ADCP's Application to Ocean Current Measurement in Cape Town Port

1. Where is Cape Town Port

Cape Town Port is situated in Cape Town, South Africa. It is a large, big-scale, and high-throughput port. The port is among the most important parts constituting the maritime infrastructure and economy of South Africa.

It is a huge port area by size, with lengths of quays and storage facilities matching that size. The Cape Town port is one of the busiest, with a high volume of containers, bulk commodities like grains and ores, and liquid cargo such as petroleum products. It is an important part of the South African international trade linkage to most other global routes.

The port has various business operations. It is a hub for container shipping, with numerous shipping lines having it as a port of call. The routes of Cape Town Port reach various continents, enabling the import and export of goods. As far as port management and operation are concerned, there is a properly systematic administrative arrangement. The vessel traffic management, cargo handling operations, and maintenance of the safety and security of the port area are looked after by the port authorities.

Available Facilities: Cape Town Port has the best facilities available. Modern container terminals at the port have advanced facilities like gantry cranes which work very fast and efficiently while loading and unloading the containers. In addition to this, it has particular berths for different varieties of vessels like bulk carriers and tankers. The channels to the port are maintained at the highest standards to enable the passing of ships of varied sizes safely. Direct shipping connectivity to major ports around the globe increases the standing of Cape Town Port in the global network of shipping.

2. Why should we measure the ocean currents in the Cape Town Port?

In addition, the measurement of ocean currents is also crucial for efficient operation and management of Cape Town Port. Ocean current data enables the enhancement of vessel navigation. Courses and speeds can be changed based on current patterns, thereby cutting fuel consumption and reducing traveling time by ships that come in and go out of the port. In particular, it helps huge commercial vessels such as container ships and oil tankers, which usually have tight schedules.

Precise current measurements are also basic to port operations safety. Currents, in fact, render ships vulnerable during the berthing and unberthing procedures. Knowledge of strength and direction enables the port authorities to give precise guidance to ships and adopt necessary safety measures to avert collisions and other mishaps.

Understanding the effects of ocean currents is important in the long-term management of port infrastructure. Currents may cause erosion to quay walls and other structures. By monitoring currents, port engineers can more effectively design maintenance and protection strategies for such structures.

Compared to the conventional techniques for the measurement of currents, Acoustic Doppler Current Profiler(ADCP) is more advanced and convenient. It can present a highly detailed and real-time view of ocean currents for a wide range of depths, thus enabling port operators to have quite accurate knowledge of the conditions at the current location of the port area.

3. How do the Doppler Principle ADCPs work?

Principle of working: ADCPs work on the principle of the 'Doppler effect'. They emit acoustic pulses into the water. When the pulses come across particles or any other objects which are moving along with the ocean current the frequency of the reflected sound waves changes. The change in frequency depends upon the velocity of the moving objects.

The Doppler effect in ADCP is basically represented by the formula: $f_d=2f_0\\frac{v}{c}$, where $f_d$ is the frequency shift due to Doppler effect, $f_0$ is the frequency transmitted, $v$ is the velocity of the moving object-ocean current in this case-and $c$ is the speed of sound through water. By measuring the frequency shift due to the Doppler effect, one is able to ascertain the velocity of the ocean current.

The following deployments for ADCPs are possible in the Cape Town Port for different applications: The ship-borne ADCP is installed on a vessel. During the movement of the ship around the port, the ADCP measures ocean currents in different locations. In this way, the measurement of current patterns is mobile and wide-area. On the other hand, the fixed ADCP is mounted at some point in the port-a pier or a submerged structure-and continuously monitors the currents of the ocean at that very point, hence long - term and stable current data.

4. What is required for high - quality measurement of Cape Town port currents?

The equipment to be used for high-quality current measurement in Cape Town Port should possess a number of characteristics. First, the material of the equipment should be reliable, able to withstand the harsh marine environment with high salinity, strong water pressure, and possible impacts from floating debris.

The equipment should be small in size with lightweight. Small and lightweight ADCP is easy to install and operate whether it installed on a ship or a fixed location. Besides, the power consumption of the equipment should be low. In this way, the equipment can work continuously for a very long period of time without frequently changing the batteries or taking a highly energetic supply.

It also must be cost-effective. Low-cost equipment allows wider deployments for current measurement. It is preferred that ADCP casing should be fabricated from titanium alloy because the properties of titanium alloy, such as high strength that could resist the mechanical forces in the marine environment, are very good. It also has good corrosion resistance, which can resist the corrosive effect of seawater.

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

It all depends on the application when choosing the equipment in Cape Town Port for the measurement of current. For ship-based measurements, a ship-borne ADCP shall be appropriate as that can cover a big area of the port when the ship moves around.

If the goal is to measure the current at some fixed location, a sit - on - bottom ADCP or a fixed - mounted ADCP would be better. They are capable of continuous and long - term data at a particular point.

A buoy-mounted ADCP can be considered for floating measurement applications.

Different frequencies correspond to different water depths with regard to frequency selection. This implies that a 600kHz ADCP is suitable for waters of up to 70m in depth, whereas a 300kHz ADCP can go up to 110 meters, and a 75kHz ADCP can go into much deeper waters of as far as 1000 meters.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a recommended Chinese brand is China Sonar PandaADCP. It is made of all - titanium alloy material and offers excellent performance at a very competitive price. You can find more information about it on its website: (https://china-sonar.com/).

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