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Non-Local Modelling
Posted 06.04.2016, 14:53 GMT-4 Charged Particle Tracing, Microfluidics, Particle Tracing for Fluid Flow, Results & Visualization Version 5.0, Version 5.1 5 Replies
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I just started using comsol, moving from ABAQUS. I was hoping to gain advice on how to procceed with non-local modelling.
I would like to know if comsol can for every point compute an integral over a finite volume surrounding that point and use it in the solution.
e.g. every point can sense and use variables a finite distance away, like a sphere (3D) smaller than the modelled part but some multiple of the mesh size.
I appreciate I should bury myself in the documentation and figure this out myself but I hope there is some speed up by asking the community while searching.
Kind Regards and thank you in advance,
Alex
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Can you explain for what purpose you want to do this? What is the ultimate goal?
Reason I am asking is that what you ultimately want to do may be best achieved in COMSOL through an alternate approach than the one you suggest.
Best,
Jeff
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Some formulations of structural mechanics are expressed as integrals over a finite volumes instead of forces being conveyed by the material an infintesimal small distance away (continuum mechanics). The advantage of describing the stress on a single point as the sum of forces a finite ditance away means the stress tensor contains no singularities at crack tip. Regular continuum mechanics has the derivative of a discontinuuity as inf but by defining force as an integral over a tinyy surrounding volume stress at discontinuities is finite.
I have been playing with comsol for a few hours now and am seeing some success with defining another physical field and using the antiderivative.
i was going for du/dx = T(x)*weighting function(dest(x)) which could be a step representing the neighbourhood.
where u is the dummy physics variable and T is the variable of interest in making non-local.
But I am not sure yet, if you know a smarter or more Comsol way I am interested.
Regards,
Alex
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Have you checked the ballint() and similar operators?
"The ballint(r, expr) operator computes the volume integral of the expression expr in a ball with radius r around the point in which it is evaluated. The ballint operator can be evaluated on all entities in 3D. "
Regards,
Henrik
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And can it be used in solution or post process only?
I will give it a go.
I have had some success by defining a new physics field and using the current position and destination position with a weight function integrate over arbitrary volumes but I still need to validate that it behaves properly.
Regards.
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I have some interests in the “Build in Operators”,particularly the "ballint, sphint ,circint" ,but have no idea how to use it.
Here is the situation:
I want to model a microfluidic system that involves drag force and inertial (lift) forces on particles travelling inside a microchannel, and to my knowledge :the model "particle tracing for fluid flow" have drag force ,but CAN NOT find where to add the inertial lift force.
To get the force exerted on the particle induced by “stress tensor”,I want to do the "particle surface integration of the stress tensor in 3D, sphint(r,expr)" or circle curve integration in 2D, circint(r,expr).
Here is my questions:
The particle in my model moved along the fluid flow, I don't know how to do the integration on the surface of particle.
Looking forward for your reply.