Stagnant flow

bb21 · March 5, 2012, 05:51

I have a problem occurring of stagnant flow in a simple tube. For the velocity of the flow I am using a table (time). The problem that is occurring is that once the velocity is dropped to 0m/s the flow remains stationary in the tube is there anyway of preventing this from occurring?

I have 2 phases in the tube one that has no velocity and is contained in the tube and the 2nd phase enters the tube, travelling through the first phase. I have 2 field function incorporated in Volume of Fraction under the Inlet boundary. My field functions are position functions. I amusing a velocity inlet and flow split outlet as my boundary conditions

Is it possible to incorporate into the functions the prevention of stagnant flow occuring when the velocity changes to 0m/s or inputting it somewhere else??

abdul099 · March 7, 2012, 17:13

As long as your flow is incompressible, the velocity needs to drop to zero when the inlet velocity is zero. Otherwise mass would disappear. And a flow split outlet means, the same amount of mass which enters the domain will leave it. No inflow means no outflow, which means no velocity.
The only option how there still could be a non-zero velocity without inlet velocity is when mass shifts within your domain - but that depends on your physical problem.

March 5, 2012, 05:51	Stagnant flow	#1
bb21 New Member BButler Join Date: Jan 2012 Posts: 3 Rep Power: 14	I have a problem occurring of stagnant flow in a simple tube. For the velocity of the flow I am using a table (time). The problem that is occurring is that once the velocity is dropped to 0m/s the flow remains stationary in the tube is there anyway of preventing this from occurring? I have 2 phases in the tube one that has no velocity and is contained in the tube and the 2nd phase enters the tube, travelling through the first phase. I have 2 field function incorporated in Volume of Fraction under the Inlet boundary. My field functions are position functions. I amusing a velocity inlet and flow split outlet as my boundary conditions Is it possible to incorporate into the functions the prevention of stagnant flow occuring when the velocity changes to 0m/s or inputting it somewhere else??

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March 7, 2012, 17:13		#2
abdul099 Senior Member Join Date: Oct 2009 Location: Germany Posts: 636 Rep Power: 21	As long as your flow is incompressible, the velocity needs to drop to zero when the inlet velocity is zero. Otherwise mass would disappear. And a flow split outlet means, the same amount of mass which enters the domain will leave it. No inflow means no outflow, which means no velocity. The only option how there still could be a non-zero velocity without inlet velocity is when mass shifts within your domain - but that depends on your physical problem.