Learning Forum

[helen.durand]

Good evening,

We are simulating a three-way diverter valve with an inflow F1 and outflows Fa1 and Fb1. The pipe that carries the flow Fb1 joints another flow downstream at a T-junction. At a certain time of the simulation, the diverter valve closes the flow Fb1 (i.e., the valve only allows the flow Fa1). This means that the T-junction now does not receive any flow from Fb1. How does ANSYS solve a situation like this where there the mass flow rate at a boundary of a pipe becomes zero?

[Rob]

It depends. The flowing section will be OK, ie the bit with the open path from inlet to outlet.
The closed section will be different. If the valve is closed slowly (relative to the time step) then as the gap disappears the flow will slow and you'll get a fairly static zone. If it's fast then stability may be an issue as the flow cannot create a vacuum, and can't change phase or expand if the appropriate models aren't active.

[helen.durand]

Thank you very much, Rob. That is very helpful. To check if there is a dead fluid in the pipe after the valve fully closes the flow Fb1 (to create the static zone you referred to), is there a way to measure mass instead of mass flows?

[Rob]

There will be dead fluid in the pipe as we don't have a vacuum. It'll just stop flowing.
To answer the asked question, the volume monitors allow you to report the mass in a zone.