Conditional patching?
 

How do I do conditional patching? Basically I am looking at two different scenarios:

1) Timed change. Let's say that I want to change a temperature of a certain region in the mesh at t = t0.

2) Property conditional change. Let's say that I want to open a valve when I reach a certain pressure value (let's say, max(p) = p_max)?

Can be this done without meddling with the code?

Yup. Use a mixed boundary condition and switch the value fraction. That will do most things.

If you want to be really fancy, you can have a topologically changing mesh and a rematch topo modifier to move faces from one patch to another

First of all, thank you for the reply.

But this works only on the boundaries. What if I want to suddenly change something inside the computational domain? Let's say that I have an ignition source that I shut off after a certain time?

That seems somewhat cumbersome. Is there a simpler way?

You can use groovyBC for that task, it will let you use conditional expressions without digging with the boundary condition code