Tide is a kind of tide that occurs in coastal areasnatural phenomenaRefers to the sea water in celestial bodies (mainlyMoonAnd the sun)Tidal forceThe periodic movement caused by the action.The rise and fall of the sea surface in the vertical direction is traditionally called tide, and the sea water in thehorizontal directionThe flow of is called tide.In order to express the time of sea water fluctuation, human ancestors called the sea water fluctuation in the daytime tide, and the sea water fluctuation in the evening tide, collectively called tide.This is the origin of the name of tide.
Tide is a periodic fluctuation phenomenon of sea water formed under the gravity of the moon and the sun.Tide in the daytime and tide at night are collectively called "tide".Generally, it fluctuates twice a day, and sometimes it fluctuates once.Tidal waves in the open sea go upstream along rivers, which in turn causes tides in the lower reaches of rivers.becauseSummer CalendarYesLunar phase changeAs a basis, it has a major role in reflecting the tide. The moon plays a leading role in the tide phenomenon. The summer calendar based on the changes of the moon phase is a guide to maritime activities in ancient times.The moon is attractive to the earth's sea water. The distance between each point on the earth's surface and the moon is different. The place facing the moon is strongly attracted, and the sea water expands outward;The sea water at the place back to the moon is less attractive, and the centrifugal force becomes larger. Under the centrifugal force,BackwardWhen the place on the moon expands, the tide will also rise.
Extended meaning
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The extended definition of the term "tide" refers to something with similar characteristics to the tide phenomenon, which is used to describe the rising and falling, moving and changing things, and is often used as a positive phrase, such as:Tidal lane, tidal families, tidal passenger flow, etc.
Tidal (like the tide, the rising and falling, and the periodic change of things) means the extended meaning of the tide, and is often used in positive phrases, such as tidal lanes, tidal passenger flow, etc.
BeiqiYan Zhitui"Yan Family Instructions - Returning to Heart": "When the tide goes back, who will be abstemious?" Song Suzhe《Hezi Zhan Snow Wave Studio》: "In front of the doorStone bankSet up refined iron, and the tide will wash away the berry moss and make it faint. "brightLiu JiThe seventh part of "Miscellaneous Poems on the River": "Kun Ling is not generousGround fissureThe tide should lead to Fusang. "Ye Shengtao's "Sorrow": "Once the gambling den is broken, the whole city is noisy. People come here to see what the bloggers are like, and the noisy city is like the tide."
Define classification
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tide
Due to the effect of the tidal force of the sun and the moonlithosphere、HydrosphereandAtmosphereThe periodic movements and changes generated in the are collectively called tides.In a broad sense, tide is divided into solid tide (earth tide), liquid tide and gas tide (gas tide).In the liquid tide, except the ocean tide, the river tide fluctuation is very small and can be ignored.So the general liquid tide refers to the sea tide.As a complete tidal science, its research object is alsoTheThe earth tide, sea tide and air tide are a unified whole, but because the sea tide phenomenon is very obvious, and is closely related to people's lifeeconomic activity、TransportationIs closely related, so it is customary to interpret the term tide in a narrow sense asocean tide 。Solid EarthThe elastic plastic deformation caused by the action of the sun and moon tide generating force is called solid tideEarth tideorGround tide。
Tides vary from place to placetideThey all obtain energy from deep-sea tide waves, but they have their own unique characteristics.
The periodic rise and fall, fluctuation, advance and retreat of the sea surface caused by the daily and monthly tidal forces of the sea is called ocean tide, or sea tide for short.
Saltwater tide, mainly bydrought severityIt usually occurs during the period from the winter solstice of the previous year to the Qingming Festival of the next spring. Due to the small amount of water and rainfall in the upstream river, the water level of the river drops, which causes the sea water in coastal areas to flow back to inland areas through rivers or other channels.The impact of salt tide is mainly shown inchlorideAccording to the relevant national standards, if the chlorine content of water exceeds 250 mg/L, it should not be drunk.This water quality will also endanger the survival of local plants.
Saltwater tideIt belongs to a unique monsoon in coastal areasnatural phenomena, mostly in dry seasons and dry periods.Salty water upstream means that the pumping ports located in the lower reaches of rivers are not drinking and irrigating fresh water, but sea water that land life cannot rely on.Salt tides in China mostly occur inPearl River Estuary。
according toTidal periodIt can also be divided into the following three categories:
Half dayTidal pattern: There are two high tides and two low tides in a lunar dayTidal rangeThe tidal range is roughly the same as that of the next high tide and low tide,tideThe time of the process and ebb tide process is almost the same (6 hours and 12.5 minutes).Chinathe bohai sea, DonghaiYellow SeaMost of the locations of are semi diurnal tide, such as DaguQingdao、XiamenEtc.
Diurnal tideType A: There is only one high tide and one low tide in a lunar day.Such as the South China SeaShantou, Bohai SeaqinghuangdaoEtc.South China SeaBeibu GulfIt is a typical diurnal tidal sea area in the world.
Mixed tide type: there are two high tides and two low tides on some days in a month, but the tidal range between the two high tides and low tides is quite different, and the time of rising tide process and falling tide process is also different;On other days, there was a high tide and a low tide.Most places in the South China Sea belong to mixed tide type.asYulin , appear in 15 daysDiurnal tide, other days are irregularSemidiurnal tide，Tidal rangeLarger.
Regardless of the type of tide, the spring tide with the largest tidal range will occur within two or three days after the first and fifteenth days of each lunar month. At that time, the tide will rise the highest and fall the lowest.In the eighth and twenty third days of each lunar month, there is a minimum tidal rangeNeap tideAt that time, the tide will not rise too high and fall too low.
Without considering the weak effects of other planets, the tidal force of the moon and the sun on the ocean is the cause of the rise and fall of seawater.What kind of force is tidal force?In physicsNon inertial frameNext, the tidal force is the universal gravitation of the moon and its corresponding inertia, as well as the universal gravitation of the sun and its correspondinginertia forceThe resultant of the four forces.Some data mention that "centrifugal force" is also a tidal forceComponent forceOne, there areCentrifugal phenomenonHowever, there is no concept and definition of "centrifugal force".However, the original meaning of "centrifugal force" is inertia.
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Only the gravitational effect of the moon can not explain why the rising tide phenomenon occurs at the same time in the two regions of the sea surface closest to the moon and the sea surface farthest from the moon, so that the sphericalsea levelBecome a spindle, as shown in Figure 1.The same is true of the sun's gravity.By 2012, the most novel concept and definition of gravity had appeared in the physics community.The definition is: "In thestaticsWithin the range, the support for placing objects or the objects themselves are non inertialobject of referenceGravity is the resultant force of the universal gravitation and inertial forces on an object. "This definition can successfully explain the origin of tides.It should be noted here that in the case of considering the stars as particles, when calculating the gravity of objects on the ground, only the universal gravity of the earth on objects andearth rotationOfcentripetal forceThe corresponding inertial force is involved in the calculation, and the universal gravitation of other planets is offset by the corresponding inertia.
The causes of tides are as follows:
Let's start with the role of the moon.Think of the earth and the moon as particles, and say that the moon orbits the earthCircular motionIn fact, the moon and the earth both circle the samecentroidTo move in a circle, the earth's orbit is much smaller.（KonductraThe circumference of two planets with similar massOrbital approximationEqual) With the earth center as the non inertial reference, the universal gravitation of the earth particle by the moon particle is the centripetal force of the earth particle moving around the common center of mass, and the inertia force corresponding to this centripetal force is opposite to the direction of the same magnitude of this centripetal force.Therefore, the gravitational force of the earth particle is offset by the inertial force of the moon particle.
Since the earth is regarded as a particle, thepath of particleandDynamic lawIt is regarded as the same as the earth particle.The universal gravitation of the moon and the corresponding inertial force of the object counteract each other.
In fact, the volume of the earth is very large, and the orbit radius of the objects on the ground closest to the moon that move in a circle around the common center of mass of the earth and the moon is obviously smaller than the orbit radius of the earth particle, so the object will be subject to the universal gravitation of the moongreater thanThese two forces can't be offset by the corresponding inertial force, and the resultant force is opposite to the direction of the object's universal gravitation, which makes the gravity of the object significantly smaller.If the "object" is the sea water here, then there will be high tide.Use the samemethod studyThe object on the ground farthest from the moon, and the moon's gravitational force on the objectless thanThe corresponding inertial force, their resultant force is opposite to the universal gravitation direction of the earth to this object, and also makes the gravity of the object significantly smaller.Therefore, the water at the farthest part from the moon will also have high tide.This makes the sea level, which is supposed to be spherical, slightly present a spindle shape.
The study of the effect of the sun on tides is the same as that of the moon.If we think that the earth moves in a circle around the center of the sun, the problem is simple.It will not be discussed in detail here.
The occurrence of ground tide, sea tide and air tide are all caused by the above reasons, and they affect each other.Since the moon is closer to the earth than the sun, the ratio of the moon to the sun's tidal force is 11:5. For the ocean, the moon tide is more significant than the sun tide.Elasticity and plasticity of the crust at the bottom of the oceanTidal deformation, will cause the corresponding ocean tide, that is, for the ocean tide, there is the influence of the earth tide effect;And caused by sea tideSea water qualityThe migration ofRecoverableThe distortion of.The air tide is above the sea tide, which acts on the sea surface and causes its additional vibration, making the changes of the sea tide more complex.
This energy dissipates at the rate of 1.7TW (1.7x10 ^ 12W) through the friction between the shallow sea area and the coastal area.
That is, at the time of new moon, the sun and moon are on the side of the earth, so there is the maximum tidal force, which will cause "spring tide". At the 15th or 16th day of the lunar month, the sun and moon are on both sides of the earth, and the tidal force of the sun and moon will also cause "spring tide";stayphase of the moonIs the sum of the top chord andBottom chordAt 8 and 23 o'clock on the eighth day of the lunar calendar, the tidal forces of the sun and the moon offset each other, so "neap tide" occurredAgricultural proverbsThere is a saying that "spring tide rises on the first 15 days of the lunar calendar, and beaches are everywhere on the eighth 23 days of the lunar calendar".In addition, the rising tide also occurred on day, because the moon moves more than 13 degrees eastward on the earth every day, which totals about 50 minutes, that is, every day on the moonMidheaven time(is 1Lunar day=24:50) about 50 minutes later（Lower MidheavenThe tide will also occur twice a day), so the time of rising tide every day is also postponed for about 50 minutes.
Tidal energy is based onpotential energyAppearing in the form ofOcean energy, refers to sea waterTidal riseAnd the potential energy of water formed by tide fall.FluctuatingTidal phenomenonIs made up of the earth andCelestial motionAnd the interaction between them.In the ocean, the gravity of the moon raises the water level of the earth toward and away from the moon.Due to the rotation of the earth, the water level rises in a period of 12 hours and 25 minutesamplitudeDeep sea waves less than 1m propagate from east to west.The effect of solar gravity is similar, butForceSmaller, the cycle is 12 hours.When the sun, moon and earth are in a straight line, spring tides will occur;When they are at right angles, neaps occur.Except for semidiurnal tide andMonthly periodIn addition to the change of tideRotary motionThere are also many other periodic cycles, which can range from days to years.At the same time, the sea water on the surface is affected byEarth movementcentrifugal forceThe combined force of lunar gravity and centrifugal force is the tidal force that causes the fluctuation of sea water.
Tidal range contrast
Tidal formation
Apart from the moon and the sun, other celestial bodies will also generate tidal forces on the earth.Although the mass of the sun is much larger than that of the moon, the distance between the sun and the earth is also much larger than that between the moon and the earth, so its tidal force is less than half of that of the moon.The tidal generating force of other celestial bodies is insignificant due to being far away from the Earth or being too small in mass.According to the theory of equilibrium tide, if the earth is completely covered by bathymetric sea waterUniversal gravitationIt is calculated that the maximum tidal force generated by the moon can raise the sea surface by 0.563m, and the effect of the solar tidal force is 0.246m.The tidal range is increased through rising, convergence, resonance and other movements.The energy of tidal energy is proportional to the tidal volume and tidal range.In other words, it is proportional to the square of tidal range and the area of reservoir.Compared with hydropower, tidal energyenergy density Very low, equivalent toMicro waterThe level of hair electricity.The larger tidal range in the world is about 13~15m, but generally speaking,Average tidal rangeAbove 3m, it has practical application value.
tap potential
Tides vary from place to place. Different regions often have different tidal systems. They all come from the deep seaTidal waveGet energy, but have their own unique characteristics.Although the tides are complex, they can be accurately predicted anywhere.Ocean tides obtain energy from the earth's rotation and slow the earth's rotation in the process of absorbing energy.But this slowdown of the earth's rotation is almost imperceptible in human life, and will not be accelerated by the development and utilization of tidal energy.This energy passes throughShallow sea areaandCoastal zoneAnd dissipate at the rate of 1.7TW.Only when spring tide, energy concentration, andgeographical conditions Suitable for constructionTidal power stationIt is possible to extract energy from the tide.Although such places are not everywhere, countries around the world have selected a considerable number of suitable tidal energyxxh 。According to the latest estimation, the potential tidal energy is about 200TW · h per year.
Theory of tidal energy in the worldReserveAbout 3 × 10 ^ 9kw.China's coastline is tortuous, with a total length of about 1.8 × 10 ^ 4km. There are more than 6000 islands of different sizes along the coast, forming a 1.4 × 10 ^ 4km coastline. The long coast contains very rich tidal energy resources.The theoretical reserve of tidal energy in China is 1.1 × 10 ^ 8kw, of which Zhejiang and Fujian provinces have the largest reserves, accounting for 80.9% of the national total. However, these are theoretical estimates, and the actual available values are far less than the above figures.
Power generation principle
Tidal power generationSimilar to the principle of ordinary hydropower, through the reservoirAt high tideThe seawater is stored in the reservoir in the form of potential energy, and thenAt ebb tideRelease seawater, and use the fall between high and low tide levels to promoteWater turbineRotate to drive the generator to generate electricity.The difference is that the sea water is different from the river water. The accumulated sea water has a small drop, but the flow is large and intermittent. Therefore, the turbine structure of tidal power generation should be suitable for the characteristics of low head and large flow.
power station
Tidal power station
Countries around the world have selected a considerable number of stations suitable for developing tidal energy.According to the latest estimation, the potential tidal energy is about 200TW · h per year.In 1912, the world's firstTidal power stationBuilt in Bootham, Germany.In 1966, the world's largest tidal power stationLanceCompleted.Since 1958, China has successivelyGuangdong ProvinceOfShundeandDongwan、Shandong ProvinceOfRushan、ShanghaiOfChongmingAnd other places, establishedtidal powerStation.
CanadaAnnapolis Tidal Power Station, FranceLance Tidal Power StationKislaya Tidal Power Station is one of the three famous tidal power stations in the world.
Military applications
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On April 21, 1661,Zheng ChenggongLed 25000 soldiers fromGolden Gate IslandDeparture, arrivalPenghu Islands, enter Taiwan to attackZelandia 。Zheng Chenggong's army abandoned the Dagang Waterway, which is wide and deep, easy to access, but heavily guarded on the shore, and choseLakjemuyse waterway.Lu'ermen Waterway is shallow with many reefs. The channel is not only narrow, but also blocked by broken ships sunk by the Dutch army. Therefore, the Dutch army is weak here.Zheng Chenggong led the armytideThe channel is widened andDeep time, attack the enemy unprepared, quickly pass through Luer Gate downstreamHeliaoAfter landing in Hong Kong, we went straight to Chichen City and landed successfully at one fell swoop.
In 1939, Germany set up mines to block the entry and exit at nightEnglish channelBritish ships.The German army determined themooring mineDepth, orientationDrifting thunderThe tactics have achieved great success.1950Korean WarAt the beginning,people's army of KoreaIf the wind sweeps the debris, drive straight in to hitBusanOne Belt.The United States gathered in a hurrythe United Nationsmultinational force, fought fiercely to the DPRK, but made a mistake when choosing the landing site - all ports suitable for landing are heavily guarded by the Korean People's Army, and forced landing will inevitably cost a lot.After careful consideration, MacArthur, the commander of the US military, finally commanded the US military to land successfully in Incheon.original,Incheon PortIt is located on the west coast of North Korea, 28 kilometers west of the capital Seoul, and plays the role of closing the door of Seoul.The sea isAsiaTidal rangeLargest, up to 9.2m, nearshore at low tideSilt beachWith a length of more than 5000 meters, landing ships, amphibious vehicles and landing troops are easily stranded;There are stone structures 4 meters high along the coastbreakwater, constituting obstacles for landing troops and amphibious vehicles;There is only one Feiyu Gorge channel for ships entering the port. If one ship sinks, the channel will be blocked;Shore artillery can destroy all ships, amphibious vehicles and landing troops near the shore.The Korean People's Army believes that it is impossible for the US military toInchon landing In addition, the battle line is too long, so the defense of Incheon Port is weak.However, there are three highest spring tides in Incheon Port every yearTidal rangeIt can reach 9.2 meters, including September 15.Through analysis and calculation, on September 15, the US military used the spring tide to pass through the narrow and muddy Feiyu Gorge waterway andReef shoal, unexpectedly landed at Incheon Port.As a result, the Korean People's Army was cut off, and the front logistics were completely out of support. It suffered heavy losses and almost fell into a desperate situation.The US military commanded by MacArthur andUnited Nations Command, only one month, almost sweepingKorean Peninsula, BinglinYalu RiverAnd won unprecedented victory.
However, this successful landing example also failed. The US military miscalculated the time of high tide in Incheon Port that day, and the real high tide came ahead of schedule.Therefore, although the US troops in front had successfully landed ahead of schedule, the artillery bombarded the troops before landing at the scheduled time, which resulted in the destruction of the landed troops and the loss of a battalion of officers and soldiers.
Impact on celestial bodies
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The tide and the earth's rotation slow down. Because the viscous force and the friction between the sea water and the land and seabed will occur when each layer of sea water moves relative to each other, the tide has a braking effect on the earth's rotation, making the earth's rotation slow down gradually. Research shows that the earth's rotation cycle increases by 1-2 milliseconds every century. If this slowdown effect is applied to a long time span,There were about 400 days a year before 370 million years ago (Devonian), which is consistent with the number of growth rings of Devonian coral fossils (coral rings grow one ring a day).
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The moon always faces us with the same side. People found that the moon always faces us with the same side. The other side of the moon is invisible on the earth. This is because the period of the moon's rotation is exactly the same as the period of the moon's rotation around the earth. The same period of the two is the result of long-term tidal action.According to the calculation, the tidal force of the earth to the moon is 22.17 times that of the moon to the earth.Such a strong tide generating force and the rotational inertia of the moon is much smaller than that of the earth, so the slowdown of the rotation speed caused by tides is particularly significant for the moon. It can be assumed that the early moon has a large rotation speed, and under the effect of tides, the rotation of the moon is gradually slowed down. Finally, the rotation period of the moon is equal to the period of the moon rotating around the earth, at this time, the moon tide disappears,The rotation period of the moon no longer changes, so the moon always faces the earth with the same side.
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The increase of the tide and the distance between the moon and the earth causes the earth's rotation to slow down, resulting in the decrease of the earth's angular momentum. Since the total angular momentum of the earth January system should remain unchanged, and the direction of the moon's rotation around the earth is basically the same as the direction of the earth's rotation, the decrease of the earth's angular momentum will inevitably increase the angular momentum of the moon to the center of mass of the earth January system,To maintain the conservation of the total angular momentum of the Earth January system. The actual effect of this effect is to slowly increase the distance between the moon and the earth. According to recent observations, the moon is moving away from the earth at a speed of 3.81 cm per year. The moon is slowly moving away from the earth, which can also be explained by the acceleration of the moon formed by the earth's tidal bulge.Since the bulge part of the tide is brought eastward by the earth's rotation, bulge part A is closer to the moon than bulge part B, so the two parts have different gravitations to the moon, making the gravity center of the earth drift to the east of the line between the mass centers of the earth and the moon. So the moon produces a very small acceleration in its orbital movement direction, making the moon speed up and slowly circle outward
Qiantang River spring tide is the world's three largestTidal boreOne is the celestial gravity andearth rotationCentrifuge, plusHangzhou BayBell mouthThe extraordinary tidal bore caused by the special terrain of.Qiantang EstuaryIt is wide on the outside and narrow on the inside, showing obvious trumpet shape.The river at the mouth of the river is 100 kilometers wide, and the river narrows toHainingYanguan TownThe river suddenly drops to only 3 kilometers wide.
Qiantang RiverThe torrential flood tide and theYangtze RiverTide.It is mainly due to the tidal current flowing upstream along the channel of the river flowing into the sea.Tidal influxtriangleIn the bay, the tide level rises and the tidal range increases.When the tide comes, the tide end rises steeply and the water splashes all around, like a vertical water wall advancing at a high speed. The front has not been dredged yet, and the waves behind catch upWave heightAfter a wave, it is very spectacular, forming a "towering sky"Turbid wave emptyingCome on, the spectacular scene of crossing the river and falling into the sea and mountains.
Yu Yafei said in a poem: "When Qiantang looks at the ripples, the waves immediately cross our eyes; it seems that there is energy in the ordinary river, which is amazing.".At the beginning of the tide, a white line flashed on the river, accompanied by a rumbling sound. The tide came from far to near, rushing forward. The tide pushed and hugged, and the sound was like thunder. In an instant, the tide peak raised a water wall three or four meters high and stood upright on the river, spraying beads and splashing jade, as if ten thousand horses were galloping forward.Tide watching began in the Han and Wei Dynasties,Sheng inTang and Song dynasties, after more than 2000 years, have become local customs.
