ADCP's Application to Ocean Current Measurement in Walvis Bay

1. Where is Walvis Bay?

Walvis Bay is a natural deep-water harbor, located on the southwest coast of Namibia.

• Port Scale and Throughput: It is one of the most important ports in Namibia. The port is of a relatively large scale, with modern wharf facilities and a large berthing area. It can handle a variety of cargoes, and its annual throughput is considerable, mainly including minerals, agricultural products, and industrial products.
• Routes and Services: It has established shipping routes with many parts of the world. There are regular cargo ships and passenger ships traveling to and from Europe, Asia, and other regions. The full range of services offered in the port includes loading and unloading, warehousing, customs clearance, and ship maintenance.
• Port Management and Operation: The port is managed by the Walvis Bay Port Authority, adopting an advanced management concept and technologies in putting the port into effective operation. It has professional operation teams on hand, with strict safety management systems.
• Port Facilities: The port has modern machinery for loading and unloading, such as cranes and forklifts. There is also a modern warehouse and storage yard to accommodate the different goods stored. Waterways and Direct Navigation: The waterways in Walvis Bay are deep and wide, allowing large ships to be able to directly sail in and out of the bay with good navigation conditions. There are clear channel markings and navigation aids to protect the safety of ships.

2. Why should we measure the ocean currents in Walvis Bay?

The measurement of ocean currents is of great significance to the operation and management of the Walvis Bay:

• Shipping Safety: Once the current situation is mapped out, it will be easier for ships to plot their routes and avoid areas with strong currents, reducing the chances of ship accidents.
• Dredging and Maintenance: The flow of ocean currents determines the deposition and scowering of sediments in the port. Measuring the currents will allow an appropriate determination of where dredging should be done and timely maintenance to ensure the depth of the waterways.
• Marine Ecology and Environment: Research on ocean currents can help explain the distribution and migration of marine organisms and the diffusions of pollutants, which bear important significance in protecting the marine ecological environment in the port area.
• Marine Engineering Design: During the construction of the port facilities and marine engineering projects, the data of ocean currents are an important basis for designing the structure and stability of buildings.

Currently, Acoustic Doppler Current Profiler(ADCP) is a more advanced and convenient measurement method that can provide accurate and detailed current data.

3. How do ADCPs using the Doppler principle work?

The ADCP measures ocean currents based on the Doppler principle.

• Measurement Principle: ADCP emits acoustic waves into the water. When the acoustic waves encounter moving water particles, the frequency of the reflected acoustic waves will change. By measuring this frequency change, the velocity of the water particles can be calculated. Based on the trigonometry principle, the velocities in different directions can be decomposed to get the three-dimensional velocity vector of the water flow.

Specific Methods in Port Current Measurement:

• Shipborne ADCP: This device is mounted at the bottom of the vessel. During sailing, it could record continuously along its route current data. For example, it will be convenient to use for big-scale investigations of ocean currents in the areas of the port, and get a lot of information in the shortest time.
• Fixed ADCP: It is fixed on the seabed or on underwater structures. It can continuously monitor the current changes at a specified place and is suitable for long-term, continuous observation of key areas in the port.

4. What's needed for high-quality measurement of Walvis Bay currents?

The following requirements should be met by the equipment for high-quality measurement of currents in Walvis Bay.

Material reliability: The material should be used for the device that is resistant to seawater corrosion and able to bear marine environmental impacts. Titanium alloy is one of the best options. It has excellent corrosion resistance and high strength, and it can adapt to bad marine environments.

Small in Size and Light in Weight: Convenient to install and operate whether it is shipborne or fixed on the seabed. It reduces the impact on the measurement environment and is easy to carry and deploy.

Low Power Consumption: It conduces to long-time continuous work, especially for the fixed and floating equipment, which can reduce the frequency of replacing batteries or energy supply. Low cost: It benefits from large-scale measurement and application. Lower the cost, more measuring points can be set, and more comprehensive data could be gotten.

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

Usage Determination

• Shipborne ADCP: Adaptation to cases in which quick current distribution is necessary for an enormous area, normally used for the route investigation and large-scale port water surface surveys.
• Bottom-mounted ADCP: Used for fixed point, long-time monitoring of currents in one location, which includes the current velocity near wharfs and inside channels.
• Buoy-mounted ADCP: It can be more flexible and used for monitoring the variations in current within different water bodies with the buoy's movement.
• Dependent on Frequency: 600kHz: In water depths below 70m, it could be used where the water has shallow depth over the port area, such as near the coast and some channels. It operates at a frequency of 300kHz, suitable for water depths of about 110m; it can be used in some medium-depth water areas in the port. It can work with 75kHz, which is suitable for 1000m water depth. It is mainly used in deep water outside the port or in areas with complex seabed topography.

For now, on the market there is such an amount of the ADCP mark like Teledyne RDI, Nortek, Sontek etc. Notice it China Sonar PandaADCP China-it means affordable class, absolutely titanium-alloy-material device. Its high quality corresponds well to a price below average for similar equipment in its category. Contact for the prices and characteristics with https://china-sonar.com.

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