A dual synthetic jet vibration damping and protection device with a cylindrical structure

Abstract

The present invention discloses a double synthetic jet vibration damping and protection device with a cylindrical structure, which includes a jet slit and a jet channel. The jet slit is located near the flow separation point on the surface of the protected cylindrical structure. There are two jet slits, and the two jet slits are symmetrically distributed along the oncoming flow direction on the surface of the cylindrical structure. The jet channel is arranged inside the cylindrical structure and penetrates the entire cylindrical structure. The inner side of the jet slit communicates with the jet channel. One end of the jet channel is movably connected to an external piston, and the piston is driven by a servo motor. By adopting the above-mentioned double synthetic jet vibration damping and protection device with a cylindrical structure, the present invention can produce a good control effect on the wind-induced vibration of the cylindrical structure.

Description

Technical Field

[0001] The present invention relates to the technical field of wind-induced vibration control for cylindrical structures, and particularly to a double synthetic jet vibration reduction and protection device for cylindrical structures. Background Art

[0002] Cylindrical structures are a common structural form, such as the suspenders in bridge engineering, the columns of offshore drilling platforms, and the lightning rods at the tops of high-rise buildings. Due to the relatively long length of cylindrical structures, the flexibility effect is obvious, and complex dynamic responses are likely to occur under the action of airflows. When the airflow flows over a cylindrical structure, flow separation and vortex shedding will occur. When the vortex shedding period is close to the period of a certain natural vibration mode of the structure, obvious fluid-structure coupling phenomena will occur, resulting in wind-induced vibration of the structure. The occurrence of wind-induced vibration is relatively frequent, and in some cases, it may seriously affect the normal use and service life of the structure. Therefore, it is necessary to develop effective devices to control the wind-induced vibration of such structures. Summary of the Invention

[0003] The object of the present invention is to provide a double synthetic jet vibration reduction and protection device for cylindrical structures, which can produce a good control effect on the wind-induced vibration of cylindrical structures.

[0004] To achieve the above object, the present invention provides a double synthetic jet vibration reduction and protection device for cylindrical structures, including a jet slit and a jet channel. The jet slit is located near the flow separation point on the surface of the protected cylindrical structure. There are two jet slits, and the two jet slits are symmetrically distributed along the oncoming flow direction on the surface of the cylindrical structure. The jet channel is arranged inside the cylindrical structure and runs through the entire cylindrical structure. The inner side of the jet slit is communicated with the jet channel. One end of the jet channel is movably connected to an external piston, and the piston is driven by a servo motor.

[0005] Preferably, the jet slit is strip-shaped, and the jet channel is circular.

[0006] Preferably, there are two jet channels, and the two jet channels are separately connected to the jet slits on each side.

[0007] Preferably, the servo motor rotates at a fixed frequency to drive the reciprocating motion of the piston, and the reciprocating motion of the piston generates symmetric double synthetic jets at each side of the jet slit.

[0008] Preferably, a plurality of double synthetic jet vibration reduction and protection devices are evenly spaced near the flow separation points in the areas prone to wind-induced vibration in a relatively long cylindrical structure.

[0009] Preferably, the jet velocity amplitude u of the double synthetic jet vibration reduction and protection device is set in the cylindrical structure sj The method is as follows:

[0010] where w is the width of the jet slit, D is the diameter of the cylindrical structure, C μ is the dimensionless jet momentum coefficient, and U0 is the mean wind speed of the oncoming flow. In practical applications, first, according to the desired effect of suppressing wind-induced vibration, the jet momentum coefficient C μ is determined, and then the jet velocity amplitude (i.e., the air velocity amplitude in the slit) u sj is obtained.

[0011] Advantages of the present invention:

[0012] The double synthetic jet vibration reduction and protection device of the present invention belongs to a kind of active flow control measure, with high control efficiency and obvious control effect on the flow field around the structure. In practical applications, the jet momentum coefficient can be selected according to needs, the required jet velocity amplitude is derived based on the selected jet momentum coefficient, and then the required width of the jet slit can be calculated according to the jet velocity amplitude, the diameter of the cylindrical structure, and the mean wind speed of the oncoming flow. That is, the control intensity of the flow field can be changed by controlling the width of the slit. This device can change the flow separation and vortex shedding processes in the flow field around the structure and can effectively suppress the wind-induced vibration of the cylindrical structure.

[0013] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Brief description of the drawings

[0014] Figure 1 is a schematic structural diagram of the double synthetic jet vibration reduction and protection device for the cylindrical structure of the present invention;

[0015] Figure 2 is a schematic radial cross-sectional view of the double synthetic jet vibration reduction and protection device for the cylindrical structure of the present invention;

[0016] Figure 3 is a schematic working principle diagram of the double synthetic jet vibration reduction and protection device for the cylindrical structure of the present invention;

[0017] Figure 4 is an instantaneous flow field vorticity diagram of the embodiment of the present invention under uncontrolled conditions;

[0018] Figure 5 is a time-averaged flow field streamline and turbulent kinetic energy diagram of the embodiment of the present invention under uncontrolled conditions;

[0019] Figure 6 is an instantaneous flow field vorticity diagram of the embodiment of the present invention under the condition of installing the double synthetic jet vibration reduction and protection device;

[0020] Figure 7 is a time-averaged flow field streamline and turbulent kinetic energy diagram of the embodiment of the present invention under the condition of installing the double synthetic jet vibration reduction and protection device.

[0021] Reference numerals:

[0022] 1, cylindrical structure; 2, jet slit; 3, jet channel. Detailed implementation manners

[0023] The present invention will be further described below in conjunction with embodiments.

[0024] Embodiment

[0025] As Figure 1-2 shown, a dual synthetic jet vibration reduction and protection device with a cylindrical structure includes a jet slit 2 and a jet channel 3. The jet slit 2 is strip-shaped, and the jet channel 3 is circular-hole-shaped. The jet slit 2 is located near the flow separation point on the surface of the protected cylindrical structure 1. There are two jet slits 2, and the two jet slits 2 are symmetrically distributed along the oncoming flow direction on the surface of the cylindrical structure 1. The jet channel 3 is arranged inside the cylindrical structure 1 and penetrates the entire cylindrical structure 1. The inner side of the jet slit 2 communicates with the jet channel 3. There are two jet channels 3, and the two jet channels 3 are respectively and independently connected to the jet slit 2 on each side.

[0026] One end of the jet channel 3 is movably connected to an external piston, that is, the jet channel 3 is used to connect the jet slit 2 and the external piston, and the piston is driven by a servo motor. The servo motor rotates at a fixed frequency to drive the reciprocating motion of the piston. The reciprocating motion of the piston generates symmetric dual synthetic jets at each side of the jet slit 2. Through the periodic suction and blowing of the synthetic jets, the momentum exchange with the airflow of the cylindrical structure 1 is realized, and the flow separation, vortex shedding, and fluid-structure coupling processes are changed, thereby controlling the wind-induced vibration of the cylindrical structure 1.

[0027] As Figure 3 shown, when the oncoming flow passes through the cylindrical structure 1, a flow separation phenomenon will occur, and a series of periodically antisymmetrically shedding vortices will be generated in the wake region. The dual synthetic jet vibration reduction and protection device generates a pair of synthetic jets with periodic suction and blowing at the slit, realizing the control of the flow separation and wake vortex shedding processes. When it is not necessary to control the wind-induced vibration of the cylindrical structure 1, the servo motor can be turned off, and no synthetic jet is generated. At this time, the flow separation, vortex shedding, and fluid-structure coupling processes when the oncoming flow passes through the cylindrical structure 1 are the same as those of an ordinary uncontrolled structure.

[0028] For a relatively long cylindrical structure 1, a plurality of dual synthetic jet vibration reduction and protection devices can be evenly arranged at intervals near the flow separation points in the regions of the relatively long cylindrical structure 1 that are prone to wind-induced vibration.

[0029] Combined with Figure 3 , the formula for determining the jet velocity usj required for setting the present vibration reduction and protection device on the cylindrical structure is as follows:

[0030]

[0031] where w is the width of the jet slit, D is the diameter of the cylindrical structure, C μ is the dimensionless jet momentum coefficient, and U0 is the mean incoming flow velocity. In practical applications, first, according to the desired effect of suppressing wind-induced vibration, the jet momentum coefficient C μ is determined, and then the jet velocity amplitude u sj is obtained.

[0032] Experimental tests

[0033] Using a particle image velocimetry (PIV) system, the flow field around the cylindrical structure before and after installing the double synthetic jet vibration reduction and protection device is measured and visually analyzed. The obtained results are as Figures 4-7 shown.

[0034] Figure 4 This is the instantaneous flow field vorticity diagram of the embodiment of the present invention under uncontrolled conditions, as Figure 4 shown, indicating that there are obvious flow separations and periodic antisymmetric vortex shedding phenomena in the wake of the cylindrical structure.

[0035] Figure 5 This is the time-averaged flow field streamline and turbulent kinetic energy diagram of the embodiment of the present invention under uncontrolled conditions, as Figure 5 shown, indicating that the vortex formation length in the wake area of the uncontrolled cylindrical structure is relatively long, and the range of the recirculation area is relatively large.

[0036] Figure 6 This is the instantaneous flow field vorticity diagram of the embodiment of the present invention under the condition of installing the double synthetic jet vibration reduction and protection device. From the Figure 6 instantaneous vorticity results, it can be seen that the flow separation phenomenon in the wake area of the cylindrical structure after being controlled by this device has been significantly controlled, and the antisymmetric vortex shedding mode has been converted into a symmetric vortex shedding mode. The vortex shedding process is controlled by the velocity amplitude and frequency of the double synthetic jet.

[0037] Figure 7 This is the time-averaged flow field streamline and turbulent kinetic energy diagram of the embodiment of the present invention under the condition of installing the double synthetic jet vibration reduction and protection device. From the Figure 7 time-averaged streamline results, it can be seen that the vortex formation length in the wake area of the cylinder after being controlled by this device is significantly shortened, the range of the recirculation area is reduced, and the flow velocity near the wall surface of the cylindrical structure and downstream is significantly restored. The above results indicate that the flow separation and vortex shedding processes in the wake area of the cylindrical structure after being controlled by this device have been significantly controlled, which will weaken the fluid-structure coupling degree, thereby achieving the effect of suppressing the wind-induced vibration of the cylindrical structure.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A dual synthetic jet vibration damping and protection device with a cylindrical structure, characterized in that: It includes a jet slit and a jet channel. The jet slit is located near the flow separation point on the surface of the protected cylindrical structure. There are two jet slits, and the two jet slits are symmetrically distributed along the oncoming flow direction on the surface of the cylindrical structure. The jet channel is arranged inside the cylindrical structure and penetrates the entire cylindrical structure. The inner side of the jet slit communicates with the jet channel. One end of the jet channel is movably connected to an external piston, and the piston is driven by a servo motor.

2. The double-synthetic jet damping and protection device with a cylindrical structure according to claim 1, characterized in that: The jet slit is strip-shaped, and the jet channel is round-hole-shaped.

3. A double-synthetic jet vibration damping and protection device with a cylindrical structure according to any one of claims 1-2, characterized in that: There are two jet channels, and the two jet channels are separately connected to the jet slits on each side.

4. The dual synthetic jet damping and protection device with a cylindrical structure according to claim 1, characterized in that: The servo motor rotates at a fixed frequency to drive the reciprocating motion of the piston, and the reciprocating motion of the piston generates symmetric double synthetic jets at each side of the jet slit.

5. A double-synthetic jet damping and protection device with a cylindrical structure according to claim 1, characterized in that: A plurality of double synthetic jet vibration damping and protection devices are evenly spaced near the flow separation points in the areas prone to wind-induced vibration in a longer cylindrical structure.

6. A double synthetic jet damping and protection device with a cylindrical structure according to claim 1, characterized in that: The jet velocity amplitude u of the dual synthetic jet vibration reduction and protection device arranged in the cylindrical structure sj The method is as follows: where w is the width of the jet slit, D is the diameter of the cylindrical structure, C μ is the dimensionless jet momentum coefficient, U0 is the average incoming flow velocity. In practical applications, first, according to the required wind-induced vibration suppression effect, determine the jet momentum coefficient C μ , and then obtain the jet velocity amplitude u sj .

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