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The "Long Grant" stranded by the quay wall effect

 　　On March 24, 2021, the heavy cargo ship Long Grant, flying the Panamanian flag, ran aground on the new channel of the Suez Canal, causing serious blockage of the channel. This congestion incident has disrupted the rhythm of the world. As we all know, the Suez Canal is known as the "Eurasian Artery". It connects the Red Sea and the Mediterranean Sea. It is one of the busiest trade routes in the world. About 12% of global trade flows through this place. According to estimates by Lloyd’s Register, the daily trade volume in the westbound direction of the canal is approximately US$5.1 billion, and the trade volume in the eastbound direction is approximately US$4.5 billion per day. Fortunately, after 6 days and 6 nights of rescue, the Suez Canal finally resumed navigation.

　　After learning from it, why did a great ship run aground on the Suez Canal?

　　Many media have claimed in reports that the cargo ship "Longci" was hit by sandstorms and strong winds. The hull of the ship suddenly deviated from the channel and finally bottomed and ran aground. Is it really? We might as well think about it. Compared with the magnificent ocean, the Suez Canal can be said to be calm and safe in the wind and waves, but the cargo ship "Long Give" is the world's largest container ship. If it is really due to sandstorms. Stranded and stranded, isn't it "captured in the gutter"? But if it was not caused by the sandstorm, what would be the reason?

　　Not long ago, Evert Latel, head of the Department of Marine Technology at Ghent University in Belgium, believed that the grounding of the "Long Give" cargo ship may be related to the classic physical phenomenon of the quay wall effect.

　　The cargo ship "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 stern of a large ship is easily sucked up by the river bank when it is running, which is the quay wall effect.

　　In fact, when the ship is advancing in a narrow waterway, the water level at the bow is always higher than the hull and stern, so when the water flows from the bow to the stern along the hull, it will enter a wider channel Narrow area. According to the Venturi effect, we can know that when the liquid passes through a narrow area, the flow rate will increase and the pressure will decrease. This means that compared with the bow, the vicinity of the hull is a low-pressure area. If the ship approaches the river bank or other ships are too close, it is easy to be sucked, causing a quay wall effect.

　　According to the quay wall effect, when driving in a narrow waterway, when the bow of the ship starts to turn, the hull closer to the river bank can easily be sucked over by the river bank. Judging from the travel records, it is very likely that a similar situation occurred on the cargo ship "Longci". According to the tracking records of the navigation posture of the "Changci" cargo ship at the time by the ship's automatic tracking website, when the "Changci" cargo ship encountered strong westerly winds, it tried to steer westward against the wind, and as a result, it fell into the quay wall effect. In a dilemma, the hull eventually rotated clockwise and the bow plunged into the east bank.

　　Major accidents caused by quay wall effects in history are not uncommon. For example, in January 1934, the British Nelson-class battleship left Portsmouth, England at a speed of 4.6 meters per second, and as a result, it ran aground due to the quay wall effect.

　　The quay wall effect is only one of the physical phenomena in narrow waterways. When a large ship travels in a narrow waterway, due to the depth of the water and the speed of the ship, unpredictable troubles of one kind or another may occur. For example, when encountering shallow water, it is difficult for a large ship to steer, and it is easy to follow the underwater terrain or spin in shallow water; when a heavy cargo ship travels too fast, it is prone to "buttock squat" phenomenon, and some may even cause the ship to run aground. On July 8, 1992, the "Queen Elizabeth 2" ocean-going cruise ship ran aground on the sandbank near Katyhangk Island in Massachusetts because of underestimating the speed of the ship.

　　In short, if you want to drive a big ship well in waterways such as canals and shoals, you need to learn fluid mechanics well.


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