HULL DESIGN

We have been designing high performance hulls in a broad diversity ranging from 5 to 90 meters of length. Whether you are looking for a speedy pleasure yacht, displacement commercial vessel or a semi-planning naval ship; we have the tools and experience to design an optimized hull.

Methodology

Most of our designs are one design where the vessel is built only once for a specific need. These designs are often built with high expectations in performance. Production hulls also occur in our daily work which most often are built on a tight budget. It is here important to design a hull that is effectively produced.

We use CFD tools to verify the performance of our designs which enable us to present the final product to our customers long before the ship is built.

APPENDAGE DESIGN

Underwater appendages operate in a rough environment. We have earned a good reputation for our cavitation free sea water intake as well as our underwater exhaust outlet. Furthermore, we have participated in appendage designs currently on the market; such as the Humphree interceptor and fin systems and the Volvo Penta folded propellers.

We offer not only our in-house designs such as the sea chest inlet or exhaust outlet but also special appendages such as fins or rudder designs optimized for your vessel. Our broad hydrodynamic knowledge and long experience in marine designs enables us to localize the root of the problem and suggest an optimal solution.

sea chest inlet

The sea chest inlet design is optimized and tailor-made for each system. During the design stage, we study the risk of cavitation and the wake occurrence. A well-designed system is cavitation free, which reduces noise and vibration, and generates a minimal wake which does not interfere with propeller and water jet efficiency.

exhaust outlet

The exhaust design follows a one-design principle, similar to the sea chest, where each outlet is designed for your particular vessel, engine and speed range.

It is important to keep correct back pressure in the exhaust in order for the engine to work properly. Our experience and knowledge enables us to optimize the outlet to obtain an optimal back pressure. The result is verified through a CFD analysis. Furthermore, a small interceptor is often designed in front of the outlet in order to receive a constant flow of gases, which reduces pulsations and thereby reduces noise and vibrations.

To the left: Exhaust outlet designed by Profjord with constant flow of gases.
To the right: An exhaust outlet with pulsating flow of gases.

CASE STUDY

The prize winning Humphree zero speed anti-roll fin was designed in collaboration with Profjord. We optimized the shape of the fin regarding resistance during speed and investigated the hydrodynamic loads that the fin is exposed to during usage. The study enabled Humphree to produce a fail-safe design with minimum added resistance, a design that ended up winning the 2015 DAME Design award.

COMPUTATIONAL FLUID DYNAMICS

Computational fluid dynamics (CFD) is a tool used by naval architects among others to predict the performance of e.g. a ship. It is best described as a virtual sea trial where the ship's behavior is investigated long before the ship is even built.

We offer in-house CFD services through state-of-the-art software. Long experience in CFD combined with an unrivalled knowledge of ship design enables us to offer not only a result, but a solution and a recommendation based on the results received.

A sample of what we are able to offer is listed below, the simulations are just as accurate for planning hulls which is helpful to determine for example the hump.

The outcome of a CFD simulation is highly dependent on the end user. It is important to treat the numerics correctly and we are therefore verifying all of our simulations to similar vessels or model tests, if available. The figure below shows the difference between turbulence models for two different  cases. Note that the model which is good for Vessel A is underpredicting the results rather severe for Vessel B. However, note the accuracy for the chosen models.

numerical sea trials

We evaluate hulls in numerical sea trials by utilizing modified CFD-methods. It is an efficient method to predict resistance, trim angle and hydrodynamic properties of a hull design. Compared to model tests, the simulations are carried out in full scale and problems with scale effects are thereby effectively removed. Propeller thrust and various appendages can be included in the simulations to get information about cavitation risks, wake fields and lift/drag from appendages.

If you want to make a quick evaluation of several hull designs, a model test is probably too expensive or too time consuming to be realistic. In such situations, a numerical sea trial is a good option. The analysis will provide you with the desired results without use of an expensive model. If you provide us with a 3D model and some basic ship parameters such as center of gravity and displacement, we are able to execute the analysis. The result can be presented in a rendered view to look more realistic in your marketing material.

numerical sea keeping and motion analysis

Sea keeping and motion analysis is a costly operation at a model test facility. We have developed a cost-efficient method where a combination of CFD and strip theory is used to predict the vessel's motions. The result is presented in operation curves where the operability is shown for a predefined speed and sea state.

By using linear strip theory software, we can assess the seakeeping performance of ships by simulate wave induced motions. Using basic hull data as input, important aspect of ship safety can be predicted such as roll and pitch angle, accelerations and probability of slamming and green water. It is also possible to evaluate the effect of various active and passive appendages such as roll stabilizing fins, bilge keels or interceptors.

MODEL TEST SUPERVISION

A model test is usually executed to verify the final design once the hull is optimized through CFD. We have long experience when it comes to model tests and have supervised several projects at different facilities.

Model test PROGRAM

Similar to a numerical sea trial, a model test is divided into different segments. Calm water resistance tests are carried out in a long basin whilst sea keeping and maneuverability tests are carried out in a bigger basin with wave generators to recreate different sea states. The model test results are preferably compared to CFD simulations in order to verify the performance of the designs. We have conducted several model tests to verify the in-house prediction methods we use.