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Old   November 19, 2012, 11:59
Default Periodic B.C
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Quote:
Originally Posted by sbaffini View Post
In the custom field function above, the pressure is the one effectively solved for by Fluent; in this case it gives you p_in = p_out (at least for the straight pipe case).

If you performed a periodic computation by fixing the mass flow, then dp/dx is available in the periodic b.c. panel (it also has a direction, which you needed to fix... hopefully, along the pipe axis). So, to know the presure jump in your case you just need to compute dp/dx * L where L is the length of the pipe
Thanks Paolo, i get it now. Are you a workbench user? How do you in this case have this pressure gradient available in workbench for optimization studies?
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Old   November 19, 2012, 17:25
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Dear Kamu,

for several reasons i am not a Workbench user and i know nothing about the setting of the parameters for their external use in workbench. However, while in theory there should not be any difficulty in setting the pressure as a parameter, it happens that this variable is also very weird (it is an output for fixed mass flow rate cases, its monitoring is far from being straightforward, etc.)... so, there might be chances that it actually can't be used as parameter.
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Old   November 20, 2012, 01:48
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Quote:
Originally Posted by sbaffini View Post
Dear Kamu,

for several reasons i am not a Workbench user and i know nothing about the setting of the parameters for their external use in workbench. However, while in theory there should not be any difficulty in setting the pressure as a parameter, it happens that this variable is also very weird (it is an output for fixed mass flow rate cases, its monitoring is far from being straightforward, etc.)... so, there might be chances that it actually can't be used as parameter.
Dear Paolo,
Thanks alot, looks like i will have to get it manually from FLUENT. I have tried all possible post-processing options to see if there is anything that is related to it in vain. Otherwise thanks once again
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Old   November 6, 2016, 08:36
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Quote:
Originally Posted by prasanthnitt View Post
Hi All,

I have written a 2D Incompressible NS solver for solving a channel flow with periodic boundary conditions. I am using a fractional step method(Kim and Moin 1985 JCP). I have non dimensionalized the equations. The rey_no is set to 100.

Channel Dimensions:
2 units: in the stream-wise and in the normal direction
Time integration scheme:
AB-2

A constant pressure gradient of value -2.0/rey_no is specified.
Staggered grid.
Periodic bcn in the stream-wise direction:
u(ni,.)=u(1,.)
u(0,.)=u(ni-1,.)

V(ni+1,.)=v(1,.)
v(0,.)=v(ni,.)

p(ni+1,.)=p(1,.)
p(0,.)=p(ni,.)

u and v represent the horizontal velocity components.
p represents pressure.

Boundary conditions in the normal direction:
u(:,0)=-u(:,1) //No Slip
u(:,nj+1)=-u(:,nj) //No penetration

v(:,0)=0.0
v(:,nj)=0.0

dp/dn =0 at y=0 and y=2

Initial condition:
I have tried several:
u(:, j )=1.0
u(:,j)=parabola with centerline velocity=1

So, the analytical solution for this problem is a parabola with centerline velocity=1.
But in my case the centerline velocity is greater than 1. I don't know why this is happening.
Help of any kind would be appreciated. I would be more than happy to provide any extra information.

Cheers
Prasanth
Hi All,
I have written a 3D Incompressible NS solver for solving a rectangular duct flow with periodic boundary conditions along the direction of flow (x). In my case of staggered grid, pressure was set based on finite volume method, for ux velocity i used finite volume along y, z and finite difference along x. it works for coarse grids and I have fully developed flow in domain but as I generate smaller grid size, residual of u, v, w and continuity oscillates and did not converge. I changed the relaxation factors to small values of 0.001, bu it did not work. Please, someone can help me... What is wrong?
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Old   November 6, 2016, 09:02
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I suggest to open a new post and provide full details fo your problem...however, I really don't understand the reason for using FV and FD in the same code.
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