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Thanks for your interest in Energy2D. The simulation depends also on the boundary. A flow that is stable in a small box may not be in a large box, vice versa. I will take a further look once I get some free time.July 12, 2019 at 11:54 am in reply to: Simulation of foam insulated hot water pipe system #273
I looked at your model and I don’t know what is wrong. Can you elaborate?
Many users have requested supporting a material library. Unfortunately, I have very limited time and I am maintaining this software in my spare time. It is not funded by anyone since about five years ago.
Hopefully it will continue to exist.June 7, 2019 at 4:26 pm in reply to: Convection and conduction in water – lake heat exchanger #264
I can reproduce your problems. Not sure if this is caused by a huge distortion of the grid cells (400 times larger in the horizontal direction than in the vertical direction). I will keep looking.
Expanding the grid size would cause the simulation to slow down by N^2. So this is currently locked. But I agree there should be such an option in the future.
That is right. Since the computational grid is 100×100, you can’t set the size of a component below 1/100th of the size of the window. If you could, it would be ignored by the engine.
PS: Don’t forget to set the time step to be small to be compatible with the micron scale. Otherwise you will get a fatal error.
This is done. See the attached image.
I am just back from running a workshop. I will find some time to change the lowest dimension allowed in the program. Thanks for your encouragement!
I will look into this. I didn’t expect users who would use this at micron scale.June 1, 2019 at 7:53 pm in reply to: Convection and conduction in water – lake heat exchanger #248
Sorry for the delay in responding. Can you annotate your model a bit so that I can understand what you are trying to accomplish?
I am also working on an app based on FLIR ONE (literally as I am replying your questions). So we have overlapping interest.
Of course you are correct, Stefano. This problem is related to the relatively large grid cells used by default in Energy2D (100×100). If we can reduce the size, the effect can be reduced, but I suspect we can’t get rid of it completely as this is the side effect of numerical simulation based on discretization. A numerical solution is always only an approximation.
You may notice that the leaking only happens at the interface. Although the medium has zero conductivity, in reality does it really prevent the layer from getting any energy through the contact? What would happen to the molecules of such a hypothetical (and non-existent) medium at that interface do when they are in contact with a heat source? The physicist part of me would say they would heat up no matter what. Otherwise, this would be an open violation of fundamental laws.
So this offers an “explanation” for the numerical problem if that comforts us.
- This reply was modified 2 months, 2 weeks ago by Charles Xie.
Good question. I confirmed this with your model.
Now, if the specific heat of the square is larger than or equal to that of the ambient, we can find out that the thermometer will read almost the same value or slightly smaller as initial.
The interesting thing happens whenever the specific heat of the ambient is larger than that of the square–the thermometer starts to register a lower value. But it eventually stops dropping further and settles at a certain temperature. The larger the specific heat of the ambient is, the lower the final temperature is. Which is exactly what you reported here.
The reason, I figured, is because of the boundary layer effect. When you have a layer that has a huge heat capacity next to the square, it will draw some energy from the square into it. The zero conductivity of the ambient stops the flow of energy through the ambient, but it doesn’t necessarily prevent the energy from getting into the contact layer.
I attached a screenshot of a revised model and the actual model file for your reference.
Hope this helps.April 13, 2019 at 12:43 am in reply to: How to to simulate an unheated cross-ventilated space? #228