Small Marine Vehicle Hydrostatics: Software?

[dtoshni]

Hey Everyone!

I am working on a small diving vehicle at IST, Lisbon. I have the shape of the vehicle modeled in SolidWorks. Now I wish to carry out normal hydrostatic calculations for the vehicle and also resistance calculations.

I was wondering if I can maybe export an IGES file from SolidWorks, and then use it in Maxsurf( and Hydromax and HullSpeed) to do the calculations. Will this work (given that the body is underwater) ?

Is there any other good reliable software (preferable free, as I dont have the budget to buy an expensive one. I'm just an undergraduate student :\ ) which I can use for this purpose?

I'd be highly obliged if anyone can help me out with this.

Thank you.

[dtoshni]

Anyone? Can you just tell me if Maxsurf would be enough to do the calculations? I mean to ask, is it reliable? Even this would be enough.

Thank you.

[daiquiri]

Don't know about Maxsurf but there are several methods for calculating a drag of a body fully immersed in a fluid flow. Some more theoretical, some more empirical. Depends a lots on the geometrical shape and complexity of your vehicle. Do you have some pic to post?

[Guest625101138]

Michlet will give a good result. It will also cope well with near surface operation where wave drag has an influence.

If it is for deep water then you can do a quick calculation using the ITTC skin friction formula. If the vehicle has large control surfaces or other appendages then the friction for these done separately would give slightly better result.

Rick W

[zeroname]

hy
you can try to import it in maxsurf, watch at first the model after importing is it same as u modeled. then set up zero point, and frame of reference , perform hydrostatic calculation and save it. then export it to hull speed for power and resistance calculation.
you can also use navcad for resistance calculation .

[Humberto]

Hi,

You can try jSDN. Although it is not oriented to submersibles, you can do standard hydrostatics plus longitudinal and transversal stability calculations (which may be useful for both surface and underwater operation).

For resistance, it may be trickier. You can do friction with ITCC line, but form drag would be difficult, because most available series are based on surface crafts. jSDN uses the Delft series, which are not adequate to a small submersible.

I you want to give a try, go to http://www.jsdn.es and ask for a demo license (which will make available the options you require).

Hope this helps,
Humberto

[dtoshni]

Thank you so much everyone.

@daquiri: I dont have a picture at the moment of the vehicle, but I can tell you that it looks like an airplane almost, with a central ellipsoidal body and two wings which have thrusters on the ends. Its a very small vehicle, almost 0.5 m in length.

@Rick: Yeah, I guess the major area of operation of the vehicle will be near surface. Is there any site from which I can download Michlet? And also, I have another vehicle, which might also go in deep waters. Which software should I use for that vehicle?

@zeroname: OK. Thanks for the procedure. And will these results(the ones given by Maxsurf) be reliable for an underwater vehicle (which will be traveling at a shallow depth mostly) ?

@Humbert: Thank you. I shall try out jSDN. What do you suggest I do for the resistance calculations then?

[daiquiri]

If the vehicle's body shape is streamlined and if it has to operate near the surface, then I agree with Rick - the best way to go is probably Michlet software, which takes into account both friction and wave drag.

If you need to evaluate accelleration rates and power requirements, then you will need to include a correction for added-mass. Don't know if Michlet does this, but you can find some added-mass coefficients for various axysimmetric bodies in internet - mainy from studies on airships and submersibles.

[Guest625101138]

Originally Posted by dtoshni

.....
@Rick: Yeah, I guess the major area of operation of the vehicle will be near surface. Is there any site from which I can download Michlet? And also, I have another vehicle, which might also go in deep waters. Which software should I use for that vehicle?

...?

Michlet is no longer available as a free download. If you want you can send me an igs file or hull offset file and I can run Michlet.

Michlet will probably give the most accurate result for near surface operation. That is less than say within 3 hull diameters of the surface.

For a deep water vehicle you do not need to worry about wave drag. I have got satisfactory results with Michlet for hull fineness ratio of 8. The particular hull had one small appendage and essentially elliptical form with a pointy tail.

Rick W

[dtoshni]

Hey, thanks. But I dont think I'll trouble you with all that. I managed to get myself a copy of michlet. I shall see what I'm able to do with the thing.

Thank you everyone for your replies.

[dtoshni]

I had one other question too. If you all could please take out time to visit this thread, I'd really appreciate it. Thank you.

AUV: CFDAnalysis

Thank you once again for helping me out.