# reducing grid size

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 January 5, 2009, 10:34 reducing grid size #1 Marjon van Ginneken Guest   Posts: n/a Looking at droplet (17.5 mu) impact on porous media (d = 50nm)in 2D for different grid sizes, the time where equilibrium is reached significantly differs (as too the solution). Using a grid size of 1/2 mu leads to lots of absorption and no further fluid penetration up to t = 0.8 seconds. As I reduce the grid size to 1/6 mu absorption stops around t = 7e-4 seconds and only very little absorbtion is observed. As I decrease the grid size I suspect (hope) the solution to converge eventually, but have you got any idea of the grid size I should adopt in order to model this problem properly? Also, when reaching this 'equilibrium solution', the total volume decreases tremendously. Can you help me with this?

 January 9, 2009, 01:25 Re: reducing grid size #2 michael barkhudarov Guest   Posts: n/a Hi Marjon, What physical and numerical options are you using? Any implicit solvers other than for the pressure? Michael

 January 9, 2009, 04:51 Re: reducing grid size #3 Marjon van Ginneken Guest   Posts: n/a All explicit solvers and the SOR method for pressure, no heat transfer, itb=1, iwsh=1, ifsft=1, ifvisc=1, icmprs=0 and cfpk=0.1. Calculation is in 2D as I am using just 1 grid cell in y-direction with symmetrical boundary conditions. Capillary pressure equals 1120000 (d= 50nm and theta=30), porosity = 0.40. Can you help me?

 January 9, 2009, 11:52 Re: reducing grid size #4 michael barkhudarov Guest   Posts: n/a Thanks, Marjon. What is the drag model and the drag coefficient for the porous media? Are you using capillary pressure in the porous media? It is hard to pinpoint the problem without seeing the results or running the problem. Have you tried contacting the support? Michael

 January 12, 2009, 10:18 Re: reducing grid size #5 Marjon van Ginneken Guest   Posts: n/a I am using the Reynolds Number Dependent Drag model and capillary pressure in the porous medium (1120000). I shall send you my prepin file by email. Hope to hearing from you soon. Marjon

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