Bernoulli theorem demonstration device

Abstract

The utility model belongs to the field of aircraft aerodynamics and flight mechanics teaching, and relates to a Bernoulli theorem demonstration device, which comprises a multi-tube pressure gauge, a hose, a Pitot tube, a fastening knob, an organic glass cavity, a contraction block, a ruler and a wind speed generation device, and is characterized in that the multi-tube pressure gauge is connected with the Pitot tube through the hose, and the Pitot tube is fixed on the fastening knob; the contraction block is fixed inside the organic glass cavity, the ruler is fixed on the side wall of the organic glass cavity, and the wind speed generating device is placed at an inlet of the organic glass cavity. By continuously adjusting the position of the Pitot tube in the organic glass cavity, the Bernoulli theorem is clearly and visually displayed to students by using the total pressure and static pressure liquid level height and change conditions displayed by the multi-tube pressure gauge, and meanwhile, a continuity equation can be demonstrated in an auxiliary manner by means of simple calculation, the theory and practice are combined, the teaching effect is improved, and the teaching efficiency is improved. And the device has the characteristics of convenience in observation, low cost, simplicity in operation, good portability and the like, and can well meet teaching requirements.

Description

Technical Field

[0001] This utility model belongs to the field of aircraft aerodynamics and flight mechanics teaching, and involves an important means of teaching and researching aircraft aerodynamics and flight mechanics—simulation demonstration, specifically involving a Bernoulli theorem demonstration device. Background Technology

[0002] Simulation demonstrations are an important teaching method to enhance trainees' intuitive and perceptual understanding. Simulation demonstrations involve realistically replicating physical objects. Due to objective limitations, classroom teaching for flight trainees cannot vividly describe some important phenomena that occur during actual flight, and watching videos lacks immersion. Individual experimental teaching or visits are difficult to guarantee in terms of both time and effectiveness. Simulation demonstrations, however, can combine important flight phenomena, concepts, and definitions with real-time classroom teaching. In the development of fluid mechanics, almost every theoretical breakthrough and its engineering application began with the demonstration and observation of flow phenomena. For example, the Reynolds transition experiment, the Mach shock wave experiment, Prandtl's introduction of the boundary layer concept in 1904, and von Kármán's analysis of vortex streets around cylinders in 1912—all were based on demonstrations.

[0003] There are several explanations for the principle of lift generation in aircraft, the most classic and widely accepted being the application of Bernoulli's theorem. Bernoulli's theorem states that for an ideal, incompressible, adiabatic fluid, the sum of static and dynamic pressures (total pressure) is equal at all cross-sections of the same flow tube. This means that static pressure is lower where the flow velocity is higher and higher where the flow velocity is lower. The unique cross-sectional shape of an aircraft wing determines that airflow velocity is higher over the upper surface and lower over the lower surface, creating a pressure difference between the upper and lower wing surfaces. The component of this total pressure difference perpendicular to the direction of the incoming flow is what we commonly know as lift. For beginners, understanding and mastering Bernoulli's theorem for the first time is challenging, but mastering it is fundamental to understanding the generation and variation of lift, and even aircraft control. A direct and intuitive understanding of Bernoulli's theorem is crucial. Traditional classroom teaching, however, often relies on video animations or theoretical explanations, making it difficult for students to gain a direct and intuitive understanding of Bernoulli's theorem.

[0004] Therefore, it is of great significance to design a Bernoulli theorem demonstration device that is practical, simple, convenient, easy to use, and effective. Utility Model Content

[0005] To address the contradictions and problems existing in traditional classroom teaching and to implement the concept of broad scope and solid foundation, this utility model proposes a Bernoulli theorem demonstration device. This device is not only suitable for classroom demonstration teaching, but also has important reference and practical value for popular science teaching.

[0006] This utility model discloses a Bernoulli's theorem demonstration device, comprising: a multi-tube manometer, a flexible hose, a Pitot tube, a fastening knob, an acrylic glass cavity, a shrinkage block, a ruler, and a wind speed generator. The multi-tube manometer is connected to the Pitot tube via the flexible hose. The Pitot tube is fixed to the fastening knob, and its movement is achieved by adjusting the tightness of the knob. The fastening knob is installed at the outlet of the acrylic glass cavity. The shrinkage block is fixed inside the acrylic glass cavity, the ruler is fixed to the side wall of the acrylic glass cavity, and the wind speed generator is placed at the inlet of the acrylic glass cavity. By continuously adjusting the position of the Pitot tube within the acrylic glass cavity, and utilizing the total pressure and static pressure level height and changes displayed by the multi-tube manometer, Bernoulli's theorem is clearly and intuitively presented to the trainees. This not only allows trainees to gain a deep understanding of Bernoulli's theorem but also effectively promotes their subsequent learning.

[0007] Preferably, the length of the Pitot tube is not less than 1.5 times the length of the acrylic cavity. The Pitot tube can measure the static pressure and total pressure of a fluid. Typically, the Pitot tube body is placed parallel to the incoming flow, and the total pressure orifice and static pressure orifice are connected through internal channels. The static pressure orifice outlet is perpendicular to the Pitot tube body. The fact that the Pitot tube length is not less than 1.5 times the length of the acrylic cavity helps to reduce or avoid the influence and interference of the static pressure orifice outlet on the airflow at the outlet of the acrylic cavity.

[0008] Preferably, the fastening knob is located at a distance of 0.1 to 0.2 times the length of the acrylic cavity outlet. If the airflow at the acrylic cavity outlet is obstructed, the airflow pressure inside the cavity will change, leading to a large error in the Pitot tube measurement results. Conversely, if the fastening knob fixing the Pitot tube is too far from the outlet, the rigidity of the connecting plate will decrease, resulting in greater deformation and making it difficult for the Pitot tube to be parallel with the axis of the acrylic cavity, also causing a large error. After repeated experiments and comparisons, it was found that when the fastening knob is located at 0.1 to 0.2 times the length of the acrylic cavity, the results displayed by the multi-tube manometer are accurate with very small errors.

[0009] Preferably, the shrinkage block, after being installed inside the plexiglass cavity, forms a flow channel that first contracts and then expands. Within the same flow channel, the change in the cross-sectional area of ​​the flow channel causes the static pressure of the fluid to change continuously. That is, dynamic pressure and static pressure can be converted into each other, but the total pressure remains constant. Therefore, to change the cross-sectional area of ​​the flow channel, the shrinkage block can be installed on the inner wall of the plexiglass cavity to create a constantly changing cross-sectional area of ​​the flow channel.

[0010] Preferably, the ruler is the same length as the acrylic cavity and is installed on the side wall of the acrylic cavity, with the 0 mark flush with the inlet end of the acrylic cavity. Installing the ruler on the side wall of the acrylic cavity makes it easy to determine the position of the Pitot tube, which not only allows for a visual demonstration of Bernoulli's theorem but also, combined with the flow channel cross-sectional area data, assists in demonstrating the continuity equation—achieving multiple benefits. However, if the ruler protrudes from the inlet of the acrylic cavity, it will affect the stability of the incoming flow. Therefore, to ensure the accuracy and reliability of the demonstration, the ruler must be flush with the inlet of the acrylic cavity.

[0011] Preferably, the wind speed generating device is a frequency converter. Frequency converters not only allow for demonstrations of Bernoulli's theorem at various wind speeds but are also energy-efficient and reliable. Specifically, the wind speed generating device is a miniature axial flow fan or a miniature centrifugal fan. Using a small or miniature axial flow fan or a miniature centrifugal fan effectively reduces costs and also considers portability when used as a teaching aid. Of course, electric fans or other wind speed generating devices can also be used.

[0012] This invention provides a Bernoulli's theorem demonstration device. By continuously adjusting the position of the Pitot tube within the plexiglass cavity and utilizing a multi-tube manometer to display the total pressure and static pressure levels and their changes, Bernoulli's theorem is clearly and intuitively presented to students. This not only allows students to gain a deep understanding of Bernoulli's theorem but also assists in demonstrating the continuity equation through simple calculations. Furthermore, it effectively promotes the learning of subsequent knowledge, combining theory and practice to enhance teaching effectiveness. This device effectively demonstrates Bernoulli's theorem and the continuity equation, and features convenient observation, excellent demonstration results, low cost, simple operation, and good portability, thus well meeting teaching requirements. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the Bernoulli theorem demonstration device of this utility model. Detailed Implementation

[0014] The specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0015] Example 1

[0016] This embodiment of a Bernoulli theorem demonstration device is characterized by comprising: a multi-tube pressure gauge 1, a flexible tube 2, a Pitot tube 3, a fastening knob 4, an acrylic cavity 5, a shrink block 6, a ruler 7, and a wind speed generator 8. The multi-tube pressure gauge 1 is connected to the Pitot tube 3 via the flexible tube 2. The Pitot tube 3 is fixed to the fastening knob 4. The movement of the Pitot tube 3 is achieved by adjusting the tightness of the fastening knob 4. The fastening knob 4 is installed at the outlet position of the acrylic cavity 5. The shrink block 6 is fixed inside the acrylic cavity 5. The ruler 7 is fixed to the side wall of the acrylic cavity 5. The wind speed generator 8 is placed at the inlet position of the acrylic cavity 5.

[0017] During the demonstration, pour sufficient water or colored solution into the solution container of the multi-tube manometer 1. After the liquid levels in each tube stabilize, connect the total pressure and static pressure interfaces of the Pitot tube 3 to the hose 2. Then connect the hose 2 to any two tubes of the multi-tube manometer 1. Secure the shrink block to the lower or upper wall of the acrylic cavity 5. Loosen the fastening knob 4 and slowly move the head of the Pitot tube 3 to the 0 mark on the ruler inside the acrylic cavity 5. Tighten the fastening knob 4 to fix the Pitot tube 3. Then turn on the power of the wind speed generator 8, set it to operating mode, adjust the wind speed, and fix a certain frequency. After the wind speed stabilizes, observe the total pressure and static pressure liquid level height of the multi-tube manometer 1 (the lower liquid level is the total pressure, and the higher liquid level is the static pressure) and record the corresponding positions. Loosen and tighten knob 4, gradually moving the Pitot tube 3 outwards at intervals (e.g., 30mm). When it reaches the corresponding position, tighten knob 4, record the position data of the Pitot tube 3, and read and record the liquid level heights of the total pressure pipe and static pressure pipe. Then loosen knob 4 again, move the Pitot tube 3 to a certain position, and record the corresponding position and the total and static pressure liquid level heights. Repeat this process until the Pitot tube 3 is removed from the acrylic glass cavity 5. Throughout the demonstration, regardless of the position of the Pitot tube 3 inside the acrylic glass cavity 5, the static pressure liquid level height will continuously change with the movement of the Pitot tube 3, but the total pressure liquid level height will remain constant (due to extremely small fluctuations in error). This effectively demonstrates Bernoulli's theorem to the students. After obtaining relevant data on the inner wall dimensions or flow channel cross-sectional area of ​​the acrylic glass cavity 5, it can also assist students in demonstrating the continuity equation. The intuitive phenomena and data demonstrations help students better understand the abstract Bernoulli's theorem and the continuity equation, thus laying a solid foundation for learning subsequent aeronautical theory.

[0018] Finally, it should be noted that the above description is only a preferred embodiment of this utility model and is not intended to limit this utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A device for demonstrating Bernoulli's theorem, characterized in that The utility model relates to a kind of wind speed measurement device, including: Multi-tube pressure gauge (1), hose (2), pitot tube (3), fastening knob (4), plexiglass cavity (5), shrink block (6), ruler (7), wind speed generating device (8), the multi-tube pressure gauge (1) is connected with pitot tube (3) by hose (2), pitot tube (3) is fixed on fastening knob (4), the tightness of fastening knob (4) is adjusted to realize the movement of pitot tube (3), fastening knob (4) is installed at the outlet position of plexiglass cavity (5), shrink block (6) is fixed inside plexiglass cavity (5), ruler (7) is fixed in plexiglass cavity (5) side wall, wind speed generating device (8) is placed at the inlet position of plexiglass cavity (5).

2. A device for demonstrating Bernoulli's theorem as claimed in claim 1, characterized in that The pitot tube (3) is not less than 1.5 times the length of the plexiglass cavity (5).

3. A device for demonstrating Bernoulli's theorem as claimed in claim 1 or 2, characterized in that The fastening knob (4) is located at 0.1-0.2 times the length of the plexiglass cavity (5) from the outlet of the plexiglass cavity (5).

4. A demonstration of Bernoulli's theorem as claimed in claim 1, characterized in that, The shrink block (6) is installed inside the plexiglass cavity (5) to form a flow channel that first shrinks and then expands.

5. A demonstration of Bernoulli's theorem as claimed in claim 1, characterized in that, The ruler (7) has the same length as the plexiglass cavity (5) and is installed on the side wall of the plexiglass cavity (5), and the 0 scale is flush with the inlet end of the plexiglass cavity (5).

6. A demonstration of Bernoulli's theorem as claimed in claim 1 or 4, characterized in that, The wind speed generating device (8) is frequency-regulated.

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