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Why Comsol can not give me the correct Nu number for the higher Rayleigh number ?
Posted 30 apr 2018, 11:24 GMT-4 Fluid & Heat, Computational Fluid Dynamics (CFD), Heat Transfer 0 Replies
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Hi Everyone ,
I am working on a 2D Mantle convection model in a square box with constant parameter , where the only value is, i am changing is Rayleigh number . When I put the value Ra=10^4 & 10^5 , Comsol give the 4/5 decimal coorect Nusselt number , but when i switched to 10^6 , it give me the 2 decimal correct Nusselt number , and when Ra=10^7 , it just go high than the benchmark value (Blankenbach et al.)
Physics: 1. creeping flow(p2+p1) & 2. heat transfer in fluids(quadratic)
Mesh : used extra fine mesh for the whole domain and at the boundary i apply (200*200) distribution.
Study: in my study , i use the 10^5 model's solution as initial value then changing the parameter gradually like (210^5 ,410^5....) , then finally get the Nu number , which should be for Ra=10^6 is 21.972465 , but Comsol gives 21.9744.......... and for Ra=10^7 Nu should be 45.62 , where as Comsol give Nu=45.68......
my question is if the model setup is right why for the higher value of Ra, comsol can not give the good results like they did give the nice result for the case of 10^4 & 10^5 ? Do i have to congure the solver configaration , if so how to do that ?
what i am missing ? i hope to hear from you.
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Hello Moti Blue
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