# Dfbi

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 September 2, 2010, 02:58 Dfbi #1 Senior Member   Henry Arrigo Join Date: Jun 2010 Location: Italy Posts: 100 Rep Power: 7 I v a problem with solving a DFBI case. I want too run a boat with thrust force in a domain. is that possible? I mean instead of setting a velocity inlet i want to move the boat using a force acting on it. this case is very helpful to study maneuvering. I v already solved a simple case, but the results are not reliable for example free surface deformation is unreasonable and drag force plot is strange too, but as i expected the whole domain moves in the direction of applied force, and also boat motions seems to be rational. do you have any idea how to come up with this case? thank you

 September 12, 2010, 19:57 #2 Senior Member   Join Date: Oct 2009 Location: Germany Posts: 637 Rep Power: 12 If your results are looking strange, there is an error in the set up. Is your domain wide enough? Which boundary conditions do you have? What about the mesh resolution near the surface?

 September 13, 2010, 07:36 #3 Senior Member   Henry Arrigo Join Date: Jun 2010 Location: Italy Posts: 100 Rep Power: 7 A domain is created to extend 2*L aft-ward,L forward, and L side-ward from the boat. also L to the top of the domain and 2*L to the bottom. I sett B.Cs as mass flow inlet with rate value equal to zero for inlet and outlet and non-sleep wall for other four faces. and about the mesh resolution, here is the report of volume range: Volume range: [3.9930201368e-009, 9.4388723373e-002] m^3.

 September 23, 2010, 15:03 DFBI maneuvering #4 Member   Naimish Harpal (MS Aerospace Engr) Join Date: Jul 2009 Location: Long Beach, CA Posts: 50 Rep Power: 8 Hi, First of all, I wanted to know what CFD tool do you use for your DFBI problem? BTW, I am doing the same kind of analysis using NUMECA Fine/Marine. Instead of specifying Inlet BC velocity, I specified various maneuvering style (constant, ramp, sinusoidal, ...etc) to the body centroid. For constant velocities cases, my CFD results were matching with the experimental data. Anyways, there is a option for external forces under Motion laws, but I havn't tried this option yet. May be you can look into more details at http://www.numeca.com/index.php?id=finemarine. Thanks.

 September 23, 2010, 15:21 #5 Senior Member   Henry Arrigo Join Date: Jun 2010 Location: Italy Posts: 100 Rep Power: 7 It s obviously STAR-CCM+. Anyway, thank you for your recommendation but I m trying to do this with STAR-CCM+. I know it s feasible. Anyway, Thank you again.

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