CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

Importance of Hydraulic Diameter Value for Compressible Flow

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

LinkBack Thread Tools Search this Thread Display Modes
Old   August 6, 2009, 10:58
Question Importance of Hydraulic Diameter Value for Compressible Flow
New Member
Join Date: Jul 2009
Location: Windsor
Posts: 9
Rep Power: 16
RyGuy is on a distinguished road
Hello All,

I am simulating a single phase supersonic gas flow in a convergent-divergent de-Laval type nozzle.

I am using the density based implicit formulation (2D, steady state), along with the standard k-epsilon viscous model. I have defined the ideal gas law for compressible flow in the Density field for the Gas (in the materials panel) along with the Sutherland viscosity law. I defined the operating pressure to be atmospheric. As well, I have enabled the Intensity & Hydraulic Diameter option in the drop down menu for the boundary conditions (due to the internal flow of my simulation)

Boundary Conditions are as follows:
Main Inlet - pressure of 6.15 atm and temperature of 500 K, intensity ratio of 3% and the default hydraulic diameter of 1m.
Outlet - atmospheric gauge pressure and 300 K, intensity ratio of 3% and the default hydraulic diameter of 1m.
Walls - enabled specified shear and temperature.

My Problem:
When I use the default values for the hydraulic diameter I am able to get my solution to converge without a problem and the results seem reasonable (nothing unphysical). But, I would think that since there is an equation defined for the hydraulic diameter I should actually put in the exact value (for precision of results). So when I use the actual hydraulic diameter values and try to get the simulation to converge, it does not.

Therefore, I propose the following questions:

1 - What is the significance of the hydraulic diameter?
2 - How will this value affect my simulation? (Whether it be default or the actual value)
3 - Should I use the actual values defined by the equation instead of the default value?

If anyone can help me with this topic it would be greatly appreciated...

RyGuy is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
flow over a cylinder urgent! kevin FLUENT 8 August 11, 2015 13:00
Hydraulic diameter for external flow. pah FLUENT 0 July 20, 2005 04:27
Hydraulic Diameter Chris FLUENT 0 June 24, 2005 18:22
Question on 3D potential flow Adrin Gharakhani Main CFD Forum 13 June 21, 1999 05:18
computation about flow around a yawed cone Tylor Xie Main CFD Forum 0 June 9, 1999 07:33

All times are GMT -4. The time now is 04:08.