金字塔附近的流體力學效應
陸地上的金字塔無時無刻沒有受到氣體的包覆，這個實驗透過風洞模擬金字塔模型，在流體中的壓力變化，並藉由煙線來觀察流體的移動情形，可具體看到當流體經過物體週遭時流場的改變。經由測量壓力，可更深入的探討風速與壓力的關係。在實驗中，可發現當流體迎面而來，在金字塔後方形成的流場變化中，以渦流最易觀察；且透過壓力的測量，發現模型的前、後方，會有明顯的壓差，會對模型造成力矩，可能會使金字塔結構不穩定。越往金字塔上方壓差越小，因此其受阻力所產生的合力矩應較同底面積、同高的長方體小，故金字塔可以長久在沙漠中屹立不搖。此外，流體流過模型兩側會產生分離的情況，分離點的位置會影響渦流區的大小；一般而言，分離點發生在物體的越後方，尾流的尺寸越小，壓差所造成的阻力越低，實驗中發現流速對分離點的位置影響不大，金字塔的擺放形狀卻會對分離點的位置產生明顯的影響，所以越流線型的物體，其受到壓差所產生的阻力越小。希望透過以上的研究，能夠對金字塔周圍複雜的流場有更深入的了解。The pyramid on land is constantly surrounded by gas. Using the wind tunnel, we can investigate the distribution of pressure surrounding the model of pyramid; furthermore, we can discuss about the relationship between pressure and wind velocity. In addition, with the smoke wire, we can visually observe the dynamic flow filed. In our experiment, we discovered that when fluid comes, there will be obvious difference of pressure between the front and the back of the pyramidal model, causing a torque to the model. At higher parts of the model, there is less difference of the pressure, so the resulting torques of a pyramid should be less than that of a cuboid. Therefore, a pyramid can stand in the desert for a long time. Besides, when the fluid flows through the two sides of the model, it will separate, and the position of the separation points will influence the size of the turbulence area. Generally speaking, the farther the separation points are to the back, the smaller the size of the turbulence area, and the less the drag caused by the difference of pressure. With the study above, I expect to have more understanding about the complex flow field of pyramid.
Inverter
PURPOSE: The purpose of making an Inverter which gets charged with the help of sound energy, produced by speakers for instance, and regenerative shock absorbers which are used in cars so that we can easily charge the inverter with the help of sources which we use in daily life. PROCEDURE: The regenerative shock absorbers are capable of generating electricity when a car moves over bumps. It works by hydraulic fluid passing through a turbine. When the fluid passes through turbine, the turbine turns a small generator and more power is created. A piston is disposed for reciprocating motion within a cylinder as a vehicle’s suspension system deflects. Hydraulic fluid passes through a hydraulic motor to turn its shaft. The hydraulic motor shaft is connected to an electric generator to generate electricity. The second source of energy to charge the inverter is by the help of sound produced in day to day life. Some piezoelectric sensors attached to the board as soon there is a tap or any kind of vibration on the board these and convert them to electrical signals. This means that parasitic energy of busy roads, railroads, footpaths and runways near population centers can be converted into electrical energy that can run public lighting, or fed back into the grid. DATA: The data which have been collected with some experiments is that on an average piezoelectric can produce 330W of power. • When sound pressure is around 62 dB, the frequency is of 102 Hz. • Sound pressure is of 65 dB the frequency is of 500 Hz. Another case when the regenerative shock absorbers come in contact with the piston it produces an average power of 340W-350W. CONCLUSION: With the use age of piezoelectric sensors and regenerative shock absorbers we can produce electricity at a very low cost for inverters; these inverters can provide electrical supplies to the house. The most important reason to make such kind of innovation is one because it is money efficient, second this can come in handy for those who can’t afford to buy inverters at a very high cost and then when charging these inverter these people have to use their electrical supply!
甩毛巾與音爆
在網路上看到甩毛巾、皮鞭的影片，會產生巨大的聲響，查找了資料，我們知道當發聲體超過音速時便會產生音爆。部分文獻提到，毛巾或皮鞭生成音爆原因是來自於角動量守衡理論，我們想利用實驗方法來驗證其正確性，因此利用video point 來分析影片討論手的加速度和毛巾末端質量、長度的關係，並用crocodile physics 做電腦模擬，我們發現毛巾長度與音爆產生無關，這樣和角動量理論模型有所不同。所以我們嘗試利用能量守恆及自由端反射駐波理論來解釋毛巾產生音爆關係，並利用影片分析及crocodile physics 驗證其正確性。We saw the film clippings on the Internet about snapping towels and whips, which made a big noise. After going through related literature, we found out that it is called the sonic boom .Some papers say that the sonic boom results from the Location momentum conservation theory. To prove its accuracy, we used a kind of computer software called Video Point to analyze in the clippings the movement of the hand, understanding the relationship between the mass of the towel end and the length of the towel. We also used another software called Crocodile Physics to simulate the whole process. We discovered that there is no connection between the length of the towel and the sonic boom. It does not conform to the Location momentum conservation theory. We then in turn employed energy conservation theory and the trait of the standing wave (specific wave length) to explain, when we also used Video Point and Crocodile Physics to prove.
口琴簧片振動與氣流的影響
本研究主題在測量口琴簧片受到各種氣流因子影響後，所產生音色、音頻等變化之探討。在過去我們認為，一片簧片不論如何吹奏，其發出的頻率皆相同。但是事實上，演奏家控制氣流的強弱、方向、渦流等，便可吹奏出多樣的音頻。探討形狀因子對簧片頻率的影響，如：長度、寬度、厚度對頻率所造成的影響。自製口琴，利用變壓器控制送風機風速。探討氣流因子對簧片主頻之影響，利用各種不同的自製吹嘴，改變風速、角度、渦流…等，找出可能使簧片改變頻率的氣流因素。實驗結果發現改變風速會影響簧片主頻的變化，風速越大，頻率越大，為一條平滑線。但並非一直都會上升，當簧片頻率上升至某一極限，便無法再利用風速使頻率上升。例如實驗四吸音標準狀態下，風速大於8 Kt 後，頻率一直停在429Hz。在外加障礙物時(模擬吹奏舌頭時隆起)和標準狀態(正常零度入射)下頻率比較吹音和吸音有明顯的差異。吹音時，同風速下，其頻率比標準狀態高，發生音升；吸音時，同風速下，其頻率比標準狀態低，發生音降，具應用性。我們發現在頻率改變時，簧片的振動型態會有所不同，所以利用高畫素像機拍攝和電腦相位差算出簧片之曲折點至尾端的距離，發現頻率和簧片之曲折點至尾端的距離成正向關係。如實驗五中頻率從414 至419Hz，簧片的曲折點到振動端距離也明顯變大。我們發現吹嘴和口琴只要稍有一點空隙(大約在0.2cm 左右)，便會和完全吻合時有顯著的頻率差距(吻合後大約比有空隙低20Hz 左右)，此實驗頻率變化現象和現實壓音頻率變化極為相近。實驗過程中發現，改變簧片吹嘴的吻合程度，吹入口琴的風速相近，但頻率變化卻也有壓音的音頻變化。在實驗三加入各種氣流因子發現入射角度和標準情形差異不明顯，因此推論壓音的頻率變化和風力強度、入射角度關係不大，壓音主要為渦流所造成的現象。簧片振動模式改變，導致簧片振動頻率發生變化，且簧片的自然頻率不變。當壓音產生時，氣流在振動面造成妨礙簧片振動的抗力，但琴格內部同時也給簧片的風壓，使簧片產生一種非自然振動的頻率。The theme of the research is to explore the changes on its timbre and frequency after the harmonica reed is influenced by each kind of air current factor .In the past ,most people think no matter how to play the reed ,the frequency it produced was supposed to be the same. But in fact the frequency will be changeable under different direction, turbulent flow and air intension by the perform. First to explore the basic feature of harmonica reed, for example: The length, the width, thickness cause the influence on the frequency. To make the self-made harmonica, using the transformer control air feeder wind speed. To discussion the influenced caused by air current factors,and use each kind of different self-restraint to boast, change the wind speed, angle, turbulent flow ,in order to discover possible factors the reed causes to change the frequency of the air current factor. The experimental result discovered the change of wind speed can affect the change of basic frequency , the stronger speed cause the bigger frequency, It will be a curve. But it will not be rising continuously, when the reed frequency rise to some limit, it is unable to cause the frequency rise again by using the wind speed. For example experiment four sound absorption standard conditions, after the wind speed is higher than 8 Kt, the frequency continuously stops in 429Hz. To compare obstacle (simulation plays when tongue sticks out) and the standard condition (normal zero degree incidence) , comparison blows the sound agreement sound absorption to have the obvious difference. When blows the sound, under the same wind speed, its frequency is higher than the standard condition, has the sound to rise; When sound absorption, under the same wind speed, its frequency is lower than the standard condition, has the sound to fall. The harmonica terminology for presses the sound, extremely has the application. We discovered when frequency change, the reed vibration condition have differently, therefore use the camera photography and the computer phase different figures out the reed winding point to the end distance, discovered the frequency and the reed winding point relate to end distance is being connected. If tests five medium frequencies from 414 to 419Hz, the reed winding point is away from to the vibration end also obviously changes . The different reed vibration condition cause the frequency to change. Natural frequency is constant. When cause “bending” (the frequency is lower than the standard condition), the airflow make a force keep from reed vibration. But the chamber air pressure still drive reed. therefore cause the reed to give off not natural frequency sound
Ring-shaped Round Wing
The purpose of our experiment is to analysis a specific ring shaped airplane called 'Round Wing' to know its characteristic. We've done several experiments to find its characteristics.\r First, Unlike other airplanes, Round Wing needs little time to recover its stability by comparing duration of flight.\r Second, as the eccentricity of the ring increase from 0.5 to 0.95, the stability and duration of flight are increased too. Also the size of body increase 1, 2, 3 times, the duration of flight is increased to 184%, 204%, 222%.\r Third, when Round Wings are attached each other by 2, 3, 4 they flew with high stability than before and stayed in the air much longer.\r Conclusion, Round Wing has unique characteristic (like high stability, and long duration of flight). And if additional power plant added, it can stay in the air very long. Also it can be used for leisure, patrol, broadcasting, and geological purposes.
見微知「駐」-水珠律動與圓駐波
It is always fascinating to see water droplet’s dancing around on a Japanese teppanyaki hotplate surface. The water usually does not evaporate immediately, but form interesting shapes, dance around and follow by evaporation of gaseous water and disappear. In this experiment, we designed a very simple experimental set-up to observe the little water droplets dancing on a heated hotplate. A homemade stainless plate and a small heater attached to the plate, and a thermal couple was assembled. With this simple setup, we observed the variation of water droplet’s shape as a function of the hotplate temperatures. The temperature of the water droplets, the duration of the water on the hotplate, and the shape number were measured. The shape formation mechanism was proposed. We found when the water droplet was subject to high heat due to the contact of the surface and the hotplate, the abrupt evaporation of the water molecules and violent vibration cause the formation of the various shapes to reach thermal equilibrium; the number of the shapes and the oscillation can be described by Laplace’s equation,Using a high-speed camera, we found the higher the temperature of the water, the more variations of the water droplet shapes can be observed. In addition, at a certain temperature range, the number of the water shapes did not change, suggesting a similar phase transformation behavior on the shape formation.
緣起： 邂逅專題研究、水珠漫舞、剪輯影片，引起我們想更進一步揭開它的神秘面紗。
緣續： 了解熱平台上水滴大小的變化及水珠基本的形狀及變化律動。
緣繫： 進一步研究水珠多變的面貌，並探討水珠的大小、溫度、停滯時間及變化規律相關機制。
緣定： 糾纏在水珠圓舞曲中有如大珠小珠落玉盤的曼妙，其中埋藏了平均圓與能量量子化的律動。