pressure load by air expansion in cube

Please login with a confirmed email address before reporting spam

Hello,

I'm new to COMSOL and I'm trying to make a model of cube filled with air. When the cube is heated, so does the air. But the volume of air is constant(=cube), the pressure of the air will increase with increasing temperature. I want to calculate the stress the cube receives due to the increased pressure. So I chose the physics of "Heat transfer in solids and fluids" and "Structure mechanics". I set the heat flux on the top surface of the cube, and set the boundary load on the inner surface of the cube in function(p=po*T/T0). Unfortunatley, it doesn't work but I wonder the way I chose is correct. And I want to ask you about another way to simulate my model.

Thanks


1 Reply Last Post 3 juil. 2024, 08:36 UTC−4
Jeff Hiller COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 10 hours ago 3 juil. 2024, 08:36 UTC−4
Updated: 9 hours ago 3 juil. 2024, 09:15 UTC−4

Hello Hyeontak,

If you want to capture how the air pressure is affected by the (presumably small) change in the volume occupied by the air due to the deformation of the cube, without including the space occupied by the air in your geometry, consider using the method based on Gauss's theorem (a.k.a. the divergence theorem), which is discussed in this Discussion Forum thread and this blog post.

If not, things are simpler. Your idea of applying a pressure on the internal boundaries of the cube is correct although I would remove the volume occupied by the air from the model and use a "Heat Transfer in Solids" physics interface. I would imagine that the temperature of the air can be considered uniform within the cavity and equal to the temperature of the inner walls of the container, so I would use that temperature in the formula for the pressure on the inner walls.

Other than that, make sure that you have sufficient constraints to remove all 6 rigid body motions, and you should be all set.

Best,

Jeff

-------------------
Jeff Hiller
Hello Hyeontak, If you want to capture how the air pressure is affected by the (presumably small) change in the volume occupied by the air due to the deformation of the cube, without including the space occupied by the air in your geometry, consider using the method based on Gauss's theorem (a.k.a. the divergence theorem), which is discussed in [this Discussion Forum thread](https://www.comsol.com/forum/thread/317481/how-to-calculate-the-volume-of-a-hole-inside-an-axisymmetric-2d-domain?last=2023-01-25T14:54:09Z) and [this blog post](https://www.comsol.com/blogs/computing-controlling-volume-cavity). If not, things are simpler. Your idea of applying a pressure on the internal boundaries of the cube is correct although I would remove the volume occupied by the air from the model and use a "Heat Transfer in Solids" physics interface. I would imagine that the temperature of the air can be considered uniform within the cavity and equal to the temperature of the inner walls of the container, so I would use that temperature in the formula for the pressure on the inner walls. Other than that, make sure that you have sufficient constraints to remove all 6 rigid body motions, and you should be all set. Best, Jeff

Reply

Please read the discussion forum rules before posting.

Please log in to post a reply.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.