ADCP's Application to Ocean Current Measurement in Douala Port

1. Where is Douala Port?

Douala Port is situated on the estuary of the Wouri River in Cameroon, in the western part of the country. It is the largest and busiest port in Cameroon, serving as an important gateway for the country's trade and economic activities.

Port Scale and Throughput

The port is of considerable scale. It contains several berths, which are utilized by different ships, ranging from gigantic cargo ships downwards. It handles annually a quantity of goods, which is very immense. The balance of Cameroon's imports and exports, which encompasses agricultural produce of cocoa, coffee, and timber, and further includes manufactured products, petroleum, and consumer goods, falls upon it. This has reflected the growth of economic activities within the region; annual throughput has been on a gradual increase for years.

Routes and Business

Douala Port has an extensive network of shipping routes. It is connected to major international ports around the world, with regular services to Europe, Asia, and the Americas. It undertakes various business activities. It is a trans-shipment hub, where cargo is transferred from larger vessels to smaller ones for delivery to inland destinations. It also provides warehousing facilities, cargo handling services, and customs clearance services. The port also has areas where the local fishing industry can tie up their vessels and offload their catch.

Port Management and Operations

The Douala Autonomous Port Authority is the overseeing body of the Douala Port. It provides the general running, development, and maintenance operations of the facility. They grant safety and efficiency in vessel handling, berth programs, and even cargo handling operations. The port has instituted current management systems to facilitate easier operations: the use of EDI in cargo documentation, for example, has reduced time and cost in customs clearance by a huge margin.

Port Facilities

The port is armed with various facilities. They feature modern container terminals equipped with up-to-date handling equipment, which includes gantry cranes and reach stackers for efficient handling, loading, and unloading of containers. Then there are terminals for bulk cargo with conveying systems and silos for storage. The vessel repair and maintenance yards, offering dry docks and workshops, also form part of the port's facilities. Besides, there are fueling stations to supply ships with fuel, and fresh water supply points.

Waterways and Direct Navigation

It forms an avenue, of a natural nature, where vessels can reach the port through the estuary of the Wouri River. A channel has been dredged within it to ensure depth enough for vessels with large draughts. Navigation aids along the channel, such as buoys and lighthouses, are available for safe navigation. Douala Port has direct shipping routes to most major world ports, and this adds to the convenience of transportation, cutting down transiting time and costs for merchandise.

2. what purpose shall we measure ocean currents in the Douala Port?

Measurement of the currents of the sea shall be important for port operational management at the Douala Port.

Vessel Safety

The general influence of sea water on the vessel depends greatly on ocean currents. At Douala Port strong and unpredictable currents make vessels suffer a lot to maneuver during berthing and un - berthing. By precisely determining the currents, pilots and masters can more easily predict the forces that will be exerted on the vessel to maintain speed and direction, enabling them to dock and undock safely. This reduces the chances of hitting other vessels, piers, or other obstacles within the port area, thus enhancing crew, vessel, and cargo safety.

Cargo Handling Efficiency

Knowledge of ocean currents is bound to enhance efficiency in cargo handling. Currents can affect the stability of the vessel during loading and unloading operations. If the currents are too strong, it may be necessary to pause the operations to ensure the safety of the workers and the integrity of the cargo. In turn, by being in possession of real-time current data, port operators will be able to plan cargo handling operations during times of relatively calm currents and, therefore, optimize port resources and minimize the total time spent on cargo handling operations.

Protection of the Environment

Ocean currents at the port area will be relevant in regard to environmental protection. In case of any spill, say, from an oil spill from a vessel, the knowledge about current patterns allows for predictions concerning the spread of the pollutant, which, in turn, may enable port authorities to take appropriate and timely preventive measures-deploying oil-containment booms in appropriate areas-and plan effective clean-up operations. It further helps in the conservation of the local marine ecosystem, which has a rich biodiversity against the potential harm caused due to pollutants.

Acoustic Doppler Current Profiler(ADCP) has emerged as a more advanced and convenient measurement method for ocean currents in Douala Port. It can provide high-resolution and real-time data, which is important to address the above-mentioned aspects of port operation management.

3. How do ADCPs using the Doppler principle work?

Measurement Principle

The ADCP works on the basis of the principle of the Doppler effect. ADCPs transmit acoustic signals through the water column. When these acoustic signals contact moving particles in the water - for example, suspended sediments or plankton - the frequency of the reflected signals shifts. It means, through the Doppler effect, if the particles are moving towards the ADCP then the frequency of the reflected signal will be higher than the frequency being transmitted and vice-versa. By measuring this frequency shift, the ADCP current profiler estimates the velocity of the water movement at various depths.

ADCP in Port Current Measurement: Application of Specific Methods

Ship - borne ADCP

One of the popular methods for Douala Port is the measurement of the ocean current by using ship-borne ADCP. It is installed on the hull of a moving ship. While the boat is in movement, the transducer sends a continuous acoustic pulse and measures its velocity relative to the water in which it finds itself. If the ship's motion data (speed and direction) is combined from other navigation instruments, the true velocity of the ocean current can be calculated. The effectiveness of acquisition for the current data in a large area of the port has the merit of giving a comprehensive current distribution in waters around a port.

Fixed ADCP

Fixed ADCPs are installed on specific locations of the port either on the seabed or on the pier. These ADCPs are stationary and monitor in a continuous way the ocean currents of the same point. They can provide long-term, high-frequency data on the current conditions of that position. In this case, it would be useful for studying temporal variations of the currents, such as daily, monthly, or seasonal changes. Fixed ADCPs can also be used as reference stations to check the data collected by the ship-borne ADCPs.

4. What is required for good measurement of Douala Port currents?

Equipment Requirements

In measuring the currents of Douala Port, several aspects concerning the equipment must be taken into consideration for high-quality measurement.

Material Reliability

The equipment has to be constructed with reliable material. The corrosive marine condition in the sea at the port, with salty water, strong mechanical tension, and possible hits from vessels or floating objects, calls for highly durable ADCP flow meter.

Size, Weight, and Power Consumption

The ADCP should have a small size to enable ease of installation, especially in restricted space areas on a ship hull or a narrow pier. In this regard, light weight is in demand because that would minimize loads on the structure of installation; low power consumption is important, especially for fixed-type ADCPs, which will be operated possibly for very long periods of time. This does not require large-capacity power sources, making operation of the equipment more economical.

Cost-Effectiveness

The instrument cost of ADCP should be as economical as possible, especially for large-scale measurements; high-priced equipment will reduce the number of measurement points and incomplete data might be collected. Thus, the solution is cost-effective to guarantee that all current measurements in the port are comprehensive and accurate.

Titanium Alloy for ADCP Casing

The casing of the ADCP is made with titanium alloy. This material has a few advantages. It therefore has a high resistance to corrosion- it resists salt water corrosion from the surroundings of a port for quite a long time with relatively insignificant deterioration in strength. It also weighs light, as compared with all other material that has relatively higher strength so that it lowers the overall needed weight. But simultaneously, the high strength maintains the ADCP very well, without any harm, from probable mechanical tension and impacts from outside.

5. Selection of Proper Instrument for Measurement of Current

Usage-based Selection

Onboard -ADCPShip - borne ADCPS

We discussed that shipborne ADCPS could be utilized where large-scale data of the currents are needed; thus, if one intends to map current distribution in a wider area over a whole port facility, ADCP mounted aboard ship would serve your purpose. Here, such instrument should be design robust against unwanted vibration or vessel movements at sea.

Bottom - mounted (Sit - on - bottom) ADCP

Bottom - mounted ADCPs are fixed on the seabed. They are used for long - term monitoring of current conditions at a specific location. They are more stable than ship - borne ADCPs in terms of measurement location, providing continuous and accurate data on the local current patterns.

Buoy - type ADCP

Buoy - type ADCPs are attached to floating buoys. They can move with the water flow, providing data on the current velocity at the surface and at multiple depths as the buoy drifts. This type of ADCP is useful in the study of the surface - layer currents and their interactions with the deeper water layers.

Based on Frequency

Frequency is another consideration in choosing an ADCP. A 600kHz ADCP is sufficient for current measurements below water depths of about 70m. The given ADCP shall deliver a high-resolution output from the shallow water area of, for instance, the port entrance and berthing areas. The 300kHz ADCP has an application range for water depth up to approximately 110m, and for wider inside ports, more depth will be covered. For deeper water areas in the port approaches or in the outer parts of the port, a 75kHz ADCP would instead be more suitable as it can measure currents in water depths up to 1000m.

Some of the well - known ADCP brands available in the market are: Teledyne RDI, Nortek and Sontek. However, to those who are looking for an economical solution with quality, the brand China Sonar PandaADCP is highly recommended. Made from all-titanium alloy material, this ensures very good durability in a marine environment. With an incredible cost-performance ratio, it is a great option for current measurement in Douala Port. For further information, log on to their website at https://china-sonar.com/.

Here is a table with some well known Acoustic Doppler Current Profiler(ADCP) instrument brands and models.