ADCP Applied to Ocean Current Measurement, Port of Seattle

1. Location of Port of Seattle

The Port of Seattle is located in Seattle, Washington, on the West Coast of the United States. It is a major doorway to international trade and a crucial part of the transportation infrastructure in the Pacific Northwest.

Port Scale and Throughput

The port is one of the largest and busiest in North America. It has a huge throughput that was originally set to handle everything: from containers, automobiles, up to bulk commodities such as grains and coals. Container traffic, on record, runs to several millions of TEUs annually. And it acts as a critical supply chain linkage from the United States to Asia, primarily in countries such as China, Japan, and South Korea.

Routes and Business

The Port of Seattle is linked with major shipping lanes across the Pacific Ocean, having an extensive network of trade routes supporting the importation of consumer goods like electronics, clothes, and furniture, as well as the exportation of agricultural products and high-tech goods. It facilitates the exportation of parts of Boeing aircraft and apples grown in the state of Washington.

Port Management and Operation

The port is managed by a professional organization responsible for all aspects of the operation of the port, including vessel traffic control, cargo handling, and security. The port authority develops cooperation with shipping lines, terminal operators, and other stakeholders in pursuit of efficient operations. They also focus on environmental sustainability and community relations.

Port Facilities

Facilities in this port are very modern. This has various deep-water berths that can accommodate larger container ships and other vessels. There are modern container terminals with high-capacity cranes and automated handling systems for the efficient loading and unloading of containers. Besides that, there are storage areas of different types of cargo, with refrigerated storage facilities for perishable goods.

Channels and Direct Routes

The port maintains appropriate depth in its channels for safe navigation of ships. It has direct courses to most of the important ports in Asia and other areas, which minimizes time and cost in transiting. These direct connections increase the port's competitiveness in the global shipping market.

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

Measuring ocean currents in the Port of Seattle is important for several reasons. First, for safe navigation, accurate current data is very important. Ocean currents can greatly affect the speed and course of a ship. By understanding the current patterns, ship captains can make more informed decisions during navigation. For example, in areas with strong tidal currents, ships need to adjust their approach to avoid collisions or running aground.

From the perspective of port operations, knowledge of ocean currents is essential in the handling of cargo efficiently. Currents have the capacity to influence the positioning of ships during loading and unloading operations. With full knowledge of the current situation, port operators can better plan the berthing of vessels and the movement of equipment that handles cargo.

Besides, current measurement with regard to environmental protection is important. For example, in case of an accidental spill of dangerous substances like oil or chemicals, knowledge of the current direction and speed helps predict the spread of the pollutants, which permits the adoption of effective emergency measures that minimize environmental impact.

The ADCP current meter is a more effective and efficient way of measuring ocean currents compared to the traditional techniques. It can provide real-time and continuous data, covering different depths and areas of the port water, which is extremely valuable for a comprehensive understanding of the current situation.

3. How do ADCPs using the Doppler principle work?

ADCPs are based on the principle of the Doppler effect. They transmit acoustic signals into the water. These acoustic waves scatter off moving particles in the water, such as sediment or small organisms. The reflected waves, carrying the Doppler shift, have a different frequency from the ones transmitted when they are reflected back to the ADCP profiler.

The frequency shift varies with the velocity of the moving particles and, therefore, with the velocity of the water current. By observing this frequency shift, the ADCP flow meter can work out the speed and direction of the current at various depths.

Ship-borne ADCP

If a ship-borne ADCP is used, then the device is mounted on a ship. The ADCP current profiler generates acoustic pulses downwards and laterally while the ship is in motion through the water. It measures the current velocity at various depths along the track of the ship. The data collected provides a detailed profile of the current structure in the area covered by the movement of the ship. This is useful for surveying a wide area of the port water as the ship travels.

Fixed ADCP

Fixed ADCPs are usually deployed in structures such as pier, buoy, or seabed. They record continuously the current of the ocean that passes across a given site. Since they remain at one position, they can deliver long-term stable data about current conditions at one particular point. This has helped in acquiring knowledge about temporal and spatial variability of currents at the port area.

4. What is necessary in the measurement of the Port of Seattle's currents?

High-quality measurements of currents across the Port of Seattle will require that equipment meet these stipulations or requirements: it must be made of materials that can handle the water because it's salty, plus withstand wave and current actions in both high and very low temperatures.

Thereafter, a small size and lightweight are desirable, whereby a reduced size and light machine offers very easy installation whether on any floating ship or some fixed structure and is generally easier to work. The power consumptions should also be low: this will facilitate the equipment continuously over an extended period, without frequent change of batteries or some substantial-sized power supply unit.

The equipment has to be as cost-effective as possible to allow measurement on a large scale in the port area. The casing for ADCPs is preferred to be of titanium alloy due to its very good corrosion resistance to overcome the corrosive action of seawater. The strength-to-weight ratio is also high for this alloy to make the device tough yet keep the weight relatively low.

5. How to Select appropriate equipment for current measurement?

According to the Purpose of Use

• Ship-borne ADCP: If the purpose is to get the current information along with the voyage or studies related to navigation, the ship-borne ADCP will be a good choice. It can cover almost all the port areas since the ship will be moving around.
• Bottom-mounted ADCP: In case of operational monitoring of the currents from the seabed or near the port facilities with longtime operations, bottom - mounted ADCP is a good option, which in turn produces quite stable and continuous data on prevailing current conditions at particular locations in time.
• Buoy-mounted ADCP: These are useful in monitoring currents either in open water areas or in areas where the installation of a fixed device on the seabed is impractical. They are capable of moving with waves and tides while making measurements of currents.

Based on Frequency Selection

The choice of frequency of ADCP depends upon the depth of water. For instance, a 600 kHz ADCP would be appropriate for water as deep as approximately 70 meters and provide high-resolution data, whereas a 300 kHz ADCP could work on water up to around 110 meters, striking a balance between measurement range and resolution. A 75 kHz ADCP is more appropriate for deeper waters, up to about 1000 meters, and is useful for understanding the current conditions in the deeper parts of the port area.

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

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