Submarine Analysis using SHIPFLOW

[Mr. SHIJU JOHN 0]

I am trying to design a submarine as part of my Masters project.

 

My Prof. has suggested me to try using SHIPFLOW.

 

Basically, I would like to use SHIPFLOW for the following:

 

1. Resistance estimation of Submarine in deep submerged condition.

2. Self Propulsion Tests (using Pump-Jet propulsor) in deep submerged condition.

3. Maneuverability (Straight line tests and Rotating Arm) of Submarine

 

Please advice if its possible to do such simulations in SHIPFLOW. Is it possible to switch off the free surface effects?

Is there a separate module for maneuvering?

 

Regards,

Shiju John

 

[Matthias Maasch 21]

Hi John,

 

First things first: I am not 100 % sure about the following facts (or guesses), so please contact support@flowtech.se for clarification.

 

1. It is possible to run resistance computations for submarines as there is a hull type "SUBMARINE". XGRID will generate a grid that is a half of a cylinder.

XMESH and XPAN will assume a fully submerged body.

 

2. Self-propulsion computations are possible. The propeller is represented by a lifting line actuator disc.

If this fits your expectations you can model the nozzle as a XCHAP-Volume-Grid.

 

3. Most likely not possible! As far as I know shipflow does not offer such code.

 

4. XFlow allows flows with and without free surface.

 

5. In the ExamplesManual which comes with the shipflow software you can find some more detailed descriptions with regard to submarines, such as offset files and command files. If you don't have the ExamplesManual available I can surely upload it here.

 

I hope this helps.

 

Sounds quite challenging :-)

 

Kind regards

 

Matthias

[Mr. SHIJU JOHN 0]

Thankyou Maasch,

 

"3. Most likely not possible! As far as I know shipflow does not offer such code."

 

I have seen a couple of published papers in which maneuvering of surface ships were carried out using SHIPFLOW. (linear derivatives of velocity and accelerations)

So I hope there should be a method to extend it to submarines.

 

"5. In the ExamplesManual which comes with the shipflow software you can find some more detailed descriptions with regard to submarines, such as offset files and command files. If you don't have the ExamplesManual available I can surely upload it here."

 

Please upload the examples file. It would be very helpful.

 

And finally, ya it seems very challenging. We also have PARAMARINE here which is a lot easier for submarines.

But I hope I can crack it with SHIPFLOW as well.

 

Thanks a lot for your encouraging reply.

Shiju John

Scientist, DRDO

M.Tech Scholar, IIT Madras

[Matthias Maasch 21]

Hi Shiju,

 

I contacted Flowtech and got an promising answer, here we are:

It is possible to do the steady drift and rotation the same way as for a monohull. You can take a look at kvlcc2m_cg_drift06 and kvlcc2m_cg_turn then combine it with a submarine example sub_xchap.

Please find attached the files mentioned and in addition the ExamplesManual and the UsersManual.

 

If you have further questions do not hesitate to ask.

 

Cheers

 

Matthias

shipflow_files.zip

[Mr. SHIJU JOHN 0]

Hi Maasch,

 

Very encouraging to see your mail.

Thankyou.

 

I am going through these files.

Hope to start working once initial hull form is finalised.

 

Regards,

Shiju John

[Mr. SHIJU JOHN 0]

I have modified the submarine offset file off_sub for my design.
I am trying to run xpan it through SHIPFLOW GUI using this offset.
 
First, I imported the offset file. The 3D view shows my sub as ok.
But, on running i am getting an error message as follows:
 
***ERROR (401) - FILE COULD NOT BE OPENED
SYSTEM DEPENDENT ERROR STATUS NUMBER = 29
LOGICAL UNIT = 4
FILENAME = ../off_sub
xferrm: Error
 
 
Pls help.
I am attaching the fdb file for reference.trial1.fdb

 

[Mr. Mattia Brenner 6]

Hi John,

 

if you are running the case through the SHIPFLOW GUI, you have to make sure that the offsets are exported.

 

In the XFLOW/OFFSET/FILE configuration entry you just had the string "off_sub", which means that this file is located on the harddrive. But this file did not exist, since your offsets are inside the project. Therfore the error message. To make sure that they are exported to a file before the computation is started, you have to use this command

 

 

Then it works fine.

 

Cheers,

Mattia

[Mr. SHIJU JOHN 0]

Thankyou.

 

It worked.

 

Regards,

Shiju John

[Mr. SHIJU JOHN 0]

Hi,

 

When you run XPAN for a deep submerged submarine, the resistance should be zero. (D'Alembert's paradox)

What is this basic resistance coeff that XPAN gives for deep submerged submarine? Is it the pressure coeff or any residual error?

 

Basic model resistance coefficient (force/0.5*density*Sref*U*U)

CXPI   -0.000833

CYPI   0

CZPI    0.0022034

 

Pls explain.

Regards,

Shiju John

[Mr. Paul Riesen 0]

Hi Shiju,

 

have you managed to run a propulsion computation of your subm? I am working on my bachelor thesis. Therefore I need to get the propulsion results of an AUV. Would you mind to help me with your configuration data specifically for the propul. calc.? Resp. did you use the ITTC78 command?

 

Would be great!

Regards,

Paul

[Mr. Paul Riesen 0]

Actually why are using XPAN? You don’t need the potential calc. because it is submerged. You can use XCHAP only, isn’t it?!?

[Mr. SHIJU JOHN 0]

So far I have not used the propulsion calculations. But I am heading into it soon.

 

I tried using XPAN to get the velocity contours.