Application of ADCP to Ocean Current Measurement in the Port of Manzanillo

1. Where is Manzanillo port?

Manzanillo port is situated in Colima on the Pacific coast of Mexico. It is one of the most important harbors in Mexico and acts as a very active hub in foreign trade in the region.

Port Scale and Throughput The scale of the port is huge, with an enormous volume of cargo throughput. It is one of the leading container ports in Mexico and also deals in quite a good amount of bulk cargo. Its annual throughput contains thousands of containers carrying everything from electronic devices and textiles to automobile parts. In the case of bulk cargo, the commodities it handles range from grains and ores to even chemicals. With this strategic location, the port developed itself into a crucial link in facilitating the exchange of goods and products between Asia, the Americas, and the rest of the world.

Route and Business

Manzanillo is a port with an extended network of shipping routes. Manzanillo connects to numerous other ports across the Pacific-from key Asian ports, which also happen to be some of the biggest in the world, Shanghai, Yokohama, and Singapore, to other American ports within the United States and Latin America. The imports and exports that form the business activities of the port are highly diversified, with manufactured goods and consumer products forming the bulk of imports, while agricultural exports include coffee, fruits, and processed food from the surrounding regions, minerals, and industrial products.

Port Management and Operation It operates through a professional management team focusing on efficiency, safety, and security. There are strict regulations concerning vessel traffic control, cargo handling, and customs clearance. The port is continuously improving and maintaining its facilities to keep pace with the expanding shipping industry. Besides this, the port coordinates activities involving shipping lines, freight forwarders, among other stakeholders, in reducing operation time and consequently decreasing the time taken for cargos to pass through.

It is a fully-equipped facility with state-of-the-art facilities. There are long quay walls with a number of berths accommodating large container ships, bulk carriers, and other vessels. The port has advanced container terminals with high-capacity cranes for quick and efficient loading and unloading of containers. For bulk cargo, there are specialized storage areas such as silos and warehouses. It also provides services such as ship repair yards, fueling stations, and fresh water and electricity to the vessels.

Channel and Navigation The channel to the port is deep and wide, with regular dredging to ensure safe access for large vessels. At the channel, there are sufficient navigation aids: buoys, lights, and radar systems that make the approach to and departure from the port smooth and safe. This allows for a direct and smooth navigation even in different weather and tidal conditions.

2. Why should the ocean currents in the Manzanillo port be measured?

Improved Navigation for Vessels Measuring the ocean currents of the Manzanillo port enables better vessel navigation. Currents from the Pacific Ocean may tremendously affect a ship's speed, course, and fuel consumption. With actual current conditions around the area, ship captains will be able to plot routes more easily to take advantage of favorable currents that could decrease travel time and fuel costs. Knowing the current direction and strength in this case enables a skipper to make accurate maneuvers, for example, while approaching or leaving the port without risking collisions or running into sand.

Infrastructure Protection The port's structure is incessantly under ocean current stresses. Heavy or uncontrollable currents result in erosion, scours, and eventually structural damage. Continuous measurement of currents assists the port authorities to ascertain potential liabilities and timely correction actions such as reinforcement of the structure or alteration to dredging programs with a view to safeguarding the structural integrity of the port and increasing the useful life of the installations.

Marine Environmental Management Effective marine environmental management is related to proper perception from the ocean currents around a port area. Currents have an important function in dispersion: to distribute pollutants, sediments, and heat. Necessary actions should be undertaken after observation with the purpose of either hindering the process of spread of any future contamination, sedimentation control, and aquatic protection. It is so essential in having a healthy marine environment and, at the same time, meeting environmental stipulations.

Acoustic Doppler Current Profiler(ADCP) provides a more intelligent and easy way of measurement in ocean currents compared to traditional methods. It could also provide detailed and real-time information on the speed and direction of currents at different depths within the port, thus enabling better decision-making for port operations and environmental protection.

3. How do ADCPs using the principle of the Doppler work?

Working Principle: ADCPs work on the principle of the Doppler effect. ADCPs emit acoustic signals in water. The emitted acoustic waves interact with particles entrained by the currents in an ocean-like suspended sediments, plankton, and other minute entities present within the column of water.

With the acoustic waves emitted, when they reflect back after hitting the moving particles, the frequency of the reflected waves changes due to the Doppler effect. This shift in frequency is measured by the ADCP. Through sophisticated algorithms, it calculates the velocity of the moving particles based on the frequency shift. This information on velocity is then converted into the speed and direction of the ocean currents.

In the context of Manzanillo port, there are two main methods of using ADCPs, namely:

Ship-borne ADCP It is installed on a ship that may be a survey ship, cargo ship, or a specialized research vessel. While the ship moves in the port area and adjacent waters, the ADCP continuously emits and receives the acoustic signals. These are then combined with the vessel's own motion data to build a comprehensive picture of ocean current patterns throughout different areas of the port and environs.

Fixed ADCP The fixed ADCPs are placed at key locations around the port, such as on the seabed at the entrance, along quay walls, or at other important positions in the navigation channel. These ADCPs are fixed in one place and, correspondingly, continuously measure the current conditions at their respective places. The long-term series obtained from fixed ADCPs are of great value for the understanding of the regular flow of currents, detection of any unusual changes or trends, and provide important information concerning port planning and safety.

4. What do high-quality measurements of Manzanillo port currents require?

• Reliable and Durable Materials The equipment should be made from materials that can bear the harsh marine environment for high-quality measurement of ocean currents in Manzanillo port. Seawater is very corrosive, and equipment may also be put under extreme variations in pressure, depending on the depth at which it is deployed. Materials resistant to corrosion and holding their structural integrity over a long period are essential for accurate and consistent measurements.
• Compact Size and Light Weight Size and weight of equipment-Size is a crucial and handy factor, whereby given that the environment is rather busy and space constrained around a port, the small -sized ADCPs in installation would be rather handy-on a ship or otherwise for a fixed location. Being of lesser weight also is useful mostly while being carried on a vessel by water, for not weighing down on it would serve to keep stability intact of the vessel for sailing effectively.
• Low Power Consumption Particularly for fixed ADCPs, which are designed to operate over extended time spans, low power consumption is especially important. In this regard, besides minimum operating cost, low power consumption has the added advantages of making the power supply conditions much simpler and improving the long-term reliability of the equipment.
• Titanium Alloy Casing The casing of the ADCP shall be fabricated from a Titanium alloy: it has very good resistance to corrosion and, therefore, is well-suited to the marine environment. It also has a high strength-to-weight ratio, hence providing a durable yet relatively lightweight design that will enable the ADCP to be resistant to pressures and impacts it may experience in port waters without losing performance and accuracy.

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

• Based on Usage Scenarios Ship-borne ADCP: When the object is to obtain the detailed mapping of the current pattern on a large area inside the port and the surroundings, a ship-borne ADCP will serve the purpose. It could also be utilized in the framework of routine inspections at a port as well as during the design phase of some new infrastructure, or when the need for determination of the current influence on vessel traffic arises.
• Bottom-mounted (sit-on-bottom) ADCP: For long-term and stable monitoring of current conditions at some critical locations within the port, such as entrance areas, areas near important berths, or other submerged structures, a bottom-mounted ADCP is highly desirable. It provides continuous data essential to understand the regular flow and sudden changes that might affect the safety of the port or its operations.
• Buoy-mounted ADCP: When the measurement point needs to be more flexible and movable, perhaps to take current data in different areas based on specific needs or to cover areas that are not easily accessible by other means, a buoy-mounted ADCP can be considered.

Frequency Selection

• For water depths up to 70m, an ADCP with a frequency of 600kHz is usually a good option.
• For depths up to 110m, a 300kHz ADCP is more appropriate.
• For deeper waters up to 1000m, a 75kHz ADCP can provide accurate measurements.

There are several well - known ADCP brands in the market, such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is worth highlighting. It is made entirely of titanium alloy material, ensuring its durability and excellent performance in the marine environment. Moreover, it offers an outstanding cost - performance ratio. You can find more information on its website: (https://china-sonar.com/)

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