This article is from WeChat official account:Bring science home (ID: steamforkids) span> , author: seven Jun, the original title: “Suez Canal blocked, possibly because of the scary physical phenomena,” head Figure from: vision China
On March 24 of this year, the giant container ship Changsui, made in Japan, with crew from India, operating company from Taiwan, China, flying Panamanian flags, and finally towed away by the Dutch and Egyptians, was on the Suez Canal. stranded.
The stranded Long Ci giant container ship, see the watermark for its source
The Suez Canal connects the Red Sea and the Mediterranean Sea. 12% of the world’s trade passes through this canal, so it is often referred to as the “Eurasian artery”. However, the Long Grant blocked the blood vessels of this important international transportation route. More than 200 ships got stuck in the river and passed through it again after 6 days and 6 nights.
Suez Canal Authority(Suez Canal Authority) Director Osama Rabie said that during the stranding, Egypt alone lost 12 million per day ~15 million US dollars. Some analysts pointed out that the overall loss caused by the stranding of the Long Grant could reach 10 billion U.S. dollars a day.
So, how did the Long Grant be stranded?
This may be due to a classic physical phenomenon. According to Evert Lataire, Dean of the Department of Marine Technology, Ghent University, Belgium, the possibility of the Stranding of the Long Grant and the quay wall effect(bank effect) about.
Long Grant Number, picture source: vesselfinder
Changci is 400 meters long and 60 meters high. It can block the Suez Canal when it crosses over. In such a narrow waterway, the buttocks are easily sucked by the river bank when the big ship is running. This is the quay wall effect.
Actually, when the ship is moving in a narrow waterway, the water level at the bow is always higher than that at the hull and stern. Therefore, when the water flows from the bow to the stern along the hull, it will enter a narrow area from a wider channel.
The water level at the bow is always higher than the hull and stern. Image source: wikipedia
This problem can be solved by using the Venturi effect (venturi effect): When the liquid passes through a narrow area, the flow rate will Increase, and pressure decrease. This means that compared to the bow, the vicinity of the hull is a low pressure area. If the ship is too close to the river bank or other ships, it is easy to be attracted, causing a quay wall effect.
Venturi effect: When passing through a narrow channel, the liquid velocity increases and the pressure decreases.
You can take a look at the demonstration of the quay wall effect made by a model ship by the University of Ghent in Belgium. The small balls on the shore are attracted by the hull.
According to the quay wall effect, when driving in a narrow waterway, when the bow starts to turn, the side of the ship closer to the river bank will easily be sucked past by the river bank. Therefore, all those who learn about ships know that when a big ship crosses a small path, you must pay special attention not to let the hull and the river bank or other ships get too close, not too fast, and try to follow the center line of the river.
The water pressure near the hull is lower than that of the bow, and it is easier to be attracted by the river bank. Image source: themarinestudy
In history, the quay wall effect has caused some major accidents.
For example, in January 1934, the British Nelson-class battleship left Portsmouth, England at a speed of 4.6 meters per second, and the result was stranded because of the quay wall effect.
British Nelson-class battleship
From the driving record, a similar incident may have happened on the Long Grant.
At 7:30 in the morning on March 23, local time, the Long Grant encountered a sandstorm shortly after entering the Suez Canal. The Suez Canal Authority stated on March 26 that the Long Give was unable to steer the helm after encountering strong winds and sandstorms.
According to VesselFinder’s tracking record of the navigational posture of the Long Ci at that time, when Long Ci encountered a strong westerly wind, it tried to steer to the west against the wind, so it fell into the quay wall effect. In the end, the hull rotated clockwise and the bow plunged into the east bank.
The stranded path of the Long Grant in the Suez Canal.
However, the physical phenomenon of evil gates in narrow waterways is not only the quay wall effect, but the stern effect should be paid attention to when large ships pass through small passages.(squat effect).
As mentioned earlier, when the ship is moving forward in a narrow waterway, the water level at the bow is always higher than the hull and stern, so the water flow on the hull is faster than the bow and the pressure is lower. In fact, this also applies to the bottom of the ship, because when the water flows from the bow to the bottom of the ship, it also passes through a narrower passage. In this way, the bottom of the boat will also be attracted by the riverbed, which means that the bottom of the boat is easy to sink in shallow waters. This is the stern effect.
In the deep sea (upper) ships are not easily affected by the stern effect, but the stern effect is obvious in the shallows (lower). Image source: wikipedia
The stern effect is mainly related to water depth and ship speed. When the ship speed is higher, the ship is more likely to squat. The stern effect is very obvious when the water depth is less than the draft (the deepest length of the underwater part when the ship sinks in the water) 2.5 times.
When the water depth is less than 2.5 times the draught (the deepest length of the underwater part of the ship when it sinks in the water), the stern effect is obvious. Image source: fas.org
Because of the stern effect, large ships are difficult to steer in shallow water, it is easy to follow the underwater terrain or spin around in shallow water. The stern effect has also caused many accidents.
On July 8, 1992, the Queen Elizabeth II ocean liner was on Cuttyhunk Island in Massachusetts, USA(cuttyhunk island) stranded on a nearby sandbank. A subsequent investigation by the National Transportation Safety Board (NTSB) pointed out that the crew did not know the topography of the water bottom and therefore underestimated the stern sitting caused by the excessively high ship speed. The effect directly led to the occurrence of the incident.
The newspaper reported that Queen Elizabeth II was stranded.
In 2000, the Tecam Sea and the Federal Fuji bulk carrier collided at the Sorell Tracy Port in Quebec, Canada. Later accident analysis reports pointed out that the stern effect was also the cause of the accident.
There are even ships that use the stern effect to forcefully lower their “height” to avoid strange operations that exceed the maximum safe navigable altitude.
On November 1, 2009, the world’s third largest cruise ship, the Oasis of the Sea, 72 meters above the water, accelerated to 37 kilometers per hour when crossing the Great Belt Bridge in Denmark, successfully allowing the ship to pass through the Great Belt Bridge in Denmark. It entered the water 30 centimeters more, and finally crossed the bridge at a distance of 4 centimeters less than the maximum safe navigable height, showing off the “bridge-crossing rice noodle” technology.
Ocean Oasis crossed the Great Belt Bridge. Image source: cnn
In short, the canals, shallows, and these waterways are pits everywhere for big ships, and the crew who didn’t learn fluid mechanics might be blocked every minute.
Cold Knowledge: The trajectory of the Long Give before entering the Suez Canal ——
Reference materials are stored in graphite:https://shimo.im/docs/3qvwjrcjc8vjJW3j/
This article is from WeChat official account:Bring science home (ID: steamforkids) span> , author: seven Jun