Boundary conditions

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

 December 15, 2007, 11:02 Boundary conditions #1 Rashmi Guest   Posts: n/a Hi Iam doing simulations for stationary fluid inside a closed cylinder. its left wall is hot at 310K and right at 285K and the curved wall is adaibatic. I want to measure the thermal conductivity of the fluid inside. what boundary conditions i should apply for this. there is only temperature flow. thank U Rashmi

 December 15, 2007, 12:55 Re: Boundary conditions #2 Ramesh.K Guest   Posts: n/a Hi, specify left wall and right wall separately next, the curved surface is also specify as wall in fluent, you can specify the left wall at 310k and right wall at 285k. Imagining this to be a horizontal cylinder where u can visualize the things try it, it may work bye

 December 15, 2007, 12:59 Re: Boundary conditions #3 Ramesh.K Guest   Posts: n/a HI In the materilas panal, you take density to vary with temperature you may take density variation to be of boussinesq's approximation do this with the above said conditions bye

 December 15, 2007, 13:36 Re: Boundary conditions #4 Vijay Guest   Posts: n/a Hi Rashma, In ur presprocessor(gambit) select left surface and give one name, and do the same for rest right hand and curved surface and go to fluent, select left wall give the value and do the same for right and curved walls. With Regards, Vijay

 December 16, 2007, 07:59 Re: Boundary conditions #5 Rashmi Guest   Posts: n/a Hi Ramesh yes i did exactly the same..Iam uisng UDF for density, viscosity of fluid and mixture viscosity, specific heat and thermal conductivity. when i spcify left wall at 310K and right at 285k and curved wall at 0k my results converge in just two iterations at 1e-6.and whn i try to plot the UDM values all gives me zero..pls chk my UDF for viscosity.my udf dosent read the value of T frm fluent. DEFINE_PROPERTY(vis_eff,c,t) { real vis_ref,vis_f,vis_eff,Tref,T,phi_p; Tref = 293; T = C_T(c,t); vis_ref = 0.001788; phi_p = 0.01; vis_f = vis_ref*((exp(-1.704-5.306(Tref/T)+7.003(pow(Tref/T),2))); vis_eff = ((1+(2.5*phi_p)*vis_f); C_UDMI(c,t,8) = vis_eff; return vis_eff; } Ia following the paper my Ramesh K Agarwal for numerical simultion of natural convection heat transfer in nanofluids

 December 17, 2007, 07:18 Re: Boundary conditions #6 sushii Guest   Posts: n/a Yeah vijay have suggested right thing...! you hv to give different names to these three walls..! n wen you go to fluent you can set the temp for walls or you can set it to adiabatic ..!

 December 18, 2007, 02:46 Re: Boundary conditions #7 Rashmi Guest   Posts: n/a ok thanks vijay and sushil how do i set adaibatic wall? by setting temp =0 right. but when i try to iterate it gives me floating point error: invalid number

 December 18, 2007, 06:34 Re: Boundary conditions #8 Ramesh. K Guest   Posts: n/a Hi, Temp cant be zero, U should make Heat flux to be zero I suppose, for that boundary condition of curved wall. Just check it.

 December 18, 2007, 08:50 Re: Boundary conditions #9 Rashmi Guest   Posts: n/a Thx Ramesh I did that...I was getting floating point error because I entered temp as zero for curved surface. But my simulations get converged in just 4 iterations to 1e-6...i dont think so it is correct...any more suggestions..?? Rashmi

 December 19, 2007, 00:12 Re: Boundary conditions #10 Vijay Guest   Posts: n/a Hi Friend, In wall B.C panel enter the value of heat flux as zero for adiabatic condition......... With regards, Vijay

 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 Anindya Main CFD Forum 25 February 27, 2016 13:58 lost.identity CFX 41 May 22, 2013 07:21 NickolasPl OpenFOAM Programming & Development 2 May 19, 2011 05:37 vaina74 Open Source Meshers: Gmsh, Netgen, CGNS, ... 2 May 27, 2010 09:38 michele OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 2 July 15, 2005 04:15

All times are GMT -4. The time now is 23:12.