Applying natural convection Boundary condition in Acusolve and Polyhex mesh

Manotosh Baidya

1. How do I apply the initial thermal boundary condition in Acusolve? For example, if there is natural convection on a thermal plate with an initial temperature of 350K and it starts cooling with external air. I am interested to know how much time it will take to reach equilibrium. So how to apply thermal BC here. 

2. How do I create a polyhex mesh in Acusolve? 

 

acupro

1 - It seems you are referring to initial conditions, versus boundary conditions.  In HyperWorks CFD go to the Solution ribbon, then you'll see different options in the 'Initialize' section, where you can assign initial conditions by Part (a solid body volume), Surface, Zones (cylinder, box, sphere), etc.

2 - Not sure what you mean by polyhex.  AcuSolve does not support polyhedral elements.  There is also no benefit to running AcuSolve with a hex mesh - as tets, prisms/wedges, pyramids give excellent results.

acupro

1 - It seems you are referring to initial conditions, versus boundary conditions.  In HyperWorks CFD go to the Solution ribbon, then you'll see different options in the 'Initialize' section, where you can assign initial conditions by Part (a solid body volume), Surface, Zones (cylinder, box, sphere), etc.

2 - Not sure what you mean by polyhex.  AcuSolve does not support polyhedral elements.  There is also no benefit to running AcuSolve with a hex mesh - as tets, prisms/wedges, pyramids give excellent results.

Manotosh Baidya

Thanks for the quick reply.

Maybe I am not clear on the questions, let me clear: If we take a problem of air flow over a hot flat surface and want to give the initial temperature of the plate as 350K (for exp) at time=0. Now I want to study a transient simulation to check the temperature of the plate over time. This is a natural convection study. The temperature of the plate is likely to decrease over time. This is not a fix temp BC. Hope Its clear. I think its different with solver initialization. Hyperwork CFD is new to me, and I am working with a different solver. 

Advance thanks

acupro

Manotosh Baidya said:

Thanks for the quick reply.

Maybe I am not clear on the questions, let me clear: If we take a problem of air flow over a hot flat surface and want to give the initial temperature of the plate as 350K (for exp) at time=0. Now I want to study a transient simulation to check the temperature of the plate over time. This is a natural convection study. The temperature of the plate is likely to decrease over time. This is not a fix temp BC. Hope Its clear. I think its different with solver initialization. Hyperwork CFD is new to me, and I am working with a different solver. 

Advance thanks

You would still apply the initial condition for the starting temperature.  The default wall boundary condition would suffice - zero additional heat flux added - but no heat loss to the 'outside', either.  This would be an insulated wall condition.  You would see the temperature change in time.

Manotosh Baidya

Hello, thanks for the reply again. I would appreciate it very much if you have some time to reply on this too: On the above condition, if we apply the default boundary condition with zero flux and a given temperature, then it leads to an insulated plate as you suggested. But I need heat transfer above the hot surface. 

Let me clarify the problem statement again: I want to check the time to cool a steel ball with an initial starting temperature of 400 °C on a surface. The ball is being cooled by only natural convection. I just place the hot ball on a surface. 

My question is here, how do I apply the thermal boundary conditions for the above problem in HyperWorks cfd 2021.2 Acusolve. 

It's also good if you can share any tutorial video or slide or a team meeting if support can attend..

acupro

Manotosh Baidya said:

Hello, thanks for the reply again. I would appreciate it very much if you have some time to reply on this too: On the above condition, if we apply the default boundary condition with zero flux and a given temperature, then it leads to an insulated plate as you suggested. But I need heat transfer above the hot surface. 

Let me clarify the problem statement again: I want to check the time to cool a steel ball with an initial starting temperature of 400 °C on a surface. The ball is being cooled by only natural convection. I just place the hot ball on a surface. 

My question is here, how do I apply the thermal boundary conditions for the above problem in HyperWorks cfd 2021.2 Acusolve. 

It's also good if you can share any tutorial video or slide or a team meeting if support can attend..

It's still the same answer.  The zero heat flux condition means you're not adding any heat flux or removing any heat flux to/from the 'non-meshed' side of the surface.  You will still get temperature variation - as the 400 is the initial condition, not a boundary condition.  You'll still get heat transfer from/to the meshed fluid volume - just nothing to the other non-meshed/void space.  Maybe you could add an image of your geometry representation - showing where you have fluid volume(s), solid volume(s), etc.

You mentioned you're using a different solver.  Which solver are you using?

OR - Did you simply mean you're using AcuSolve for this, but you've used other solvers previously?