CN115806047A - Umbrella sequence spoke structure capable of generating separation vortex ring - Google Patents
Umbrella sequence spoke structure capable of generating separation vortex ring Download PDFInfo
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- CN115806047A CN115806047A CN202211577442.3A CN202211577442A CN115806047A CN 115806047 A CN115806047 A CN 115806047A CN 202211577442 A CN202211577442 A CN 202211577442A CN 115806047 A CN115806047 A CN 115806047A
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Abstract
The invention discloses an umbrella sequence spoke structure capable of generating a separation vortex ring, which consists of a central disc and a plurality of spokes arranged at the periphery of the central disc in an umbrella sequence, wherein the umbrella sequence spoke structure can generate a stable separation vortex ring under the interference of vertical incoming flow, thereby ensuring the stability of flight; compared with a solid disc with the same characteristic length, the umbrella spoke structure can consume less materials under the condition of generating almost the same aerodynamic force, can maintain stable flight for a longer distance under the unpowered condition, and better saves energy and cost.
Description
Technical Field
The invention relates to the technical field of aircrafts, in particular to an umbrella spoke structure capable of generating a separation vortex ring.
Background
Dandelion seeds can float in the air for a long distance only by wind power, and the high flying capacity attracts the attention of aircraft designers in recent years. If the excellent unpowered flight capability can be applied to the design and development of the aircraft, the subversive development of the future bionic aircraft is probably brought.
Early aerodynamic studies on feather-like seeds such as dandelion with crowns have shown that such seeds can bear large resistance during flight, thereby effectively slowing down the terminal speed of falling and achieving long-distance flight, but a mechanism for generating such high resistance by means of a limited area is pending. In 2018, cummins et al observe that a unique vortex ring separated from a body is generated in a wake flow when a crown and hair structure of dandelion seeds fly through wind tunnel experiments and flow visualization for the first time, and think that the Separated Vortex Ring (SVR) is a key for efficient flying of the dandelion seeds.
At present, the research on the newly found flow behavior of separating vortex rings at home and abroad is still in a starting stage, and the mysterious flight of dandelion seeds is not yet uncovered. In the prior art, most researches in the field are based on a porous medium flow analysis method, the crown and hair structure of dandelion seeds is simplified into a porous thin disc model, but the flight performance of the dandelion seeds is far from reaching an ideal state.
Therefore, whether to develop a structure that truly simulates the flying of dandelion seeds, i.e. a structure that can form a separation vortex ring, is a problem that people need to solve urgently.
Disclosure of Invention
In view of this, the present invention provides an umbrella spoke structure capable of generating a separating vortex ring to solve the problems in the background art.
The technical scheme provided by the invention is specifically that an umbrella spoke structure capable of generating a separation vortex ring comprises: a central disc and a plurality of spokes;
the spokes are arranged on the periphery of the central disc in an umbrella sequence, each spoke is provided with a connecting end and a free end, and the connecting end of each spoke is connected with the outer edge of the central disc.
Preferably, the central disc has axial and central symmetry.
Further preferably, the porosity of the umbrella spoke structure is 0.75-0.92, wherein the porosity is the ratio of the projected area of the void part in the umbrella spoke structure to the total projected area of the imaginary solid disc.
Further preferably, the characteristic length of the umbrella sequence spoke structure is D =2R, wherein R is an umbrella sequence spokeThe characteristic radius of the structure, the diameter ratio of the characteristic length of the section of the spoke to the central disk is
The number n of the spokes is
Further preferably, the connecting ends of the spokes are all rigidly connected to the outer edge of the central disc.
Further preferably, the connecting ends of the spokes are movably connected with the outer edge of the central disc, and the spokes can rotate around any axis.
Further preferably, the spokes are rigid straight rods, rigid curved rods or flexible rods.
Further preferably, the degree of curvature of the rigid curved bar is adjustable.
The umbrella-sequence spoke structure capable of generating the separation vortex ring provided by the invention is composed of a central disc and a plurality of spokes arranged at the periphery of the central disc in an umbrella sequence, and the umbrella-sequence spoke structure can generate a stable separation vortex ring under the interference of vertical incoming flow, so that the stability of flight is ensured.
Compared with a solid disc with the same characteristic length, the umbrella-like spoke structure capable of generating the separation vortex ring provided by the invention can consume less materials under the condition of generating almost the same aerodynamic force, can maintain stable flight for a long distance under the unpowered condition, and better saves energy and cost.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a schematic structural view of an umbrella spoke structure with rigid straight spokes according to an embodiment of the present disclosure;
FIG. 2 is a top view of a umbrella spoke structure with rigid straight bars as spokes according to an embodiment of the present disclosure;
FIG. 3 is a side view of a gore spoke structure with spokes as rigid straight rods according to the disclosed embodiment of the invention;
FIG. 4 is a schematic view of a separating vortex ring generated above an umbrella spoke structure according to the disclosed embodiment of the invention;
FIG. 5 is a velocity vector diagram of a flow field above a central disk of an umbrella spoke structure according to an embodiment of the present disclosure;
FIG. 6 is a particle trace plot of the structured flow field when no separation of the vortex ring occurs;
FIG. 7 is a velocity vector diagram of the flow field above the central disk when no separation of the vortex rings occurs.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus consistent with certain aspects of the invention, as detailed in the appended claims.
The existing research mostly depends on a porous medium structure, a three-dimensional model established according to the dandelion seed crown hair structure is simply called a porous thin disc, and the porous structure in the traditional sense such as a honeycomb disc and the like cannot be accurately distinguished. In addition, in order to really apply the structure as a core component to an aircraft in the follow-up process, the dandelion seed canopies are used as the structure as the basis, and the research range is further expanded to a structure capable of generating the separation vortex ring.
The crown hair of dandelion seeds in nature is composed of central pillow leaf and peripheral seta-like filaments, which radiate outward from the pillow leaf like the spokes of a bicycle wheel. In the field of fluid mechanics, the same wing series arranged according to a certain rule have been studied for circumferential motion, i.e. cascade theory. Similarly, the embodiment is based on the appearance characteristics of dandelion seed crown hair, and a structure capable of generating a separation vortex ring is regarded as being composed of a central disc and a series of same columns regularly arranged on the periphery of the central disc, the columns radiate outwards from the central disc, and the axes of the columns and the plane of the central disc have a certain angle, and the columns are arranged like umbrella ribs of an umbrella in an umbrella sequence on the periphery of the central disc. In summary, based on the shape characteristics of the structure, the present embodiment defines such a structure as an umbrella spoke structure.
Referring to fig. 1-3, the spoke structure of the umbrella sequence mainly comprises a central disc 1 and a plurality of spokes 2, wherein the plurality of spokes 2 are respectively arranged at the periphery of the central disc 1 in the umbrella sequence, each spoke 2 is provided with a connecting end and a free end, and the connecting end of each spoke 2 is connected with the outer edge of the central disc 1.
Wherein, the umbrella preface is a plurality of spokes 2 and evenly arranges along the periphery interval of central disk 1, and has certain angle between spoke 2 and the central disk 1, and specific angle can be set for according to actual conditions.
For the umbrella spoke structure, when ascending air current exists, partial air current bypasses the spokes 2 and flows through the gap, thick boundary layers are generated around the spokes 2, the boundary layers of two adjacent spokes interact to generate a wall effect, the air current flowing through the structure is obviously reduced, the umbrella spoke structure is similar to a continuous surface, and the air current above the central disk 1 and the edge air current are sheared with each other to form a vortex ring. At the same time, the presence of a large positive radial pressure gradient between the roots of the spokes near the central disk 1 helps to "lift" this vortex ring, thus creating a separating vortex ring above the central disk 1. Due to the existence of the separation vortex ring, the upper surface of the structure is a low-pressure area, the lower surface of the structure is a high-pressure area, and the pressure difference between the upper surface and the lower surface enables the umbrella-shaped spoke structure to obtain upward force, so that the falling speed is effectively delayed, the umbrella-shaped spoke structure can stably fly for a long distance, and the performance of the umbrella-shaped spoke structure is obviously superior to that of the existing porous thin disc model.
In the umbrella spoke structure, the central disc 1 has axial symmetry and central symmetry, the section shape of the spoke is not limited, and the symmetry of the central disc 1 is mainly used for ensuring the symmetry of the generated vortex ring so as to improve the stability of flight.
In order to ensure that the structure can generate stable separation vortex ring under the designated flight state, as an improvement of the technical scheme, the porosity of the umbrella-series spoke structure is designed to be 0.75-0.92, wherein the porosity is the ratio of the projected area of the hollow part in the umbrella-series spoke structure to the total projected area of the imaginary solid disk.
Wherein, the specific calculation formula of the porosity is as follows:
In practical experiments, it is found that: if the porosity is less than 0.75, when the ascending air current flows through the structure, the ascending air current bypasses the spokes 2 and participates in the shearing process with the surrounding air to form a vortex ring, the structure is more similar to a solid disk, and the vortex ring can not be completely separated from the surface of the structure by obtaining enough pressure gradient; if the porosity is greater than 0.92, the distance between the roots of two adjacent spokes 2 is too large, which can weaken the wall effect to some extent, thereby affecting the generation of the separation vortex ring.
More preferably, the characteristic length D =2R of the gore spoke structure is the characteristic radius of the gore spoke structure, and the diameter ratio of the characteristic length of the section of the spoke 2 to the central disk 1 is
Number of said spokes (2)
By controlling the above parameters, the distance between the roots of the adjacent spokes 2 can be further adjusted, so that the airflow has the optimum pressure gradient and wall effect intensity after flowing through the spoke, thereby being beneficial to the generation of the separation vortex ring in the range.
Wherein, the connecting ends of the spokes 2 and the outer edge of the central disk 1 can adopt rigid connection.
In practical application, in order to improve the maneuverability of the umbrella spoke structure, the connecting ends of the spokes 2 and the outer edge of the central disk 1 can be movably connected in a hinged mode and the like, so that the function of the spokes is equivalent to that of an aircraft control surface, the change of the opening angle, symmetry or porosity of the umbrella spoke structure is realized by controlling the rotation of all or part of the spokes around any axis, the flight attitude can be adjusted, and therefore the original balance state can be kept to the maximum extent or a larger restoring moment can be generated when the structure is interfered by incoming flow with horizontal direction components or the flight environment is changed.
For the spoke 2, the spoke can be a rigid straight rod or a rigid deformed curved rod, and can also be designed into a flexible rod according to the flexible characteristics of the dandelion seed crown hair-shaped filaments. Preferably, the rigid curved bar is designed as a curved bar with adjustable curvature, so that the control of the flying attitude of the structure can be realized by controlling the curvature degree of the bar.
The embodiment is inspired by dandelion seeds, one type of structure capable of generating the separation vortex ring is defined as an umbrella spoke structure, and the structure can be accurately distinguished from a traditional porous structure, so that the concept is unified for the subsequent research in the field.
The umbrella-sequence spoke structure provided by the embodiment flies in a newly discovered mode, namely, the separated vortex ring generated in the wake vortex is depended on, when the appearance and various size parameters of the structure are reasonably designed, the structure can generate the stable separated vortex ring under the interference of vertical incoming flow, the stability of the flight is ensured, and in the design of a future aircraft, if the structure is used as a core component, the stability and the maneuverability of the aircraft are greatly increased. Compared with a solid disc with the same characteristic length, the aerodynamic structure can consume less material under the condition of generating almost the same aerodynamic force, and can maintain stable flight for a longer distance under the condition of no power, thereby better saving energy and cost.
The invention is further illustrated and described with reference to specific examples, which should not be construed as limiting the scope of the invention.
Example 1
An umbrella sequence spoke structure, as shown in fig. 1-3, comprising: the umbrella comprises a central disc 1 and a plurality of spokes 2, wherein the spokes 2 radiate outwards from the central disc 1 and are arranged in an umbrella sequence, namely the spokes 2 are uniformly distributed along the periphery of the central disc 1 at intervals, the spokes 2 are provided with fixed ends and free ends, and the fixed ends of the spokes 2 are connected with the outer edge of the central disc 1. The spokes 2 in the umbrella sequence spoke structure are control surfaces, and the flight attitude can be controlled by controlling the movement and the shape of the spokes.
In the umbrella-like spoke structure, the characteristic length D =14mm, the porosity epsilon =0.916, the central disc 1 is circular, the section of the spoke 2 is circular, and a series of same spokes 2 are arranged on the periphery of the central disc 1 in an umbrella-like manner, so that the opening angle of the umbrella-like spoke structure is 120 degrees. In addition, the number of spokes n =42, and the diameter ratio of the section diameter of the spokes to the central disk
The central disk 1 is rigidly connected with the spokes 2, the flying Reynolds number Re =287.5, and the flow field of the umbrella spoke structure during flying is subjected to numerical simulation analysis by a computer, so that the separation vortex ring generated above the umbrella spoke structure is obtained as shown in FIG. 4.
As shown in fig. 5, which is a velocity vector diagram of a flow field above the central disk 1 of the umbrella spoke structure, a part of vector with a vertical upward velocity component is generated above the central disk 1, so that the vortex ring is separated from the central disk 1, and finally a stable separated vortex ring is formed.
The principle of generation of the analytical separation vortex ring is as follows:
when ascending air flows exist, part of the air flows bypass the spokes 2 and flow through the gaps, thick boundary layers are generated around the spokes 2, the boundary layers of two adjacent spokes interact to generate a wall effect, the air flow flowing through the structure is obviously reduced, the umbrella-shaped spoke structure is similar to a continuous surface, and the air flow above the central disk 1 and the edge air flow are sheared with each other to form a vortex ring. At the same time, the presence of a large positive radial pressure gradient between the roots of the spokes near the central disk 1 helps to "lift" this vortex ring, thus creating a detached vortex ring above the central disk 1. Due to the existence of the separation vortex ring, the upper surface of the structure is a low-pressure area, the lower surface of the structure is a high-pressure area, and the pressure difference between the upper surface and the lower surface enables the umbrella-shaped spoke structure to obtain upward force, so that the falling speed is effectively delayed, and the umbrella-shaped spoke structure can stably fly for a long distance.
In contrast, when the parameters of the structural part are obtained outside the limited range, such as when the porosity ∈ =0.94 and the number of spokes n =30, and the remaining parameters are consistent with the above-described embodiment, the umbrella-type spoke structure is numerically simulated, and the particle trace pattern of the flow field above the central disk is also obtained as shown in fig. 6, it can be found that the vortex ring generated in the wake is not separated from the central disk but attached thereto, and as can also be seen from the velocity vector diagram shown in fig. 7, in this case, the velocity vector having a vertically upward directional component is not generated above the central disk, and the vortex ring cannot be "lifted up", so that the separated vortex ring cannot be generated finally.
In practical application, the determination of the dimensional parameters, the appearance characteristics, the materials, the processing technology and the like of all parts of the umbrella sequence spoke structure ensures that the structure can have the most excellent flight capability in a specified flight state.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (8)
1. An umbrella-like spoke structure capable of producing a separating vortex ring, comprising: a central disc (1) and a plurality of spokes (2);
the spokes (2) are arranged on the periphery of the central disc (1) in an umbrella sequence, each spoke (2) is provided with a connecting end and a free end, and the connecting end of each spoke (2) is connected with the outer edge of the central disc (1).
2. Umbrella-like spoke structure capable of producing separating volutes according to claim 1, characterized in that said central disk (1) has axial and central symmetry.
3. The umbrella sequence spoke structure capable of producing a separating scroll ring according to claim 1, wherein the umbrella sequence spoke structure has a porosity of 0.75-0.92, wherein the porosity is a ratio of a projected area of a hollow part in the umbrella sequence spoke structure to a total projected area of an imaginary solid disk.
4. Umbrella-like spoke structure capable of producing separate volutes according to claim 1, characterized in that it has a characteristic length D =2R, where R is the characteristic radius of the umbrella-like spoke structure and the ratio of the characteristic length of the cross section of the spoke (2) to the diameter of the central disk (1) is such that
The number n of the spokes (2) is
5. Umbrella-like spoke structure capable of producing separate volutes according to claim 1, characterized in that the connection ends of the spokes (2) are all rigidly connected to the outer edge of the central disk (1).
6. Umbrella sequence spoke structure capable of generating separating vortex rings according to claim 1, characterized in that the connecting ends of the spokes (2) are all movably connected with the outer edge of the central disk (1), and the spokes (2) can rotate around any axis.
7. Umbrella spoke structure capable of producing separate volutes according to claim 1, characterized in that said spokes (2) are rigid straight, curved or flexible rods.
8. The umbrella-like spoke structure capable of producing separate scroll rings of claim 7, wherein the degree of curvature of the rigid curved bar is adjustable.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211577442.3A CN115806047A (en) | 2022-12-09 | 2022-12-09 | Umbrella sequence spoke structure capable of generating separation vortex ring |
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| CN202211577442.3A CN115806047A (en) | 2022-12-09 | 2022-12-09 | Umbrella sequence spoke structure capable of generating separation vortex ring |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012130856A1 (en) * | 2011-03-29 | 2012-10-04 | Institut Supérieur De L'aéronautique Et De L'espace | Remotely controlled micro/nanoscale aerial vehicle comprising a system for traveling on the ground, vertical takeoff, and landing |
| CN209479987U (en) * | 2018-11-12 | 2019-10-11 | 浙江大学 | A kind of imitative dandelion aircraft of unpowered type |
| CN110816891A (en) * | 2019-11-18 | 2020-02-21 | 沈阳航空航天大学 | Rigid lunar vehicle wheel |
| CN113255065A (en) * | 2021-06-23 | 2021-08-13 | 南京航空航天大学 | Dandelion-imitated aircraft and design method and analysis method of aircraft |
| CN115320861A (en) * | 2021-05-11 | 2022-11-11 | 南京理工大学 | Disc structure for inducing separation vortex ring |
-
2022
- 2022-12-09 CN CN202211577442.3A patent/CN115806047A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012130856A1 (en) * | 2011-03-29 | 2012-10-04 | Institut Supérieur De L'aéronautique Et De L'espace | Remotely controlled micro/nanoscale aerial vehicle comprising a system for traveling on the ground, vertical takeoff, and landing |
| CN209479987U (en) * | 2018-11-12 | 2019-10-11 | 浙江大学 | A kind of imitative dandelion aircraft of unpowered type |
| CN110816891A (en) * | 2019-11-18 | 2020-02-21 | 沈阳航空航天大学 | Rigid lunar vehicle wheel |
| CN115320861A (en) * | 2021-05-11 | 2022-11-11 | 南京理工大学 | Disc structure for inducing separation vortex ring |
| CN113255065A (en) * | 2021-06-23 | 2021-08-13 | 南京航空航天大学 | Dandelion-imitated aircraft and design method and analysis method of aircraft |
Non-Patent Citations (1)
| Title |
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| 鲍雯昱: "风速对蒲公英种子尾涡的影响", 沈阳航空航天大学学报, 25 June 2021 (2021-06-25), pages 14 - 23 * |
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