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Modeling as heat source (Q) a supergaussian diode laser beam profile for studying heat transfer and structural stress in a cylindrical crystal rod.

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Hi to everybody! I hope to find here some help since I am a super novel user of COMSOL Multiphysics (demo version so far) and I already found myself in trouble.
My intention is to determine the thermal distribution and stress distribution inside a yttrium aluminum garnet crystal (Material included in the Material Browser) in order to calculate in a second step the thermal lensing effect in the laser rod. (This is a particular optical effect that must be taken in account when designing solid-state lasers).

So far I have been able to create the geometry, assign the material information and I understand more or less the basic functions among the boundaries condition. I noticed that as heat source it is possible only a linear thermal implementation. How can I implement a Q(x,y,z) ( following the labels in the heat equation) definition that cover the supergaussian profile of the laser beam incident on the end-face of the cyulidrical rod? Anybody as a clue on this? Should I use the Mathematics option and throw in a Helmotz Equation or something? Anybody got some similar model to analyze? Thanks a lot to all.

Mich

1 Reply Last Post Apr 13, 2012, 12:29 p.m. EDT

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Posted: 1 decade ago Apr 13, 2012, 12:29 p.m. EDT
Hi there! Thanks to my university I got the chance to start using comsol with the academic vpn connection and I started building the model. Here I will explain my model better:

The physics behind is rather simple. A cylindrical rod of yttrium aluminum garnet is illuminated by a focused diode laser beam on one of the two circular end surfaces. At the moment I want to simplify the conditions, so I will model it with an Analytic Function defined below. The rod is interested by mainly 2 effects: a thermal gradient formation in radial direction and a strain given by the thermal mechanical stress. The volumetric heat load would be:

(A/(wx*wy))*exp(-2*(abs(x/wx))^2-2*(abs(y/wy))^2-tau*z)

where A, wx, wy, tau are parameters that I want to be able to control afterwards to see the change of the thermal gradient and the stain due to the thermal stress.

As first point I constructed a work plane with a rectangle and I builded the revolved rod. Now in Definitions I am countering "dummie user" problem and I do not know how to define the function properly and then how to couple this function to the heat transfer physics node where I suppose I should add the heat load.

--

Mich
Hi there! Thanks to my university I got the chance to start using comsol with the academic vpn connection and I started building the model. Here I will explain my model better: The physics behind is rather simple. A cylindrical rod of yttrium aluminum garnet is illuminated by a focused diode laser beam on one of the two circular end surfaces. At the moment I want to simplify the conditions, so I will model it with an Analytic Function defined below. The rod is interested by mainly 2 effects: a thermal gradient formation in radial direction and a strain given by the thermal mechanical stress. The volumetric heat load would be: (A/(wx*wy))*exp(-2*(abs(x/wx))^2-2*(abs(y/wy))^2-tau*z) where A, wx, wy, tau are parameters that I want to be able to control afterwards to see the change of the thermal gradient and the stain due to the thermal stress. As first point I constructed a work plane with a rectangle and I builded the revolved rod. Now in Definitions I am countering "dummie user" problem and I do not know how to define the function properly and then how to couple this function to the heat transfer physics node where I suppose I should add the heat load. -- Mich

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