Yplus calculation for buoyant flow

rajeshinap · December 19, 2017, 09:51

Hello,
I have to refine mesh near wall in a natural convection case and the y plus should between 30 and 300. but in the buoyant case my internal fluid has initial conditions of velocity as (0 0 0).

How can I calculate y plus with zero velocity in the domain?

The flow should pass from hot wall to cold wall.

Thank you

flotus1 · December 19, 2017, 10:14

You could calculate y+ for u=0 (it will be 0) but you should not.
Y+ is only interesting for the final solution, not for the initial conditions.

FMDenaro · December 19, 2017, 11:29

You could use the characteristic bouyancy velocity, that one that gives you the Rayleigh number of your problem.

rajeshinap · December 19, 2017, 18:29

Thank you for the reply guys,

I was given a closed room geometry with an air-conditioner attached to one of the walls. and gave an outside temp to be 50degree Centigrades and coefficent of heat transfer is 0.5 W/(m^2 K) for walls.

asked to setup yplus between 30 and 300
and correct choice of turbulence model and its parameters.

Should I give any inlet velocity at AC vents and outlet pressures? or the air in the room has zero velocity without any inlet velocity.

I am new to simulating with energy equation included. Any references to read can be greatly helpful.

December 19, 2017, 09:51	Yplus calculation for buoyant flow	#1
rajeshinap New Member Rajesh Join Date: Jan 2016 Posts: 2 Rep Power: 0	Hello, I have to refine mesh near wall in a natural convection case and the y plus should between 30 and 300. but in the buoyant case my internal fluid has initial conditions of velocity as (0 0 0). How can I calculate y plus with zero velocity in the domain? The flow should pass from hot wall to cold wall. Thank you

December 19, 2017, 10:14		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,412 Rep Power: 49	You could calculate y+ for u=0 (it will be 0) but you should not. Y+ is only interesting for the final solution, not for the initial conditions. lcarasik likes this.

December 19, 2017, 11:29		#3
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,813 Rep Power: 73	You could use the characteristic bouyancy velocity, that one that gives you the Rayleigh number of your problem. lcarasik likes this.

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December 19, 2017, 18:29		#4
rajeshinap New Member Rajesh Join Date: Jan 2016 Posts: 2 Rep Power: 0	Thank you for the reply guys, I was given a closed room geometry with an air-conditioner attached to one of the walls. and gave an outside temp to be 50degree Centigrades and coefficent of heat transfer is 0.5 W/(m^2 K) for walls. asked to setup yplus between 30 and 300 and correct choice of turbulence model and its parameters. Should I give any inlet velocity at AC vents and outlet pressures? or the air in the room has zero velocity without any inlet velocity. I am new to simulating with energy equation included. Any references to read can be greatly helpful.