Minimize the effect on ship in shallow water

[manon]

We all know about the effects of shallow water or shallow draft on the performance with respect to deep water. Well, for the vessels, that moves in the inland water ways, often have to move through the shallow water.

Can anyone suggest, how should be the design of a vessel in order to minimize the effect of shallow water on the ship performance? Help me with some possible methods, calculations or tradition or anything else.

Thanks in advance

[Leo Lazauskas]

Originally Posted by manon

We all know about the effects of shallow water or shallow draft on the performance with respect to deep water. Well, for the vessels, that moves in the inland water ways, often have to move through the shallow water.

Can anyone suggest, how should be the design of a vessel in order to minimize the effect of shallow water on the ship performance? Help me with some possible methods, calculations or tradition or anything else.

Thanks in advance

"Performance" is a very broad topic.

My (free) program Michlet can calculate the total resistance of thin ships in finite depth. The optimisation module "Godzilla" can also search for ships with minimum total resistance given a set of constraints on the hull geometry. Of course, resistance is just one aspect of performance.

Good luck!
Leo.

[Ad Hoc]

Originally Posted by Leo Lazauskas

"Performance" is a very broad topic.

Exactly!

Also, what type of boats, slow, fast, etc etc...

[manon]

Thank you Leo Lazauskas and Ad Hoc, for your response. I am apologize for not being so exact.
Well, the type of vessels are general cargo vessel Lbp up to 70m, beam 10-15m, draft max 4m.
Also, passenger vessels of maximum permissible 70m.
Also, feeder vessel.
Actually, I just need some suggestion from experienced Naval Architects and hull form designer, in order to improve the performance of inland vessels of our country, as the type,dimension and speed described above. Here, performance can be figured out, in the point of view of improvement in the power requirement/fuel consumption/speed.

Best Regards

[Ad Hoc]

Originally Posted by manon

.
Actually, I just need some suggestion from experienced Naval Architects and hull form designer, in order to improve the performance of inland vessels of our country.....

Good training of the crew, proper and regular maintenance of the vessel, using up to date charts and competent experienced Captains, coupled with proper navigation aids in the waterways and emergency services on the routes planned.

If you don’t address these, no matter how well designed the boat is you’ll continue to have accidents/problems.

[MikeJohns]

Originally Posted by manon

We all know about the effects of shallow water or shallow draft on the performance with respect to deep water. Well, for the vessels, that moves in the inland water ways, often have to move through the shallow water.

Can anyone suggest, how should be the design of a vessel in order to minimize the effect of shallow water on the ship performance? Help me with some possible methods, calculations or tradition or anything else.

Thanks in advance

I'm not sure if this is what you are after, bit it might help, is this a student exercise?

There have been some good papers on reducing squat. For an overview of what parameters you can change and their relationship have a look here:

http://www.ship-squat.com/How_do_I_p...Ship_Squat.htm

[Leo Lazauskas]

Dr. Tim Gourlay has also published extensively on the topic of squat. See:
http://cmst.curtin.edu.au/people/gourlay-pubs.cfm

[Tackwise]

Development Centre for Ship Technology (DST) in Duisburg Germany is one of the few institutes with a lot of experience in shallow water effects on inland waterway vessels. Their site has some interesting articles which gives you some idea of the factors involved (for specifics you will need to contact them directly)
http://www.dst-org.de/intro_e.htm

Some relevant papers:
http://www.iwwwfb.org/Abstracts/iwww...wwwfb08_06.pdf
http://cmst.curtin.edu.au/local/docs..._clearance.pdf

What is the average waterdepth you will be designing for?

Tackwise

[daiquiri]

This is akin to another topic discussed here quite some time ago, see my post #5: Dead Water for Designers

Leo & Tackwise:
Very good links, thank you.

[manon]

Many many thanks to all of you, the links provided will certainly help me a lot.

Mike Johns: Yes sir, this is a student exercise, but actually I am interested to go as deep as possible regarding this problem for my better understanding.

Tackwise: Average water depth 4,5 meter (in dry season)

[Tackwise]

Manon,

Take into consideration that at an average waterdepth of 4,5m, your ship will most likely not be able to navigate at its maximum draught (4m)! (Depending speed and ship, squat can be as much as 0,5m) Your payload will therefore be considerably less during the dry seasons.

My advise on design:
Focus a good deal of your design effort on the aft ship. Take into consideration that the required inward flow of water to fill up the 'void' in the aft ship, needs to come from the sides of the vessel. You can generally assume that no flow will originate from under the vessel.

Tackwise

[manon]

Tackwise,
What should be the minimum depth under the keel to the river bed for which there will be no squat. I cant remember where I have found, but I have read somewhere that the minimum depth under the keel or ship bottom to the river bed should be greater than the half of the ship draft in order to have no effect of squat on that ship.......Is this assumption correct?

Manon

[Tackwise]

Manon,

There is a guideline that when the ration H/T drops below 1,5 the effects of squat becomes measurable. However beware of using such guidelines, as there are to many variables dictating the squat phenomena, such as the speed, shape of the ship, blockage effects, bottom characteristics (sand/mud), etc.

I have looked into several squat calculations, and found the results to be scattered. Most calculations have been written for sea vessels entering shallow water. All of the effects encountered by an IWV navigating rivers and canals will therefore not have been taken into consideration!

As so often seems to be the case in boat building: The infinite variables of real life are hard to summarize in an accurate but short calculation!!

Tackwise