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How Can A Temperature Dependent Variable Changes Permanently?
Posted 23.08.2013, 19:42 GMT-4 Heat Transfer & Phase Change, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.0, Version 4.0a, Version 4.1, Version 4.2, Version 4.2a, Version 4.3, Version 4.3a, Version 4.3b 2 Replies
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However I've found out, according to the simulation result, these properties couldn't be changed permanently. Take the material density for an example*, the material's density changes with increased temperature as a result of absorption to laser induced energy, which is correct, however it changes back to original value when material cools down after laser beam moves away, which is physically incorrect as the material's composition has changed, which led a permanent density change, so the density value shouldn't be supposed to return back.
* rho v.s T is plotted as: farm8.staticflickr.com/7316/9580528024_451830a09c.jpg
Therefore may anyone could kindly offer any advice(s) for suggesting how I can specify a one-way directional relationship for making sure that a predefined physical property ONLY changes with INCREASING temperature please? In other words, reverse change is forbidden. (in this case, density reduction with decreasing temperature is not allowed)
Thanks!
P.S. I have thought about an alternative, which I can convert these physical properties to time-dependent values, based on a good assumption that could fix the model.
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Create a new time dependent "Domain ODEs and DAEs" equation to represent the variable material density (or any) and let us call it "max_rho_mat". If you did not know, this is available from "Mathematics > ODE and DAE interfaces > Domain ODEs and DAEs (dode)".
Once you have added the model, define the following coefficients:
f = ((nojac(rho_mat)-max_rho_mat)/timestep)*(rho_mat>max_rho_mat)
da = 1
ea = 0
under the sub-node "initial values" give the initial value of your material density, don't forget this aspect
rho_mat is your material density that is a function of temperature.
This will remember the largest value of the material density ever reached at any location at any give time (because this is what you asked for). So just use max_rho_mat instead of rho_mat in your heat transfer equation.
Suresh
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Thanks so much for your suggestion! I will have a try later today.
Best regards,
Liwei
Hi,
Create a new time dependent "Domain ODEs and DAEs" equation to represent the variable material density (or any) and let us call it "max_rho_mat". If you did not know, this is available from "Mathematics > ODE and DAE interfaces > Domain ODEs and DAEs (dode)".
Once you have added the model, define the following coefficients:
f = ((nojac(rho_mat)-max_rho_mat)/timestep)*(rho_mat>max_rho_mat)
da = 1
ea = 0
under the sub-node "initial values" give the initial value of your material density, don't forget this aspect
rho_mat is your material density that is a function of temperature.
This will remember the largest value of the material density ever reached at any location at any give time (because this is what you asked for). So just use max_rho_mat instead of rho_mat in your heat transfer equation.
Suresh