Thin vortex ring generation system and method based on sawtooth wave electric signal and loudspeaker
By using a thin vortex ring generation system based on sawtooth wave electrical signals and a moving coil loudspeaker, the problems of controlling vortex ring thickness and stability were solved, and a thin vortex ring with stable propagation under low energy consumption was realized, improving the continuity and stability of the vortex ring.
Patent Information
- Application Number
- CN202510859664.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-25
- Publication Date
- 2025-09-19
AI Technical Summary
Existing vortex ring generation systems have difficulty precisely controlling the thickness, stability, and repeatability of vortex rings, which limits the effectiveness of thin vortex rings in precision experiments and specific application scenarios.
A thin vortex ring generation system based on sawtooth wave electrical signals and a moving coil loudspeaker is adopted, including a signal generation module, a power amplification module, a pneumatic drive module, and a vortex ring generation module. By generating and adjusting the sawtooth wave electrical signals, the initial travel speed, thickness, and propagation stability of the vortex ring are controlled.
A thin gas vortex ring with stable propagation was generated with low energy consumption. The ratio of vortex ring core diameter to ring diameter was less than 0.3, and the size change during the journey was small, which improved the continuity and stability of the vortex ring.
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Figure CN120676305A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of fluid mechanics, and in particular relates to a thin vortex ring generation system based on a sawtooth wave electrical signal and a loudspeaker and a method thereof. Background Art
[0002] In the field of fluid mechanics, vortex rings, as a special flow structure, have attracted widespread attention due to their unique physical properties and potential application value. Vortex rings are closed ring-shaped structures formed by the rotational motion of a fluid. The fluid inside them rotates at high speed along a circular path while simultaneously propelling the fluid forward. This phenomenon not only occurs in natural environments, such as smoke rings, but also plays an important role in engineering applications, such as aerodynamic research, gas mixing, and propulsion systems. Traditional vortex ring generation systems typically rely on mechanical methods or airflow injection to generate vortex rings. These methods are mostly used to produce thick vortex rings with large impulse and momentum. However, in some specific vortex ring experimental research and engineering applications, there is a higher demand for stable, thin vortex rings. Existing technical methods for generating thin vortex rings have many problems, such as difficulty in accurately controlling the vortex ring's thickness, stability, and repeatability. This significantly limits the effectiveness of vortex rings in precision experiments and specific application scenarios. Therefore, improvements are needed to achieve high-precision control of the characteristics of thin vortex rings and promote the development of related fields.
[0003] To this end, the present invention proposes a thin vortex ring generation system and method based on a sawtooth wave electrical signal and a loudspeaker. Summary of the Invention
[0004] To address these shortcomings of the existing technology, this paper, based on extensive theoretical and experimental research on vortex rings, proposes a novel, user-friendly and adaptable thin-film gas vortex ring generation system using sawtooth wave electrical signals and a dynamic loudspeaker. This system is easy to operate and can generate stable, propagating thin-film gas vortex rings with low energy consumption.
[0005] In order to achieve the above objectives, the present invention adopts the following technical solutions: a thin vortex ring generation system based on a sawtooth wave electrical signal and a speaker, comprising: A signal generating module is used to generate a sawtooth wave electrical signal with a duty cycle of 0% or 100% and a frequency range of 0.1 to 2 Hz; A power amplifier module, connected to the signal generating module, for amplifying the sawtooth wave electrical signal by 2 to 10 times; a pneumatic drive module including a dynamic loudspeaker whose diaphragm generates periodic vibrations in response to an amplified sawtooth wave electrical signal; The vortex ring generating module comprises a cylindrical chamber and a vortex ring nozzle, wherein two ends of the cylindrical chamber are sealedly connected to the dynamic loudspeaker and the vortex ring nozzle respectively.
[0006] Preferably, the vortex ring nozzle is a sudden-contraction nozzle, and the diameter of the sudden-contraction nozzle is between 1 / 4 and 1 / 2 of the inner diameter of the cylindrical chamber.
[0007] Preferably, the diaphragm diameter of the dynamic speaker is equal to the inner diameter of the cylindrical chamber, and the two ends of the cylindrical chamber are sealedly connected to the dynamic speaker and the vortex ring nozzle through flanges, and the flange material is PP or PVC.
[0008] Preferably, the power amplification module is a linear power amplifier, and signal transmission adopts a BNC interface connection.
[0009] Preferably, the signal generating module adopts a signal generator, and the amplitude of the sawtooth wave electrical signal is adjustable, which is used to control the vibration amplitude of the diaphragm to adjust the initial travel speed of the vortex ring.
[0010] Preferably, the diaphragm vibrates and squeezes the gas in the chamber to be ejected through the vortex ring nozzle to form a thin vortex ring with a ratio of vortex core diameter to vortex ring diameter less than 0.5, and the stable propagation distance of the vortex ring is not less than 30 times its own diameter.
[0011] On the other hand, the present invention proposes a method for generating a thin vortex ring based on the system, comprising: Generates a fixed frequency sawtooth wave electrical signal with a duty cycle of 0% or 100% and a frequency of 0.1~2 Hz; amplifying the sawtooth wave electrical signal by 2 to 10 times and then inputting the signal into a dynamic loudspeaker; The electrical signal is converted into periodic mechanical vibration through the speaker diaphragm, squeezing the gas in the cylindrical chamber; When the gas is ejected from the sudden-converging nozzle, it is subjected to shear force to form a thin vortex ring, and the ratio of the vortex core diameter to the vortex ring diameter is less than 0.5.
[0012] Preferably, the dimensionless formation time of the vortex ring is express:
[0013] in, is the vibration speed of the speaker diaphragm, is the diaphragm vibration time, and are the inner diameter of the vortex ring outlet and the inner diameter of the cylindrical chamber respectively.
[0014] Preferably, the diameter of the sudden contraction nozzle is The selection satisfies: When the Reynolds number When lowering, use a larger To reduce the thickness of the vortex ring; where R is the vortex ring radius, is the air viscosity at 25°C, is the initial maximum rotation speed of the vortex ring.
[0015] Preferably, the initial travel speed, thickness and propagation stability of the vortex ring are controlled by synchronously adjusting the amplitude, frequency and power amplification factor of the sawtooth wave signal.
[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The electrical signal amplitude used to drive the speaker is relatively small. Compared to mechanical piston and compressed air power systems, this invention can generate a stably propagating vortex ring using lower energy. The core diameter / ring diameter of the vortex ring is less than 0.3, representing a standard thin vortex ring with minimal dimensional change during propulsion. 2. The diaphragm vibration speed and frequency of the present invention are relatively high, and can continuously generate gas vortex rings with a relatively fast travel speed in a short period of time. By adjusting the signal generator, the diaphragm vibration speed and time, and the emission frequency of the vortex ring can be changed, and the thickness, travel speed, generation frequency and other parameters of the generated vortex ring can be accurately controlled, thereby improving the continuity and stability of the generation of thin gas vortex rings. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 This is a complete schematic diagram of the vortex ring generation system proposed in the present invention.
[0018] Figure 2 This is a diagram of the speed and size changes of the vortex ring generated by the system in Example 1.
[0019] Figure 3 This is a diagram of the speed and size changes of the vortex ring generated by the system in Example 2.
[0020] Figure 4 This is a graph showing how the thickness of the vortex ring generated by the system in Example 2 changes with the outlet diameter and Reynolds number.
[0021] Legend: 1-Function signal generator; 2-BNC adapter cable; 3-Power amplifier; 4-Dynamic speaker; 5-Cylindrical chamber; 6-Connecting flange; 7-Vortex ring nozzle; 8-Gas vortex ring. DETAILED DESCRIPTION
[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0023] Reference Figure 1 , Figure 1Figure 1 is a schematic diagram of a thin gas vortex ring generation system. The thin vortex ring generation system based on a sawtooth wave electrical signal and a speaker in an embodiment of the present invention includes a function signal generator 1, a BNC adapter cable 2, a power amplifier 3, a dynamic speaker 4, a cylindrical chamber 5, a connecting flange 6, and a vortex ring nozzle 7. The function signal generator 1, power amplifier 3, and dynamic speaker 4 are connected via a BNC adapter cable 2.
[0024] Furthermore, both left and right ends of the cylindrical chamber 5 are connected to the speaker 4 and the nozzle 7 via connecting flanges 6 .
[0025] Furthermore, the vortex ring outlet 7 is a replaceable component, and its diameter is between 1 / 4 and 1 / 2 of the inner diameter of the cylindrical chamber 5 .
[0026] The stable generation and propagation of a gas vortex ring is achieved using a thin vortex ring generation system based on a sawtooth wave electrical signal and a speaker, including the following steps: 1) Generate a fixed-frequency sawtooth wave electrical signal using a function signal generator 1. The duty cycle should be set to 0% or 100%, the frequency should be set between 0.1 and 2 Hz, and the amplitude should be appropriately adjusted based on the amplification factor of the power amplifier 3 and the maximum input power of the dynamic speaker 4. 2) The sawtooth wave signal generated by the function signal generator 1 needs to be amplified by the power amplifier 3, and its amplification factor is preferably 2 to 10 times; 3) After the amplified sawtooth wave signal enters the dynamic speaker 4, it is converted into periodic vibration of the speaker diaphragm. The vibration frequency is the same as the generation frequency of the sawtooth wave signal, and the vibration amplitude is adjusted by the amplitude of the signal generator 1; 4) The vibration of the speaker diaphragm causes the gas in the cylindrical chamber 5 to move toward the vortex ring outlet 7, where a gas vortex ring is formed due to shear force. After leaving the outlet, the vortex ring will perform stable linear motion along the axial direction of the cylindrical chamber. The vortex core of the vortex ring will continue to rotate and draw in the surrounding gas.
[0027] It should be made clear that in the field of fluid mechanics, the thickness of the vortex ring is usually described by the ratio of the thickness of the vortex ring to its diameter, that is:
[0028] in, It is usually called the boundary layer thickness ratio or vortex ring thickness ratio, where r and R are the thickness of the vortex ring (vortex core diameter) and the diameter of the vortex ring, respectively. When the ratio is close to 0, the vortex ring is considered thin, and when the ratio is close to 1, the vortex ring is considered thick. The thickness ratio of the vortex ring generated in the embodiment of the present system is always lower than 0.3 during its propagation, which is a standard thin vortex ring.
[0029] Furthermore, it must be clarified that a sawtooth wave is a non-sinusoidal waveform characterized by a linear rise or fall in time (depending on the direction of the waveform) followed by an abrupt change in direction. The speaker mechanically moves in response to the received sawtooth signal, moving its diaphragm and instantly changing direction when the sawtooth wave reaches its apex. This characteristic favors the generation of vortex rings, and due to the design limitations of the speaker, its vibration amplitude is relatively limited, making it easy to generate thin vortex rings with a small thickness. The vortex ring parameters generated by this system can be expressed using the dimensionless formation time T* of the vortex ring: ; in, is the vibration speed of the speaker diaphragm, is the diaphragm vibration time, and are the inner diameter of the vortex ring outlet and the inner diameter of the cylindrical chamber respectively. When T* is fixed, a larger value means a greater amount of gas is pushed into the cylindrical chamber, and the resulting vortex ring is thicker. When T* reaches a certain value, the gas in the chamber no longer contributes to the formation of the vortex ring, but instead becomes a wake, a phenomenon known as vortex ring pinching. Therefore, T* can be used to adjust the parameters of the sawtooth signal and the dimensions of the cylindrical chamber to determine the specific dimensions and parameter design of the vortex ring generation system.
[0030] The following two specific embodiments are used to describe the effects of the present invention in detail.
[0031] Example 1:
[0032] In this embodiment, the overall structure of the vortex ring generating system is shown in the attached figure. Figure 1As shown, the gas medium used to form the vortex ring is air, the ambient temperature is 24°C, and the humidity is 65%. Signal generator 1 is a DG1062Z dual-channel function / arbitrary waveform generator capable of generating extremely low-frequency sawtooth signals with an input voltage of 220 V. Power amplifier 2 is a T5-class 600 W power amplifier with an input voltage of 220 V. Speaker 3 is a large 15-inch speaker with a 220mm magnetic 100mm core and a 4-ohm 1000W cast aluminum cone. The cylindrical chamber designed in this embodiment is 0.3 m long, with an inner diameter of 0.34 m, and a vortex ring outlet diameter of 0.12 m. The speaker amplitude is adjusted to 9 V, the amplification factor is 6x, and the frequency is 0.3 Hz. Under these conditions, the speaker diaphragm displacement velocity is 0.4 m / s, the single displacement time is 0.025 s, and the air displacement of a single vibration is approximately 0.9 L. The dimensionless formation time T* of the vortex ring is approximately 0.67. Generally, when T* is less than 3, the piston gas output will be mainly used to form the vortex ring body. The smaller the T* value, the smaller the influence range of the wake flow, making it easier to produce a stable thin gas vortex ring. The power consumption of the vortex ring generation system in this embodiment is about 40 W.
[0033] like Figure 2 As shown, Figure 2 Figure 2 shows the variation of air vortex ring velocity and size parameters with travel distance: (a) travel speed; (b) vortex ring diameter; (c) vortex core diameter; (d) diameter ratio. In this embodiment, the generated air vortex ring can stably propagate for approximately 3 m. Based on the initial vortex ring size, its travel distance is approximately 30 times the initial vortex ring diameter. Because the tracer smoke gradually fades and is difficult to calibrate, only the air vortex ring within a travel distance of 1.5 m is calibrated and measured. The obtained velocity and size parameter results are shown in Figure 2. Figure 3 Figure 3 shows the changes in the speed and size parameters of the air vortex ring (reduced size) with the travel distance: (a) travel speed; (b) vortex ring diameter; (c) vortex core diameter; (d) diameter ratio; First, Figure 3 In figure a, the air vortex ring forms at the exit with an initial velocity of approximately 3.2 m / s, which then decreases linearly as it travels. By the time it reaches a distance of 1.5 m, the velocity has slowed by only about 50%, with no sudden drop in velocity due to dissipation. Figure 3 In bd, as the vortex core entrains more air during its movement, the vortex ring diameter, the vortex core diameter, and the ratio of the two diameters gradually increase. Generally, a sudden change in the vortex ring size indicates that the vortex ring structure is no longer stable and will dissipate instantly within a very short period of time. However, in this embodiment, the vortex ring increases in size relatively slowly during its stable movement, preventing significant changes due to interference from ambient airflow, demonstrating superior stability.
[0034] Example 2:
[0035] In this embodiment, the overall structure of the vortex ring generating system is also as shown in the attached Figure 1 As shown, the overall size of the system has been reduced to produce a relatively small and thin vortex ring. Signal generator 1 was changed to a JDS2900 fully digitally controlled dual-channel DDS function signal generator with an input voltage of 5V; power amplifier 2 was changed to a DPA1698 dual-channel DDS function signal power amplifier with an input voltage of 12V; speaker 3 was changed to a small speaker with a 3-inch 60-magnet 4-ohm 15-watt PU basin; the remaining components were adjusted accordingly, with the dimensions of the cylindrical chamber being 5 cm long, 6 cm inner diameter, and the vortex ring outlet diameter being 3 cm. The signal amplitude was set to 3.5V and the amplification factor was 2 times. At this time, the single displacement velocity of the speaker diaphragm was about 0.7 m / s, and the displacement time was 0.005 s. From this, the dimensionless formation time T of the vortex ring can be calculated. * It is about 0.5, which meets the conditions for vortex ring generation.
[0036] In this embodiment, the generated air vortex ring can travel a distance of about 80 to 10 cm, which is about 30 times the outlet diameter. Also, because the smoke becomes thinner and difficult to calibrate, the size and speed are only measured within a range of about 30 cm after the vortex ring is formed. The changes in the air vortex ring's travel speed, vortex ring diameter, vortex core diameter, vortex ring thickness, etc. with the travel distance are shown in the attached figure. Figure 3 As shown. The vortex ring diameter, vortex core diameter and vortex ring thickness will also gradually increase with the entrainment of the vortex ring during its movement. When the local thickness of the vortex ring increases, that is, the amount of air entrained in a certain part of the vortex ring suddenly increases, it will cause the vortex ring movement trajectory to deviate and dissipate in advance. For example, when the thickness of the bottom of the vortex ring becomes larger, its local rotation speed decreases, making the movement speed above the vortex ring greater than that below, and eventually causing the vortex ring trajectory to move upward. When the speed difference is too large, the overall structure of the vortex ring is torn, and the rotating airflow is eventually dissipated. Since the vortex core of a thin vortex ring is smaller than the overall size of the vortex ring, and the strength of a thin vortex ring is generally weaker than that of a thick vortex ring, it is more susceptible to external interference and deflection and dissipation during movement. In this embodiment, Figure 3 The change of travel speed in a and Figure 3 The dimensional changes in bd are relatively stable, with dimensional errors within 6%. This demonstrates that the thin air vortex rings generated by this system can propagate stably in an air environment, with minimal individual differences between the generated vortex rings, and no individual vortex rings will dissipate prematurely or deviate from their direction of travel.
[0037] In order to further explore the influence of vortex ring generation strength and vortex ring initial size on vortex ring thickness, in this embodiment, the vortex ring thickness is also compared with the Reynolds number ( ) and the changes in the outlet diameter. First, the vortex ring Reynolds number is calculated as: ; Where R is the vortex ring radius, is the air viscosity at 25°C, is the initial maximum rotation speed of the vortex ring, which is calculated as follows: ; in, is the volume of gas pushed by the speaker diaphragm in one time, is the time of a single vibration of the diaphragm, is the vortex ring outlet diameter. The test results are as follows Figure 4 As shown, it can be seen that the smaller the outlet diameter of the vortex ring generating system, the thicker the vortex ring. This is because the amount of gas pushed by the speaker diaphragm when it vibrates is the same. When the outlet diameter is smaller, the gas will gather locally at the outlet and rotate outward, resulting in a larger velocity gradient at the outlet edge (because the flow velocity is higher at the same flow rate), that is, the vorticity in the shear layer is more concentrated. According to Kelvin's theorem, vorticity is conserved in ideal fluids. Highly concentrated vorticity will form a thicker vortex core, which is manifested as an increase in the thickness of the vortex ring. In addition, the wall area of the small diameter outlet is relatively larger (relative to the gas volume), and the influence of the viscous boundary layer is more significant. The friction between the fluid and the wall will slow down the edge flow velocity, causing the shear layer to curl earlier and form a thicker vortex ring structure. This is especially obvious at low Reynolds numbers. Therefore, Figure 4 In the figure, when the vortex ring Reynolds number is relatively small, different outlet diameters will cause a large difference in vortex ring thickness. However, when the Reynolds number increases, this difference gradually decreases and no longer changes due to the pinching phenomenon of the vortex ring.
[0038] The above two embodiments demonstrate that the thin gas vortex ring generation system described in the present invention can generate a thin vortex ring that propagates stably, and its thickness is related to the parameters and dimensions of the vortex ring generation system. It should be noted that the system dimensions in the above embodiments are only examples. The thin gas vortex ring generation method described in the present invention is applicable to generation systems of different sizes. The dimensions of the cylindrical chamber and the vortex ring outlet can be adjusted according to actual needs to generate gas vortex rings of different sizes. At the same time, when the system size parameters are fixed, the amplitude and frequency of the signal generator, as well as the amplification factor of the power amplifier, can be adjusted to generate thin gas vortex rings of different intensities, different emission frequencies, and different initial travel speeds.
Claims
1. A thin vortex ring generation system based on sawtooth wave electrical signal and speaker, characterized in that: include: A signal generating module is used to generate a sawtooth wave electrical signal with a duty cycle of 0% or 100% and a frequency range of 0.1 to 2 Hz; A power amplifier module, connected to the signal generating module, for amplifying the sawtooth wave electrical signal by 2 to 10 times; a pneumatic drive module including a dynamic loudspeaker whose diaphragm generates periodic vibrations in response to an amplified sawtooth wave electrical signal; The vortex ring generating module comprises a cylindrical chamber and a vortex ring nozzle, wherein two ends of the cylindrical chamber are respectively sealedly connected to the dynamic loudspeaker and the vortex ring nozzle.
2. A thin vortex ring generating system based on sawtooth wave electrical signal and speaker according to claim 1, characterized in that: The vortex ring nozzle is a sudden contraction nozzle, and the diameter of the sudden contraction nozzle is between 1 / 4 and 1 / 2 of the inner diameter of the cylindrical chamber.
3. A thin vortex ring generating system based on sawtooth wave electrical signal and speaker according to claim 2, characterized in that: The diaphragm diameter of the dynamic loudspeaker is equal to the inner diameter of the cylindrical chamber. The two ends of the cylindrical chamber are sealed and connected to the dynamic loudspeaker and the vortex ring nozzle through flanges. The flange material is PP or PVC.
4. A thin vortex ring generating system based on sawtooth wave electrical signal and speaker according to claim 3, characterized in that: The power amplifier module is a linear power amplifier, and signal transmission adopts BNC interface connection.
5. The thin vortex ring generation system based on sawtooth wave electrical signal and speaker according to claim 1 is characterized in that: The signal generating module adopts a signal generator, and the amplitude of the sawtooth wave electrical signal is adjustable, which is used to control the vibration amplitude of the diaphragm to adjust the initial travel speed of the vortex ring.
6. The thin vortex ring generation system based on sawtooth wave electrical signal and speaker according to claim 1, characterized in that: The diaphragm vibrates and squeezes the gas in the chamber to be ejected through the vortex ring nozzle, forming a thin vortex ring with a ratio of vortex core diameter to vortex ring diameter less than 0.5, and the stable propagation distance of the vortex ring is not less than 30 times its own diameter.
7. A method for generating a thin vortex ring based on the system according to any one of claims 1 to 6, characterized in that: include: Generates a fixed frequency sawtooth wave electrical signal with a duty cycle of 0% or 100% and a frequency of 0.1~2 Hz; amplifying the sawtooth wave electrical signal by 2 to 10 times and then inputting the signal into a dynamic loudspeaker; The electrical signal is converted into periodic mechanical vibration through the speaker diaphragm, squeezing the gas in the cylindrical chamber; When the gas is ejected from the sudden-converging nozzle, it is subjected to shear force to form a thin vortex ring, and the ratio of the vortex core diameter to the vortex ring diameter is less than 0.
5.
8. The method according to claim 7, characterized in that The dimensionless formation time of the vortex ring express: ； in, is the vibration speed of the speaker diaphragm, is the diaphragm vibration time, and are the inner diameter of the vortex ring outlet and the inner diameter of the cylindrical chamber respectively.
9. The method according to claim 7, characterized in that The diameter of the sudden contraction nozzle The selection satisfies: When the Reynolds number When lowering, use a larger To reduce the thickness of the vortex ring; where R is the vortex ring radius, is the air viscosity at 25°C, is the initial maximum rotation speed of the vortex ring.
10. The method according to claim 7, characterized in that By synchronously adjusting the amplitude, frequency and power amplification factor of the sawtooth wave signal, the initial travel speed, thickness and propagation stability of the vortex ring are controlled.