CN203946234U - A kind of hydrofoil of surface band pit - Google Patents

Abstract

The utility model provides a kind of hydrofoil of surface band pit, this hydrofoil comprises hydrofoil plate and hydrofoil pillar, hydrofoil plate water flowing cabane strut is fixedly mounted on naval vessels below, and the outside face of hydrofoil plate is provided with the drag reduction structure being made up of rough strip, groove, pit or texture structure.Possesses the hydrofoil plate of this drag reduction structure in the time of underwater exercise, possesses higher 1ift-drag ratio, can reduce friction drag and the viscous resistance of hydrofoil to water, increase the energy efficiency that drives the means of deliverys such as hydrofoil boat, in improving ship speed, reach the beneficial effect of energy-saving and emission-reduction.

Description

A hydrofoil with dimples on the surface

technical field

The utility model relates to a hydrofoil device, in particular to a hydrofoil with dimples on the surface.

Background technique

Hydrofoil boats or hydrofoil boats are water vehicles that can navigate at high speeds. The bottom of the hull is equipped with a support, and a hydrofoil is installed under the support, and the hydrofoil is completely or partially submerged in water. According to the principles of fluid mechanics, the greater the flow velocity, the lower the pressure. When the ship sails in the water, the water flows quickly relative to the hydrofoil, and the velocity of the water flow passing through its upper surface is large, while the velocity of the water flow on the lower surface is small, so that a pressure difference is formed between the upper and lower surfaces of the hydrofoil. When the pressure difference is strong To a certain extent, the hull will be raised, even higher than the water surface. The volume of the hull submerged in water is reduced, and the resistance of the water is also greatly reduced accordingly. In this way, under the same propulsion force, the ship with hydrofoils can reach a higher speed. Compared with other high-speed ship technologies, the main advantage of hydrofoil boats (mainly fully submerged) is that they can sail in harsher sea conditions with less bumping of the hull. Moreover, the waves generated during high-speed navigation are relatively small, and the impact on the shore is relatively low.

Due to the current requirements for energy saving and emission reduction, the entire shipping industry and shipbuilding industry have reached new heights in terms of energy consumption indicators. For shipbuilding, how to reduce the resistance of navigation has always been a research direction of many research institutes. The reduction of ship resistance can achieve faster speed under rated power and achieve the purpose of energy saving and emission reduction. Although the installation of hydrofoils can effectively improve the navigation speed of ships, there are still many problems to be solved. For example, when a hydrofoil moves in water, the upper and lower surfaces of the wing are in contact with the water. When water flows over the hydrofoil, a boundary layer is formed on the surface of the hydrofoil due to the viscosity of the water itself. The boundary layer is a thin layer, which is close to the surface of the hydrofoil, and there is a flow region with a large velocity gradient and curl along the normal direction of the surface of the hydrofoil. Viscous stress is resistance to the water body in the boundary layer, so as the water body flows backward along the object surface, the water body in the boundary layer will gradually slow down and pressurize. Due to the continuum of water flow, the boundary layer thickens to allow more low-velocity water to flow at the same time. Therefore, there is a reverse pressure gradient in the boundary layer, and the flow will further decelerate under the action of the reverse pressure gradient. Finally, the kinetic energy of the water body in the entire boundary layer is not enough to maintain the flow downstream for a long time, so that somewhere on the surface of the object The velocity will be in the opposite direction to the velocity of the potential flow, ie countercurrent. This countercurrent will push the boundary layer into the potential flow, causing the boundary layer to suddenly thicken or separate. The separation of the boundary layer will increase the drag, especially because the pressure difference of the water body before and after the hydrofoil increases, so that the pressure difference drag becomes larger. The increase in resistance will cause the speed to decrease, which will not play the role that the hydrofoil should play.

In addition, the hydrofoil has a certain angle of attack with the incoming flow, and the section of the wing has a camber, thus generating lift. As the movement speed of the hydrofoil continues to increase, the negative pressure on the surface of the airfoil will continue to decrease. When the negative pressure drops below the saturated vapor pressure of water at the current temperature, bubbles will appear on the water on the local surface of the airfoil. When the water flow moves to the high-pressure zone, the bubbles are squeezed, shrink or even collapse, and the cycle process of bubble generation, development and collapse is the process of cavitation. Cavitation is a very harmful phenomenon. It will cause mechanical damage, increase noise and other consequences, and it will cause increased resistance and unstable lift, and even cause disasters.

Utility model content

The technical problem to be solved by the utility model is to provide a hydrofoil with more excellent performance, which can avoid the difficulties of the low-resistance hydrofoil in the prior art, reduce the frictional resistance and viscous resistance of the hydrofoil to the water, increase Driving the energy efficiency of vehicles such as hydrofoil boats can achieve the beneficial effects of energy saving and emission reduction while increasing the speed of ships.

Correspondingly, in a non-limiting embodiment, the utility model provides a hydrofoil with dimples on the surface to solve the above-mentioned technical problems. The lower end of the hydrofoil strut, the upper end of the hydrofoil strut is fixedly installed under the hull of the ship, and the outer surface of the hydrofoil plate is provided with a drag reducing structure. ) is wing-shaped or bow-shaped or crescent-shaped, and the drag reduction structure can be a rough strip distributed on the surface of the hydrofoil. It can be horizontally or vertically parallel distributed or regularly distributed in the form of an array, or it can be distributed randomly on the outer surface of the hydrofoil. According to the test, the rough zone is located at a distance of 10% to 30% of the chord length from the leading edge of the hydrofoil. The width is 5% to 20% of the chord length, and the height is 0.05mm to 0.2mm, which can achieve better utility model effects.

In addition to rough strips, the drag reduction structure can also use grooves and criss-cross grid-like texture structures arranged on the surface of the hydrofoil. The grooves and texture structures can be linear or curved, or in the shape of random lines, and the distribution of grooves and texture structures on the surface of the hydrofoil can be horizontally and vertically parallel, or randomly distributed on the surface of the hydrofoil. on the outer surface of the hydrofoil.

In many embodiments of the present utility model, as an optimal choice, the drag reducing structure should adopt the structure of dimples distributed on the surface of the hydrofoil. The number of pits may be one or more. The shape of these pits is one or a combination of circular pits, oval pits, polygonal pits and irregular pits. When there are multiple dimples, the dimples can be arranged in the following ways on the outer surface of the hydrofoil: vertically and horizontally aligned, vertically and horizontally staggered, and irregularly arranged. When the depth of the pits ranges from 10 mm to 40 mm, a relatively ideal drag reduction effect can be obtained. The area ratio of dimples on the surface of the hydrofoil can be selected within the range of 5% to 60%.

The boundary layer when the hydrofoil moves in the water body, according to the Reynolds number of the local flow field, the fluid in the boundary layer can be divided into laminar flow or turbulent flow. The flow in the boundary layer of a smooth foil surface is usually laminar, while the flow in the boundary layer of a rough foil is turbulent. The boundary layer of turbulent flow is less affected by the adverse pressure gradient, so the separation point of the boundary layer on the surface of the rough hydrofoil is relatively behind, and its viscous resistance is lower than that of the smooth hydrofoil, and the pressure difference resistance is even greater. can be greatly reduced.

In addition, setting a drag-reducing structure on the surface of the hydrofoil can increase the smooth turbulent flow on the surface of the hydrofoil, advance the transition point, significantly increase the flow field pressure on the surface of the hydrofoil, delay the occurrence of cavitation, and have a relatively small influence on the lift of the hydrofoil. Small.

Compared with the prior art, the utility model is beneficial in that:

1. It can effectively push back the boundary separation point and reduce resistance. Usually, when the hydrofoil sails, the Reynolds number Re can reach more than 105, which is far greater than the requirement of Re=60 for boundary layer separation. When the wing boat sails normally, the separation of the boundary layer will occur, and the drag reduction structure on the hydrofoil can delay the separation point of the boundary layer, reduce the viscous resistance on the hydrofoil, and reduce the pressure of the hydrofoil boat when it is sailing. energy consumption;

2. Significantly increase the flow field pressure on the surface of the hydrofoil, delay the occurrence of cavitation, and effectively reduce the adverse consequences such as mechanical damage, increased resistance, unstable lift and increased noise.

Description of drawings

Fig. 1 is the structural representation of the specific embodiment one of the utility model;

Figure 2 is a histogram of hydrofoil lift changing with the angle of attack (the abscissa is the angle of attack);

Figure 3 is a histogram of hydrofoil resistance changing with the angle of attack (the abscissa is the angle of attack);

Figure 4 is a line diagram of hydrofoil resistance changing with the angle of attack (the abscissa is the angle of attack);

Figure 5 is a broken line diagram of the lift-drag ratio of the hydrofoil with the angle of attack (the abscissa is the angle of attack);

Fig. 6 is a broken-line diagram of the hydrofoil resistance changing with the speed at a fixed angle of attack (the abscissa is the speed);

Figure 7 is a broken line diagram of the lift-drag ratio of the hydrofoil changing with the speed at a fixed angle of attack (the abscissa is the speed);

Fig. 8 is a schematic structural diagram of a second embodiment;

Fig. 9 is a schematic structural view of the third embodiment;

Fig. 10 is a schematic structural diagram of Embodiment 4.

Detailed ways

The utility model will be further described below according to specific embodiments and accompanying drawings.

The low-resistance hydrofoil shown in Figure 1 and Figure 2 includes a hydrofoil strut 1 and a hydrofoil plate 2. The wing section shape of the hydrofoil plate 2 is an airfoil shape, the wingspan of the hydrofoil plate is 15m, and the chord length is 3m, on the surface of the hydrofoil 2, circular pits 3 are aligned vertically and horizontally. The depth of these dimples 3 is 30 mm, and the area ratio of the dimples 3 on the surface of the hydrofoil 2 is 50%.

Due to traditional habits, people think that the smoother the surface, the smaller the frictional resistance, and good materials such as titanium alloy materials will have a better anti-cavitation effect. Therefore, the traditional research and development direction is mostly focused on reducing For the resistance it receives, better materials are used to resist the cavitation effect, but the effect is either unsatisfactory, or the production cost of the hydrofoil is increased. The inventor of the utility model has overcome the traditional technical prejudice that a rough surface will increase the frictional resistance, and a drag-reducing structure is set on the surface of the hydrofoil 2 to generate a turbulent boundary layer and delay the boundary separation point , the turning point is brought forward, no matter in terms of reducing the drag on the hydrofoil or reducing the harm of cavitation, good results have been achieved, and it has been confirmed in the experiment.

Under the condition of fixed speed V=20m/s, the lift (L, unit: Newton), resistance (R, R, Unit: Newton) and lift-to-drag ratio (K), the following experimental results can be obtained:

Table 1-1 Experimental data of lift (L), drag (R), and lift-to-drag ratio (K) of traditional smooth hydrofoils

Angle of attack L(N) R(N) K 0 2826.194392 7222.073574 0.39133 3 45115.42233 8589.438942 5.25243 5 76782.85787 8668.696498 8.85749 6 93015.70574 8687.20853 10.99839 7 109047.414 8770.476949 12.43346 8 125011.2142 8815.957461 14.18011

Table 1-2 Experimental data of lift (L), drag (R) and lift-to-drag ratio (K) of the utility model hydrofoil

Angle of attack L(N) R(N) K 0 2228.87036 5574.07128 0.39986 3 45164.70515 6815.78273 6.62648 5 76742.92862 6964.77417 11.0187 6 92942.20538 6979.53639 13.3163 7 109126.79475 7006.83628 15.5743 8 120997.89375 7048.74047 17.1658

It can be seen from Table 1-1 and Figures 2 and 3 that the dimples 3 on the surface of the hydrofoil plate 2 have almost no effect on the lift of the hydrofoil, but the resistance suffered by the hydrofoil is significantly reduced. Then the drag and lift-to-drag ratio of the hydrofoil are studied separately. As can be seen from Fig. 4 and Fig. 5, as the angle of attack increases, the resistance of this specific embodiment and the traditional smooth hydrofoil increases accordingly, but the resistance of the traditional smooth hydrofoil is always higher than that of this specific embodiment. The example should be large. Fig. 5 shows more clearly that the lift-to-drag ratio of this specific embodiment is always larger than that of the traditional smooth surface hydrofoil, which is more conducive to the navigation of ships equipped with the hydrofoil provided by the utility model.

In order to further verify the beneficial effect of the utility model, a further simulation experiment was carried out by changing the fluid speed (simulated speed) under the condition of a fixed angle of attack (6°). The following experimental data can be obtained:

Table 1-3 The lift, drag and lift-to-drag ratio of traditional smooth hydrofoil change data with fluid velocity

Speed (m/s) L(N) R(N) K 15 52449.514 3088.6234 16.98151 20 93015.705 8687.2085 10.99839 22.5 118261.114 5066.2598 23.34288 25 121008.691 7220.4245 16.75922

Table 1-4 The lift, drag and lift-to-drag ratio of the utility model hydrofoil change data with fluid velocity

Speed (m/s) L(N) R(N) K 15 51145.983 2447.5882 20.8108 20 92942.20538 6979.53639 13.3163

22.5 116806.026 4153.461 28.31453 25 120510.251 4782.5431 25.19793

Combining Figures 6 and 7, it can be known that the overall lift-to-drag ratio of the hydrofoil of the utility model is greater than that of the conventional smooth hydrofoil within the range of 15-25m/s (close to the conventional sailing speed of the hydrofoil) when the fluid velocity is within the range .

Therefore, it can be concluded that the utility model significantly improves the overall lift-to-drag ratio of the hydrofoil, optimizes the performance of the hydrofoil, and achieves expected effects.

In this specific embodiment, the depth of the pit 3 can be selected within the range of 10-40mm, and the depth of the pit 3 is 10mm, 15mm, 20mm, 30mm, 35mm, and 40mm for testing, and an ideal increase in lift resistance can be obtained. Compared with the technical effect.

In addition, the shape of the pit 3 can also be in the form of one or more groups of circular pits, elliptical pits, polygonal pits and irregular pits, and can be arranged regularly or irregularly. The ideal technical effect of increasing the lift-to-drag ratio is obtained.

The area ratio of dimples on the surface of the hydrofoil is between 5% and 60%, and 5%, 10%, 20%, 30%, 45%, 50%, 55%, and 60% are used for testing, and the results are very satisfactory .

The specific embodiment 2 shown in Figure 8 differs from the specific embodiment 1 only in that the drag reduction structure on the surface of the hydrofoil 2 is a rough strip 4, which is located at a distance of 10% to 10% from the leading edge of the hydrofoil. At 30% of the chord length, its width is 20% of the chord length and its height is 0.1mm. After testing, it can also achieve ideal technical effects of increasing lift-to-drag ratio and reducing cavitation.

The specific embodiment three shown in Figure 9 differs from the specific embodiment one only in that the drag reducing structure on the surface of the hydrofoil 2 is several parallel grooves 5, the depth of these grooves is 30mm, parallel to Foil leading edge setting.

The fourth embodiment shown in Fig. 10 differs from the first embodiment only in that the drag reduction structure on the surface of the hydrofoil 2 is a piece of interlaced textured structure 6, and the depth of these textured structures is 5 mm.

The above embodiments are for the purpose of understanding the utility model, and are not limitations to the utility model. Those of ordinary skill in the related art can also make various changes or shapes on the basis of the technical solution described in the claims, such as the above-mentioned The various drag reducing structures in the specific embodiments can be arranged regularly or irregularly as shown in the specific embodiments, and can also be a combination of various drag reducing structures, such as pits and rough strips, pits and grooves, and grooves. Pit and texture structure, etc., these changes or modifications should be understood as still belonging to the protection scope of the present utility model.

Claims (10)

1. A hydrofoil with dimples on the surface, comprising a hydrofoil plate and a hydrofoil strut, the hydrofoil plate is fixedly mounted on the lower end of the hydrofoil strut, and the upper end of the hydrofoil strut is fixedly mounted below the hull of the ship, characterized in that : the outer surface of the hydrofoil is provided with a drag reducing structure, and the drag reducing structure is one or more combinations of rough bands, grooves, textured structures or pits distributed on the surface of the hydrofoil, so The minimum number of rough bands, grooves, textures or pits is one. 2. The hydrofoil with dimples on the surface according to claim 1, wherein the dimples are one of circular dimples, elliptical dimples, polygonal dimples and irregular dimples or Various combinations. 3. The hydrofoil with dimples on the surface according to claim 2, characterized in that: the number of the dimples is multiple, and they are aligned vertically and horizontally on the outer surface of the hydrofoil. 4. The hydrofoil with dimples on the surface according to claim 2, characterized in that there are multiple dimples arranged in a criss-cross pattern on the outer surface of the hydrofoil. 5. The hydrofoil with dimples on the surface according to claim 2, characterized in that: there are multiple dimples arranged irregularly on the outer surface of the hydrofoil. 6. The hydrofoil with dimples on the surface according to any one of claims 1 to 5, characterized in that: the depth of the dimples is 10mm-40mm. 7. The hydrofoil with dimples on the surface according to claim 6, characterized in that: the area ratio of the dimples is 5%-20%. 8. The hydrofoil with dimples on the surface according to claim 1, characterized in that: the profile of the section of the hydrofoil plate parallel to the forward direction of the ship is an airfoil shape, and the rough strip is located at a distance from the hydrofoil plate. At 10% to 30% of the chord length of the edge, the width of the rough belt is 5% to 20% of the chord length, and the height is 0.05mm to 0.2mm. 9. The hydrofoil with dimples on the surface according to claim 1, wherein the grooves are located on the surface of the hydrofoil plate and parallel to the leading edge of the hydrofoil plate. 10 . The hydrofoil with dimples on the surface according to claim 1 , wherein the texture structure is a criss-cross grid-like texture structure distributed on the surface of the hydrofoil plate. 11 .