ADCP's Application to Ocean Current Measurement in Hambantota Port

1. Where is Hambantota Port?

Hambantota Port is located in Hambantota, a city in southern Sri Lanka.

• Port Scale and Throughput: This is an infrastructure development in a big area with considerable length of the quay and more number of berths to handle different types of vessels. Throughput in the port is growing with the emergence as a node in the network of maritime trade. It handles all types of cargo: containerised, bulk cargo such as coal and grains, liquid cargo, and so on.
• Routes and Business: Hambantota Port connects the East to the West. It is linked with major shipping lanes that pass through the main ports in Asia, Europe, and Africa. The business activities entail import and export transactions. For example, it exports Sri Lankan products such as agricultural produce and handicrafts, while machinery, construction materials, and consumer goods are imported.
• Port Management and Operation: The port is managed by an effective administrative system. The management team oversees berthing vessels, cargo handling, and other operations at the port with a view of ensuring smooth logistics. Strict security measures and control procedures ensure adherence to the port's high-class services.
• Port Facilities: It is well facilitated with the availability of modern facilities. Advanced container terminals are equipped with high-capacity cranes that help in loading and unloading containers. Further, the port has a number of storage areas that also include warehouses with appropriate ventilation and temperature control for a number of goods. Besides this, it facilitates bunkering ships and maintenance services for vessels.
• Channel and Direct Shipping: The channels of the port are well designed, allowing large-scale vessels to be accommodated. The depth of the channels is maintained to a level that enables ships with considerable draft to enter and leave the port. Shipping services to various international ports have been established directly, reducing the time for transit and enhancing the competitiveness of the port.

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

The measurement of ocean currents at Hambantota Port becomes indispensable for more reasons than one. First, it is paramount in vessel traffic management. Ocean currents usually have a great impact on the speed and course of a vessel. In this regard, the port authority can give much more precise navigation information to ships after accurate measurement. This can result in reduced fuel consumption and shorter times of transit for vessels entering and leaving the port.

It is necessary not only for the safety of the port but also for the regularity of operations. Strong or unpredictable currents can threaten the stability of the ships during berthing and unberthing. Knowledge of current patterns assists in taking appropriate precautionary measures to adjust the mooring lines and operations of tugboats for accident avoidance.

Moreover, the knowledge of the currents permits better planning of the port infrastructure. Currents can affect sediment transport and deposition at the site in the vicinity of the port. The measurement of the currents will enable dredging operations to be planned with a necessary water depth and channel stability. Compared to the conventional technique of current measurement, ADCP current meter is more sophisticated and handy.

3. How do the ADCPs applying the Doppler Principle Work?

The ADCPs work on the principle of the Doppler effect. They transmit acoustic pulses into the water. These pulses interact with moving particles in the water-suspended sediments, plankton, etc.-are reflected back with a frequency shift because of the Doppler effect.

Ship-borne ADCP

In the context of Hambantota Port, a ship-borne ADCP can be installed on a research vessel or a port-service vessel. As the vessel traverses the water, the ADCP current profiler projects acoustic signals both downward and sideways. The instrument measures the frequency shift of the reflected signals from different depths and directions. By analyzing these frequency shifts, the velocity of the ocean current at different depths can be determined. The data is then processed and can be used for real-time navigation or further analysis.

Fixed ADCP

Fixed ADCPs can be installed on the seabed, on the side of piers, or other fixed structures. These ADCPs continuously emit acoustic signals and receive the reflected signals. They provide a long-term and stable record of the ocean current velocity and direction at a specific location. This data is valuable for understanding the local current patterns and their changes over time.

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

The equipment should possess certain characteristics for high-quality current measurement in Hambantota Port. The materials of the equipment should be reliable. For instance, the casing of ADCP flow meter is preferably made from titanium alloy. The reason is that titanium alloy has excellent corrosion resistance, which is very important in the marine environment. It can withstand the corrosive effects of seawater and maintain the integrity of the equipment for a long period.

The size of the equipment should be small and the weight light. A small and lightweight ADCP profiler is much easier to install and operate, whether it is on a ship or fixed at a position. It reduces the impact on the installation platform.

Another important factor is low power consumption. In a port environment, one often needs to continuously operate the equipment. Low power-consuming equipment can operate for a very long period of time without replacing the batteries every now and then or excessive energy supply, which would be convenient and economic. Thirdly, equipment cost should be low to enable extensive deployment for whole current measurement.

5. How to Select appropriate equipment for current measurement?

Selection of appropriate equipment for current measurement in Hambantota Port depends on the specific usage.

Based on Installation Type

• Ship-borne ADCP: If the purpose is to measure the current during the movement of ships or to conduct surveys in a wide area of the port, ship-borne ADCP is a good choice.
• Bottom-mounted ADCP: For long-term and fixed-point monitoring of current conditions, especially near important port facilities such as channels and berths, bottom-mounted ADCP is more suitable.
• Buoy-mounted ADCP: When the focus is on the surface and upper-layer current patterns in the open water area of the port, buoy-mounted ADCP can be considered.

Based on Frequency

The choice of frequency depends on the water depth. For example, a 600 kHz ADCP will work for water depths up to about 70m and can be used in relatively shallow areas of the port. On the other hand, a 300 kHz ADCP is suitable for water depths up to approximately 110m and can cover a wider range of depths in the main port area. For this application, a 75 kHz ADCP is designed for much deeper waters, up to 1000m, which is really applicable for deep water at some considerable depths from the shore, say around the entrance of the port.

There are well-known ADCP brands like Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth mentioning. It is made of all-titanium alloy material and has an incredible cost-performance ratio. You can find more information on its website: (https://china-sonar.com/).

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