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Jagged or oscillating 1D plot
Posted 30 apr 2012, 09:52 GMT-4 MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Results & Visualization Version 4.2 1 Reply
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Hi,
I am modelling a micro beam heated by a very short pulse heat input from a small area on the top of it. The attached picture is the temperature vs time plot of points on the beam. It was jagged before I took Ivar's suggestion to change the time stepping from "free" to "strict".
The problem is, even after doing that, the temperature plot still shows some oscillating which shouldn't occur. Anyone get any idea how it happenes?
Thanks in advance
Tianshi
I am modelling a micro beam heated by a very short pulse heat input from a small area on the top of it. The attached picture is the temperature vs time plot of points on the beam. It was jagged before I took Ivar's suggestion to change the time stepping from "free" to "strict".
The problem is, even after doing that, the temperature plot still shows some oscillating which shouldn't occur. Anyone get any idea how it happenes?
Thanks in advance
Tianshi
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1 Reply Last Post 30 apr 2012, 14:11 GMT-4
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Posted:
1 decade ago
Hi
there can be many reasons for oscillation along steep gradients, as you have during abrupt turn on or turn off phases. These could also be induced by some (too) coarse mesh regions where the gradients are hgh, that does not allow COMSOL to get a precise gradient expression.
Also depending on what you are looking after, your desied variable might be related to the derivative of your dependet variable, then it can easily become stepwise in regions with steep gradient.
Have you tried to check the mesh sensitivity ? or check your apha=k/rho/Cp heat diffusivity versus time stepping and mesh average size criteria ? these are often violated for HT in small MEMS devices with very short time responses due to the scaling issues.
What you have learned for macroscopic devices issoften quite different for small scale devices, in particular related to diffusion equations, due to scaling of the physical laws
--
Good luck
Ivar
there can be many reasons for oscillation along steep gradients, as you have during abrupt turn on or turn off phases. These could also be induced by some (too) coarse mesh regions where the gradients are hgh, that does not allow COMSOL to get a precise gradient expression.
Also depending on what you are looking after, your desied variable might be related to the derivative of your dependet variable, then it can easily become stepwise in regions with steep gradient.
Have you tried to check the mesh sensitivity ? or check your apha=k/rho/Cp heat diffusivity versus time stepping and mesh average size criteria ? these are often violated for HT in small MEMS devices with very short time responses due to the scaling issues.
What you have learned for macroscopic devices issoften quite different for small scale devices, in particular related to diffusion equations, due to scaling of the physical laws
--
Good luck
Ivar