Time dependent boundary condition in PDE toolbox possible?

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Dan
Dan 2013-3-13
评论： Steven 2018-9-20
I'm using the PDE toolbox to model the cooling of a rectangular body of material through various boundaries. I'm modeling it with a parabolic PDE.
I'd like to make one of the boundaries heat up through time, as the cooling material transfers heat to it. Is it possible to create a time-dependent boundary condition like this? I'm currently using Neumann boundaries, but would like to try it with both Neumann and Dirichlet, if possible.
Thanks in advance for any input.
-Dan
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Jannatun Nahar
Jannatun Nahar 2017-3-14
编辑：Jannatun Nahar 2017-3-14
Hi, I have same problem. I can use both neumann and dirichlet under mixed form with respect to region, but how to switch between these two types based on time or some conditions? Like, if u>0 or t>1 use dirichlet else use neumann.

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回答（1 个）

Bill Greene
Bill Greene 2013-3-14
Hi,
Defining boundary conditions to be functions of time is fairly straightforward. Neumann and Dirichlet conditions are handled in essentially the same way.
If you are using the pdetool GUI, you just define the boundary condition term (e.g. g) as an expression involving the variable "t"-- e.g. 5*t^2.
If you are solving the pde from the command line, the easiest way to specify such a boundary condition is by writing a "boundary file"-- a MATLAB function that you write for defining the boundary conditions on each geometry edge. An example is shown at the bottom of this documentation page: http://www.mathworks.com/help/pde/ug/boundary-conditions-for-scalar-pde.html A function handle to this function is then passed to the parabolic function as the b argument.
Bill

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