ADCP in Raahe Port: Ocean Current Measurement

Explore ADCP's application for ocean current measurement in Raahe Port, its working principle, equipment requirements, and selection.

1. Where is Raahe Port?

Overview of Raahe Port

Raahe Port is in the town of Raahe, Finland. It is a major port, strategically positioned along the Finnish coast. The moderate-scale port has a good throughput and acts as an important transportation node both locally and regionally.

It handles diversified cargo: forest products, like timber and pulp, but also other bulk cargoes of minerals and industrial products. Shipping connections at the port are well established, nationally and internationally. Raahe Port's management is very efficient and fully focused on ensuring smooth operation and safety. There is a specialized vessel traffic team for managing vessels and cargo and for the implementation of the various functions linked with the port.

**Facilities within the Port:**The port facilities mainly include berthing facilities and their ancillary infrastructures designed to handle diverse vessel requirements, from medium-size cargo vessels, barges to tankers and container vessels. These include modern mooring and facilities for safe ship arrival and departure. Superior quality marine fenders and bollards can resist huge forces acting upon a vessel at the instance of docking or undocking.

Cargo-handling Equipment: There is a range of cargo-handling equipment along the quay. For forestry products, there are cranes and conveyor systems to move logs and pulp efficiently. In the case of bulk cargo, such as minerals, there are grabs and conveyor belts that transfer the materials from the ships to the storage areas. Other general cargo is also handled.

Storage Facilities: The storage facilities for different types of cargo include stockpiles that are well-protected from the elements, especially for forestry products. There is also a storage area for bulk materials that has containment systems to avoid spillage and other warehouses for general cargo. Provision for perishable goods can be made if need be.

Channel and Navigation Aids: The channel is dredged to an appropriate depth and width for safe passage of vessels. This requires regular dredging to maintain the channel at a depth that can be navigated by vessels of various drafts. Navigation aids include buoys, beacons, and radar systems that serve to guide vessels into and out of the port. These radar systems can provide the real-time information about other vessels' positions and their motion around the port area.

2. Why should we measure the ocean currents in the Raahe Port?

Importance for Port Operations and Management

Measurement of ocean currents at Raahe Port has vast importance; firstly, safety is one aspect concerning vessel navigation. Knowledge of the actual speed and direction is important for ship captains in approaching berths or navigating through the channel. A strong cross - current near a berth can make the process of docking challenging and hazardous. For instance, if a ship is approaching a berth against a strong current, it may need to adjust its speed and angle of approach to ensure smooth and safe docking. Accurate current measurements allow captains to make informed decisions and reduce the risk of collisions and other accidents.

The latter is essential to optimize the port's operation. Current data helps in more efficient scheduling of arrival and departure of ships. With an understanding of tidal currents and other regular flow patterns, the port authorities can plan the availability of berthing facilities and the loading and unloading operations. This results in a higher productivity since cargo - handling operations can be better coordinated.

In addition, from an environmental point of view, in the event of an accidental spill of pollutants such as oil or chemicals, knowledge of ocean currents is useful. Given the nature of the cargo handled in the port, it is important to be able to predict the spread of a spill. The current data can be used to quickly implement containment and mitigation measures to minimize environmental damage.

3. How do ADCPs using the principle of the Doppler work?

Measurement Principle

The ADCPs work on the principle of the Doppler effect. When an acoustic signal is emitted from the ADCP flow meter into the water, it encounters the moving particles of water. Since the water particles are moving due to the ocean current, they cause a frequency shift in the reflected acoustic signal that reaches the ADCP meter back. By the principle of the Doppler effect, this frequency shift is related to the velocity of the water flow.

Current Speed and Direction Calculation

From this frequency shift magnitude and direction, the ADCP profiler will work out the speed and direction of the ocean current at different depths in the water column. Because it sends signals out at multiple angles and different depths, it can produce a profile of the ocean current, showing how the current varies with depth.

ADCP Deployment in the Port

Shipborne ADCP

One ADCP flow meter installed on a ship operating in the area of Raahe Port moves around the port while continuously sending acoustic signals into the water beneath it. As the ship moves, it enables the ADCP current meter to travel over a large area, collecting current data from any location. For instance, a research ship or an inspection ship with the ability to carry a shipborne ADCP can perform an ordinary survey of the entire port and collect data related to current patterns in different sections of the port. Hence, a complete understanding can be gained regarding the situation about the water flow.

Fixed ADCP

Fixed ADCPs are located at fixed, strategic positions in the port, like on the seabed near important navigation areas or at the entrance/exit of the port. These ADCPs continuously record ocean currents from fixed positions over long periods. The recorded data helps in analyzing regular current patterns in specific areas of the port. For example, a bottom-mounded ADCP at the port entrance can log the currents moving in and out, so as to provide insight into the tidal influences and other stable flow conditions in that location.

4. What does it take to measure high - quality Raahe port currents?

Equipment Requirements

In addition, certain equipment characteristics are key to high-quality measurements of currents in Raahe port. First is the reliability of the material: the equipment must therefore be able to resist in harsh marine conditions. Seawater contains salts and several chemicals that may destroy any other material after some time. It also has to go through the pressure variation at several depths of the water, and the mechanical stress resulting from waves and current oscillations.

The second is a reduced size, weight, and low power consumption. A compact size would allow for easy installations even in various locations within the port, whether on ships, on fixed structures like piers, or on the seabed. A lighter weight will simplify the installation process, including transportation. This contributes to low power consumption, enabling the equipment to operate for long periods without needing frequent battery replacement or excessive power supply, especially for long-term monitoring applications.

Cost is another major factor. A lower-cost option will enable the port to deploy a larger number of measuring devices to monitor currents more comprehensively over different areas of the port.

The Advantage of Titanium Alloy for ADCP Casing

The casing in ADCPs is made, preferably, of Titanium Alloy. This material will withstand the corrosion from sea water over a long period with structural integrity and functionality intact, hence making it the desired material for ADCPs to be used in water. Besides, its high strength-to-weight ratio allows a case that is strong but still fairly light in weight. For example, in the deeper parts of the Raahe port where higher water pressures are present, an ADCP current profiler with a titanium alloy casing can effectively withstand these pressures and continue to provide accurate current measurements.

5. How to Choose the right equipment for current measurement?

Selection Based on Usage

Shipborne ADCP: When the aim is to carry out wide-area surveys of the port waters while the ship is in operation, then shipborne ADCP becomes a suitable choice. It covers different sections of the port while the ship moves around, collecting a large amount of data to provide an overview of the general current situation in the port. This is useful in mapping the general flow patterns and variations across different areas of the port waters.

Sitting-bottom ADCP: For long-term and fixed-point monitoring of specific locations within the port, like near important infrastructures or areas with complex current behaviors, sitting-bottom ADCPs are more appropriate. They can continuously record the current data at those fixed positions, providing valuable insights into the local current characteristics and any changes over time.

Buoy-mounted ADCP: In situations when it is not convenient to install fixed equipment on the seabed or on ships, buoy-mounted ADCPs can be used. They float on the water surface and can measure the currents in the upper layers of the water column. Being relatively easy to deploy, they can be relocated if needed, thus making them suitable for monitoring certain dynamic or hard-to-reach areas within the port.

Selection Based on Frequency

The choice of frequency for ADCPs depends on the water depth in Raahe port. For areas with a water depth of up to 70 meters, an ADCP with a frequency of 600 kHz is usually a good choice as it can provide accurate current measurements in this relatively shallow depth range. A better-suited ADCP would have a frequency of 300 kHz in the case of deeper waters, up to about 110 meters. In the deepest reaches of the port, for those sections where the water could be as deep as 1000 meters, a 75 kHz ADCP flow meter will be more appropriate for effective profiling of the ocean currents.

There are several well - known ADCP brands in the market, such as Teledyne RDI, Nortek, and Sontek. However, there is also an excellent Chinese ADCP brand-China Sonar PandaADCP. It is made entirely of titanium alloy material, which not only ensures its durability in the marine environment but also offers an excellent cost - performance ratio. For more information, you can visit its official website: (https://china-sonar.com/).

Here is a table with some well known ADCP instrument brands and models.

Brand model
Teledyne RDI Ocean Surveyor ADCP, Pinnacle ADCP, Sentinel V ADCP, Workhorse II Monitor ADCP, Workhorse II Sentinel ADCP, Workhorse II Mariner ADCP, Workhorse Long Ranger ADCP, RiverPro ADCP, RiverRay ADCP, StreamPro ADCP, ChannelMaster ADCP, etc.
NORTEK Eco, Signature VM Ocean, Signature ADCP, AWAC ADCP, Aquadopp Profiler, etc.
SonTek  SonTek-RS5, SonTek-M9, SonTek-SL, SonTek-IQ, etc.
China Sonar PandaADCP-DR-600K, PandaADCP-SC-300K, PandaADCP-DR-300K, PandaADCP-SC-600K, PandaADCP-DR-75K-PHASED, etc.
Jack Law October 12, 2024
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