Heaviside

[martinsgronli]

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.

[david-zwicker]

The support of the heaviside step function is unfortunately very buggy, but I agree that it should be better. I'll turn this suggestion into a proper issue and hope to find time to implement it reasonably soon. In the meantime, you could emulate the step function with any sigmoidal function, e.g., you could use a sufficiently steep hyperbolic tangent.