Pengaruh Sudut Serang Aerofoil Terhadap Distribusi Tekanan dan Gaya Angkat

The aerofoils are used to get the lifting force on the design of plane’s wings. The lifting force is caused by difference air velocity on upper and lower aerofoil which the magnitude depend on attack angle of aerofoil and air velocity exist surrounding. This experiment aims to show the force vector (pressure distribute) on the aerofoil. The aerofoil is attached by air with konstant velocity. The research procedure is done by change the attack angle of aerofoil on five formation. The surface of aerofoil is connected with pressure gage which disperse at 11 point of measurement. The result shows that magnitude of force vector is depended on attack angle of aerofoil. Increasing angle of aerofoil until boundary angle will be followed by increasing air velocity on the point of measurement and finally increase force vector. Upper boundary angle will be followed by decreasing air velocity and finally decrease force vector.Aerofoil digunakan untuk mendapatkan gaya angkat pada desain sayap pesawat. Gaya angkat disebabkan oleh perbedaan kecepatan udara pada aerofoil atas dan bawah yang besarnya tergantung pada sudut serang aerofoil dan kecepatan udara yang ada disekitarnya. Eksperimen ini bertujuan untuk menampilkan vektor gaya (distribusi tekanan) pada aerofoil. Aerofoil dilekatkan pada udara dengan kecepatan konstan. Prosedur penelitian dilakukan dengan cara mengubah sudut serang aerofoil pada lima formasi. Permukaan aerofoil dihubungkan dengan alat ukur tekanan yang tersebar pada 11 titik pengukuran. Hasil menunjukkan bahwa besarnya vektor gaya bergantung pada sudut serang aerofoil. Sudut aerofoil yang meningkat hingga sudut batas akan diikuti dengan peningkatan kecepatan udara pada titik pengukuran dan akhirnya meningkatkan vektor gaya. Sudut batas atas akan diikuti oleh penurunan kecepatan udara pada titik pengukuran dan akhirnya menurunkan vektor gaya.

Pressure Gage Measurements in a Dry to Wet Environment

Pressure gages are used in many fluid measurements applications. One such application is the measurement of wave impact pressures on structures. This application poses a unique problem of measuring pressures in a “wet to dry” environment. Often there is a thermal drift component in the pressure readings that makes it difficult to extract the actual pressure rise due to wave loading. These types of measurements also require high response rates to measure the detail of the short duration impacts, usually on the order of one to twenty kilohertz. Several bench tests were carried out in at the Naval Surface Warfare Center, Carderock Division, in 2008 to investigate various types of gages to find a robust gage that could withstand this type of application. Three different gages were used in this investigation. The first sensor (gage 1) is a dynamics general purpose ICP (integrated circuit piezoelectric) pressure sensor, capable of making very high frequency dynamic pressure measurements, rated to 200 psi. The second sensor (gage 2) is a voltage compensated, media isolated piezoresistive sensor, rated to 15 psi. This gage had a pressure port which was filled with water during testing to eliminate air compression effects. The third sensor (gage 3) is a semiconductor pressure gage rated to 25 psi (172.4 kPa). A water “drop” test setup was constructed of 2 inch (5.1 cm) PVC pipe. The pressure gages were mounted to the bottom of the setup facing up, and the pipe was filled from the top, with a quick acting gate valve located 2 feet (0.61 m) from the pressure sensors. Once the pipe was filled with the desired amount of water, the gate valve was opened as quickly as possible, and the impact force was measured. Vent pipes were mounted to a “cross” fitting in the vertical pipe which allowed for the air to escape. Several water “drop” tests were performed with this setup. From these tests, the thermal drift of gage 1 is evident. Gage 3 exhibits similar behavior. Gage 2 captures the water pressure impact, and then returns to a small positive static pressure as a result of the water that is sitting above it. Of the three sensors, gage 2 appears to be the most temperature stable.