# Inlet fulid splashes

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

 April 10, 2013, 02:17 Inlet fulid splashes #1 New Member   wusuhong Join Date: Jan 2013 Location: Singapore Posts: 8 Rep Power: 5 I am doing open channel flow simulations, i have a rectangular channel inlet. I set the inlet boundary condition as shown on the pictureinlet boundary condition.jpg, it supposed to be a rectangular shape at the inlet, right? However the result is inlet 3D image.jpg, the fluid spalashed and the fluid level raised up. Is there anyone can teell me what is the problem and how to solve it. thanks very very much!

April 10, 2013, 08:44
#2
New Member

Jing
Join Date: Dec 2011
Posts: 20
Rep Power: 6
Quote:
 Originally Posted by wusuhong I am doing open channel flow simulations, i have a rectangular channel inlet. I set the inlet boundary condition as shown on the pictureAttachment 20597, it supposed to be a rectangular shape at the inlet, right? However the result is Attachment 20598, the fluid spalashed and the fluid level raised up. Is there anyone can teell me what is the problem and how to solve it. thanks very very much!
It seems the first picture shows the B.C. at inlet, the left side.
You should use Outflow B.C. at right B.C.

April 10, 2013, 22:27
#3
New Member

wusuhong
Join Date: Jan 2013
Location: Singapore
Posts: 8
Rep Power: 5
Quote:
 Originally Posted by Jing_min It seems the first picture shows the B.C. at inlet, the left side. You should use Outflow B.C. at right B.C.
Thanks for your advice, but my in my case, the flow is sub-critical, i can't use Outflow B.C at the right B.C.
And, do you think the outflow B.C would affect the behavior of inflow?

 April 23, 2013, 12:06 #4 Senior Member   Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 9 That looks like an instability. Make sure that the flat surface of the water profile does not exactly match a grid line. Change the grid so that the free surface is between grid lines: this is only necessary when the free surface is flat for long stretches, normally it can cross grid lines with no problem. Make your exit boundary pressure-type w/ fluid fraction = 1 and the tailwater elevation set as the free surface elevation (Cartesian z coordinates). Also make sure that gravity is in the correct vector: i.e., gz = -9.8. Sometimes people forget that and make gravity point upward. Good luck.

April 24, 2013, 03:46
#5
New Member

wusuhong
Join Date: Jan 2013
Location: Singapore
Posts: 8
Rep Power: 5
Quote:
 Originally Posted by JBurnham That looks like an instability. Make sure that the flat surface of the water profile does not exactly match a grid line. Change the grid so that the free surface is between grid lines: this is only necessary when the free surface is flat for long stretches, normally it can cross grid lines with no problem. Make your exit boundary pressure-type w/ fluid fraction = 1 and the tailwater elevation set as the free surface elevation (Cartesian z coordinates). Also make sure that gravity is in the correct vector: i.e., gz = -9.8. Sometimes people forget that and make gravity point upward. Good luck.
But i have done all as you just said, and the problem is like this, there must be something i didn't pay attention on. Do you have any other tips for me?

Thanks again.

 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 Ozgur_ FLUENT 5 August 25, 2015 04:58 Chander CFX 3 March 11, 2012 22:18 aruelle FLUENT 1 March 18, 2010 12:53 aeroman CFX 12 August 6, 2009 18:42 Balaji FLUENT 2 August 8, 2005 07:37

All times are GMT -4. The time now is 20:38.