Free surface simulation for resistance ship

Rizal Zul · July 1, 2018, 06:59

I am Rizal, from Indonesia

now i am doing my thesis project by using CFD ansys 16 version. i intend to generate free surface simulation to predict ship resistance. the boundary condition in tutorial in term "free surface over bump" does not show good result. the simulation is always not finish. any body can help for explaining boundary condition used in free surface ship simulation in CFX? and may be also showing physical model that can be adopt?

Thank you

Regard*
Rizal

ghorrocks · July 1, 2018, 07:26

When I have done this sort of thing I used a normal outlet boundary with a defined pressure. Note you need to correct it for the hydrostatic head in the water versus air sections.

Also: consider the open source CFD code gerris. It is a little bit different and takes some time to get used to, but it can do an excellent job on ship wave patterns and wave resistance. But note that it does not a turbulence model so cannot model frictional resistance. But it has a tutorial example on wave making resistance on a yacht and it is very easy to use for this case (FAR easier than CFX) that it has to be considered.

Rizal Zul · July 2, 2018, 04:47

How about the boundary condition? What should i do?

ghorrocks · July 2, 2018, 08:01

Quote:

a normal outlet boundary with a defined pressure. Note you need to correct it for the hydrostatic head in the water versus air sections.

That is pretty clear, isn't it?

Rizal Zul · July 2, 2018, 22:22

Can you give a physical model that can be adopt? I am so Confused, because in result, water level not appropriate with UpH. I use CCL ini setup same with tutorial.

sriram9127 · February 19, 2019, 07:26

I am running a Multi-phase simulation for calculating a boat's resistance. I am having difficulty in capturing the hull's curvature. Suggest me a better mesh condition.

sriram9127 · February 21, 2019, 03:46

It is a multiphase problem(air and water).
Initial velocity zero for both phase.
I want to run a simulation for 1m/s velocity of both phases and view wave pattern.

Please find the attachment. The residuals are converged, but I can't find the entire wave pattern. Give me some suggestions.

July 1, 2018, 06:59	Free surface simulation for resistance ship	#1
Rizal Zul New Member Rizal Zulqur Join Date: Jul 2018 Posts: 4 Rep Power: 8	I am Rizal, from Indonesia now i am doing my thesis project by using CFD ansys 16 version. i intend to generate free surface simulation to predict ship resistance. the boundary condition in tutorial in term "free surface over bump" does not show good result. the simulation is always not finish. any body can help for explaining boundary condition used in free surface ship simulation in CFX? and may be also showing physical model that can be adopt? Thank you Regard* Rizal

July 1, 2018, 07:26		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	When I have done this sort of thing I used a normal outlet boundary with a defined pressure. Note you need to correct it for the hydrostatic head in the water versus air sections. Also: consider the open source CFD code gerris. It is a little bit different and takes some time to get used to, but it can do an excellent job on ship wave patterns and wave resistance. But note that it does not a turbulence model so cannot model frictional resistance. But it has a tutorial example on wave making resistance on a yacht and it is very easy to use for this case (FAR easier than CFX) that it has to be considered. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 19, 2019, 07:26	How to capture better curvature of a model	#6
sriram9127 Member sriram Join Date: Jun 2016 Posts: 48 Rep Power: 10	I am running a Multi-phase simulation for calculating a boat's resistance. I am having difficulty in capturing the hull's curvature. Suggest me a better mesh condition.

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July 2, 2018, 04:47		#3
Rizal Zul New Member Rizal Zulqur Join Date: Jul 2018 Posts: 4 Rep Power: 8	How about the boundary condition? What should i do?

July 2, 2018, 22:22		#5
Rizal Zul New Member Rizal Zulqur Join Date: Jul 2018 Posts: 4 Rep Power: 8	Can you give a physical model that can be adopt? I am so Confused, because in result, water level not appropriate with UpH. I use CCL ini setup same with tutorial.