Naval Hydrodynamics - Science topic

Hi Mohamed,

Did you find an answer to this? If so I would be interested in what that was.

Thanks,

Ali

Thanks for your contribution Liliia Kondratieva .

"How many variable input values do you have for creation of necessity data? " I did not get this question . I think, you mean the test data. If so, I don't have any :) That's point though. If I had some test data of some ships (turning circle, accelration, zig-zag, pullout,...) I could make an parameter identification.

I need all coefficients (lets say 4DOF, not 6DOF). There are papers for some. Example:

Ex: Son, K. H. and Nomoto, K. (1981). On the Coupled Motion of Steering and Rol ling of a High Speed Container Ship, J.S.N.A., Japan, Vol. 150

But I need a lot more.

The data you supplied, for which ship are they?

Hi Hariharan Kallath

For simulate this, if surge ignored, you can use morphing mesh But it is very slow. for Zig Zag motion you need to define 2 DFBI, one for body and one for rudders, and then in angular velocity for rudders, you can define Sin field functions. attention if your surge velocity assigns to DFBI, in second DFBI you need also to define translation velocity as well as first DFBI.

Best Regards

hi Iarly Vanderlei da Silveira

please call me in: seyed.reza.991@gmail.com

with hardship and trusting in god

You can perform forced oscillation at any period requested using a hydraulic or electric moving arm forcing a vertical sinusoidal motion

The SOx emission depends on the sulfur content of the oil and not on the load of the engine. Hence you can calculate this easily with a mass balance. For NOx you will need a suitable model for the combustion process which is more difficult to deduce. At least you can look for some data in the literature to get an idea of how many NOx approximately you will have.

Dear Ali

Sorry but I cannot; I left DTMB 4 years ago, and in addition never did any work with propellers

Francis

Thank you for your feedback.   I define my Reynolds number on the thickness of the ellipse, which I keep constant. After reading some articles  thoroughly I discovered that they define their Reynolds number based on the cord length, which is kept constant. This lead to two different Reynolds numbers, and my results compared much better to literature when recalculating my Reynolds numbers to their standards.

Mr Weymouth.  your claim that the Strouhal number is less consistent at lower Reynolds numbers is of interest. And it will most helpful to explain why my lower Reynolds numbers does not follow the same trends as seen for the range 10³-10⁵. If any literature where this is stated comes to mind please let me know. 

There have been several attempts to measure and model the effects of surge, and other motions in sliding-seat rowing. I don't know of any that have been made with fixed-seat rowing.

Day et al used the unsteady form of Michell's thin-ship theory to estimate wave resistance. The theory was quite successful at low stroke rates, but was very poor for the rates typically used in Olympic class events.

See:

Day A., Campbell I., Clelland D., Doctors L.J., Cichowicz J.,

"Realistic evaluation of hull performance for rowing shells, canoes, and kayaks in unsteady flow",

J Sports Sci. 2011 Jul;29(10):1059-69. doi: 10.1080/02640414.2011.576691.

The theory might be useful for fixed-seat rowing because the stroke rates are typically far lower than with sliding seats.

I released a (free) program named FIRM that allows users to model fixed- and sliding seat rowing. See:

The program accounts for the effects of hull motions on the wave resistance and viscous drag of the hulls for all Olympic classes of rowing (singles to eights).

Another alternative is to use a CFD code. There have been a few attempts to do this with kayaks, canoes and rowing, but I don't know if they have been used with fixed-seat rowing.

Dear Mojtaba

I recommend you two article entitled: "An overview of control performance assessment technology and industrial applications" and "Control performance assessment for nonlinear systems".

I hope that you already found a solution since it has been almost a year since your question. There are several well accepted software tools used in industry for marine structures (jackets). Depending on the site conditions there will be an interest for either wave - wind - current loading condition or seismic ground motion induced loads. From Kasiphon K comment you will see that soil induced damping if far higher than hydrodynamic. I believe today you can model fully "interconnected" jacket - foundation analysis with soil - structure interaction tools available through commercial software (SACS, Abaqus, etc).

Thanks Sirous , I want a clarification about your appreciated answer ,

Firstly, as per ASME B31.3: ,for, t ≥ D/6 : Y = (d + 2c)/(D+d+2c), it is not clear in the code that is  still valid to use the thickness equation only with calculated  Y coefficient without changing in the remaining  terms ,or there is another equation ,and if not can you please send me UK code covering this issue?.

You could also refer to trends of turbulence intensity deduced during experimental works. We carried out some investigation in a wave channel at our lab, for both cases of regular and irregular waves. If interested, try the following link

Additional to the very good recommendations you already got, there is a classic by German authors:

Ship design for efficiency and economy,

Herbert Schneekluth ; Volker Bertram

2. ed., Oxford [u.a.] : Butterworth-Heinemann, 1998

More general point to enter the topic could be:

K.J. Rawson ; E.C. Tupper

5. ed., Oxford [u.a.] : Butterworth-Heinemann, 2001

or as an introduction:

David G. M. Watson

1. ed., Amsterdam [u.a.] : Elsevier, 1998

If you are interested rather in small crafts, I liked this book (eventhough outdated):

The Naval Architecture of Small Craft, D. Phillips-Birt, Hutchinson scientific & technical, 1957

Have fun!

I think the book below is a very useful for you if you wish to understand the hydrodynamics of catamaran

"Molland and Trunock, Ship Resistance and Propulsin, Camb. Univ. Press".

However, if you can't go for experimental tests it is better to use CFD to study the viscous damping of your unit.

No explicit criteria are provided for deflection in standards. Some infromation can be found in API RP 2A / 2GEO or Iso 19901 series.

Traditional procedure is to perform global analysis of the jacket structure considering foundations with PY curves and superstructure and to check final results w.r.t geotechnical strength and structural strength, not forgetting group action for the foundation part.  

As a general advice I would say: when you are setting your MPC problem up you should choose your weighting matrices based on the following criteria:

- stability and feasibility of the underlying problem should be achieved. 

- elements of the weighting matrices should be first normalized and then magnified based on their importance.

Generally for the first criterion there is no solid theory in the context of "NMPC" based on my best knowledge, although some results may be found in the literature.

Regarding the second factor the simplest way is to consider physical features of all states and obtain the maximum and minimum values they will achieve in the normal operations. Alternatively, you can first design a simple controller (e.g. PID) and run the system in different points, then you can estimate min/max of each state. Finally, you can first normalize all states and so on....

Maxsurf software is very good, but my advise for resistance the program is simply estimate the resistance and not so accurate. It better to use CFD for the resistance analysis. 

It is too wide definition of a ship. As a minimum, you need for the ship type selection, dimension correlation and shape of hull(s). 

In my bachelor thesis I studied with fluent program and appropriate boundary conditions gave me approximate results. But I only studied with ships. If you are researching a submarine or some vessel in deep sea, you have to analyse the vessel like an obstacle in a pipe.

Regards.

Assuming same speed of both engines, same speed ratio and same orientation of the torque, the torque of both engines add up, meaning you are right.

REZA:

GARY has provided you with his work -- and this may be all  you require.  However, you might also consider simply contacting the earlier authors -- by phone or e-mail and ask if they have any suggestions [Gary has given you what he had, so the other authors remain to "chase."}  This technically-termed  "informal literature search" approach is often surprisingly effective.  Personally, however,  I have found it usually more effective to first do a "formal literature search" that is aimed at articles that have cited the  either the earlier articles at hand, or those provided by Gary.    Looking at these in turn, you may then identify cites of their work and further continue until you have citations and even pre-prints of work in press.   This "follow-the-citations-forward" process is well-known to research librarians (aka, "Information Scientists")....                                                                                                              One way to start the process is to Google the word Scholar  and in the resulting scholar related articles find and open "Google Scholar."   When this is opened, then type in the authors names for any article you have at hand in the format: Cokins G, Nextauthor H (or whatever).   I did this entering Cokins G and added terms "and up front costs of building ships"   My second result [orders may be slightly different with each person] was that below which is Cited by 114 which you then click-on, and sort through for articles of interest to further click-on...  

ALVAH

[BOOK] Performance management: finding the missing pieces (to close the intelligence gap)

G Cokins - 2004 - books.google.com

... 85 Activity-Based Management Model Design and Principles: Key to Success 98 Operational

(Local) Activity-Based Management for Continuous ... Gary Cokins garyfarrns@aol.com (I welcome

your e-mail.) ... modeling the data into information, and Web-reporting it to users. ...

Cited by 114 Related articles All 3 versions Cite Save More

Hello Mayur,

To model the rolling motion of a ship in Fluent, you either have to use the 6DOF solver inside the solver and define the properties of your vessel (like displacement, moment of inertia etc.) or write a UDF to solve for the fluid-structure interaction between the ship and the surrounding fluid.

I have heard that Star-CCM+ is easier to use for these types of simulations but I have never tried it myself. You might want to learn more about it if you will be doing ship motion simulations a lot in the future.

Good luck with your simulations.

Kemal

The low-frequency responses are the motions caused mainly by second-order wave loads, current, mean wind component, mooring systems and thrusters.

u can ask D.r reza, i sure he can help u

have good night

Yes, the broad ways that something could be ice capable was the problem when I looked at the database.  Ice capable fixed structures in the Arctic would be a good category, but that, too, is a giant set of potential technologies.  I'm working on a little paper where I've taken 5 'factors' that two energy experts used in a 2009 article to assess how likely it is the Arctic will get exploited as environmental change moves along. I'm looking at whether any of the factors are further along now than then. I thought the article's factors were general enough to cover lots in the Arctic and they were not specific to energy production.  New technologies might also prove useful for adapting things for those who live there all the time.  Stands to reason that technological adaptation to change would grow fast there.  But it is hard to show that. Any suggestion are welcome.  I have a former student who works North Slope, he's a field engineer.  He's trying to help me think about it, too.  But, I see you have a lot on this.  I'm not an engineer.  Any suggestions would be welcome.

Hi Hadi,

Here are a few that may help:

Introduction to Offshore Structures: Design, Fabrication, InstallationOct 1981

by W.J. Graff

Offshore Installation PracticeNov 1987

by J. Crawford

Construction of Marine and Offshore Structures, Third Edition5 Mar 2007

by Ben C. Gerwick Jr

Subsea Pipeline Design, Analysis, and Installation14 Mar 2014

by Qiang Bai and Yong Bai

Good luck!

Luiza

The air cushion shouldn't be modelled with strip theory. The sidehull hydrodynamics might be modelled with strip theory while a simple mathematical model for the air cushion dynamics (assuming uniform pressure in space) can be included in terms of two extra degrees of freedom (pressure and density) in the equations of motion. The most easily available write-up of this is found in Faltinsen "Hydrodynamics of High Speed Marine Vehicles" (2005), Cambridge Univ. Press.

... thanks a lot!

Dear Chi,

For answer this question, firstly we should know when Hydroelasticity is important. Hydroelasticity means that the fluid flow and the structural elastic reaction are considered simulaneously and that we have mutual interaction, that is,

1-The elastic vibrations cause a fluid flow with a pressure field

2-The hydrodynamic loading affects the structural elastic vibration

For study phenomenas due to Hydroelasticity, there is ways and criteria ,for example , Wagner and von Karman methods for slamming, drop test for Green water, comparison with standards (for example, DNV classification society for determine pressure loads due to Hydroelasticity in plate).

As example, for bottom slamming the Ochi (1964 ) criteria has offered. For more information, I think one of the best and classical reference is:

Hydroelasticity of ships , by Bishop and Price (1979)

Good Luck

For all Owen Clarke Design projects, the common denominator is performance, regardless of whether the yacht is a cruising or racing design. Our designs always prove to be fast. This is partly due to the tools that we have available to us, the way in which we use them and our partnerships with some of the world’s leading engineers, designers and marine technology consultants.

As professional engineers and designers we offer our skills, experience and use of the tools at our disposal to individuals, yacht designers, boat-builders and other agencies as well as applying their use to our own designs. OCD have recruited qualified naval architects in recent years in order to expand this area of our business. We have continued to invest time and resources in the application of analytical methods such as Computational Fluid Dynamics (CFD) and Finite element analysis (FE) to fluid and structural engineering problems, expanding the use of these tools through our range of designs as the software and services have become more cost effective.

The starting point of any new design is to develop a set of hull lines which define the geometry of the boat. We’ve been using Maxsurf, the world’s leading yacht design software since drawing the lines of our first racing boat, the 35’ trimaran Fiery Cross, in 1987. Since then the product has also been developed for use in the design of commercial craft and ships. It remains however the most utilised yacht design software for designers the world over.

another cases can help you are : 

1.Cavitation inside the inlet

2. Ventilation and penetration of air from

the free surface or from

entrained air in the boundary layer

Dear James,

Surge added mass (a11) of a floating object, a11 approximately equals 10 % of its mass. But, regarding restoring force, there is not any restoring force for the surge motion. For floating objects, restoring force exist for heave, pitch, and roll. In this case, you have a damping force due to surge velocity, and you can write the motion equation in the form of (m+a11)d(u)/dt+(b11)*u = External Force, if the motion is pure surge. If you have the response of your object, you can estimate both a11 and b11.

Hello Ehsan:

  I am not familiar with surface effect ships but if the porblem can be written as a non-linear ODE control systems, then our CPWL technique is suitable. Please let me know if you are interested to go into further details.

   Best regards,

PD: My e-mail is andresgarcia@frbb.utn.edu.ar