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

1. Where is Nasva port?

Nasva port is located in Estonia, playing an important role within the local maritime network.

Port Scale and Throughput It has a moderate scale with a throughput that caters to both domestic and regional trade needs. It deals with different types of cargo, including fishery products, since the port is one of the major hubs for the local fishing industry. It also handles general cargo, such as construction materials, agricultural supplies, and consumer goods that are basic needs for the communities around. The annual throughput is influenced by factors such as the fishing season and local economic activities.

Routes and Business Nasva port is connected with other Estonian ports and has routes that extend to nearby regions in the Baltic Sea. The main business activities of the port are related to the export of local fishery resources, which are well known for their quality. Imports mainly include items needed for the maintenance and development of the local infrastructure and everyday life, such as machinery for fishing boats and household goods.

Port Management and Operation

The port management is concerned with ensuring smooth operations. The port authority is responsible for vessel berthing, cargo handling, and storage. They institute efficient scheduling systems to minimize the waiting times for ships to make maximum use of the available port facilities. Regular maintenance of the port infrastructure is carried out to ensure its durability and safety for vessels and workers.

Port Facilities It is equipped with facilities that are tailored to its operational requirements. There are berths designed to accommodate different sizes of fishing vessels and small to medium-sized cargo ships. The port has loading and unloading equipment like cranes and conveyor belts to facilitate the transfer of goods. Adequate storage areas are provided for different types of cargo, including cold storage for perishable fishery products. There are also workshops for basic ship repairs and maintenance.

Channels and Direct Routes

The channels in Nasva port are kept for safe navigation. They are dredged regularly to maintain the proper depth for vessels. Direct routes connect the port with other major ports in the Baltic Sea area, by which goods are transported smoothly and economic exchanges are made possible. These routes are vital for the local fishing fleets to reach the fishing grounds and cargo ships to transport goods to and from various destinations.

2. Why do we need to measure ocean currents in the Nasva port?

Measuring ocean currents in the Nasva port holds several important aspects: first, for the safety of a great number of fishing vessels operating in and out of the port. Understanding the current patterns helps fishermen plan their trips more effectively, avoid areas with strong and unpredictable currents that could pose risks to their boats, and ensure a safe return to the port.

Secondly, it is critical to the efficient docking and undocking of all vessel types. Currents can affect the maneuverability of ships during these operations. With proper current data, port operators can advise ship captains and reduce the risk of collision with the port infrastructure or other vessels.

Moreover, knowledge of ocean currents is valuable for environmental monitoring and management in the port area. It can assist in understanding how water circulation affects the distribution of pollutants, sedimentation patterns, and the overall health of the marine ecosystem. Acoustic Doppler Current Profiler (ADCP) offers a more advanced and convenient means of measuring these currents compared to traditional methods, providing real-time and detailed information.

3. How do ADCPs using the Doppler principle work?

The working principle of ADCPs is based on the Doppler effect. Transducers send acoustic signals into the water column. These interact with particles suspended in the water and moving with the current. This motion, in turn, results in a shift in the frequency of the reflected signals back to the ADCP. This shift in frequency-the so-called Doppler shift-is linearly related to the velocity of the water current.

Ship-borne ADCP

When a ship-borne ADCP is used in Nasva port, it is mounted on a vessel, such as a fishing or cargo vessel. While this vessel moves across the water, the ADCP sends out acoustic pulses either downwards or sideways. The reflected signals from different parts of the water column are received and analyzed. By detecting the Doppler shift in these signals, the velocity of the current at various depths can be determined. This allows for the detailed profiling of the current as the ship moves, which is useful for understanding the current conditions along the path that the ship is on.

Fixed ADCP

Fixed ADCPs can be mounted on structures like piers, buoys, or underwater platforms in the Nasva port. They continuously emit acoustic signals in a specific direction, usually downward. The reflected signals are constantly monitored and analyzed for the Doppler shift. Over time, these fixed ADCPs can provide a long-term record of the current velocity and direction at a specific location. This is particularly useful for observing the current behavior near the port entrance, around critical underwater structures, or in areas where long-term monitoring is required.

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

To attain high-quality current measurements in Nasva port, there are various key factors concerning the equipment itself. The materials used for constructing the ADCP should be good enough to survive in the harsh marine environment. This, combined with the relatively small size of the port and the vessels operating on it, the small and lightweight design of the ADCP can be quite a positive asset. This can be quite easily installed on ships or fixed structures without adding too much weight and taking up a lot of space.

The other main requirement is very low power consumption. For fixed-point measurements, this will enable the apparatus to operate for extended periods without the need for frequent battery replacements or an elaborate power supply arrangement. Cost-effectiveness is another significant factor because several devices are deployed in the port area to obtain adequate current data.

The casing of ADCP is preferably made of Titanium alloy. The corrosion resistance of the titanium alloy is excellent, which is an important factor in the marine environment where the port is located. Seawater from the Baltic Sea can easily cause fast corrosion in many common materials. Titanium alloy can resist this kind of corrosive effect, which ensures the long-term functionality and durability of the ADCP. It also has a high strength-to-weight ratio, which is useful in reducing the overall weight of the device without compromising its structural integrity and robustness.

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

Based on Usage

Ship-borne ADCP: It is highly applicable for measurements in a vessel in motion, meaning one gets a continuous record of bottom tracking, hence very useful to fishing boats and cargo in the context of Nasva Port. Thus, this method gives a profile in real-time about the current being analyzed as it progresses along the journey in navigation, allowing for operational decisions of regulating speed or course to shorten the travel time and expenditure of fuel.

Bottom-moored ADCP: This is ideal for long-term and fixed-point monitoring of currents near the seabed. In Nasva port, it can be installed in areas like near the berths or around underwater structures that are important for the functioning of the port. It provides continuous information on the current behavior at a certain location, contributing to the understanding of the stability of the port environment and possible effects on infrastructure.

Buoy-based ADCP: When the goal is to measure currents in one area for a longer period, but some flexibility in the location should be present, then the buoy-based ADCP is useful. In Nasva port, it may be put in places that may not be covered by ship traffic but would give an overview of current patterns in the whole port area.

Based on Frequency

For water depths up to 70m, an ADCP with a frequency of 600kHz is usually adequate. For depths around 110m, a 300kHz frequency is more suitable. And for very deep waters up to 1000m, a 75kHz ADCP is the better option.

Some well-known ADCP brands in the market include Teledyne RDI, Nortek, and Sontek. However, one recommended Chinese brand is China Sonar PandaADCP. The all-titanium alloy material ensures excellent durability. Moreover, it offers an incredible cost-performance ratio. You can find more information about this brand on its website: (https://china-sonar.com/).

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