مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

محاسبه عددی صدای حاصل از جریان باد حول سیلندر و تصحیح شدت صوت با افزایش طول

نویسندگان
1 دانشجوی کارشناسی ارشد، مجتمع دانشگاهی هوافضا، دانشگاه صنعتی مالک اشتر، تهران، ایران
2 استادیار، مجتمع دانشگاهی هوافضا، دانشگاه صنعتی مالک اشتر، تهران، ایران
چکیده
در تحقیق حاضر، از توانایی حل عددی نرم‌افزار انسیس فلوئنت استفاده شده است تا صدای تولید شده توسط جریان سرعت بالا بر روی یک استوانه با استفاده از قیاس آکوستیکی لایت‌هیل محاسبه شود. محاسبات بر روی یک استوانه (بخشی از ارابه فرود هواپیما) در سرعت 70 متر بر ثانیه (سرعت نشست و برخواست هواپیماهای مسافربری) انجام شده است. در روش حاضر، ابتدا مسئله همانند یک حل عددی معمولی به صورت گذرا با زمان انجام می‌شود. در طی حل، اطلاعات منابع تولید نویز آیرودینامیکی به‌عنوان ورودی تحلیل‌های آکوستیکی در فایل‌هایی ذخیره می‌شود. سپس با حل معادلات آکوستیکی، میزان صدای تولید شده (با واحد دسیبل) در نقاطی که از پیش به عنوان میکروفون در مختصات دلخواه تعریف شده‌اند، محاسبه می‌گردد. هدف از این تحقیق، علاوه بر بررسی توانایی حل عددی فلوئنت در محاسبه صدای حاصل از جریان، استفاده از روشی برای تخمین میزان افزایش صدا با افزایش طول سیلندر می‌باشد. در اصل با توجه به زمان‌گیر بودن حل عددی، می‌توان صدای طول کوچکی از سیلندر را محاسبه کرد و بعد با استفاده از تقریب مهندسی، صدای جریان حول سیلندر با طول‌های بزرگتر را تخمین زد. پس از انجام محاسبات لازم، نتایج مدل‌سازی به‌صورت منحنی‌های سطح فشار صوت حاصل از آنالوژی آکوستیکی و آنالیز طیفی فوریه، ارائه شده‌است. نتایج حل نشان می‌دهد که مدل آشفتگی شبیه‌سازی گردابه بزرگ مناسب‌ترین مدل برای شبیه‌سازی‌های آکوستیکی می‌باشد. همچنین فشار صوتی حاصل از روش تخمینی برای بررسی اثر افزایش طول سیلندر، تطابق خوبی با نتایج تجربی دارد.
کلیدواژه‌ها

عنوان مقاله English

Numerical Calculation of the Sound Produced by the Wind Flow Around the Cylinder and Correction of the Sound Amplitude by Increasing the Length

نویسندگان English

Arezoo Najafian 1
Hamid Parhizkar 2
Sajjad Ghasemlooy 2
Abbas Tarabi 2
1 Department of Aerospace Engineering, Malek Ashtar University, Tehran, Iran
2 Department of Aerospace Engineering, Malek Ashtar University, Tehran, Iran
چکیده English

In the present study, the numerical solution of the Ansys Fluent software has been used to calculate the sound produced by the high-speed flow on a cylinder using the Lighthill acoustic analogy. The calculations were carried out on a cylinder (part of the landing gear) at a speed of 70 m/s (take-off and landing speeds of airliners). The problem is initially caried out as a regular unsteady numerical solution. During the solution, aerodynamic noise data sources are stored as inputs of acoustic analyzes in files. Then, by solving the acoustic equations, the volume of produced sound (in decibel) is calculated at points that are pre-defined as the microphone in the desired coordinates. The purpose of this study is to study the ability of Fluent solution to calculate the sound generated by the flow, in addition of using a method for estimating the amount of sound increase by increasing the length of the cylinder. In the other words, due to the timing of the numerical solution, one can calculate sound generated by small length cylinder, and then, using engineering approximation, it estimates the sound of the flow around the larger-length cylinder. After the necessary calculations, results are provided as sound pressure level curves using the acoustic analogy and fourier spectral analysis. The results show that large eddy simulation turbulence model is most appropriate model for acoustic simulations. Also, the approximate method for evaluating the effect of increasing the length of the cylinder is in good agreement with the experimental results.

کلیدواژه‌ها English

Aeroacoustic simulation
Ffowcs-Williams & Hawkings model
Large Eddy Simulation
Sound pressure level
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