# transient boundary condition(Transient profile)

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

 May 30, 2011, 11:58 transient boundary condition(Transient profile) #1 Senior Member   Govindaraju Join Date: Apr 2010 Posts: 206 Rep Power: 8 Dear friends I have questions on transient boundary condition "In some cases boundary conditions arise from measurements or mathematical functions". My questions are : 1. Is it possible to calculate the mean value of the measurements or mathematical function at the inlet and middle of the fluid model? 2. If the inlet is transient ( example: pressure) , How to set up the outlet condition? (example : Mass flow rate). Will the outlet boundary condition (Mass flow rate) be a function or Number? Thank you Regards Govind

 May 30, 2011, 20:20 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,958 Rep Power: 85 Q1: Yes, this is possible Q2: You set the boundary conditions to match what you are modelling.

May 30, 2011, 22:29
transient analysis
#3
Senior Member

Govindaraju
Join Date: Apr 2010
Posts: 206
Rep Power: 8
Quote:
 Originally Posted by ghorrocks Q1: Yes, this is possible Q2: You set the boundary conditions to match what you are modelling.
Dear friend

Can you please explain how to calculate the average value (example: Pressure) at the inlet or middle of the fluid model.

2. For example, I set step pulse pressure at the inlet and I set a function at the outlet ( example sinusoidal Mass flow rate or sinusoidal velocity) , How will this match?

Thanks you

Regards

Govind

 May 31, 2011, 08:23 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,958 Rep Power: 85 Use a CEL expression like areaAve(p)@inlet. What do you mean by match? As it converges it will reduce the imbalances. If incompressible that means flow in equals flow out, regardless or pressure or flow rate.

June 2, 2011, 21:41
transient analysis
#5
Senior Member

Govindaraju
Join Date: Apr 2010
Posts: 206
Rep Power: 8
Quote:
 Originally Posted by ghorrocks Use a CEL expression like areaAve(p)@inlet. What do you mean by match? As it converges it will reduce the imbalances. If incompressible that means flow in equals flow out, regardless or pressure or flow rate.
Dear friend
My fluid flow is pulsatile flow. mean flow rate is 50ml/min. Density is 1040 kg/m^3 . The mass flow rate = density*flow rate. How do I give this pulsatile mass flow rate value at the outlet.

Thank you

Regards
Govind

 June 2, 2011, 23:17 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,958 Rep Power: 85 Use a CEL expression like if or step, or a 1D interpolation function. Then use the function/expression in the boundary condition.

June 3, 2011, 00:22
transient analysis
#7
Senior Member

Govindaraju
Join Date: Apr 2010
Posts: 206
Rep Power: 8
Quote:
 Originally Posted by ghorrocks Use a CEL expression like if or step, or a 1D interpolation function. Then use the function/expression in the boundary condition.
Dear friend

How do I know the flow rate expression/function at the outlet?. I know average flow rate is 50ml/min

Thank you
Govind

 June 3, 2011, 07:10 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,958 Rep Power: 85 Is this an external input, that is you specify the flow rate; or is this an output of the simulation?

 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 Arianna FLUENT 27 August 9, 2015 14:56 bk CD-adapco 0 August 4, 2005 01:48 michele OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 2 July 15, 2005 04:15 James Date CFX 5 September 13, 2004 11:34 Tudor Miron CFX 15 April 2, 2004 06:18

All times are GMT -4. The time now is 03:07.