Pulsating laser source in the rotation axis of a cylinder

General discussions about how to formulate a script for FlexPDE.

Pulsating laser source in the rotation axis of a cylinder

Postby k123456 on Fri Jun 09, 2017 4:08 am

Hello,

i am new to flexpde (student version 6.5) and i want to simulate the heat propagation in a cylinder (quarter cylinder represented in 2D). A laser source should be placed on the top surface of the cylinder and have to lie on the rotation axis. The temperature of the cylinder is fixed by 320 K. As result i want to get illustrated informations about the expected time dependent temperature and laser energy distributions.

purpose:
1. suitable choice of the energy input (point load doesn't work in a 2D-script)
idea: set a line on the radius of the laser beam (0->RL; representation of an area load -> laser spot)
2. if this problem is smartly solved i want to model a pulsed gaussian laser beam in a preferably easy way

problems:
1. model the energy input and the pulsed laser source
2. "timestep hast fallen below halt threshold"
3. interpreting the functions ustep, uramp,...

thank you in advance :)
k123456
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cylinder.pde
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Re: Pulsating laser source in the rotation axis of a cylinder

Postby moderator on Mon Jun 12, 2017 6:43 pm

You have done several things wrong.
Value(u)=u is a tautology. If you are going to specify a value you should specify a value.
Natural(u) specifies a flux of U. Natural(u)=u implies a convective surface loss to an environment at zero units, with a coupling coefficient of 1.0 in whatever units are implied by the conversion from U to flux of U.
Value(u)=u+Ql is a tautology if Ql is zero, and an impossibility if Ql is not zero. Besides, you are adding temperature to energy.

See our example Samples|Applications|Stress|Elasticity.pde for a more complex problem that computes temperature and stress from laser energy deposition. In this case, the laser energy is Gaussian in cross-section, and is deposited in the volume in an exponentially decreasing amount as the laser is absorbed.
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