# Flow around ship hull, multiphase setup!!

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 June 20, 2010, 17:45 Flow around ship hull, multiphase setup!! #1 New Member   Ali Join Date: Jun 2010 Posts: 2 Rep Power: 0 Hi everyone, I am trying to find the flow characteristics around a ship hull by using Fluent. I did the model, I did the meshing in Gambit everything is fine until so far. It is a multiphase problem (air and water), I have two velocity inlets, hence two continuum volumes, hence two interior boundary conditions etc. I have two pressure outlets (when I imported the meshing in fluent, it divided my outlet into two since there are two continuums). However I am having some difficulties in setting the problem in fluent. First of all, I am trying to use the VOF model. When I have two continuum like this, how do I set up the problem? How do I define free surface in this case. My aim is to get the drag coefficient, surface elevation and wave profile on the hull. I searched every thread in these forums but I could not get a solid answer for my case. Do I have to write a UDF for VOF or is there any other way to get the results by using two phases like how I have done? Or should I start the problem with one continuum in Gambit and one inlet and then introduce it in fluent as a multiphase model? If so, then how to do it? I seriously need some help. Thank you very much in advance. Ali

 June 22, 2010, 16:58 #2 Senior Member   Jouke de Baar Join Date: Oct 2009 Posts: 125 Rep Power: 8 Hi, What you could do is: - Have a split water velocity inlet and air velocity inlet. You can set the volume fraction of the water inlet to 1 in the boundary conditions panel - For all other boundaries you will not have to make a distinction for the phase. This means you can have a single wall boundary and a single pressure outlet (with udf) Have a look at pages 62 - 65 of https://docs.google.com/fileview?id=...MjNkZGJl&hl=en Another option is open channel flow s7evin and Dumith like this.

 June 23, 2010, 19:30 #3 New Member   Ali Join Date: Jun 2010 Posts: 2 Rep Power: 0 That was what I needed.. Thank you very much for the info and for the document..

 June 25, 2010, 09:23 #4 New Member   Hermanus Henning Join Date: Jun 2010 Posts: 6 Rep Power: 7 Good day everyone, I'm new to the CFD world and I would just like to say hi! Alibul, thank you for posting the question, I'm in the same "boat". Jack, thank you for the advice to Alibul, its very useful Regards

 February 9, 2011, 07:00 ship #5 Member   kabilan.B Join Date: Jul 2010 Location: chennai Posts: 77 Rep Power: 7 hai, i want to know which multiphase is suitable for ship analysis. when i solve by using vof, unstructure mesh, the error occurs i.e) over spills. pls rply (vof or euler or mixture.....)

 February 9, 2011, 08:40 Vof #6 New Member   Hermanus Henning Join Date: Jun 2010 Posts: 6 Rep Power: 7 Hello Kabilan, I used the vof method because I'm moddeling a free surface and two immiscible fluids. What turbulence model are you using (if you are using ine at all)? Regards

 February 10, 2011, 06:28 vof #7 Member   kabilan.B Join Date: Jul 2010 Location: chennai Posts: 77 Rep Power: 7 very thank you for reply, i used k-e turbulence model............

 February 10, 2011, 09:43 #8 New Member   Hermanus Henning Join Date: Jun 2010 Posts: 6 Rep Power: 7 Pleasure, I used the Transition SST model for my case...

April 23, 2012, 05:51
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rohit
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Quote:
 Originally Posted by jack1980 Hi, What you could do is: - Have a split water velocity inlet and air velocity inlet. You can set the volume fraction of the water inlet to 1 in the boundary conditions panel - For all other boundaries you will not have to make a distinction for the phase. This means you can have a single wall boundary and a single pressure outlet (with udf) Have a look at pages 62 - 65 of https://docs.google.com/fileview?id=...MjNkZGJl&hl=en Another option is open channel flow
Dear Jacks,
I have certain doubts like you said you have single outlet how it is possible bcz then udf will give different pressure for air outlet as air is having different density.
Also should we include wall adhesion and surface tension also.
Air should be compressible or incompressible.

If you can mail me on my mail id - rrmore@gmail.com i will verymuch thankful to you......

 November 30, 2012, 02:43 #10 Member   Join Date: Mar 2009 Posts: 39 Rep Power: 8 Hi, I am trying to simulate flow around the ship hull using 2D, steady state, VOF simulation. I have given air and water velocity as 1m/s, but due to some reason within 10 iterations velocity is going to high !!! Can any buddy help in identify the reason for such a high velocity? Thanks in advance. Mehul

 September 20, 2013, 11:02 #11 Member   like.no.other Join Date: Sep 2011 Posts: 35 Rep Power: 6 Hi guys This is a good pdf for ship hull simulation Heave and Pitch Simulation of Ship hull moving through head sea waves enjoy! __________________ www.CFDiran.ir Join Us on Facebook

September 25, 2013, 03:50
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Quote:
 Originally Posted by like.no.other Hi guys This is a good pdf for ship hull simulation Heave and Pitch Simulation of Ship hull moving through head sea waves enjoy!
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I'M NOT A GYNECOLOGIST BUT I'LL TAKE A LOOK.

 September 4, 2015, 09:01 Collaborative project for multiphase flow around a boat hull #13 New Member   Join Date: Sep 2015 Posts: 1 Rep Power: 0 Hi all, if you are still interested in a simulation for a boat hull, then we started working on a collaborative project for a multiphase flow around a boat hull. We already have a group of people involved in it and the project is fully open to anyone additional who wants to join. We are posting all the results, images on the forum here: https://forum.simscale.com/t/collabo...oat-hull/71/30 Would be great to have you join! Cheers, Agata

 Tags hull, multiphase modelling, vof model

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