CN111611661A - A transverse V-groove structure based on stable vortex string drag reduction and its application - Google Patents

Abstract

The present disclosure provides a transverse V-groove structure based on stable vortex string drag reduction. The structure is composed of several V-shaped grooves. The arrangement direction of the V-shaped grooves is perpendicular to the flow direction of the fluid. The width is W; the height of the V-shaped groove is H; the aspect ratio W/H of the V-shaped groove is 2. When the structure of the present disclosure is used, a stable boundary vortex can be generated in the V-shaped groove, so as to significantly increase the drag reduction effect.

Description

A transverse V-groove structure based on stable vortex string drag reduction and its application

technical field

The present disclosure relates to the technical field of airflow drag reduction, and in particular, to a transverse V-groove structure based on stable vortex string drag reduction and its application.

Background technique

In aerospace fields such as wings, compressor blades, and rotors, when fluid passes through the above-mentioned structures, resistance will be generated. The current drag reduction methods usually use additional control mechanisms or inject additional substances to achieve drag reduction. It can be seen that the existing drag reduction technology requires additional injection of substances, consumes additional energy, or the device is difficult to manufacture, high in cost, and unstable in drag reduction effect.

SUMMARY OF THE INVENTION

In order to solve at least one of the above technical problems, the present disclosure provides a transverse V-groove structure based on stable vortex string drag reduction, using a specific groove structure to form vortices in the groove, so that the flow vortex string boundary replaces the solid wall boundary , thereby producing a high-efficiency drag reduction effect.

According to one aspect of the present disclosure, a transverse V-groove structure based on stable vortex string drag reduction is provided. The structure is composed of several V-shaped grooves. The arrangement direction of the V-shaped grooves is perpendicular to the flow direction of the fluid. The width of the shaped groove is W; the height of the V-shaped groove is H; the aspect ratio W/H of the V-shaped groove is 2.

According to at least one embodiment of the present disclosure, the apex angle of the V-shaped groove is 90°.

According to at least one embodiment of the present disclosure, the height H of the V-shaped groove is such that the fluid generates a stable vortex in the groove.

According to at least one embodiment of the present disclosure, the height H of the V-groove is determined by the fluid flow rate U and the fluid kinematic viscosity υ, and:

其中L代表特征长度。Wherein: the height of the V-shaped groove is H, and the unit of H is m; the fluid velocity is U, and the unit of U is m/s; the kinematic viscosity of the fluid is υ, and the unit of υ is m ² /s; Re represents the Reynolds number,

where L represents the feature length.

The present disclosure also provides a wing with a lateral V-groove structure based on stable vortex string drag reduction, and all or part of the surface of the wing has the above-mentioned lateral V-groove structure based on stable vortex train drag reduction.

The present disclosure also provides a compressor blade with a transverse V-groove structure based on stable vortex string drag reduction.

The present disclosure also provides a revolving body based on the stable vortex string drag reduction transverse V-groove structure, all or part of the surface of the revolving body is the above-mentioned transverse V-groove structure based on the stable vortex string drag reduction.

Description of drawings

The accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure, are included to provide a further understanding of the disclosure, and are incorporated in and constitute the present specification part of the manual.

FIG. 1 is a schematic structural diagram according to at least one embodiment of the present disclosure.

2 is a schematic diagram of a stable vortex in accordance with at least one embodiment of the present disclosure.

3 is a kinetic model of vortex stabilization within a slot in accordance with at least one embodiment of the present disclosure.

4 is a schematic diagram of drag reduction of a vortex string according to at least one embodiment of the present disclosure.

5 is a numerical experimental verification of vortex stabilization in accordance with at least one embodiment of the present disclosure.

FIG. 6 is an experimental verification of drag reduction characteristics according to the present disclosure.

Detailed ways

The present disclosure will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the related content, but not to limit the present disclosure. In addition, it should be noted that, for the convenience of description, only the parts related to the present disclosure are shown in the drawings.

It should be noted that the embodiments of the present disclosure and the features of the embodiments may be combined with each other unless there is conflict. The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

Example

As shown in FIG. 1 , the present disclosure provides a transverse V-groove structure 100 based on stable vortex string drag reduction. The structure is composed of several V-shaped grooves 1 , and the arrangement direction of the V-shaped grooves and the flow direction of the fluid are mutually Vertical, the direction indicated by the arrow in Figure 1 is the flow direction of the fluid, and the width of the V-shaped groove is set as W; the height of the V-shaped groove is set as H, and the height H of the V-shaped groove is to make the fluid The height of the stable vortex is generated in the groove; the aspect ratio W/H of the V-shaped groove is 2, and the apex angle of the V-shaped groove is 90°. As shown in FIG. 2 , the present disclosure generates a stable vortex in the groove through a specific transverse V-groove configuration, thereby realizing the formation of a “vortex boundary” between the fluid and the solid, thereby reducing frictional resistance and realizing the function of efficient drag reduction, Among them, the top two horizontal arrows in Figure 2 represent the flow direction of the fluid; the three clockwise arrows in the V-shaped groove represent the vortex in the groove.

According to at least one embodiment of the present disclosure, the height H of the V-groove is determined by the fluid flow rate U and the fluid kinematic viscosity υ, and:

其中L代表特征长度。本公开同时给出了控制参数随来流的变化规律，根据不同来流工况，通过上述公式以达到最佳的减阻效果。Wherein: the height of the V-shaped groove is H, and the unit of H is m; the fluid velocity is U, and the unit of U is m/s; the kinematic viscosity of the fluid is υ, and the unit of υ is m ² /s; Re represents the Reynolds number,

where L represents the feature length. The present disclosure also provides the variation law of the control parameters with the incoming flow, and according to different incoming flow conditions, the above formula is used to achieve the best drag reduction effect.

代表迁移流在滑移面的速度大小。依涡动力学的观点，只有镜像涡的诱导速度与迁移流对槽内涡的迁移速度在槽内涡核处叠加为0时，即图中

时，V槽内漩涡才保持稳定。本公开中，V槽宽高比为2保证了

这一必要条件，故槽内涡稳定在V槽内部，其减阻示意图如图4(a)所示，在槽内产生稳定的漩涡，这种漩涡对边界层产生的效果类似于滑移边界，使得流体速度型更加饱满，减小了流体的摩擦阻力；另外如图4(b)、图4(c)所示，分别为V槽宽高比不为2，槽内涡左偏置及槽内涡右偏置的示意图；漩涡随着流体迁移或者在槽内发生左右偏置，从而不能形成稳定的滑移边界，不能实现“锁涡”功能，因此不能取得最佳的减阻效果。The transverse V-groove adopted in the present disclosure can ensure that the vortex is stable in the groove due to the special geometric feature: that is, the aspect ratio is 2. The drag reduction principle of the present disclosure is that when the fluid flows vertically through the transverse V-groove, vortices are formed inside the V-groove, and multiple vortices are combined into a series of vortex strings. When the vortex in the groove is stabilized inside the V-groove, it turns the fluid-solid boundary into a fluid-flow slip boundary similar to a "fluid ball bearing", which will greatly reduce the frictional resistance. As shown in Fig. 3, from the point of view of vortex dynamics, the action of the solid wall on the vortex in the groove is like the action of two mirror vortices (shown as 1 and 2 in Fig. 3) with equal vorticity and opposite directions. The mirror vortex induces velocity to the vortex in the slot. As shown in Fig. 3, U ₁₃ represents the induced velocity of the mirror vortex 1 to the vortex 3 in the slot, and U ₂₃ represents the induced velocity of the mirror vortex 2 to the vortex 3 in the slot. U _m represents the combined induced velocity of the mirror vortices 1 and 2 at the vortex core in the slot, and represents the migration velocity of the vortex in the slot by the migration flow to the vortex core in the slot,

It represents the velocity of the migration flow on the slip surface. From the point of view of vortex dynamics, only when the induced velocity of the mirror vortex and the migration velocity of the vortex in the trough by the migration flow are superimposed to 0 at the vortex core in the trough, that is, in Fig.

When the vortex in the V-groove remains stable. In this disclosure, the V-groove aspect ratio of 2 ensures that

Due to this necessary condition, the vortex in the groove is stable inside the V groove. The drag reduction schematic diagram is shown in Figure 4(a), and a stable vortex is generated in the groove. The effect of this vortex on the boundary layer is similar to that of the slip boundary. , making the fluid velocity pattern more saturated and reducing the frictional resistance of the fluid; in addition, as shown in Fig. 4(b) and Fig. 4(c), the aspect ratio of the V groove is not 2, the left offset of the vortex in the groove and the Schematic diagram of the right offset of the vortex in the groove; the vortex migrates with the fluid or offsets left and right in the groove, so that a stable slip boundary cannot be formed, and the "vortex locking" function cannot be achieved, so the optimal drag reduction effect cannot be achieved.

Effect Verification Numerical Experiment of Vortex Stability

In the present disclosure, transverse V-grooves with aspect ratios greater than 2, equal to 2, and less than 2 are respectively arranged on a two-dimensional flat plate, and numerical experiments are carried out on them to observe the stability of the vortex and the drag reduction performance. As shown in Figure 5, it is the vorticity cloud diagram of the numerical experiment. Figure 5(a) represents the movement of the vortex (the part indicated by the arrow in Figure 5(a)) when the aspect ratio of the lateral V groove is greater than 2. It can be seen that Over time (74T-80T), the vortex swayed in the tank. Figure 5(c) represents the case where the aspect ratio of the lateral V groove is less than 2. At this time, the vortex (the part indicated by the arrow in Figure 5(c)) is mainly affected by the mirror vortex and migrates along the solid wall in the groove, while Migrated downstream by migration flow. Figure 5(b) represents the case where the aspect ratio of the transverse V-groove is equal to 2, at which time the vortex (indicated by the arrow in Figure 5(b)) is very stably stationed in the groove.

As shown in Figure 6, the relationship between speed and drag reduction rate is given, where 0.1-0.2 represents a height of 0.1mm and a width of 0.2mm. It can be seen from the figure that the drag reduction rate is the best when the aspect ratio is 2 (that is, the transverse V-groove of 0.1-0.2 in the figure) in the full operating range. This is because the vortices stably stay in the grooves, thereby forming a stable slip surface, thereby achieving high-efficiency drag reduction.

By adopting the solution of the present disclosure, the present disclosure can realize that the vortex stably resides inside the V-groove, thereby achieving the best drag reduction effect. For example, under the condition of 10m/s inflow, compared with the lateral V-groove with an aspect ratio of 1, the drag reduction rate is increased by more than 24.6%, and the drag reduction effect is obvious. It can be seen that a boundary vortex can be formed inside the lateral groove, but only the lateral groove of the shape described in the present disclosure can stabilize the boundary vortex inside the V-groove, thereby forming a stable slip boundary, thereby achieving efficient drag reduction.

There is no limit to the number of V-grooves in the present disclosure, and can be arranged in any length; no additional control device and injection of additional substances are required; the processing is simple, and there is no limitation on materials; it has a wide range of applications and can be applied to aerospace (wings, compressor blades) , Rotary body) field.

In the description of this specification, references to the terms "one embodiment/mode", "some embodiments/modes", "example", "specific example", or "some examples", etc. are intended to be combined with the description of the embodiment/mode A particular feature, structure, material, or characteristic described by way of example or example is included in at least one embodiment/mode or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment/mode or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments/means or examples. Furthermore, those skilled in the art may combine and combine the different embodiments/modes or examples described in this specification and the features of the different embodiments/modes or examples without conflicting each other.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature delimited with "first", "second" may expressly or implicitly include at least one of that feature. In the description of the present application, "plurality" means at least two, such as two, three, etc., unless expressly and specifically defined otherwise.

Those skilled in the art should understand that the above-mentioned embodiments are only for clearly illustrating the present disclosure, rather than limiting the scope of the present disclosure. For those skilled in the art, other changes or modifications may also be made on the basis of the above disclosure, and these changes or modifications are still within the scope of the present disclosure.

Claims (6)

1. A transverse V-shaped groove structure based on stable vortex string resistance reduction is characterized in that the structure is formed by combining a plurality of V-shaped grooves, the arrangement direction of the V-shaped grooves is perpendicular to the flow direction of fluid, and the width of each V-shaped groove is W; the height of the V-shaped groove is H; the width-to-height ratio W/H of the V-shaped groove is 2.

2. The V-groove structure of claim 1, wherein the V-groove apex angle is 90 °.

3. The V-groove structure of claim 1 wherein the V-groove height H is determined by the fluid flow rate U and the fluid kinematic viscosity V, and:

wherein: the height of the V-shaped groove is H, and the unit of H is m; the flow rate of the fluid is U, and the unit of U is m/s; the kinematic viscosity of the fluid is upsilon, which is expressed in m²S; re represents the Reynolds number,

wherein L represents the characteristic length.

4. An airfoil having the stabilized vortex-string drag reduction-based transverse V-groove structure of any one of claims 1 to 3, wherein all or part of the surface of the airfoil has the stabilized vortex-string drag reduction-based transverse V-groove structure of any one of claims 1 to 4.

5. A compressor blade having the stabilized vortex-string drag reduction-based transverse V-groove structure of any one of claims 1 to 3, wherein all or part of the surface of the compressor blade has the stabilized vortex-string drag reduction-based transverse V-groove structure of any one of claims 1 to 4.

6. A rotor having the stabilized vortex-string drag reduction-based transverse V-groove structure of any one of claims 1 to 3, characterized in that all or part of the surface of the rotor has the stabilized vortex-string drag reduction-based transverse V-groove structure of any one of claims 1 to 3.

Images