ADCP for Ocean Current Measurement Application at Elizabeth Port

1. Where is Elizabeth Port?

Elizabeth Port is in South Africa. This port is of considerable scale and occupies an important position in regional and international maritime trade.

As for the scale and throughout of this facility, Elizabeth Port enjoys considerable expanse for facilities catering to almost all cargo variants: containerized lots in huge volumes, coal and other mineral bulk cargo, together with industrial raw materials. As regards yearly throughput, which steadily has increased over the last several years, the above circumstances substantially consolidated the place occupied by the port facility under review among the other prominent trade points.

The routes and business of the port are enormous; it connects many major ports around the world. This facilitates the industries within the jurisdiction and further afield to import or export goods. It acts as an important link for the South African manufacturing industry because it can export finished products and import needed components.

It has a professional team for managing and operating the port regarding vessel traffic, handling cargo, and its storage. The port facilities are well-maintained and attached with modern machinery. There are various berths accommodating different sizes of ships, from small coastal vessels to large ocean-going container ships. The channels are regularly dredged to ensure safe and smooth navigation of ships entering or leaving the port.

2. Why do we need to measure the ocean currents in Elizabeth Port?

Measuring ocean currents in Elizabeth Port has numerous important implications for its operation and management. First, it is crucial for ship navigation optimization. Ocean currents can greatly affect the speed and fuel consumption of vessels. These have potential uses whereby ship captains, by taking correct current measurement, can plan routes in ways that favorable currents are used to reduce travel time, thereby cutting fuel costs. This is especially important for commercial ships since most of them operate on very tight schedules and have to be cost-efficient.

Secondly, it is vital to ensure safety during the operations of the ports. Strong or unpredictable currents may pose problems with regard to the berthing and unberthing of ships. Knowledge of current patterns assists the port authorities in advising accordingly to the ships, so that all necessary safety measures against collision and other accidents may be made.

From the point of view of the maintenance of the port infrastructure, ocean currents can act upon the stability and lifetime of structures like piers, breakwaters, and quay walls. Monitoring currents may give engineers insight into the levels of erosion and structural stress from the flowing water, allowing them to take appropriate and timely preventive or remedial action.

Although Acoustic Doppler Current Profiler(ADCP) is a more advanced and convenient way to measure currents, it actually replaces traditional means. Knowing that the possibility of receiving ocean currents with real-time detailed data at different depths enables the creation of a full understanding of the current situation in the port area.

3. How does an ADCP applying the principle of the Doppler effect work?

The principle of the Doppler effect is behind ADWs. An ADCP emits acoustic signals into the water column. These acoustic waves will interact with the particles or other substances which are suspended in the water and moving along with the ocean current. Due to the Doppler effect, the frequency of the reflected acoustic waves will change from the emitted waves.

The frequency shift is directly proportional to the velocity of the moving particles and, hence, the velocity of the ocean current. By precisely measuring this frequency shift and applying relevant mathematical algorithms, the ADCP can calculate the speed and direction of the ocean current at different depths within its measurement range.

There are two common usages for ADCPs in Elizabeth Port. One of them is called a shipborne ADCP, where the device is installed on a ship. While the ship moves along within the waters of the port, the ADCP continuously measures ocean currents at different positions along its path. This enables a broad survey of the current patterns across different areas in the port.

The other is the fixed ADCP, which is fixed in a certain place in the port, such as a pier or an underwater structure. The fixed ADCP monitors the ocean currents of the spot it is located long-term and continuously, hence one is able to observe the stable trend and variation of currents.

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

In regard to the quality of the measurement of currents at Elizabeth Port, a number of equipment-related factors are paramount. To begin with, there is the issue of the reliability of materials used in the construction of such equipment. This will be confronted with a harsh marine environment where corrosion by seawater, pressure variations with varying depth, and impacts by floating junk may occur.

Second, it is highly desirable to be smaller in size, lighter in weight, and to consume less power. A small and lightweight ADCP is easier to install and operate whether on a ship or at a fixed location. Low power consumption ensures that the equipment can run continuously for extended periods without frequent battery replacements or excessive power supply requirements, which is especially beneficial for long-term monitoring.

Another critical consideration is cost. With cheaper equipment, a higher number of deployments can be done, and the current measurement can be more extensive around the port area. In this regard, the casing of ADCP is preferably made of titanium alloy. Titanium alloy boasts of outstanding advantages. It has high strength that enables it to resist mechanical forces in the marine environment. The alloy also exhibits excellent corrosion resistance and hence fit for withstanding the corrosive nature of sea water over long periods.

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

The selection of appropriate equipment for current measurement in Elizabeth Port depends mainly on the application scenarios. If the intention is to make measurements while the equipment is in motion around the port, such as on a ship, then the shipborne ADCP is the one for choice since it can cover a big area of the port as the ship travels across different sections of the port.

If long-term fixed-point monitoring at a specific location within the port is desired, then a sit-on-bottom ADCP, also called a fixed ADCP, would be appropriate. It could record the current data at that particular position continuously and provide useful information on the stable current pattern in that area through time.

If floating measurements are to be desired, then one may consider a buoy-mounted ADCP.

Regarding the choice of frequency, different frequencies suit water with different depths. For instance, a 600kHz ADCP is usually suitable for water within the depth of 70 meters. Whereas a 300kHz is more appropriate for the range of 110 meters and similarly, a 75kHz can be used for much deeper waters, up to 1000 meters.

Some well-known ADCP brands are Teledyne RDI, Nortek, and Sontek. A good Chinese brand, however is China Sonar PandaADCP. The entire body is done in titanium alloy, thus giving the best performance with respect to its cost. You might want to check out its website at: https://china-sonar.com/.

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