|
[Sponsors] |
May 20, 2012, 23:34 |
set the outflow curve at downstream
|
#1 |
Member
Yi-Lang Chen
Join Date: May 2009
Posts: 58
Rep Power: 16 |
Dear experts:
When I set the outflow curve(B.C. use volume flow rate) at downstream. Then water flow toward upstream. That is not right. It Should toward downstream by gravity. How did I set Boundary condition if I want to set the outflow curve at downstream. Thanks your help!! |
|
May 21, 2012, 10:34 |
|
#2 |
Senior Member
Jeff Burnham
Join Date: Apr 2010
Posts: 204
Rep Power: 17 |
Set the velocity component to a positive or negative vector that points out of the domain. By default, the volumetric-flow boundary vector points into the domain, normal to the boundary, and you have to specify it if you want a different direction. Note that a downstream Vfr boundary will only remove the fluid which is in contact with the boundary. If dry spots appear, the flow rate will oscillate. Why not use a Vfr upstream instead?
|
|
May 21, 2012, 21:09 |
|
#3 |
Member
Yi-Lang Chen
Join Date: May 2009
Posts: 58
Rep Power: 16 |
First of all, thanks your reply, JBurnham.
I simulated the reservoir case. It should be controlled by gate at downstream. But I don't know how did use gate in FLOW-3D. So, our team consider that will set outflow curve(volume flow rate of B.C.) at downstream to solve the problem. Do you have any suggest can provide our team? Thanks!! |
|
May 24, 2012, 22:05 |
|
#4 | |
Senior Member
michael barkhudarov
Join Date: Mar 2009
Location: Sante Fe, New Mexico, USA
Posts: 336
Rep Power: 18 |
Quote:
|
||
May 25, 2012, 10:19 |
|
#5 |
Member
Yi-Lang Chen
Join Date: May 2009
Posts: 58
Rep Power: 16 |
Yes, I already solved about flow direction vector problem. I just reply that Jeff said "the flow rate will oscillate. Why not use a Vfr upstream instead?". I simulated the resvoir and it was controlled by gate at downstream(I set Vfr at upstream). So, our team consider that could set Vfr at downstream. Maybe it can solve about "the resvoir was controlled by gate" problem. That was I do why I set Vfr at downstream
|
|
May 25, 2012, 11:21 |
|
#6 |
Senior Member
Jeff Burnham
Join Date: Apr 2010
Posts: 204
Rep Power: 17 |
I assume that 'the reservoir is controlled by a downstream gate' means that there is gravity-fed overflow through (over or under) a gate, and that the flow is critical (Fr = 1) somewhere on the gate. Is the gate inside of the domain? If it's not, then you might as well use Vfr at the downstream boundary. If the gate is in the domain, however, you will want to let the flow go over the gate under the control of gravity, and be solved by the Navier-Stokes equations. In that case, it would be over-specifying the problem to define a flowrate at the downstream boundary. If I'm correct in my assumption (that Fr = 1 at the gate) then the downstream boundary will not have an effect on the reservoir level itself (no information propagates upstream from the critical transition point, and you could use an Outflow-type boundary downstream instead). You can use the Vfr boundary downstream - it will remove fluid at the rate you specify. I was just suggesting that you think carefully about whether that's a physical representation of the problem or not.
|
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Installation problems | indy | OpenFOAM Installation | 7 | April 3, 2009 09:40 |
Propeller Fan Curve Simulation | Teng_YJ | FLUENT | 2 | February 16, 2009 19:37 |
Problem installing on 64bit with ver13 | jonititan | OpenFOAM Installation | 0 | April 28, 2006 05:45 |
Problems with installation | jonititan | OpenFOAM Installation | 4 | November 6, 2005 04:16 |
CFX4.3 -build analysis form | Chie Min | CFX | 5 | July 12, 2001 23:19 |