Determining Pressure Drop via Reynolds Number

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 February 15, 2001, 11:14 Determining Pressure Drop via Reynolds Number #1 Bob Haase Guest   Posts: n/a Hi, I have just run a pressure loss simulation in CFD2000 for a very long duct. Now I want to validate my solution with an experiment. I have a blower to generate the volume flow, however, I don't have the means to heat the air to match the conditions in my simulation. The temperature of the air in my simulation was 773K. The temperature of the air for my experiment is more like 300K. Here is my question. Can I use the Reynolds Number from my simullation to determine the air volume flow for the experiment? If I do this, can I expect that the measured pressure loss in the experiment will match the pressure loss under the same Reynolds Number flow at a higher temperature? thanks, Bob

 February 15, 2001, 14:20 Re: Determining Pressure Drop via Reynolds Number #2 John C. Chien Guest   Posts: n/a (1). The viscous loss in a pipe is a function of the Reynolds number. (2). You can vary the temperature, the diameter, the velocity (or the mass flow rate), as long as the Reynolds number remains the same.

 February 16, 2001, 10:57 Re: Determining Pressure Drop via Reynolds Number #3 Bob Haase Guest   Posts: n/a O.K., so what if one of the flows is highly compressible? The high temperature flow has a Mach Number of 0.6, and the low temperature flow has a Mach Number of 0.2. Does the compressiblility contribute to the pressure loss in the duct? thanks, Bob

 February 16, 2001, 12:51 Re: Determining Pressure Drop via Reynolds Number #4 sylvain Guest   Posts: n/a In that case, you should have to respect the Mach numbers also, to get the right compressible behavior. This comes from the application of the Pi-theorem (or Bughingham-theorem).

 February 16, 2001, 14:21 Re: Determining Pressure Drop via Reynolds Number #5 John C. Chien Guest   Posts: n/a (1). The loss comes from the skin friction. And the skin friction coefficient is a function of Mach number. (2). You need to take a look at the book "Boundary Layer Theory", by Schlichting. It has a chapter on skin friction drag of a flat plate at sero incidence, which includes charts and formula to estimate the skin friction coefficient for compressible flows as a function of Mach number. (3). In your Mach number range, the effect is about 5% smaller based on the incompressible value. The higher the Mach number, the lower the skin friction coefficient. (3). You must try to get the book, it has all the information you need.(it is a popular standard reference book)

 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 bigfans FLUENT 7 November 8, 2016 12:28 blackemperor FLUENT 2 March 6, 2016 04:40 Diana FLUENT 5 December 13, 2007 10:33 Dongying Qian FLUENT 4 January 2, 2004 15:38 Dan Moskal Main CFD Forum 0 October 24, 2002 22:02

All times are GMT -4. The time now is 12:05.

 Contact Us - CFD Online - Top