# Importance of Hydraulic Diameter Value for Compressible Flow

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

 August 6, 2009, 10:58 Importance of Hydraulic Diameter Value for Compressible Flow #1 New Member   Ryan Join Date: Jul 2009 Location: Windsor Posts: 9 Rep Power: 10 Sponsored Links 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... Thanks, Ryan

 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 kevin FLUENT 8 August 11, 2015 13:00 pah FLUENT 0 July 20, 2005 04:27 Chris FLUENT 0 June 24, 2005 18:22 Adrin Gharakhani Main CFD Forum 13 June 21, 1999 05:18 Tylor Xie Main CFD Forum 0 June 9, 1999 07:33