you for your kind reply.
But, I don't know how to apply a velocity or mass flow rate boundary condition at a contact interface (with coupled boundary condition) without slit-face-zone.

For example, if the mass flow rate through the contact face should be 1 kg/m3 or if the velocity at the face should be 1 m/s, then how can I impose these boundary conditions at the face???

I would really appreciate it, if you can provide an answer.

Best regards,

[AlexanderZ]

what's your case?

if you know the mass flow rate - it is boundary condition,
so why do you need the domain before that face?

if you are trying to transfer the flow from outlet to inlet - this is kind of interface (not external boundary) - which is different, cause you don't specify mass flow rate in that case, it comes from domain before

so what are you trying to model?

[Shoh]

Dear AlexanderZ,

I'm trying to model the flow induced by an axial flow fan which is located at the bottom of the domain (please see the attached image: https://ibb.co/S03CFch ).

In the image, the fan is represented by a red line and all other sides are treated as walls.

Since its mass flow rate is given (2.5 kg/s), the left side of the fan (red line in the figure) was modeled as a with mass-flow-outlet boundary condition. Here, I tried to impose a velocity-inlet boundary condition at the right side of the fan (red line in figure) with the same velocity profile as that at the left side.

Please let me know if there is another simple way to simulate the flow inside the domain.

[AlexanderZ]

https://www.youtube.com/watch?v=UXaeyCGE3nk

dont have experience on using that BC

[Shoh]

Many thanks for your kind reply.

As done in the movie, I used a fan boundary condition at the face. The results seems plausible, but I found that I should adjust pressure rise (dp) or an empirical formula between pressure rise and flow rate (http://jullio.pe.kr/fluent6.1/help/html/ug/node242.htm) to obtain a specific mass flow rate.

Do you know how to fix mass flow rate?

Best regards,

[AlexanderZ]

unfortunately, I have no experience