CFD Online Logo CFD Online URL
Home > Forums > CFX

Large error in Pressure Drop in pipe

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

LinkBack Thread Tools Display Modes
Old   July 3, 2013, 17:39
Default Large error in Pressure Drop in pipe
New Member
AJ Hunter
Join Date: Feb 2013
Posts: 29
Rep Power: 6
ajhunte is on a distinguished road
I have a single pipe with a triangular input and output:

Picture of the geometry (basically a pipe filled with water shaped like a triangle)

When i do a hand calculation based on the width and height of the flow path and the velocity at the inlet, I get about 10 psi pressure drop that I should be getting from inlet to outlet. When I run Ansys, I get approximately 20 psi.

I have made sure that I have an inflation for the boundary layer, I have made the mesh ridiculously fine, and that I run it to 1e-5 convergence criteria. I have also confirmed with my professor that I should be getting around 10 psi (meaning that I did not make a math error when doing the hand calculation).

Any ideas why this is occurring?
ajhunte is offline   Reply With Quote

Old   July 3, 2013, 19:14
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,808
Rep Power: 107
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
What is the hand calculation based on? Is the hand calculation based on fully developed flow? Did you model fully developed flow in CFX? If you just modelled a constant velocity across the entire inlet the flow would develop in the simulation and have a much higher pressure drop - his could explain your error.

The mesh you show is horribly coarse. I trust that is not the mesh you used.

Is the triangle cut out of the cylinder (ie the flow is a cylinder pipe with a triangle in the middle ) or does the flow go through the triangle bit?

Also, have you looked at the FAQ:
ghorrocks is offline   Reply With Quote


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
Pressure drop in a pipe mark FLUENT 7 April 1, 2016 12:51
a problem in calculating pressure drop in Fluent? yu chun FLUENT 1 May 18, 2004 03:40
Terrible Mistake In Fluid Dynamics History Abhi Main CFD Forum 12 July 8, 2002 09:11
what the result is negatif pressure at inlet chong chee nan FLUENT 0 December 29, 2001 06:13
Hydrostatic pressure in 2-phase flow modeling (long) DS & HB Main CFD Forum 0 January 8, 2000 16:00

All times are GMT -4. The time now is 01:25.