Application of ADCP to Ocean Current Measurement in Lerwick Harbour

1. Where is the Lerwick Harbour

The harbor is in Shetland, Scotland. It is an important port situated in the northern part of the British Isles and one of the well-placed ports in the North Sea.

Port Scale and Throughput

The scale of the harbour is massive and can accommodate most vessel types. It is a high-throughput port handling all types of cargo, including oil and gas equipment, fish, and general merchandise. It is also close to rich fishing grounds and the North Sea oil and gas fields, making it an important base for the fishing and offshore energy industries. The harbour also has facilities to handle large cargo ships and ferries, facilitating trade and transportation between the Shetland Islands and other regions.

Routes and Business

Lerwick Harbour is connected to many ports in the UK, Scandinavia, and other European countries. Its main business includes fishing, where a large number of fishing vessels dock to unload their catch and take on supplies. The harbour is also used by the oil and gas industry for transporting people and equipment to and from its offshore platforms. It is also an important ferry port, which links the Shetland Islands to the mainland and other islands and allows the transportation of passengers and vehicles.

Port Management and Operation

The harbour is managed by a professional team that focuses on efficient and safe operations. Advanced technologies are used for the control of ship traffic, handling cargo, and managing storage. The port facilities are maintained and upgraded periodically to meet the needs of modern shipping and trade. Stringent safety and environmental regulations exist in order to ensure smooth running of operations with minimal impact on the surroundings.

Facilities within the Port The port has an array of facilities: deep-water berths for vessels of larger vessels, modern cranes which are put into use when loading and unloading cargoes take place, and space for storage that is enormously large. The waterway that advances towards this harbour is maintained very well; it has regular dredging that always guarantees smooth passage. Equally important is a well-equipped pilotage system that would lead the vessels safely to the harbour area.

2. Why should we measure the ocean currents in the Lerwick Harbour?

Navigation Safety

The measurement of ocean currents in Lerwick Harbour is essential in ensuring navigation safety. The harbour receives a high volume of shipping traffic, such as fishing boats, cargo vessels, and ferries. Ocean currents can have a profound impact on the movement of these vessels. The existence of powerful and erratic currents at some places around the entrance can quite nicely throw ships off course. Additionally, this can make collision with other ships, piers, or running onto the beach highly likely. A correct measurement of the speed and direction of currents will enable the captains to plan more appropriately while approaching and leaving. This is done by making relevant adjustments in respect of course and speed necessary for securing a passage.

Optimization of Port Operations

Ocean current knowledge helps optimize port operations. Current flow may affect the duration and efficiency of the berthing and unberthing of ships. For example, if the current direction is favorable, it aids in assisting with docking and thus one does not have to employ too much tugboat assistance; it actually saves time and resources. It also helps in understanding the pattern of the current to provide for better scheduling of loading and unloading of cargo. In the fishing industry, it can also inform fishermen on better fishing areas, as currents carry nutrient and fish.

Infrastructure Planning and Maintenance

Current measurement is indispensable for the long-term planning and maintenance of the port infrastructure. Currents can influence sedimentation patterns around the port. Conclusively, this would offer a good basis for making informed decisions on dredging to keep the depth of the waterway and stability of berths, by the appropriate authority. Such knowledge, moreover, provides guidelines for planning future expansion and improvements in the port, including building plans for new berths, shifting facilities, or so, taking into account how currents act upon the seabed and, in general, the port environment.

Thus, ADCPs offer a more efficient way of measuring currents than conventional techniques. In this manner, real-time and precise data can be acquired, which is essential to the effective running and management of Lerwick Harbour.

3. How do Doppler principle ADCPs work?

The working of ADCPs is based on the Doppler principle. ADCPs emit acoustic signals into the water. The acoustic waves interact with moving particles in the water, such as suspended sediments, plankton, or small organisms. If the particles are in motion, then due to the Doppler effect, the frequency of the reflected acoustic waves changes.

This frequency shift is measured by the ADCP profiler, which then derives the velocity of the moving particles from this. Due to the relation of movement of these particles and that of the ocean current, the ADCP current meter becomes capable to ascertain the speed and direction of the latter.

Ship-borne ADCP in Lerwick Harbour

When deployed in the harbour, an ADCP current profiler is deployed on a vessel. During its motion through the waters of the harbour, with the use of the ship, it continuously emits acoustic signals downwards and sideways. In this way, the ADCP flow meter continuously monitors ocean currents of different depths and positions of the current as the ship moves. It thus provides the current situation over a big area of the harbour.

Fixed ADCP in Lerwick Harbour

A fixed ADCP is normally installed at a particular place within the harbour, either on a pier or on a submerged structure. It constantly monitors the ocean currents passing its position. The fixed ADCP provides long-term and stable current data for a particular area of the harbour, which is useful for analyzing the regular patterns and changes of the currents in that specific location.

4. What would improve the quality of the current measurements at Lerwick Harbour?

Reliability of Material

The equipment should be manufactured with high material reliability for high-quality current measurement in Lerwick Harbour. The external conditions in the harbour are harsh; the equipment will be under seawater, which is corrosive, and probably also exposed to mechanical impacts. Therefore, the manufacture of equipment with resistant materials is necessary to bear such conditions for a long-lasting and accurate measurement process.

Small Size, Light Weight, and Low Power Consumption

Smaller size, lightweight, and low power consumption are desirable features. A small-sized ADCP can be much easier to install in various locations within the harbour whether on ships or fixed structures. A light-weight device will make its transportation and installation process easy and light, which would reduce labor and hence costs. The low power consumption enables the instrument to operate continuously over extended periods of time without frequent replacement or high energy wastage, which is an essential feature for long-term measurement of currents.

Cost-economical

Among all other factors, cost comes as a prime factor. Equipment cost should be moderate to allow large-scale ocean current measurement in a given harbor area. The casing of the ADCP meter shall be of material preferably made of Titanium Alloy. The following advantages have been associated with Titanium Alloy. It is strong with high strength; thus, it may very well endure the pressure underwater, apart from mechanical forces this equipment may face in a harbour. Corrosion resistance is great to such an extent that this piece of equipment resists seawater corrosion effects for a pretty long time. Besides, its relatively light weight compared to other materials makes it more suitable for installation in the harbour.

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

Based on Usage Purpose

The equipment choice for current measurement in Lerwick Harbour depends on the purpose it is intended for. Should the intention be to make mobile measurements while the ship is navigating in the harbour, then the ship-borne ADCP will be suitable for this. It can cover different areas of the harbour as the ship moves around, giving a comprehensive view of the current situation.

The sit-on-bottom ADCP will be more suitable for long-term fixed-point monitoring of a certain area in the harbour. It can stay at one location and monitor the current condition at the point continuously, which is very useful in analyzing the local current pattern.

In the case of having to monitor a wider area on the water surface with some mobility, one may consider the buoy-mounted ADCP.

Based on Water Depth

The frequency of ADCP should also be selected with regard to water depth. A 600kHz ADCP generally provides good accuracy in current profiling for relatively shallow waters whose water depths are up to 70m. The 300kHz ADCP will be more appropriate for water depths of about 110m, while the 75kHz model is recommended for deeper waters, going up to 1000m.

There are well-known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese ADCP brand-China Sonar PandaADCP is also worth mentioning. It is made of all - titanium alloy material, combining excellent durability and corrosion resistance with an incredible cost-performance ratio. You can find more information about it on its website: (https://china-sonar.com/).

In general, ADCP plays an important role in the measurement of ocean currents in Lerwick Harbour, and choosing appropriate equipment for specific needs will be a guarantee toward better port operation and management.

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