University of Twente Student Theses


High lift noise reduction with carbon nanotubes thermophones

Landriscina, Giovanni (2018) High lift noise reduction with carbon nanotubes thermophones.

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Abstract:One of the main problem due to the presence of airports close to urban centers is the noise. Since the engines have been optimized in order to reduce the emission of noise, a considerable source of sound comes from the aerodynamics phenomena. In particular, the main area of the airframe where the noise is produced are the landing gear and the flaps.    At the National Research Council of Canada, the main research center of the country, in the department of aerospace, one of the several challenges is to help to investigate and to reduce the noise pollution. The center has several wind tunnels, where tests can be performed, especially in winter, where temperature are extremely low and can simulate realistically the atmospheric conditions for flights at considerably altitude. One of these wind tunnel has been designed and build by Dr. Jerry Syms. It has the particularity to be soundproofed, hence the external noise and any sound reflections will not spoil the experiments. Considering the Buckingham Theorem, or π-theorem, the problem of a flow around a landing gear of a commercial airplane can be reduced to a simplified model, decreasing considerably the domain, and having a cheaper and much easier structure on which work. The landing gear can be reduced to a couple of cylinders, whom centers lay on the axes parallel to the flow. This configuration allows unsteady vortex shedding to occur in the inter-gap region between the cylinder. The theorem asserts that an equation, or a set of equations as can be Navier-Stokes equations, is described by n physical variables and k physical dimensions, the problem can be reduced in term of p = n - k dimensionless variables. In other words, the problem, once being dimensionless, match the same conditions independently from the domain. The first challenge then is to design a proper model. The main dimensionless number to take into account for this project is the Reynolds Number (Re). As a reliable value it has been taken a minimum value Re=22000. Hence the model is designed in order to satisfy the turbulence regime, and reproduce at the best the aerodynamic phenomena that occurs on a landing gears. Studying the flow field and the pressure fluctuations around the body is possible then to predict and to analyze the source of the noise, and therefore act to obtain the desired results. Previous methods have already been tested, therefore a good comparison model can be used. The idea is to apply carbon nanotubes, a material with high conductivity properties, to induce destructive interference and reduce the noise generated by aeroacoustic phenomena occurring on the bluff body.
Item Type:Internship Report (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:Noise Reduction, Pressure Fluctuations, Von Karman effects, Tandem Cylinders, Pressure Sensors
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