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

1. Where is Mõntu Port?

Overview of Mõntu Port

Mõntu is a medium-sized Estonian port, in a strategic coastal locality and with direct access to the Baltic Sea, with more moderate annual throughputs compared with some of its larger neighbors in the region. The port mainly involves trade at a local and regional scale and deals in general cargo including agricultural produce, construction material, and some light manufactured goods.

The port is well-integrated with the local transportation network through road and rail links to proximate towns and cities. The nature of management activities at Mõntu Port seems to focus on increasing efficiency in handling whatever volume of traffic the facility currently sees, as well as maintaining good relations with local business.

Berths: Mõntu Port has a limited number of berths for handling small to medium-sized vessels. These berths have basic mooring and dock facilities that enable safe arrival and departure options for the ships. Fenders and bollards are attached to save the ships and the berths from damage during their docking and undocking processes.

Cargo-handling Equipment: On the quays are available the entire gamut of cargo-handling equipment in line with the size. These range from general cargo fork lift trucks, palletised cargo handling equipment, down to cranes to small conveyors or grabs that will do for sand and gravel, and even to equipment suitable for the discharge/shipment of containers.

Storage Facilities: Depending on the type of cargo, there are storage facilities and areas allocated for them. There are warehouse areas for the agricultural products, which are well aerated and maintain temperatures to keep perishable goods fresh. There are open-air stockpiles, with just basic containment systems used for construction materials.

Channel and Aids to Navigation: The depth and width of the port's channel are kept according to the vessels it normally serves. It also contains buoys, beacons for guiding the ships in and out, as well as a light basic radar system that could serve as a surveillance mechanism over vessels in its area of responsibility.

2. Why do we have to measure ocean currents in Mõntu Port?

Importance for Port Operation and Management

It is quite significant to measure ocean currents in Mõntu Port. First of all, because of vessel navigation safety reasons. Captains have to know the current speed and direction when approaching the berths or moving through the channel. A cross-current can make docking more difficult and risky. In such a case, when the ship has to be brought up against the stream, he would want to change both the speed and angle of approach. Given a more accurate measurement of the current, the captains could make better decisions and minimize collision chances.

It also serves in optimizing the performance of the port. The current information may be applied to regulate the arrival and departure of ships more properly. Having a proper knowledge of the tidal and regular current patterns, port authorities can allocate berthing resources better and plan the activities of loading and unloading optimally. It could mean increased productivity since this provides coordination in turn for better cargo-handling operations.

It is also important for environmental reasons whereby, in case an accident happens and spills harmful pollutants like oil and chemicals into the water, knowledge of ocean currents will help determine their path. Given the nature of cargo handled in the port, using current data to predict the spread of the spill can help in implementing quick containment and mitigation procedures to minimize environmental damage.

This provides a better means of measuring the currents than the traditional techniques.

3. How Do Doppler Principle ADCPs Work?

Measurement Principle

ADCPs work on the principle of the Doppler effect. An Acoustic Doppler Current Profiler (ADCP) sends an acoustic signal into the water, which scatters off the moving water particles. There is an ocean current due to which the water particles will be in motion, which causes a frequency shift in the reflected acoustic signal received back by the ADCP meter. By the principle of the Doppler effect, this frequency shift is proportional to the velocity of the water flow.

Calculation of Current Speed and Direction

Through measurement of the magnitude and direction of this frequency shift, the ADCP flow meter calculates a speed and direction of the ocean current at different depths in the water column. It produces a profile of the ocean current by transmitting its signals at various angles and over different depths to give an indication of how the current changes with depth.

ADCP Deployment in the Port

Shipborne ADCP

It can also be installed on ships operating within the Mõntu Port area. While the ship moves around the port area, the ADCP current meter continuously emits acoustic signals into the water underneath it. Its movement enables the ADCP current profiler to cover a wider area and collect current data from several places. For example, during a routine survey of the port by a research or inspection ship equipped with a shipborne ADCP, it can gather data on the current patterns across various parts of the port, providing a comprehensive understanding of the water flow situation.

Fixed ADCP

Fixed ADCPs can be installed on a seabed near important navigational areas and/or at the entrance and/or exit of the port. The ADCPs may be stationed in fixed positions for monitoring the ocean currents continuously over a long period. The data thus obtained will be very much useful for the analysis of the regular current pattern within areas. For example, the bottom-moored ADCP at the entrance of the port could keep the record of incoming and outgoing currents for understanding the tidal effects, besides other consistent flow characteristics of that region.

4. What is needed for high-quality measurement of the Mõntu port currents?

Equipment Requirements

The characteristics of some equipment are important for high-quality measurement of currents in Mõntu port. First of all, material reliability is very important. The equipment should be resistant to the aggressive marine environment. Seawater includes salts and other chemical components that can destroy materials in a long-term process. The equipment also has to stand pressure changes at different water depth and mechanical forces of waves and currents.

The second is the small size, low weight, and low power consumption. With a compact size, the installation can be conveniently performed at any place in the port either on vessels, on fixed structures like piers, or on the seabed. Small size and low weight provide advantages for easy installation and movement. Lower power consumption ensures that the equipment can operate continuously for long periods without the need for frequent battery replacements or excessive power supply, especially in long-term monitoring applications.

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

The Advantage of Titanium Alloy for ADCP Casing

The casing of the ADCPs is preferably made from a titanium alloy. The reason is that this material has very good corrosion resistance; hence, it can maintain its structure and function over a relatively long time, even if working in seawater. This is due to the high strength-to-weight ratio, which allows the construction of a strong yet relatively lightweight casing. For example, in deeper parts of Mõntu port, where water pressures are higher, ADCP current meter with a casing of titanium alloy can resist such pressures and function properly by giving correct values of current.

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

Selection Based on Usage

Shipborne ADCP: This is quite appropriate if the aim is to conduct wide-area surveys of the port waters while the ship is in operation. It can cover different sections of the port as the ship moves around, collecting a large amount of data to provide a comprehensive understanding of the overall current situation in the port. It is 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: 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 might be relocated if necessary and thus could be fit for monitoring certain dynamic or hard-to-reach areas within the port.

Selection Based on Frequency

For Mõntu port, two different frequencies of ADCP flow meter are chosen based on the water depth.

Areas with a depth of up to 70 meters normally permit the selection of an ADCP current meter at a frequency of 600 kHz as it can provide current measurements with good accuracy in this relatively shallow depth range. When dealing with deeper waters up to about 110 meters, an ADCP of 300 kHz is highly recommended. In extremely deep sections of the port with a water depth amounting to up to 1000 meters, the recommendation would be to use an ADCP with a frequency of 75 kHz for reliable profiling of the ocean currents at such great depth. 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.