Set velocity at outlet for leak in pipe?
I am modelling a leak within a domestic supply-side water pipe, and am using the Macroscopic Particle Model (MPM) to insert a particle into the pipe, which would flow into the leak due to the pressure gradient, blocking the leak. A screenshot of this geometry is below:
I am assigning boundary conditions that would simulate this. I want the pipe flow to be at gauge pressure values of 1-5 bar, and at 0.6m/s velocity. Ideally, I'd have a pressure inlet (of say 1 bar gauge), an outlet pressure for the leak (of 0 bar gauge - i.e. atmospheric), and a velocity outlet of 0.6m/s, rather than pressure at the outlet and velocity at the inlet. This is because there is going to be some pressure drop within the pipe as a result of the leak, meaning that the outlet pressure is undetermined initially, but as the leak is sealed, the low-pressure region would be eliminated, and the inlet and outlet pressure become equal (i.e. 1 bar throughout the pipe).
The reason I'd also like velocity to be at the outlet is because within my study, I want to look at the impact which turning on the house taps downstream of the leak (i.e. which would increase velocity within the pipe) would have on the particle's bond to the leak. This is because you can assign a 'detachment velocity' for MPM particles, beyond which they lose contact with the wall, which would cause the leak to become unblocked again - I'd like to know at what velocity this would occur.
My problem is that from what I understand, you can only assign 'velocity inlets' boundary conditions, but not velocity outlets. Can anyone see a way around this, or perhaps a way to redefine my problem? Thanks in advance.