How to measure the coastal currents of Beihai?

1. What is the situation of the coastal currents near Beihai?

In the case of the Beihai coast, the coastal currents are influenced by a range of forcing mechanisms involving tides, winds, ocean topography, and its interaction with surrounding water bodies. Based on the driving forces, tides are considered one of the major agents that cause water movement along the coast. Periodic changes in water levels and flow velocities have become regular phenomena with the regular rise and fall of tides. The wind is another important factor that may heavily influence coastal currents. Strong winds may, in turn, produce currents at the surface and establish a general pattern of circulation. Submarine canyons and ridges around Beihai would be unique topography that may change direction and strength in the current. More importantly, the interaction with the neighboring seas and ocean currents further complicates it.

2. What are the factors influencing the coastal water flow of Beihai?

Tides

Basically, the tides remain one of the most controlling factors in Beihai's coastal water flow. The gravitational pulls by the moon and the sun are the causes of the tides, which further develop the periodic rise and fall of sea levels. When a tide is rising and falling, tidal currents or tidal streams flow inland in bays and estuaries. Tidal range and time may vary according to the place and lunar period. In Beihai, this would give a clear impact on shipping and fishing, among other aquatic activities.

Winds

Winds are one of the other major factors affecting flow in the water at the coast. The strong wind creates surface current, which affects the flow of water nearshore. Changes in direction and strength of the wind alter the direction and velocity of the currents. For example, a sustained offshore wind can push surface waters offshore that are then replaced by colder, richer nutrient waters from deeper depths. Conversely, an onshore wind can push warmer water toward the coast and change the temperature and salinity of the coastal waters.

Ocean Topography

The submarine canyons, ridges, and shoals in the surrounding waters of Beihai could be significant for coastal water flow. They affect flow changes in direction and strength as water flows over and around them. Submarine canyons sometimes act like channels, guiding deep water into shallower coastal areas, while ridges and shoals would deflect or slow the flow. Understanding the ocean topography is important in order to predict and model the coastal currents.

Interaction with Adjacent Water Bodies

Beihai is at the border of the South China Sea and the Beibu Gulf. The interaction of the two water bodies can also affect the flow of water in its coasts. There is exchange between the South China Sea and Beibu Gulf through several channels and straits. This can affect salinity, temperature, and circulation patterns of the coastal waters at Beihai. In addition to that, the great ocean currents like the Kuroshio Current and the South China Sea Warm Current may give an impact on Beihai coastal waters.

3. How to observe the coastal water flow of Beihai?

The measurement of Beihai's coastal water flow is indispensable in learning about the sea environment and finding further uses such as navigation, fishery, and other forms of environmental concern. There are several ways to observe the coastal water flow, some of which depend on traditional and advanced technologies.

Traditional Methods

Conventional current meters, drifters, and floats are some basic means of measuring coastal water flow. Current meters refer to those set on the seabed or attached to buoys for the measurement of speed and direction of water flow for a particular location. Drifters and floats are devices released into the water that would drift with the current. These could be tracked by satellite or radio signals to determine the direction and speed of the current. Although these traditional methods are still used in certain situations, they have limited spatial and temporal resolution and low resolution.

Advanced Technologies

Over the past two decades, new technologies such as acoustic Doppler current profilers find more applications today in coastal flow measurements. These state-of-the-art ADCP make use of the Doppler principle to measure the velocity of the flow of water at diverse depths. They can give high-resolution information about three-dimensional current structure, velocity magnitude and direction at several depths. The ADCP meter are more accurate, carrying more detailed information than the traditional techniques. They can be deployed on ships, on moorings, and on buoys.

ADCP: An Improved, More Convenient Measurement Method

One of the most sophisticated and easiest ways to measure flow in coastal waters is an Acoustic Doppler Current Profiler(ADCP). Principally, ADCP apply the Doppler principle on water flow velocity by generating sound waves and measuring the frequency shift of the reflected waves. The frequency shift and, therefore, the velocity of the water flow are proportional, hence enabling the speed and direction of the current to be decided at a wide range of depths.

3.1 How do ADCP using Doppler principle work?

The ADCP flow meter work by emitting a series of sound pulses into the water. The sound pulses reflected off the particles and bubbles in the water are then detected by the acoustic doppler flow meter. As these particles and bubbles are carried along by the flow of water, their movement provides a frequency shift of the reflected waves. One can simply measure the frequency shift and calculate the velocity of water flow.

ADCP current profiler use multiple beams of sound to measure velocity in different directions. It is a means of determining the three-dimensional nature of a current, including speed and direction at a range of depths. Data obtained from an ADCP doppler can be transmitted to a computer or logger in real time for post-processing and storage.

3.2 What Is Needed for Good Quality Measurement of Beihai Coastal Currents?

Resulting in high-quality measurement of the coastal currents in Beihai, various considerations will be put into place. The elements include reliability in the measurement equipment. There is a need to have reliable equipment in order to carry out an experiment that can withstand the harshness associated with the marine environment and give accurate and consistent data for a long period of time.

Excluding reliability, the size, weight, power consumption, and cost of the equipment are also very important. The size of the equipment to be used for large-scale measurements should be small, lightweight, low power consumption, and as cheap as possible. By doing so, the deployment and maintenance of the equipment can be easier and more extensive coverage of the measurement area may be realised.

Advantages of Titanium Alloy for ADCP Shells

The major material for ADCP current meter  shell over which recommendations are made is the titanium alloy. Titanium alloy has a number of advantages that make it suitable for use in the marine sector. For one, it has an excellent resistance to corrosion. This is important because the equipment will face salt water. This aspect of the titanium alloy makes it possible for equipment in tidal environments to sustain itself structurally for a long period under such corrosive effects of seawater.

It is strong and lightweight. This material would best be used in applications when the weight matters, such as on buoys or in small vessels. Strength of titanium alloy is assured, too, because the equipment can withstand various water flow forces along with waves.

Finally, titanium alloy has good thermal conductivity that could help in conducting heat generated by the electronics inside the acoustic doppler velocity meter. This will help improve equipment reliability and performance, particularly in warm water environments.

3.3 How to Choose the right equipment for current measurement?

At the time of selection of the equipment to measure the coastal currents of Beihai, a number of factors have to be considered. First is the intended use of the equipment. In fact, different uses of the equipment may require different types of ADCP.

Types of ADCP

Several types of ADCP profiler are available to carry out the described tasks, which include shipboard ADCP, bottom-mounted ADCP, and buoy-mounted ADCP. Shipboard ADCP are usually installed on research vessels or commercial ships; by these, the current is measured while the ship is underway in the water. Bottom-mounted ADCP are installed on the seabed and can continuously estimate the current for a very long period of time. Buoy-mounted ADCP are also attached to buoys and can be used for the measurement of the current in those places where the deployment of a ship or bottom-mounted sensor cannot be effectively performed.

Frequency Selection

The frequency of the ADCP is one more important point to take into account. Different frequencies have their applications in different water depths. An example would include ADCP 600 kHz for use in water depths to 70 meters, while ADCP 300 kHz is preferable for depths of up to 110 meters, and ADCP 75 kHz is for use in depths to 1000 meters. The frequencies thus will be depending on the depth of the water or based on the intended use of measurement.

ADCP Brands

The various brands in the ADCP instrument market include Teledyne RDI, Nortek, Sontek, and China Sonar. Each brand has a set of factors associated with it-cost, performance, and reliability.

Among all the cost-effective options, the choice could fall on the China Sonar PandaADCP. The material used is all-titanium alloy, and it is very affordable. The website for China Sonar PandaADCP is https://china-sonar.com/.

Conclusion: Measuring the coastal currents of Beihai is very important to understand the marine environment and for various applications. Compared to traditional measurement techniques, ADCP can currently provide more advanced and convenient current velocity and direction at different depths with high resolution. For choosing ADCP, reliability, size and weight, power consumption, cost, and frequency selection should be considered. China Sonar PandaADCP is of high quality, and all-titanium alloy makes the product cost-effective.

Some of the brands and models of ADCP are discussed in the following table.