Good afternoon,
In the topic "initial condition" HOF (Autodesk Simulation CFD 2014/2015), there is a button "reset" (in french "réinitialiser"). What is the effect if we turn on or turn off this button on the free surface?
Best regard,
Solved! Go to Solution.
Solved by OmkarJ. Go to Solution.
Have a look at the two conditions:
Gravity is towards positive Y axis, that is downwards...
If you re-initialize the solution, as in pic 1, then the volume that you have applied initial condition to is mapped with volume fraction of 1, meaning it acts like a filled reserviour and other volumes are empty. If you don't initialize, as in pic 2, this mapping doesn't take place. As documentation states, this is probably more intuitive in forced convection flows where you first obtain a flow solution and then reinitialize the boundary/initial conditions to map the temperature, and then solve for the propagation of heat.
I haven't used free surface a lot, but from what I understand, you will always need to re-initialize the solution the first time you use free surface, to distiguish the fluid interface. In my first picture, the itnerface is where red and blue surfaces meet, indicating volume fraction of 1 (filled) and 0 (empty). If you don't initialize, all you have is full domain with fluid, with no boundary condition and nothing happening!
Be aware that you will need very small timesteps and very fine mesh in the zone where possible interface may lie because there is a discontinuity in the physical properties at interface which results in very sharp gradients that need to be captured. Otherwise the interface will be smeared and unphysical. You might also want to use RNG/kw-SST model with ADV5 scheme to reduce the smearing.
Hope this helps.