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zwicker-group / py-pde

Python package for solving partial differential equations using finite differences.
https://py-pde.readthedocs.io
MIT License
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Implement heaviside step function in expressions #445

Closed david-zwicker closed 11 months ago

david-zwicker commented 12 months ago

Discussed in https://github.com/zwicker-group/py-pde/discussions/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.