CFD Online Logo CFD Online URL
Home > Forums > OpenFOAM Running, Solving & CFD

Difficulties with validation - laminar plate flow

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

LinkBack Thread Tools Display Modes
Old   March 25, 2015, 06:12
Default Difficulties with validation - laminar plate flow
New Member
Join Date: Jun 2011
Posts: 24
Rep Power: 6
subsemitonium is on a distinguished road

I'm trying to validate my calculations with a simple example from VDI Heat Atlas, please find the attached case. I want to make sure that I can produce reasonable results before going any further. Unfortunately I get about 30% error - and all measures to reduce it failed. This is why I'm asking for help now.

Theory: The case is a 1D plate in laminar flow. Theory from VDI Heat Atlas (2013) says:
Nusselt_x = 0,332*sqrt(Re_x)*Pr^(1/3)
with the local Reynolds Number Re_x = w * x /nu with x being the distance over the plate.
In my example, the fluid is water with Prandtl = 7, beta = 2e-4, nu = 1e-6, mu = 1e-3, rho = 1000, cp = 4185

When I run my case, htc is about 30% too high. The solver is buoyantBoussinesqSimpleFoam. Turbulent Prandtl Number is without influence (laminar flow), turbulence models are turned off. I changed many parameters, the only influence I could found is the laminar Prandtl number. To my best knowledge, the laminar Prandtl number in transportProperties is the same "normal" Prandtl number as in thermophysicalProperties - which is a fluid property. Reducing it to a value of 3.5 corrects my results but seems very wrong. On the other hand, I am wondering, why Prandtl number is double-defined.

Any help is very welcome! Thank you.

Edit: Sorry, case file was too large - deleted mesh files. Please execute blockMesh ...
Attached Files
File Type: gz case.tar.gz (3.2 KB, 2 views)
subsemitonium is offline   Reply With Quote

Old   March 26, 2015, 10:39
New Member
Join Date: Jun 2011
Posts: 24
Rep Power: 6
subsemitonium is on a distinguished road
Nobody interested?

I checked the wallHeatFlux utility by calculating snGrad(T) and using thermal conductivity of water as well as T_wall and T_inlet. I could approximately verify the values by the utility .. which are still about 30% too high compared to the VDI equations. Since I've checked everything else (even tried other solvers for the pressure field) I absolutely don't know ...

Any good ideas?
subsemitonium 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
laminar flow over a flat plate blasius comparison preetam69 FLUENT 0 September 23, 2013 21:33
i dont understand: grid validation - laminar flow Diegoesteban FLUENT 6 August 19, 2013 17:08
perforated plate, flow direction Benfa CFX 10 August 2, 2013 07:33
CFX Treatment of Laminar and Turbulent Flows Jade M CFX 6 January 26, 2013 11:11
compressible laminar flow over flat plate varunjain89 Main CFD Forum 17 March 25, 2010 00:51

All times are GMT -4. The time now is 20:00.