VOF model with planning vessel

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 February 28, 2010, 14:03 VOF model with planing hull #1 Member   Vincent Meertens Join Date: Sep 2009 Location: Belgium Posts: 41 Rep Power: 10 Hi, For my master thesis i have to study the flow around a speedboat. In gambit i've created a flow volume and substracted the hull from that volume. The BC's are: Pressure inlet, pressure outlet and moving walls, the hull is a fixed wal. The water flows from left to the right with a constant speed (30m/s). In Fluent i've followed the next steps: Steady Pressure based (Gravity enabled). VOF with Realizable k-epsilon. Material, phases, BC are defined the way it should be. (with specified density set to 0). Solution methods: Scheme: Simple, Pressure: Presto, Momentum: Power Law, Volume Fraction: Modified HRIC, rest: Power Law. Under-relaxation factors are decreased. Initialization on Inlet. start calculation. When i check the results i get the following solution. In a symmetry plane i want to see the contours of the 2 phases. When i plot them i get the following (with 2 phases): There's no contact between the hull and the water. But the solution seems converged (Cl is constant and de residuals are converged till 10E-3) The wave after the hull looks correct but the forces (lift and drag) are to big. When i define 4 phases i get the following result: This seems a lot better but i cant give a physical explanation to 4 phases. So my question is: are my calculations wrong or is this 'visual' result just a part of postprocessing and i shouldn't pay to much attention to the colors? Thanks in advance! Vincent Last edited by vmeertens; February 28, 2010 at 17:03.

 March 1, 2010, 08:29 #2 Member   Vincent Meertens Join Date: Sep 2009 Location: Belgium Posts: 41 Rep Power: 10 I did a transient calculation after this, but it doesn't change anything to the results. The initial water surface is set to y=0, so it should touch the hull in the middle. The hull is set under an angle of 2° (compared with pictures of the real boat)

 March 17, 2010, 02:51 #3 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,250 Rep Power: 34 how did you initialize the vof (water) Once the initialization is done, check the distribution of vof. Does your free surface agree with what you want? __________________ In memory of my friend Hervé: CFD engineer & freerider

 March 25, 2010, 16:49 #4 Member   Vincent Meertens Join Date: Sep 2009 Location: Belgium Posts: 41 Rep Power: 10 Hey, The vof is patched as following: Adapt -> Region: dimensions of the volume of water. Initialize from inlet Patch -> Phase: water -> Volume fraction: 1 -> Hexadronr0 Patch -> X-Velocity -> Value: 30m/s -> Fluid At t = 0 the free water surface is as it should be. Now i'm doing the simulation with a better mesh thanks to mAx

 August 9, 2013, 16:12 air phase being formed on the bottom of the hull #5 New Member   Deepak Bansal Join Date: Jul 2013 Posts: 9 Rep Power: 6 hey buddy i am also facing same problem in planing craft that air phase being formed on the bottom of the hull.................how did u solve this problem.................reply as soon as possible...............

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