Panel Size Optimization in SHIPFLOW

[Mr. SHIJU JOHN 0]

How do we optimise the panel size in shipflow?

 

Before running XPAN, i tried to vary the number of panels, etc. as we normally optimise the panel size for good results; but couldnt find an option.

 

Pls help.

 

Regards,

Shiju John

Scientist, DRDO

[Mr. Mattia Brenner 6]

Hi Shiju,
 

if you use the automatic mesh option (XMAUTO), the detailed mesh settings are set automatically according to Froude number and resolution level (COARSE, MEDIUM and FINE can be selected). As far as I know, you can, however, change single settings of this configuration manually by adding them in the XMESH node. E.g. if you want to change some settings for the free surface, add the XMESH entry to the configuration, then add a FREE entry in the XMESH node and finally add the necessary paramters that you want to vary to there. A full reference of all parameters can be found in  the Shipflow manual.

 

Of course, you can also skip the automatic settings completely by using XMMANUAL and set all mesh settings manually.

 

Cheers,

Mattia

[Mr. SHIJU JOHN 0]

Hi,

 

1. Is there an option to view the panels on the hull mesh as well as the free surface?

 

2. Is it best to use hyperbolic stretch function 5 (tangent with 2 ends specified) for ship hulls? What about fins/rudders? In the case of a submarine, the sail is a large appendage. What stretch function should be suitable here?

 

Regards,

Shiju John

[Mr. SHIJU JOHN 0]

Hi,

 

reg 1. I found the answer. i am able to see the mesh panels.

 

pls throw light on 2.

 

Thankyou

[Mr. Mattia Brenner 6]

Hi,

 

sorry, but I have no experience using appendages in XPAN, therefore I cannot give you any meaningful recommendation. It is probably better if you get in touch with the Flowtech support (support@flowtech.se) about this.

 

Cheers,

Mattia

[Mr. SHIJU JOHN 0]

I am posting the replies I got and my understanding for general benefit:

 

The most important thing is to resolve the pressure gradients and the stretching will help to place larger amount of panels close to the leading and trailing edges

where we expect high pressure gradients. The best way to evaluate the required mesh size is to run several sizes and observe the changes in the pressure.

 

Michal Orych

 

 

Hi Michal,

 

Thankyou. As I understand from your advise and the manuals, the best way to do it should be:

 

1. To apply stretch function 5 (hyperbolic with both ends specified) so that there are larger amount of panels close to LE and TE.

2. For a fixed number of panels, vary the starting panel size and end panel size (df, lf) and observe the changes in pressure. Choose an optimum combination for best results.

[Mr. Mattia Brenner 6]

Hi Shiju,

 

thank you for this update. It will certainly be helpful for other users to have this information.

 

Cheers,

Mattia