Our hydrodynamics and aerodynamics simulation services give instrumental information for an optimal design below and above the water surface. We can handle the world’s biggest ships in full scale with reasonable budget and content. This remarkable feat has been achieved by developing projects, streamlining the project structure and investing in computational hardware.
We have experience in completing various demanding marine R&D projects using fluid dynamics (CFD):
- hydrodynamics: hull shape optimization, resistance prediction, self propulsion, maneuvering, appendage optimization, energy saving devices
- aerodynamics: wind loads, comfort factors, smoke dissipation
- propeller testing, hull-propeller interaction, pressure pulses and cavitation simulations
- scrubber wash water overboard nozzle optimization for classification
- cross flow, swimming pool water movement and load re-balancing
- exhaust pipe explosion simulation for gas engines: rupture disc position definition for classification
General and detailed analysis of ship hydro-and aerodynamics helps to:
- Minimize hull resistance, improve ship fuel economy
- Improve passenger comfort
- Identify shortcomings and improvements early in the design cycle
- Reduce or replace model testing
- Design model test programs
- Achieve regulatory limits
Our virtual Marine Laboratory can handle all tank tests typically done in basin, by definition they are done in full scale to yield highest possible accuracy for the performance predictions. For comparison to model tests also model size simulations are conducted.
- sea keeping
- cavitation tank/tunnel
- Energy saving systems
How does the size matter?
An ant can drink from a drop of water, but man has to use a glass. All things are not scalable. This is also true when you compare model scale prototype testing to a full-scale model. For instance, the boundary layer is relatively thinner, flow separation is usually delayed, and vortices encounter higher damping in full scale. In the picture below we have demonstrated the difference in the real-life simulation case.
Physical prototypes will always have limitations in size. Until recent years, full scale marine hydrodynamics simulations have been earlier computationally intensive for commercial use, and small scale simulations have been performed also in the simulation environment. Fortunately for the maritime industry, the computational resources have increased. At Elomatic, full scale fluid dynamics CFD simulations are in everyday commercial use.
Wake fields for full scale (left) and model scale (right). Over 10 % change observed in axial velocity in typical design point of 0.7R wake curve on the top position of the propeller.
Building the ship aerodynamics model
Modern-day CFD simulations should be performed in full scale using a sufficient amount of detail. Only with a properly performed and comprehensive set of simulations can ensure the performance of the ship or facility evaluated. A simulation should be built to provide answers to all required issues, i.e. wind loads, comfort aspects, effluent dispersions, gas safety aspects… Everything can be obtained using the same simulation model!
The simulation of ship aerodynamics replaces or extends and gives a deeper understanding of wind tunnel tests traditionally performed. The wind tunnel test performed with simulation can be similar to traditional methods, and is thus comparable to these. The best performance can anyhow be utilized from the simulation which is done for the full scale vessel, in which the details of interest can be included into the model. The benefits of the full scale simulation are quite clear; this is the only method to investigate the real scale ship performances before its manufactured, find the real wind profile impacts or harbor maneuver conditions, or include the ship velocity relative to the sea to the flow behavior detected in the aerodynamics.
Wind simulation, Mein Shif III for TUI, main engine smoke dissipation and pressure at superstructures with streamlines at service speed. Once build, the simulation model can be used for many different purposes.
Some examples of simulations included in the ship superstructure wind analysis:
Virtual towing tank tests
Virtual towing tank tests helps in ship hull design and optimization to yield energy savings and desired operability:
Based on the IMO rules, our virtual towing tank tests include:
- Resistance tests, with and without appendages
- Propulsion tests with desired propellers, design or draft (stock) propeller
- Streamline test for optimum inclination of bow thrusters openings, fin-stabilizer openings and bilge keels. Shaft brackets and bossings or pods can be included.
- Short propulsion tests for example to find out the optimum turning tilt direction of propellers and the rudder neutral steering angle at the speed range of interest
- Short trim tests (propulsion tests) with final hull in order to find out the effect of trim on propulsion power
- 3D wake measurement
- Open water tests for final propellers
- Cavitation tests and calculation of propeller induced pressure pulses in the most critical conditions.
- Wave induced motion control (6dof)
- Roll damping: with and without fin stabilizers, bilge keels, rudders, skegs and antiroll tanks
- Non-linear motions
- Events driven by GM variation
- Sudden heel angle increasement
- Wave impact loads
- Green water collapse: slamming, bow loads, safe boats etc.
- Aft slamming
- Added resistance
- Motion control devices impact on the resistance
- Shallow and deep water resistances
- Wave/wind, ship motion and added resistance, drift and steering
- Propeller loading
- Loss of thrust
- Ventilation, propeller tip suction
- Relative wave elevation
- Speed loss determination (service margin) – Propeller characteristics
- Increase of hull resistance
Manoeuvring tests are divided into IMO standard manoeuvres and additional manoeuvres. IMO standard manoeuvres:
- Zig-zag tests
- 10°/10° to both sides
- 20°/20° to both sides
- Turning circle test
- 35° rudder angle
- Full astern stopping test
- Additional manoeuvres:
- Spiral test
- Reverse spiral test
- Pull-out manoeuvre
- Very small zig-zag manoeuvre
- Harbour and low speed, crabbing
- Pole test with thrusters
Propeller testin lorem.
Marine energy saving systems
We have developed a sophisticated analysis method to carry out an Air Lubrication System analysis (ALS). Some of the possibilities are:
- Energy Saving Estimation analysis for a selected vessel
- Air flow rates for different operational speeds and positioning of the air supply devices
- The risk analysis for air entrance into the propellers
- Detection of the lubrication air spread in the flat bottom area and stern
- Amount of air fed into system vs. power required for the air supply vs. air behaviour under the hull
Variety of different appendages can be optimized for better performance
- The bow thruster tunnels
- Fin stabilizers
- Bilge keels
- Sea chest
- Stern thrusters
- Head boxes
Wind load Lorem
Exhaust gas dispersion
Exhaust gas dispersion
Helicopter shipboard operations
Helicopter shipboard operations