ADCP's Application to Ocean Current Measurement in the Port of Rathmullan

1. Where is the Port of Rathmullan?

The Port of Rathmullan is located at the north coast of County Donegal in Ireland. The port is relatively small yet with its own characteristics.

Port Scale and Throughput

The scale of Rathmullan port is relatively modest in size compared to larger commercial-scale ports. Its throughput mostly comprises local fishing activities, as well as some very small cargo shipments related to the needs of the local community. It provides the necessary link for fishermen bringing in their catches and the importing of basic supplies such as fishing gear, fuel, and building materials for the local area.

Routes and Business

It has limited networks of shipping routes for long-distance routes but links with the local coastal ports for trade and transport exchange. The port's commercial activities are therefore basic in nature, mostly oriented toward providing services to the local fishing fleet, which has traditionally been an important sector of Rathmullan's economy and social life. In addition, it can receive and handle small cargo shipment traffic for local business and industry on an occasional basis.

Port Management and Operation

It operates on the principle of catering to the needs of the community with specific emphasis on the local fishing industry. The facility provides for the berthing of fishing boats in a methodical and systematic manner. It works in securing the landing of catches in time and also providing essential supplies on time. Safety is ensured for vessels and persons operating at the port.

Port Facilities

It has basic but functional facilities. There are a few berths designed to fit the size of the local fishing vessels. There are storage areas for fish and other goods, along with some simple loading and unloading equipment to assist with the movement of cargo. The port also has a small quay where boats can dock and tie up.

Channel and Direct Shipping

The channel of the port is maintained for safe passage for the local boats. While the amount of dredging may be less compared to a more major port, the port is regularly checked to ensure no obstacles obstruct and that the water is deep enough for the vessels plying the port. It has direct connections with other nearby ports for the exchange of goods and resources.

2. Why would one measure the currents of the ocean in the Port of Rathmullan?

Measuring the current in the ocean around Rathmullan Port holds some key aspects. The protection of the local fishing fleet: Knowing the patterns of tides is important in determining their activities. Local fishermen use their boats in most occasions to navigate into or out of the port in safety. Unpredictable currents can make it challenging for them to return to the port, especially in adverse weather conditions or when carrying a full load of fish. Accurate current measurements can help in providing them with better navigational guidance and reducing the risk of accidents at sea.

Current data is also important for the effective working of the port. Although the activities run on a smaller scale, the current can cause interference in the process of docking and loading/unloading. For instance, at the time of docking boats, fishermen face problems in accurately positioning the boat if the current is too strong. The port can therefore make more efficient use of its restricted berthing space with precise current measurements.

Moreover, from an environmental point of view, knowledge of the ocean currents helps in monitoring the health of the local marine ecosystem. Currents can affect the distribution of nutrients, larvae, and other biological elements in the water. By measuring the currents, the port can help in better understanding and conservation of the surrounding marine environment. Acoustic Doppler Current Profiler (ADCP) offers a more advanced and convenient way to measure these currents compared to traditional methods.

3. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of the Doppler effect. They send acoustic signals into the water. These signals interact with moving particles in the water, such as suspended sediments or small organisms. When the acoustic signals are reflected back to the ADCP profiler, a frequency shift occurs due to the Doppler effect. The ADCP measures this frequency shift and calculates the velocity of the water particles, which in turn gives the velocity of the ocean current.

Ship-borne ADCP

Ship-borne ADCPs can be installed on the local fishing boats or other small vessels operating in the port area. While the boat is moving around the port and waters in the vicinity, the ADCP current meter sends acoustic pulses in various directions, usually downwards and sideways. The device measures the current velocity at multiple depths while the boat is in motion. This forms a high-resolution record of the present state of the area through which the boat is traveling, resulting in an accurate depiction of the currents in the territories it passes over.

Fixed ADCP

Fixed ADCPs can be installed in the port at specific locations, like on the seabed near the berths or at the entrance of the channel. These ADCPs continuously monitor the current at a single point over an extended period. The data collected over time is important for understanding the long-term current characteristics in key areas of the port, useful for analyzing trends and making decisions regarding port operations.

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

The equipment to measure the ocean currents in the Port of Rathmullan should be made of reliable materials. Since seawater is corrosive and the marine environment may cause physical damage to the device, it needs to be resistant to these effects. Small size, lightweight, and low power consumption are also advantageous. The small and lightweight ADCP current profiler allows easy installation and operation from both the boat and fixed platforms. Low power consumption also enables continuous operation without the need for frequent battery replacements and limits energy consumption. Cost-effectiveness would further enable large-scale deployment within the port.

The casing of ADCP flow meter is preferred to be made of a titanium alloy. Titanium alloy has outstanding corrosion resistance in seawater, which means long-term integrity is maintained. The material also possesses a high strength-to-weight ratio, making it strong, durable, yet relatively light. In addition, titanium alloy is biocompatible, hence causing minimal adverse effects on the marine environment.

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

The choice of the right equipment for current measurement in the Port of Rathmullan depends on the specific requirements.

Ship-borne ADCP

It does serve during the occasion when the prevailing conditions need to be overviewed within the diverse parts of a port. The shipborne ADCP can pick data while it sails through most of the areas around a port and thereby give wide range of the current pattern view for the prevailing waters at port waters.

Bottom-mounted (Sitting on the seabed) ADCP

This type of ADCP meter would be the perfect fit for long-term, fixed-point monitoring. That would be from strategic positions at the port entrance and close to berths, among other places in the port to monitor the continuous condition of that particular spot area.

Buoy-mounted ADCP

Buoy-mounted ADCPs are applied in areas where the installation of a fixed device either on the seabed or on a boat is not practical. They can be deployed in open water areas within the port to measure the currents at different depths.

Regarding frequency selection, different frequencies apply to different water depths: a 600 kHz ADCP for up to 70 meters, a 300 kHz ADCP for up to 110 meters, and a 75 kHz ADCP for much deeper waters up to 1000 meters.

There are well-known ADCP brands like Teledyne RDI, Nortek, and Sontek. However, there is also a Chinese ADCP brand, China Sonar PandaADCP. It is made of all-titanium alloy material, which ensures its durability in the marine environment and offers an excellent cost-performance ratio. You can find more information on its website: (https://china-sonar.com/).

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