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Free Surface Ship Resistance

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Old   February 23, 2019, 12:53
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It might be also connected with the mesh behind the boat being coarse,
As it is seen from the result area near the boat where the mesh is fine the water surface is well defined but when you get further away from the boat the water surface is smudged over a few rather large elements. Just a thought. The mesh could be better (thinner elements) in the area of interest.
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Old   February 23, 2019, 17:30
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Urosgrivc is right, your mesh away from the boat is far too coarse. Your free surface interface is much too blurred.
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Old   February 25, 2019, 08:56
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Thank You so much, I will work on the mesh.

I ran the simulation yesterday with reduced timestep, the density and volume fraction of water and air got disturbed too. I think I have made some mistake in the physics criteria too.

I want to maintain the air and water level fixed, and both media should move with 1m/s velocity.

How do I prevent from both phase(air and water) getting mixed up?


Please find the attachment. I have attached physics continua, initial and final volume fraction of water and density of water.
Attached Images
File Type: jpg Disturbed.jpg (35.9 KB, 17 views)
File Type: png Disturbed Density.PNG (43.9 KB, 16 views)
File Type: png Physics.PNG (59.1 KB, 15 views)
File Type: jpg Vol. Frac Scalar.jpg (33.9 KB, 17 views)
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Old   February 25, 2019, 08:58
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Again this is the CFX forum

I dont know star_ccm but in cfx there are settings for
Buoyancy reference density
and gravitational acceleration
maybe you can check this
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Old   July 1, 2021, 05:20
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Hi,

Could you share the towing tank test results of dtmb 5415 ship model with trim-sinkage and the resistance.

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Old   July 1, 2021, 05:21
Default towing tank test results of dtmb 5415 ship model with trim-sinkage and the resistance
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Quote:
Originally Posted by butterflymuzzy View Post
You are true in your side of view Glenn. But from my naval architect point of view ı did this comparision in cfd.

I had the towing tank test results of dtmb 5415 ship model with trim-sinkage and the resistance.

If I use only the fixed mesh there is no problem in every version. but for example if the experiment test resistance result is 110 Newton, I will find 90 Newton with fixed mesh.

On the other side if i use moving mesh ı will find 112 Newton. Becasue the dynamic sinkage's added resistance is coming. And the result is getting better.

And also if ı checked the trim and sinkage results with the experiment everything was ok.

And also i m using a different type of marine cfd code which is called "numeca fine marine". This program is only for marine cfd. everything is reday to use in the program. the program automaticly sets everythin (domain geometry, air water vof, water line margin line, longitudionally bouyancy point and that points gyration radiuses and mass moments etc). When i compare the results with numeca fine marine and ansys 16.2 everything is same and ok

How can i send this situation to any ansys customer service for fixing this problem in the new versions Glenn ?

Best.

hi ,

Could you share the towing tank test results of dtmb 5415 ship model with trim-sinkage and the resistance.

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Old   July 2, 2021, 12:26
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Just google it.
This ship model has its own site.
Check references at the bottom of this page.
http://www.simman2008.dk/5415/5415_link.htm
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Old   July 2, 2021, 12:51
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It is not available. If anybody has a copy kindly share.

Mail id : sachinsreedhar@gmail.com
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Old   July 2, 2021, 13:50
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Check references at the BOTTOM of this page.

http://www.simman2008.dk/5415/5415_link.htm



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Old   November 2, 2022, 01:34
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Hi, Im doing my Final Year Project and I try to connect CAESES with Numeca Fine Marine. Is there any tips or tutorial you can share? I want to try meshing and simulate in CAESES and Numeca as a background or other method you can share so I can link it
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Old   November 3, 2022, 05:19
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Quote:
Originally Posted by ainanjwasakinah@gmail.com View Post
Hi, Im doing my Final Year Project and I try to connect CAESES with Numeca Fine Marine. Is there any tips or tutorial you can share? I want to try meshing and simulate in CAESES and Numeca as a background or other method you can share so I can link it
This sounds like a question for the Numeca Forum:
https://www.cfd-online.com/Forums/numeca/
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