CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLOW-3D

Inlet fulid splashes

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 10, 2013, 02:17
Question Inlet fulid splashes
  #1
New Member
 
wusuhong
Join Date: Jan 2013
Location: Singapore
Posts: 8
Rep Power: 4
wusuhong is on a distinguished road
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!
wusuhong is offline   Reply With Quote

Old   April 10, 2013, 08:44
Default
  #2
New Member
 
Jing
Join Date: Dec 2011
Posts: 20
Rep Power: 5
Jing_min is on a distinguished road
Quote:
Originally Posted by wusuhong View Post
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.
Jing_min is offline   Reply With Quote

Old   April 10, 2013, 22:27
Default
  #3
New Member
 
wusuhong
Join Date: Jan 2013
Location: Singapore
Posts: 8
Rep Power: 4
wusuhong is on a distinguished road
Quote:
Originally Posted by Jing_min View Post
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?
wusuhong is offline   Reply With Quote

Old   April 23, 2013, 12:06
Default
  #4
Senior Member
 
Jeff Burnham
Join Date: Apr 2010
Posts: 204
Rep Power: 8
JBurnham is on a distinguished road
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.
JBurnham is offline   Reply With Quote

Old   April 24, 2013, 03:46
Default
  #5
New Member
 
wusuhong
Join Date: Jan 2013
Location: Singapore
Posts: 8
Rep Power: 4
wusuhong is on a distinguished road
Quote:
Originally Posted by JBurnham View Post
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.
thanks for your advice.
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.
wusuhong is offline   Reply With Quote

Reply

Thread Tools
Display Modes

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 Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Problem with assigned inlet velocity profile as a boundary condition Ozgur_ FLUENT 2 August 3, 2012 05:54
Velocity inlet boundary condition for porous medium Chander CFX 3 March 11, 2012 22:18
VOF Volume fraction in Velocity inlet aruelle FLUENT 1 March 18, 2010 12:53
Inlet Velocity in CFX aeroman CFX 12 August 6, 2009 18:42
Diffusion component at inlet Balaji FLUENT 2 August 8, 2005 07:37


All times are GMT -4. The time now is 03:17.