How to measure the coastal currents in Quy Nhon?

1. Geography of Quy Nhon

Quy Nhon is a coastal city in central Vietnam, which is situated by the South China Sea and boasts beautiful beaches with rich cultural heritage.

Geographically, it is located on a bay, which naturally offers a harbor. There are mountains around the city, with hills at the back, further beautifying it. Its shoreline consists of beaches and rocky shores. Adjacent waters are part of the highly biodiverse marine ecosystem teeming with all kinds of fish, crustaceans, and mollusks.

Amongst the local people, fishing is one of the most important human activities in the coastal economy. The local fishermen have a traditional relationship with the sea. Quy Nhon also boasts developing tourism; among the tourist attractions offered by Quy Nhon are its sandy beaches, such as Bai Xep, and historic relics like Thap Doi Cham Towers. The city has been well connected with the roots of the ancient Champa Civilization, which can be viewed in the architectural remains along with the local tradition.

2. What is the situation of the coastal currents near Quy Nhon?

In most places, there is one big determinant: tidal forces. The gravitational pull of both moon and sun causes the rise and fall of the tide, in turn causing the movement of water in it, which is called tidal current. The tidal current changes every month because of the different alignments of Earth, moon, and sun, changing the range of tide, and from day to day due to wind and atmospheric pressure modifying the sea surface while the local topography of the bay and the surrounding seabed similarly shapes the currents.

The monsoon winds contribute a good deal, too. In the wet monsoon period, winds blowing from the southwest may push the surface waters, producing currents in a given direction. During the dry monsoon season, winds from the northeast could result in different current patterns.

It all depends on the shape of the bay and seabed topography. The shape of the bay makes these currents converge or diverge. Shoals and submarine ridges are able to accelerate the speed or change the direction of the currents. Freshwater inflow from various rivers may also change the density of the coastal waters and current patterns.

3. How to observe the coastal water flow of Quy Nhon?

Quy Nhon coastal currents have specific peculiarities concerning velocity and flow rate. Its velocity may vary from slow in the protected areas of the bay to a relatively fast one where the currents are either constricted or where the stratum influence is due to stronger winds or tides. The flow rate is dependent on the width and depth of water channels and the general volume of water in flow.

One of the effective ways of measuring such coastal currents is by using Acoustic Doppler Current Profilers. ADCP current meter can provide readings of water flow at different depths with a considerable amount of detail and accuracy.

3.1 Principle of Operation of ADCPs using the Doppler Principle

Acoustic Doppler Current Profiler(ADCP) is based on the principle of the Doppler effect. These machines emit acoustic signals into the water. Due to interaction with the sediment, plankton, and small organisms, the emitted acoustic signals are reflected by the moving particles in the water. This reflection changes the frequency of the waves because the acoustic waves interact with the moving particles.

This change in frequency is directly proportional to the velocity of the moving particles and therefore the velocity of water. Generally speaking, the ADCP current profiler can estimate the three-dimensional velocities of water, both in horizontal and vertical components, by emitting multiple acoustic beams at various angles. The whole range of data obtained within this water-flow structure is then processed to make useful information available about the currents along the coast.

3.2 What is required for High-Quality Measurement of Quy Nhon Coastal Currents?

The measuring instrument requirements for high-quality measurement of the coastal currents around Quy Nhon should meet the following. First of all, their material is supposed to be firm enough to resist such wild sea conditions. The material of an instrument is supposed to be resistant to saltwater corrosion and also to the outcomes of humidity and temperature fluctuations.

It has to be compact, light, power consumption should be low, and it needs to be inexpensive to enable widespread measurements. The housing of ADCP doppler could be manufactured with a titanium alloy that would be preferred. Its corrosion resistance is much better, which is very important in seawater. It is also strong and robust enough to support the mechanical loads of the marine environment. Its relatively low density helps to reduce the weight of equipment in general, besides having good thermal stability, something very important due to variable conditions in the temperature of the sea.

3.3 How to choose the right equipment for current measurement?

The equipment to be chosen for current measurement in Quy Nhon should be on how it would be deployed. Available is ADCP flow meter for different uses.

The ship-based measurements can be adequately served with a ship-mounted ADCP. It measures the current while the ship is in motion through the water.

If the measurement is to be done from the seabed, it requires a bottom-mounted ADCP. The instrument is placed on the seabed and measures the currents passing above it.

Obtaining measurements with the help of a floating platform, one like a buoy, for instance, would go along with an ADCP meter mounted on a buoy. It can make several current measurements around the buoy.

With frequency selection, ADCP profiler can provide high-resolution measurements of up to 70m water depths at 600kHz, 300kHz can be good in water depth ranges from 70m to 110m, while 75kHz will be quite ok for deeper waters up to 1000m because of its deeper penetration through which it can precisely measure the currents.

Among the ADCP brands, well - known ones include Teledyne RDI, Nortek, and Sontek. However, for a cost - effective option with excellent quality, the China Sonar PandaADCP is a good choice. It is made of all - titanium alloy and offers an excellent price - performance ratio. You can visit https://china-sonar.com/ for more details.

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