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zwicker-group / py-pde

Python package for solving partial differential equations using finite differences.

Home Page:https://py-pde.readthedocs.io

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Implement heaviside step function in expressions

david-zwicker opened this issue · comments

commented

Discussed in #444

Originally posted by martinsgronli August 3, 2023
Hi!

Is there a way to use the heaviside function in the PDE expression?

I want to do something like:
eq = PDE({"T": f"(1 * heaviside(T - 273, 0.5) + 2 * heaviside(273 - T, 0.5)) * laplace(T)", bc = [bc_x, bc_y]) eq.solve(field, t_end, dt)

It looks like I need to register the heaviside function as a new operator, but I am not sure how to do this.

I am asking because I want to choose a thermal conductivity of 1 when the temperature T > 273 and 2 when T < 273 while solving the 1D heat equation. Instead of using the heaviside function, I have also tried to write the f string in the first line with a condition for the temperature. However, it looks like I cannot access the temperature inside such a condition.