ADCP's Application to Ocean Current Measurement in the Port of Oulu

1. Where is Oulu Port?

Overview of Oulu Port

Oulu Port is located in the city of Oulu, Finland. It is an important northern port in the country and plays a vital role in the local and regional economy. The port is of a moderate scale and throughput, and it is well-connected to other Finnish ports and international shipping routes.

It primarily handles cargo related to local industries: forestry, technology, and some light manufacturing. Besides that, the port has facilities for handling general cargo and containers. Oulu Port is managed focusing on efficient operations and sustainability. There are teams for vessel traffic management, cargo handling, and maintaining the port's infrastructure.

Port Facilities

Berths: Oulu Port is made up of a number of berths that are built to handle many types of vessels. This includes berths for medium-sized cargo ships and barges. They have appropriate mooring and docking facilities that ensure the safety of ships during arrival and departure. The use of fenders and bollards helps in protecting the ships and the berths during the docking and undocking processes.

Cargo-handling Equipment: On the quay, there is a set of cargo-handling equipment. There are cranes and conveyor systems for forestry products like timber and pulp. General cargo and containers have forklifts, gantry cranes, and other handling equipment that move materials between the ships and the storage areas.

Storage Facilities: There are storage areas for different types of cargo. For forestry products, there are stockpiles with proper protection from the elements. For containers and general cargo, there are container yards and warehouses with organized storage systems.

Channel and Navigation Aids: The channel in the port is maintained to a suitable depth and width to allow the safe passage of ships. Regular dredging operations are carried out to keep it navigable for vessels with different drafts. Navigation aids including buoys, beacons, and radar systems help guide ships into and out of the port. Real-time information about the position and movement of other vessels around the port is given by radar systems.

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

Importance for Port Operation and Management

The measurement of the ocean currents in the Oulu Port is very important. This serves as a basis for ensuring safe vessel navigation. Captains of ships need the current speed and direction for decision-making during the approaching berths or navigating through the channel. A strong cross-current near a berth can turn docking into quite a laborious and risky process. For instance, a vessel approaching a berth against a strong current should adjust its speed and angle of approach to be able to come alongside safely. Precise current measurement permits captains to make informed decisions, hence reducing the risk of collisions and other accidents.

Secondly, it is crucial for the optimization of the port's operations. Current data enables better scheduling of arrival and departure of ships. By knowing the tidal currents and other regular flow patterns, the port authorities can plan better the allocation of berthing resources and plan the loading and unloading activities. This results in enhanced productivity since cargo - handling operations can be coordinated more effectively.

In addition, from an environmental point of view, in the event of a spill of pollutants like oil or chemicals, knowledge of ocean currents is useful. Given the nature of cargo handled in the port, it becomes important 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 Doppler principle work?

Principle of Measurement

ADCPs work on the principle of the Doppler effect. When an acoustic signal is transmitted into the water by the ADCP flow meter, it scatters off the moving water particles. Since the water particles are in motion due to the ocean current, they cause a frequency shift in the reflected acoustic signal received back by the ADCP current meter. This frequency shift, due to the Doppler effect, is proportional to the velocity of the water flow.

Current Speed and Direction Calculation

The Acoustic Doppler Current Profiler (ADCP) calculates the speed and direction of the ocean current at discrete depths in the water column by analyzing the magnitude and direction of this frequency shift. It can emit signals at different angles and at various depths, creating a profile of the ocean current, which describes how the current varies with depth.

ADCP Deployment in the Port

Shipborne ADCP

An ADCP current meter installed on ships operating in the Oulu Port area is used. During the movement of the ship around the port, the ADCP current profiler continuously sends acoustic signals to the water beneath it. The movement of the ship enables the ADCP meter to cover a wide area and collect current data from different locations. For instance, a research or inspection ship with a shipborne ADCP that is routinely surveying the port can collect data on the current patterns over different areas of the port and therefore give a general understanding of the water flow situation.

Fixed ADCP

Fixed ADCPs are placed at certain fixed points in the port, say on the bed of important navigation areas or at/inside the entrance/exit of the port. These ADCPs would continuously monitor the current at their fixed position in the ocean over a very long period. Such data is of relevance to study the ordinary pattern of currents in specific parts of the port. For example, a bottom-mounted ADCP installed near the entrance of the port can continuously measure the incoming and outgoing currents to help quantify tidal effects and other consistent flow features in the area.

4. What's needed for high - quality measurement of Oulu port currents?

Equipment Requirements

Certain equipment characteristics are crucial for the high-quality measurement of currents in Oulu port. The reliability of the materials used for equipment is one important concern. Equipment has to go through serious tests to ensure it withstands the sea conditions: the salinity and different chemicals inside seawater would, within a certain time, wear down materials. Mechanical forces in the waves and currents or changes in pressure at the waterbed due to fluctuations in the depth, have to be taken care of as well.

It should be smaller in size, lighter in weight, and with low power consumption. A compact size allows for easier installation in various locations within the port, whether on ships, on fixed structures like piers, or on the seabed. A lighter weight makes installation and transportation processes easier. Lower power consumption ensures that the equipment can operate continuously for long periods without the need for frequent battery replacements or excessive power supply, which is especially important for long-term monitoring applications.

Cost is another significant factor: the lower the cost, the more devices the port can deploy to measure currents in greater detail over more areas of the port.

The Advantage of Titanium Alloy for ADCP Casing

The casing of ADCPs is preferably made of titanium alloy. Due to excellent corrosion resistance, titanium alloy can sustain its structure and function well even after exposure to seawater for quite a while. Its high strength-to-weight ratio allows the making of casings that are strong yet not too heavy. For example, in the deeper parts of the Oulu port where higher water pressures are present, an ADCP 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: This can be suitable for the wide-area surveys of the port waters while the ship is in operation. It would cover different sections of the port as the ship moves around and will have gathered a massive amount of data to present a general view of the current overall situation in the port. This can be useful for 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, such as near important infrastructure 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: These can be used in situations when it is not appropriate to install fixed equipment either on the seabed or on ships. They float on the water surface, and the current can be measured at the upper layers of the water column. They are quite easy to deploy and redeploy and hence are suitable for monitoring some dynamic or difficult-to-reach areas in the port.

Selection Based on Frequency

The choice of frequency for ADCPs depends on the water depth in Oulu port. For water depth up to 70 meters, usually an ADCP current meter with 600 kHz frequency is good for that depth range due to its ability to give relatively correct current measurements. In waters as deep as approximately 110 meters, a 300 kHz frequency ADCP is more advisable. For very deep sections of the port with a water depth of up to 1000 meters, an ADCP flow meter with a frequency of 75 kHz would be highly recommended to ensure the reliable profiling of ocean currents at such great depths.

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.