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بررسی تجربی اثر آشفتگی جریان ورودی بر میدان فشار ناپایا و نویز جریان پیرامون استوانه دایره‌ای | ||
| نشریه مهندسی مکانیک امیرکبیر | ||
| مقاله 12، دوره 52، شماره 4، تیر 1399، صفحه 923-942 اصل مقاله (3.3 M) | ||
| نوع مقاله: مقاله پژوهشی | ||
| شناسه دیجیتال (DOI): 10.22060/mej.2018.13842.5727 | ||
| نویسندگان | ||
| رضا مریمی1؛ علی اکبر دهقان* 2؛ عباس افشاری3 | ||
| 1گروه مکانیک، دانشکده مهندسی مکانیک، دانشگاه یزد، ایران | ||
| 2هیلت علمی-دانشگاه یزد | ||
| 3دانشجوی دکترا/ دانشگاه یزد | ||
| چکیده | ||
| میدان فشار ناپایا روی سطح استوانه‌ای با مقطع دایره‌ای، به عنوان منشأ اصلی نویز ثبت شده در دوردست، دارای رفتار فیزیکی پیچیده‌ای بوده که تاکنون مطالعات مختصری روی آن و مخصوصا در جریان آزاد آشفته انجام گرفته است. بنابراین در مطالعه حاضر نوسانات فشار ناپایا روی سطح استوانه‌ای با قطر خارجیmm 22 تحت شرایط جریان آزاد آرام و آشفته به طور تجربی بررسی شده است. تغییر شرایط آشفتگی جریان آزاد با استفاده از شبکه‌هایی با مش‌های مربعی مختلف انجام شده است. به منظور فهم دقیق رفتار نویز جریان پیرامون مدل، پارامترهایی نظیر طیف فشار سطح، تابع همدوسی، همبستگی خودکار و متقابل، طول مشخصه ساختارهای گردابه‌ای در دهانه مدل و همچنین سرعت جابه‌جایی این ساختارها در راستای جریان با استفاده از نوسانات فشار سطح محاسبه شده است. نتایج نشان دادند که تغییر ماهیت جریان آزاد از آرام به آشفته سبب افزایش سطح انرژی نویز باریک باند و پهن باند می‌شود. علاوه بر این فرکانس نویز به سمت ( f = 98Hz ) در مقایسه با مقدار متناظر در جریان آزاد آرام( f ' = 88Hz ) باریک باند در جریان آزاد آشفته فرکانس‌های پایین جابجا می‌گردد. دیگر نتایج نشان دادند که اندازه گردابه‌ها و سرعت جابه‌جایی این ساختارها در جریان آزاد آرام بزر گتر از جریان آزاد آشفته است. | ||
| کلیدواژه‌ها | ||
| نوسانات فشار سطح؛ شبکه‌های تولید کننده جریان آشفته؛ نویز باریک باند؛ فرکانس ریزش گردابه | ||
| عنوان مقاله [English] | ||
| Experimental investigation of the turbulence effect of incoming flow on the unsteady pressure field and the flow noise around circular cylinder | ||
| نویسندگان [English] | ||
| Reza Maryami1؛ Ali Akbar Dehghan2؛ abbas afshari3 | ||
| 1Mech. Eng. Dept, Factulty of Engineering, Yazd University, IRAN | ||
| 2Mech. Eng. Dept, Faculty of Engineering, Yazd University, IRAN | ||
| 3phd student / yazd university | ||
| چکیده [English] | ||
| Surface pressure fluctuations on a circular cylinder model are the main sources of far- field noise emitted and have complex physical behavior. So far, limited studies have been devoted to identifying the unsteady surface pressure behavior, especially for turbulence incident flow. In the present study to measure the surface pressure fluctuations under both smooth and turbulence incoming flows, a circular cylinder with an outer diameter of 22mm has been used. In order to change the turbulence characteristics of free stream incoming flow, different biplane grids with square meshes were designed. Power spectral density, coherence, autocorrelation and cross-correlation, spanwise length scale, and convection velocity were different interesting parameters which were calculated using measured unsteady pressures in order to better clarify the flow structure and flow noise around the model. The results revealed that the energy level of both tonal and broadband noises is increased when incident flow changes from smooth to turbulent. Moreover, the tonal noise frequency in the turbulence flow ( f ' = 88 Hz ) shifts to low frequencies compared to that of smooth flow ( f = 98 Hz ). Furthermore, results showed that the physical size of eddies and their convection velocity in turbulence flow are greater than corresponding values for smooth flow. | ||
| کلیدواژه‌ها [English] | ||
| Surface pressure fluctuations, Turbulence generation grids, Tonal noise, Vortex shedding frequency | ||
| مراجع | ||
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