The MARIN-developed FlowPike enables detailed flow measurement in operational conditions of in-service ships. The unique device utilises a stereoscopic PIV setup with two cameras and a laser sheet, able to measure all three velocity components inside a two-dimensional plane (2D3C). This measurement technique is adapted to the demanding operational conditions on board. With reliability in mind, all optical components are rigidly fixed in an underwater torpedo-shaped housing. The housing is able to rotate about its longitudinal axis, allowing a large area to be scanned.
Application includes scanning the full-scale wake field at the propeller, or resolving the full-scale vortices shed from e.g. bilge keels or other appendages.

Cameras are selected for the best image quality under expected trial conditions. For example the Phantom VEO 410 is a very light sensitive, compact camera which has a large image sensor to give the best results on propeller observations through a window. If light conditions allow, we typically shoot at 2000 or up to 3000 frames per second at full resolution. If there is limited space above the window, we might use IDT OS7 high speed cameras. This camera is half the size of the Phantom camera and also operates very well in low light conditions shooting up to 1300 frames per second. This camera can be used both for window and borescope observations.

Strain gauges are used to accurately measure forces in steel structures or shafts, for temporary or long-term applications.
Possible applications are power measurements on engine or propeller shaft, stresses in beams and fatigue monitoring.

For the measurement of loads, such as weights or the 'bollard pull' of tugs, we use specially selected load cells ranging from 6,5 to 350 Ton. Wireless read-out using our long range transmitter gives the opportunity for live feed on the bridge.

To transmit data over a long range (up to 20 km), MARIN uses 403 - 473 MHz transmitters which can be used in combination with various measurement equipment for central data acquisition of remote sensors.

Selecting the optimal motion sensor depends on the conditions to be measured. MARIN has a selection of sensors available ranging from small and easy to install MTI’s to the PHINS for high precision in harsh environments. The PHINS (Photonic Inertial Navigation System) from IXBlue is a compact device which gives all-in-one high-accuracy 3D positioning with heading, roll and pitch.

Measuring the propeller pressure pulses on full-scale vessels is one of our main full- scale applications of pressure sensors. The holes for the pressure sensors can be drilled while the vessel is in service. A typical application is verifying the theoretical pressure pulses of the propeller. Sampling rates up to 250 kHz are possible.

The MV Auris is a 5.7 m long RHIB (Rigid Hull Inflatable Boat) with a removable, modular sensor frame. The sensor frame and its control systems allow autonomous sailing inland or at sea utilizing several sensors for situational awareness. In-house developed sensor fusion, collision avoidance and path planning algorithms are implemented for autonomous operation. Situational awareness is provided by DGPS, RADAR, LIDAR, AIS and infrared cameras. The 140hp outboard gives it a max speed of 30 knots.

For sound measurements we use our B&K2250 sound level meter and analyser. It features frequency analysis, FFT and signal recording.

A range of fixed and handheld accelerometers is available, selected on the specifications of the challenge at hand. From quantifying pressure pulses, determining comfort levels to identifying vibration modes.

Ultra sonic distance sensors can measure the distance to a surface in a range from 0.5 to 10 m. The surface can be solid or liquid which makes it possible to measure the wave height of passing vessels. In The Netherlands some vessels have to meet requirements on their radiated waves. MARIN measures these waves on a carefully selected spot and separates the waves of the vessel from the undisturbed waves.

A wave radar is used to record waves from a vessel or structure. The device records the distance to the water surface and is corrected for ship motions on the platform, using a motion sensor. The wave radar provides wave height and period. The wave direction needs to be determined visually. The solution if a wave buoy cannot be deployed or retrieved in the area.

This free-floating buoy of 0.4 m diameter and a weight of approximately 30 kg is ideal for accurate wave measurements. This buoy transmits the measured data to a receiver up to a distance of 20 nm. For larger distances, position tracking by GPS is available. The system delivers:
· Wave elevation (raw data)
· Wave statistics (Hs, Tp, Tz, directions)
· Wave spectra (incl. directionality)
The buoy is free-floating and drifts with the current. A moored buoy can be used for long-term monitoring.

The usage of wave buoys can be unpractical in situations where it is hard to retrieve the buoy after use. In this case we use the C-drone which is a self-propelled wave buoy with autopilot for autonomous operation.

The ultrasonic wind meter is the easy to install solution to measure local wind speed and direction.

The WindCube 200S uses infrared laser light to measure the velocity of particles in the air up to 10 km away. Using light eliminates the need to have a structure present to measure the wind velocity at various heights and gives the unique opportunity to measure the undisturbed air flow.