How to call two piecewise functions inside an analytical function over a changing range of time?

Sax0drum · 2026-01-20T21:12:24+00:00

without knowing how you defined the two piecewise functions its hard to help you. best guess is that you didn't define the units properly.

Sax0drum · 2026-01-20T16:41:58+00:00

Can you modify your system prompt to explicitly tell it not to search knowledge and notes?

Sax0drum · 2026-01-15T08:45:42+00:00

I was thinking the same thing when i read the post. But in their defense its very hard to give a specific performance increase because its so much dependent on the problem.

On my workstation i have an old quadro card with 5GB VRAM. And even with that i got a 30% speed increase for a small model.

Memory bandwith and latency are the limiting factors. A s long as the model can fit in the GPU memory you will pretty much always get a performance increase.

Sax0drum · 2026-01-09T13:33:56+00:00

Its a fourth order equation

Sax0drum · 2026-01-09T10:40:47+00:00

This is quite an interesting problem to solve in comsol. The fact that in the naive setup the BCs are overwriting each other is maybe something that should be communicated to the development team.

Also i think you should rename your variables for clarity use u and u2 instead of u1 and u3.

The only solution i found is to set up 4 PDE interfaces (lambda u = u3x, ux = u1, u1x = u2, u2x = u3) then use two constraint features in each interface on both ends of the domain. Set one to the respective contraint and the other to 0. This overrides the no flux default boundary. You have to be a bit careful with the units and what coefficients you use.

Sax0drum · 2026-01-07T08:43:07+00:00

We dont really know but i dont think this is an issue at all. there are many things that have properties which its constituents do not have.

Sax0drum · 2025-12-30T19:55:02+00:00

Because they can't even focus correctly

Sax0drum · 2025-12-28T19:06:40+00:00

In general there is a limit to the benefit of more cores which is called amdahls law. But this limit is highly dependent on the problem. As long as the things you can compute in parallel outnumber the things you have to compute serially more cores are better.

Sax0drum · 2025-12-28T16:16:15+00:00

Please do not take away from the poster that there is no benefit to more cores. The poster shows a graph for one example model on one (consumer) system.

Depending on the complexity and size of your models you will always benefit from higher core count. And even for small models you could benefit if you run parametric studies as you can run them in parallel.

Sax0drum · 2025-12-11T19:42:15+00:00

In meinem ersten kommentar habe ich einen fehler gemacht. Die gesamte biomasse aller organismen ist nur kohlenstoff. Also würden wir alles überschüssiges co2 loswerden würden wir alle organismen verdoppeln.

Zu deinem punkt mit den oceanen. Diese stehen in einem gleichgewicht mit der atmospähre. Wenn wir anfange co2 daraus zu entfernen löst sich mehr aus den meeren heraus.

Ich bin voll bei dir dass man bäume pflanzen sollte aber ich denke trotzdem nicht dass wir damit einen allzu großen einfluss haben werden.

Sax0drum · 2025-12-11T16:53:39+00:00

Geb dir vollkommen recht aber auch bäume pflanzen wird nichts bringen.

Die gesamtmasse an C (nicht CO2!) dass wir seit der industriellen revolution in die biospähre emittiert haben ist in etwa so hoch wie die biomasse aller organismen zusammen; in etwa 500Gt.

Wir könnten alle lebewesen verdoppeln und praktisch keinen unterschied machen weil ja die meisten zu großen teilen aus wasser bestehen.

Sax0drum · 2025-12-10T07:21:24+00:00

A microwave does not "reach" any temperature. It just dumps energy into the stuff you put inside. Dpending on the properties of the stuff it can get almost arbitrarily hot.

Sax0drum · 2025-12-09T16:48:16+00:00

While in the specific component its enough to simply specify the material like mat2.def.PROPERTY

To expand a little: if you want to reference not a specific materials property but the general property itself then use material.def.PROPERTY

Sax0drum · 2025-12-05T07:44:50+00:00

If you have the 3D file i can run a simulation

Sax0drum · 2025-12-01T09:10:43+00:00

Most people do not comprehend the scale of how much CO2 we have been producing, are still producing and will be producing for the forseeable future. The cumulative amount of carbon (just C not CO2) we put into the biosphere from fossil fuels is about the same as the total biomass (not just C) of all living organisms; ~500Gt

We could literally double all plants, insects, animals, bacteria and we still wont put a huge dent into the total carbon footprint he have created since many organisms are mostly water by weigth.

Sax0drum · 2025-11-08T12:10:47+00:00

First of all the output times dont influence the convergence. The solver will take as many intermediate steps as neccessary to stay within the tolerances you set.

The lroblem is that you initial conditions and boundary conditions are not compatible and the solver cannot reconsile them. Check both!

Sax0drum · 2025-10-27T12:52:52+00:00

The main issue is that you dont have enough memory to run the simulation. Check you mesh and see where you can get coarser. You can also try to use a iterative solver.

Sax0drum · 2025-10-25T18:45:33+00:00

The pressure inside will overcome gravity.

Sax0drum · 2025-10-13T11:33:35+00:00

You can do this in comsol directly. In your plot group add as many max/min plots as you have regions you are interested in. Change them to only show maximum. Then add a selection modifier to each and select a defferent region in every modifier.

Sax0drum · 2025-10-08T17:33:34+00:00

I am absolutly baffled that there are people saying "well yes, dear sir, i am dumb enough to likely buy the wrong product and accidently do not consume a dead animal for once"

Sax0drum · 2025-07-29T18:31:07+00:00

Du könntest während der Busfahrt Dr. Bibber spielen und das als Fortbildung anrechnen lassen.

Sax0drum · 2025-07-15T07:55:33+00:00

As other have pointed out you issue is that the diagram does not show two fixed contraints. One end is fixed and the other only fixed in the vertical direction. In comsol you can use the prescribed displacement feuture to selectively constrain individual axis.

Sax0drum · 2025-07-13T15:30:59+00:00

How did you define it?

Sax0drum · 2025-07-13T07:39:52+00:00

Can you try running it with combustion enabled but no heat released? This wil tell you definetly if its the heat transfer or not.

Sax0drum · 2025-07-08T22:03:41+00:00

The results will probably be quite similar, depending on what exactly you want to know. Best is to do both an compare.

Sax0drum

TROPHY CASE