لسلام عليكم اخواني
أما بعد
أتمنى من جميع اخواتي الكرام مساعدتي في البحث عن موضوع ضوضاء الطائرات بأي سواء بمواقع الكترونيه مفيده او ببحوث تتعلق بالموضوع او بإرشادي الى كتب مساعده في هذا الموضوع … وذلك نظرا لعمق موضوع ضوضاء الطائرات وصعوبة فهمه بشكل محدد … وشكرا لكل من يتكرم بالمساعده ودعواتي الطيبه لما يتمنى مساعدتي … والسلام … أنتظر ردودكم.
بسم الله
الأخ المهندس خالد ان شاء الله ابحث لك علي مواقع هندسيه لضوضاء الطائرات أو كتب لهذا الموضوع
بس لحد مانلاقي ان شاء الله فده بحث عن ضوضاء الهليكوبتر وكيفيه التقليل منها منقول من أحد مواقع البحث باللغه الأنجليزيه
Helicopter noise reduction is a topic of research into designing helicopters which can be operated more quietly, reducing the public-relations problems with night-flying or expanding an airport. In addition, it is useful for military applications in which stealth is required: long-range propagation of helicopter noise can alert an enemy to an incoming helicopter in time to re-orient defenses.
Sources of helicopter noise
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1_Thickness noise
Loading noise
Loading noise is an aerodynamic source term due to the acceleration of the force distribution on the air around the rotor blade due to the blade passing through it, and is directed primarily below the rotor. In general, loading noise can include numerous types of blade loading: some special sources of loading noise are identified separately.
Blade-vortex interaction (BVI) noise
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2_Broadband noise
Another form of loading noise, broadband noise consists of various stochastic noise sources. Turbulence ingestion through the rotor, the rotor wake itself, and blade self-noise are each sources of broadband noise.
3_High-speed impulsive (HSI) noise
HSI noise is caused by transonic flow shock formation on the advancing rotor blade, and is distinct from loading noise. The source of HSI noise is the flow volume around the advancing blade tip, hence it cannot be captured by examining only the acoustic sources on the surface of the blade, HSI noise is typically directed in the rotor plane forward of the helicopter, like thickness noise.
4_Tail rotor noise
While most noise from a helicopter is generated by the main rotor, the tail rotor is a significant source of noise for observers relatively close to the helicopter, where the higher-frequency noise of the tail rotor has not yet been attenuated by the atmosphere. Tail rotor noise is particularly annoying to the human listener due to its higher frequency (as compared to the main rotor) which places it directly in the band in which the human ear is most sensitive.
*Methods of noise reduction
A tail-rotor which is recessed into the fairing of the tail (a fenestron) reduces the noise level directly below the aircraft, which is useful in urban areas. In addition, this type of rotor typically has anywhere from 8 to 12 blades (as compared to 2 or 4 blades on a conventional tail rotor), increasing the frequency of the noise and thus its attenuation by the atmosphere. This type of rotor is in general much quieter than its conventional counterpart: the price paid is a substantial increase in the weight of the aircraft, and the weight that must be supported by the tail boom. For example, the Eurocopter EC-135 has such a design.
For smaller helicopters it may be advantageous to use a NOTAR (from NO TAil Rotor) system. In this yaw-control method air is blown out of vents along the tail boom, producing thrust via the Coandă effect.
Some designs have been done to reduce the rotor noise itself, for example the Comanche military helicopter attempted many stealth mechanisms, including attempts to quieten the rotor.
Helicopter pilots can select operating modes which limits the engine torque and other parameters to ensure legal limits are respected to reduce noise. Pilots can disable the restrictions in an emergency to get extra power.
السلام عليكم … أشكرك عزيزي المشرف وأتمنى لك كل خيرا وأنا أنتظر مطر مساعدتك ومساعدة اخواني في المنتدى أن تنهمر علي وشكرا جزيلا لكم جميعا… حبذا لوكانت هناك أبحاث باللغه العربية والانجليزيه أيضا مبسطه ومفهمه للموضوع … الخ
الأخ العزيز خالد في الواقع البحث في ضوضاء الطائرات باء بالفشل الذريع
والموضوع ده تقريبا صعب لأنه علي درجه من السريه العسكريه…والله أعلم
بس انا كنت سألت معيد عندنا وقاللي إن الموضوع ده بيتعمل فيه رسالات دكتوراه معقده لتقليل الضوضاء بتاعه أي محرك سواء طائرات أو صواريخ
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