[tayo]

Hello Foamers,

Please I need your advice here. I'm doing a 2D simulation on rising bubble using interFoam. To simplify it for now, my boundary condition is zero velocity at inlet, zero pressure (p_rgh) on outlet and zero gradient for all other sides. Zero gradient also used on all sides of the alpha1. Volume fraction and pressure (p_rgh) inside is initialized with funkySetfField all identical to what was used in a previous trend.

http://www.cfd-online.com/Forums/ope...elocity-2.html

Bubble position is initially placed at center of the 100 mm^2 domain. nCells is 260480. Time step is 1e-4s (adjustableTimeStep also activated). liquid and gas phases are water and air, gravity is set to (0 -9.81 0). surface tension is 0.0728. Infact, I only slightly modified the damBreak tutorial to set up this case. What else. During simulation, I noticed the pressure (p_rgh) inside the bubble jumps from what I initialized (sigma/radius) to about 150N/m2. It runs fine but here is the problem, the bubble fails to rise, infact it sinks like a free fall (~0.75m/s). I've also tried to run without initializing the pressure inside the bubble, and it still sinks. I've tried changing the bubble size too, (and also actually flipped the sign of the gravity-makes no sense though but it rises with the same mag. of velocity as it falls when g is negative). How do I get the bubble to rise (with negative g ofcourse)? I've run out of ideas. Could the problem be with this p_rgh? Please I need your help/advice