# "Volume Flow Rate" Boundary Condition

 Register Blogs Members List Search Today's Posts Mark Forums Read

September 16, 2013, 15:48
"Volume Flow Rate" Boundary Condition
#1
New Member

Marcus Fernandes Araujo Filho
Join Date: Sep 2013
Posts: 10
Rep Power: 3
Dear all,

I´m trying simulate the intake of a powerhouse of a Hydroeletric Power Dam. My simulation consists of having a part of the resevoir upstream and the intake itself. See attachment for a picture.

I´m trying to use, as upstream BC´s, the option Volume Flow Rate. I would like to understand better how does it work. I´ve done a simulation and the velocity entering the domain at the BC varies at each element. So my question is how does FLOW3D understands the value of discharge I´ve described? My first thought was that he would calculate the open area and put a constant velocity into the domain but it doesn´t seem that way.

I would like to take the opportunity and also ask if anyone think of a better BC for this kind of problem.

Marcus
Attached Images
 BC.JPG (89.4 KB, 51 views)

 September 26, 2013, 15:10 #2 Senior Member   Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 8 Marcus - you are correct that FLOW-3D calculates the open area and finds velocity from the flow rate. The velocity will be the same in all cells, except where the specified fluid elevation is lower than the actual fluid elevation: in this case fluid can leave the simulation. Also, in cells that contain solid boundary (like river bed), the velocity will be modified by the near-wall effect. If you are seeing different velocities in every cell, it means that the flow is interfering with the boundary condition, and the boundary condition should be moved farther away from the region of interest. spaudel and zhouyu3092070 like this.

 September 26, 2013, 15:23 #3 Senior Member   Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 8 Marcus - one other note: based on the image you sent, it appears you have two volumetric-flow-rate boundaries that are adjacent and 90 degrees from each other. They will interfere with the flow rate near the corner, unless you specify 45-degree flow rate vectors on the boundary condition dialog. See the User Manual for instructions on how FLOW-3D interprets the flow rate vectors. Also make sure that the free surface elevation (fluid "height") on the boundary conditions is the same for both flow rate boundaries. Ideally, you would like to have only one inflow boundary, but you can work with two. - Jeff

 October 10, 2013, 15:30 #4 New Member   Marcus Fernandes Araujo Filho Join Date: Sep 2013 Posts: 10 Rep Power: 3 Dear Jeff, Thank ou for your remarks. I´ve been able to sucessfully run the simulation now. I´ve change my BC`s to stagnation pressure at the reservoir and VFR at the outlet. It´s working perfectly. Thank you for your help. Marcus Flowdy likes this.

 October 17, 2013, 10:55 #5 Senior Member   Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 8 Awesome! Thanks for asking your question so clearly. - Jeff

 October 22, 2013, 08:01 #6 New Member   Marcus Fernandes Araujo Filho Join Date: Sep 2013 Posts: 10 Rep Power: 3 Thank you for the prompt reply! Marcus

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post ripperjack OpenFOAM Running, Solving & CFD 0 September 13, 2013 11:44 JinBiao OpenFOAM Running, Solving & CFD 0 July 28, 2012 03:56 therockyy FLOW-3D 0 May 23, 2011 14:19 Pankaj CFX 9 November 23, 2009 05:05 saii CFX 2 September 18, 2009 08:07

All times are GMT -4. The time now is 20:50.