# Forced convection and active temperature?

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

 July 19, 2023, 06:41 Forced convection and active temperature? #1 New Member   Join Date: May 2022 Posts: 18 Rep Power: 3 Hi all, Is the use of the temperature as an active scalar relevant when performing a forced convection RANS or LES computation (Ri<0.01), Ri being the Richardson number? If yes, could you explain me why, since forced convection is defined as a state where the fluid motion is not controled by the temperature variations of the fluid? Thanks for your answer

 July 19, 2023, 08:33 #2 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,677 Rep Power: 66 You still need to solve a temperature equation if you want to know what is the temperature field looking like or if you want to know what is the heat transfer rate. The energy (i.e. temperature) transport equation has an advection term that is a div(U*T), UT is nonlinear. Forced convection means U is more related to dP than dT, it doesn't mean U is constant or that T is constant.

 July 19, 2023, 10:32 #3 New Member   Join Date: May 2022 Posts: 18 Rep Power: 3 Thanks for your answer, but I do not see in what it answers my question. Maybe it is because I misunderstood something. Could you confirm or correct the following points: * Temperature equation is solved in both active and passive temperature. * passive temperature -> no buoyancy effect -> density is constant -> no effect on the dynamic of the flow * active temperature -> buoyancy effect -> density depends on the temperature -> dynamic of the flow is altered So in forced convection, the buoyancy effects being negligible, why active temperature should be considered?

 July 19, 2023, 14:07 #4 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,677 Rep Power: 66 Because p=rho*R*T for an ideal gas means that the temperature change, affects the density, affects the flow. And the flow obviously affects the energy transport equation. Temperature also affects other transport properties like thermal conductivity, viscosity, etc. Passive temperature can only be used in forced convection for the limiting case with all constant properties (constant density, constant conductivity, constant viscosity, constant everything).

 Tags forced convection, temperature