Incorrect outflow at low velocities in interFoam
 

Hello,

I would like to use interFoam to simulate a thin film flow (<1mm) on a flat inclined plate. Later other structures shall follow.
Through an inlet the flow is applied and flows out through the outlet.


When the sinusoidal waves reach the outlet, they accumulate after a few time steps and the thickness of the flow increases in the entire channel.
The waves should pass through the outlet undisturbed as if the channel were continuing indefinitely.


If I increase the speed to 1m/s, the flow passes the outlet as intended. However, if I set my velocities (as in the experiments) to <0.2m/s, the flow does not pass the outlet at all or not completely. Does anyone have an idea how I can investigate very low velocities?



p_rgh:
inlet_Alpha, inlet_Air, outlet, bottom -> zeroGradient
atmosphere -> totalPressure

U:
inlet_Alpha -> flowRateInletVelocity
inlet, outlet -> zeroGradient
bottom -> noSlip
atmosphere -> pressureInletOutletVelocity

alpha.water:
inletAlpha -> fixedValue 1
inlet, bottom, outlet -> zeroGradient
atmosphere -> inletOutlet 0


I hope someone can help me with this.