Can the sailboat driven by the wind running out several times of wind speed?

In 2012, VESTAS SailrocketI Ⅱ (Sail Rocket No. 2) high -speed sailing ship set a world sailing speed record at Volvis Gulf in Namibia. At the wind speed 25 (46.3 kilometers/p,), the highest speed reached 64.78 (119.97 thousand Mi/o'clock). The average speed within 500 meters straight reached 59.23 (109.69 km/h). This speed is faster than most non -competition speedboats, and this ship that rely on wind -driven ships does not need to consume a drop of gasoline.

Sailing Rocket No. 2

Sailing is a very ancient navigation tool, which has a history of more than 6,000 years. Many people's impression of sailing may still stay in the vague scene of Tang poetry "directly hanging the cloud sails", or the good wishes of "smooth sailing" in life. So, how exactly is sailing? Is it really just "pushed" by the wind?

We all know that the sailing boat depends on the wind to do power, but things are not so simple. People usually think that sailing can only move in the direction of the wind, that is, running smoothly, but it is not. Everyone often sees that modern sailing boats using the Delta sails can also move the wind (driving in the wind). And these two different navigation methods depend on the "power". One is the stress: that is, when the air flows, it can have impact on objects blocking the road. When the sailing boat runs smoothly, it is very easy to understand by the air pressure of the air. The other is static pressure: When the air flow rate on both sides of the ship's sails is different, the pressure difference will be generated. The pressure difference will form a force on the sail. This force is static pressure. why? This involves the effect of the Bynuli, and we explain it later.

Bynul effect 效

In accordance with the convention, we first introduced Bernunley, a bull.

Daniel Bernoulli

Daniel Bernoulli (Daniel Bernoulli, 1700 ~ 1782), Swiss physicist, mathematician, medical scientist. He is the most outstanding representative of Bernunley, a mathematical family (10 people in the 4th generation). At the age of 16, he studied philosophy and logic at the University of Basel. He then received a master's degree in philosophy. He studied medicine at the age of 17 to 20. He obtained a master's degree in medical and became a professor of anatomy. But under the influence of his father and brother, he finally turned to mathematical science. Bernoulli has a wide range of success. In addition to the main field of fluid dynamics, there are also astronomical measurement, gravity, irregular tracks of planets, magnetism, ocean, tide, etc.

In 1726, Bernoulli discovered the "boundary layer surface effect" through a large number of experiments: when the fluid speed was accelerated, the pressure on the interface of objects and fluids decreased, and the pressure would increase. To commemorate his contribution, this discovery is called the "Bernoulli effect". The Berunley effect is suitable for all ideal fluids including liquid and gas. It is one of the basic phenomena when the fluid is stable and flows. It reflects the relationship between the pressure and flow rate of the fluid: the larger the fluid rate, the smaller the pressure, the smaller the pressure, the smaller the pressure. ; The smaller the flow rate of the fluid, the greater the pressure. This effect expresses the form of mathematical form is the famous Bynubi equation, that is,:

P is pressure, 度 is density, V is speed, H is height, G is gravity acceleration, C is a constant.

The Bournley effect is ubiquitous in our lives. For example, if we hold two pieces of paper and blow the two sheets in the middle of the paper, we will find that not only will the paper not float outward, but will be squeezed together by one force. Because the air in the middle of these two pieces of paper is accelerated by the flowing speed of us, the pressure becomes smaller, and the air outside the two pieces of paper does not flow, and the pressure will be large. Together. This is the simple demonstration of the "Bernoulli effect".

Two pieces of paper blowing experiments

There are also some daily examples. For example, before we take the train, high -speed rail and subway, we must wait for the platform on the platform. Will there be a yellow line there? The reason why there is this scope is because the vehicle will have a Bernuori effect, which will attract people in the direction of the vehicle. This is very dangerous. Therefore, for your own personal safety, you must not cross the yellow line.

Yellow cordon next to the high -speed rail

Aircraft is also an example that can reflect the Bernonley effect. We all know that the wing of the aircraft is generally bent on the surface and the lower surface is flat. The picture below is the cross section of an aircraft wing. The front end of the wing is called the leading edge. The last end is called the trailing edge. This green line between them is called string. The angle between the extension of the string and the relative wind is called angle of atta. During the flight of the plane, the wings cut the wind to the upper and lower parts. At the same time, the air on the surface of the upper and lower surfaces of the wing flowing through different distances, that is, the distance of the surface of the surface of the wing is long, so The flow rate is fast, and the lower surface air flows short, so the flow rate is slow. According to the principle of Bernori, the place with a large place with a large flow rate is small and the flow velocity is strong. So the aircraft can overcome gravity take -off.

Cross section of the wing

The principle of driving sailing 驶

Earlier, we have introduced that when the sailboat is driving, the driving pressure is used as a driving force. With the increase of the speed of the boat, the speed difference between the boat and the wind gradually decrease, and the thrust becomes smaller and smaller. Until the resistance of the water during the navigation, when the acceleration becomes zero, the ship will enter a constant speed. In this case, the boat speed can only approach the wind speed, but it cannot surpass the wind speed. The ancient traditional square sailing ships that most of us are familiar with are this way of sailing, so the traditional square sailing boat is impossible to surpass the wind speed. Traditional sailing

If you want to further improve the speed of navigation and advance efficiency, you must find more powerful power sources other than direct thrust. This force is static pressure, that is, the method of greeting the wind, relying on the Bernunley effect to generate thrust.

The sails have a curved shape like a wing. Here we assume that the air full of air is called the wind surface. Blowing outward to form a protruding shape is called backwind. When the airflow passes through the sails, because the airflow of the sail back of the air has a longer distance and the airflow of the wind surface, the flow velocity is accelerated. The pressure at the slow flow rate is stronger than the pressure of the flow rate. This pressure difference has formed static pressure on the sail. Of course, the static pressure of the sails cannot be used to promote the forward of the ship. What is really used to promote the marching boat is the division of the direction of the head of the bow. For lateral force.

Boat sailing force analysis

We know that exercise is relative. When sailing sailing, the wind speed and wind direction that the crew perceives is very different from the actual true wind. Here, we call the natural wind, that is, the wind from the land or the sea. In the state of sports, the wind feels that the crew feels is called "somatosensory wind" or "visual wind". The result of wind and ship speed vector superposition. When the ship is driving in different directions, the size and direction of the wind are different (as shown in the figure below). From the figure, when the sideways are sailing within the range of the side of the side to the reverse wind, the visual wind is always greater than the speed and true wind (note the proportion and angle of the three edge lengths in the vector triangle).

The relationship between the speed, the vision and the true wind of different routes

After the above introduction, we already know that the sailing boat can drive smoothly under the driving pressure of the stress, and can also drive the wind under static pressure. However, the direction of the sailboat is not completely unlimited. It is within about 45 degrees angles on the left and right of the wind (as shown in the figure below), which cannot produce effective advancement. However, it is not very good (as shown in the C area in the figure), because at this time Bernunley's effect is weak, and the sailboat is pushed by the wind pressure of the wind on the sail. We have already described before that the pressure of dynamic pressure is not a source of power for continuous and efficient power. Only area B in the picture is the best voyage direction. At this time, the direction and wind direction of the sailing ship became a certain angle. Under the pressure of static pressure, the ship could get a continuous and stable driving force, so that the sailboat could get a relatively high navigation speed.

The relationship between wind direction and smooth wind and wind driving

When the sailing boat sailed in the wind in the B area, the ship was pushed by static pressure, and the driving force for continued stability was obtained. Then, this brings a phenomenon that violates intuition. As long as the sailing boat starts under the action of true wind, with the early speed, the view of the wind will increase, and the lift on the sails will increase; The big lift further accelerates the boat, and the increase in the speed of the boat has further increased the wind speed of the visual wind, and then the lift continues to increase, and the sailing boat continues to accelerate ...

Can this cycle go out infinitely and the final speed is unlimited? It seems impossible, but there is indeed no restrictions in mathematical theory. However, for sailing, although the speed of the wind is increasing, its direction is gradually approaching the direction of the front wind as the speed of the ship increases. In this process, if the sails remain unchanged, the wicker's welcoming angle will become smaller, the pressure difference between the air flows over the wind and the backwind surface will be reduced, and the lift will become smaller until it is with the water. The resistance is balanced and driving at a constant speed. If the wind blows directly on the back of the curved boat sail, not only has no lift, but it will also blow back the boat.

When the sail is unchanged, the wind is driving the picture

Therefore, in order to continue to obtain the lift, you need to constantly adjust the sail. The adjustment of the sailing position will gradually decrease with the continuous deflection of the wind to the direction of the wind to the right wind, and at the same time, the side force gradually increases. The resistance of the wind facing the wind has also become one of the resistance of the wind. In the process of continuously increasing the optimal wind, the lift first increased, and then gradually decreased until the balance with the total forward resistance was balanced and accelerated, at this time reached the maximum speed.

Adjust the stress map of the sailing position

The keel and water wing 与

From the previous section we know that in the process of adjusting the sail to get a greater lift, the side force has gradually increased. In order to overcome the side force, there are all kinds of plate keels at the bottom of the sailboat. It can cause great resistance to horizontal motion when fast sailing in the water, thereby preventing the sailing boat from moving horizontally during the progress. However, before reaching the ideal maximum speed, the side force is still difficult to compete, and both direction and gesture may be out of control. It is easy to turn the sailing boat sideways.

Sailboat with keel

In addition to the sailing boat with keel, people are also equipped with water wings at the bottom of the hull. When the speed of the boat gradually increases, under the buoyancy provided by the wing wings, the hull will be carried away from the water surface for "flying" (called the wing wing "(called the wing wings" (called the wing wings " Flying or wing wings sail, Foilborne), which greatly reduces the resistance of water to increase the speed of navigation.

Wingspan

Sailing Rocket No. 2 2

The sail Rocket No. 2 was manufactured in the UK. Its unique side -to -tilt hard sail design can maximize the thrust and minimize the tendency, which avoids the inclined problem brought by the side force from the side force. At present, such designs are already standard configuration on ultra -high -speed sailing. But the key to really reaching such a high speed is its unique underwater wings (including keel and rudder) design. The navigation of the triangle sailboat relies on the water wings effect of the keel to generate the side force generated by resisting the main sails, thereby retaining the forward force of the main sail. However, when the sailing boat is close to 50 knots, the interaction between keels and rudder and water is too violent, and it will begin to produce an empty effect, resulting in a sharp increase in resistance, and it is difficult to increase the speed. This phenomenon is called "bubble barrier". Therefore, the previous sailing speed could not exceed 50 knots. The uniqueness of the sailing Rocket No. 2 is that its rudder and keels are equipped with several devices similar to the early aircraft wing knife, which overcomes the "bubble barrier" effect at 50 speeds and improves the speed of sailing to amazing. Section 64.78.

Sailing Rocket No. 2

Paul Lason, the driver of the sail Rocket 2, said: "The design concept of modern high -performance sailing ship was initially proposed by American physicist Berned Smith in 1963" 40 sailing boats "." Smith His insight is far ahead of his time, so that Paul Lason and his team spent nearly 50 years to fully realize the record of Sail Rocket 2. However, before the air was compressed, the speed could continue to increase in principle, and Paul Lason also believed that they could continue to create a record.

Paul Lason

Finally, let's use Paul Lason's words to encourage: "I think we have stayed on this issue for a long time, and now it's time to challenge it."

references

https://xw.qq.com/cmsid/20220501a02t0100

https://www.zhihu.com/question/47115084/answer/443511881

http://www.360doc.com/content/20/0617/12/33945099_918961311.shtml

http://www.360doc.com/content/19/0707/06/304345_847175180.shtml

Shu Yousheng. "Mechanics": Peking University Press, 2005.

Chen Binglong. Sailing and windsurfing mechanics principles [J]. Physics teacher, 2002 (10): 50-54.

Wang Yun. Talking about the mechanical principles of sailboats and windsurfing movements [J]. Digital world, 2019 (03): 123-124.

Miao Guoping. The mechanical principle of sailing sports [J]. Mechanics and practice, 1994 (01): 9-18.

- END -