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January 23, 2012, 04:00 
Experimental results do not match with simulation results

#1 
Member
Robin Gilbert
Join Date: Jan 2010
Posts: 66
Rep Power: 9 
Hello everyone,
I work on CFD simulations of data centers using OpenFoam. I am trying to validate the simulations with experimental data. I use transientSimpleFoam solver for my simulations. I place a sensor at the inlet of the cooling unit to see how the temperature varies over time. I perform the simulations using the same conditions but my results are way off. Although the steady state temperatures match, the path followed by simulations are not accurate. I am attaching the results below. The blue line is the experimental result while the red one is simulation result. Please give you suggestions to improve my simulation. 

January 23, 2012, 12:24 

#2  
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 3,998
Rep Power: 42 
Quote:
About the solver: which OFversion are you using? Because the transientSimpleFoam that I found is quite old and doesn't solve the temperature equation (it's incompressible) 

January 23, 2012, 13:09 

#3 
Member
Robin Gilbert
Join Date: Jan 2010
Posts: 66
Rep Power: 9 
Hello Bernhard Gschaider,
Sorry about not giving much details... so here goes... What I am trying to solve for is a data center room with so many servers in it and one cooling unit. The air flow through the servers and the cooling unit are constant and I modified the solver based on channelFoam to fix the flow rate (it works because I tested it with swak4Foam application thanks to you!!). Now the heat added by the servers is modeled as a source term in the temperature equation. Here is the temperature equation that I solve. I added this to the transientSimpleFoam solver. I am using OF version 1.6.x. Code:
fvScalarMatrix TEqn ( fvm::ddt(T) + fvm::div(phi, T)  fvm::laplacian(DT, T) == Q/(rho0*Cp0) ); TEqn.solve(); Code:
T[cellI]= (0.21739*T[labelOfClosestCell]+225.739); Thank you so much Last edited by robingilbert; January 23, 2012 at 17:15. 

January 23, 2012, 18:15 

#4  
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 3,998
Rep Power: 42 
Quote:
Anyway. One more thing that comes to mind: have you checked the VALUE of DT (because you probably wil have "dived" rho*cp out of that too). 

January 23, 2012, 18:39 

#5 
Member
Robin Gilbert
Join Date: Jan 2010
Posts: 66
Rep Power: 9 

Tags 
openfoam. data center, validation 
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