Neglecting viscous dissipation in the model equations, is done when large velocity gradients exist. [BSL, 2003]
In what conditions can one neglect viscous dissipation while modelling a system, if the flow is laminar, the working fluid is gas and when it is a liquid.
Is there a threshold value of velocity gradient for which viscous dissipation is neglected, irrespective of flow regime and type of fluid used.
Cody Jones
Kindly go through the query carefully.
I am asking about including/excluding the viscous dissipation term in model equations.
Right but once some thing is viscous it is always. Your only loosing impurities or vapors due to heat so removing the pressure and apply a vacuum you reduce molecular heat produced between the molecules right? If you had the answer would you ask a question? And if it was clearly defined then research but from a outside view that’s my opToon for lab trials but you must do just published articles and theories now because lab and theory makes for solid work.
Is the flow steady or unsteady?
Is it uni-directional as a flow in a pipe?
If the flow is uni-directional, steady and laminar, you have only heat conduction and viscous dissipation terms within the energy equation.
The condition for the dissipation to be negligible relative to the conduction is usually expressed by a Brinkman number much smaller than 1, Br=mu*u^2/kappa*T
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