increasing Courant number
 

Hi friends!
I'm modeling a submerged buoyant turbulent jet of brine in ambient water tank. it is obvious to use a multiphase solver for this modeling. I'm dealing with twoPhaseEulerFoam solver of OoenFOAM. i prepared the model for run. but with setting the time step about 0.005 i faced the increasing of Courant number in each time step. for example after three time steps it reaches to 9 and then to 600 for time 4*0.005!!!
i know it could be emanated from many aspect of setting of model. but is there any body to help me with this ?
all the bests

Check your residuals, usually when CFL overshoots one of the residuals is getting out of bound which causes the CFL number to get high (at this point your velocities are very hight, CFL= VL/nu where L is grid size). This divergence can have many various reasons which is hard to say not knowing anything from your output or problem set up, but a common cause of it is boundary conditions.

Courant Number
 

Courant Number Shoot up can be due to wide variety of reasons. Initially it's better to choose a deltat value in accordance with your input velocity magnitude if at all u r using a velocity input as a boundary condition. Make sure it falls within the range of deltat< mag(U)/smallets element size. it can also be due to poor mesh quality at certain times. As its a multiphase flow, i would request you to check the pressure boundary conditions with atmost care.