Naval Architect JB Marine Consultancy Naval Architect  

Tel / Fax +44 (0)1481 253053    Mobile Tel: 07781 100621    Email: john@jbmarine.biz

Hydrodynamics

Resistance/Performance Prediction   Model Tests  Propulsion Analysis   Seakeeping   Manoeuvring

The hydrodynamic design of a vessel involves the design, fairing and optimisation of the hull form to meet specific requirements. Broadly speaking, marine vessels can be divided into several categories: 

• Displacement vessel; one that travels through the water at a relatively low speed for it's length. Vertical forces on this type of craft are predominantly due to the vessels buoyancy, or hydrostatics.

• Semi-Displacement (or semi-planing) vessel; one that travels through the water at a medium speed for its length. Vertical forces on these craft are a combination of hydrostatics and hydrodynamics.

• Planing craft; one which travels at a relatively high speed for it's length and which uses dynamic forces to obtain it's running position. The vertical forces are therefore primarily due to hydrodynamics. 

• Alto-planing craft; very high speed craft whose running condition is due not only to hydrodynamics, but also due to aerodynamics (such as offshore racing boats).

• In addition there are various other styles of craft, such as high speed, wave piercing vessels, Small Waterplane Area Twin Hull (SWATH) vessels, etc. 

All of the above require some hydrodynamic design; the hydrostatics will have derived the flotation and stability requirements, and consideration must also be given to the flow of the water around the vessel and the minimisation of resistance (drag).

In addition, the appendages may require fairing to reduce resistance and propellers must be designed to provide maximum efficiency and to match the engines. 

Resistance/Performance prediction

JB has significant experience in the field of Hydrodynamics and, using model test series data can predict the speed/power requirements of a given design. 

Model Tests - Resistance, Seakeeping and Manoeuvring  

JB has undertaken model tests of various craft, ranging from resistance tests for 16 metre landing craft and various planing powerboats, through to series resistance and seakeeping tests on trimaran frigates and a stealth-corvette.

JB can also undertake the analysis of the model tests, to provide a correlated performance prediction.

Propulsion Analysis

The correct selection of a vessels' propulsion system is important; the efficiency of the system and hence through-life cost is dependant on selecting the most appropriate machinery and propulsor. Whether waterjets, conventional propellers or surface drives are intended, JB can assist with optimising the design and installation.

Seakeeping

In addition to the calm-water requirements of a design, there may be rough-water, or seakeeping requirements for the vessel. JB can undertake calculations for added resistance, or can arrange model tests to undertake the added resistance due to waves. Optimisation of the hullform for anticipated sea conditions can have a significant impact on fuel savings. JB can  undertake seakeeping calculations to predict the vessel motions, slamming pressures and the anticipated Motion Sickness Index - the probability of passenger sickness.

Manoeuvring

JB has been involved in manoeuvring studies for 'dynamically positioned' ships and can undertake various studies to assist in the prediction of vessel manoeuvring capabilities. Click here to read a paper presented by JB on the subject of ship manoeuvring.

JB uses the Maxsurf range of software tools for ship and boat design, from the hullform, through to detail construction aspects. Combined with solid modelling CAD, we can offer the design, cutting patterns and full structural drawings for your project.

If you would like JB to assist you with a hydrodynamics issue, or if you would like more information, then please contact us:   

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