مطالعۀ تجربی مشخصه‌های شکست جت‌های آب با مقاطع بیضوی، مستطیلی و دایروی

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشگاه صنعتی امیرکبیر

چکیده

در این پژوهش ناپایداری جت‌های آب بیضوی، مستطیلی و دایروی به‌صورت تجربی مورد بررسی قرار گرفته‌است. از روش سایه‌نگاری برای ثبت لحظه‌ای ستون جت استفاده شد. پارامترهای جت همچون طول شکست و طول موج تغییر محور به‌صورت کمی بررسی شده‌اند. نتایج پژوهش نشان داد که به‌دلیل مشخصه‌های مشترک جت‌های مستطیلی و بیضوی، طول شکست جت بیضوی با جت مستطیلی در رژیم باد القایی دوم تقریباً ایکسان ست. درمقایسه با جت دایروی، جت‌های بیضوی و مستطیلی زودتر تحت تأثیر اثرات آیرودینامیکی قرار می‌گیرند و بنابراین زودتر وارد رژیم جریان باد القایی اول می‌شوند. همچنین نشان داده شد که طول موج پدیده تغییر محور در اعداد وبر پایین به هندسه جت وابسته نیست و برای جت‌های مستطیلی و بیضوی یکسان است. مشاهده شد که در اعداد وبر بالا، طول موج تغییر محور جت مستطیلی بزرگ‌تر از جت بیضوی می‌باشد. براساس نتایج به‌دست‌آمده رابطه‌ای نیمه‌تجربی برای تخمین طول موج تغییر محور پیشنهاد داده شد.
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کلیدواژه‌ها


عنوان مقاله [English]

Experimental Investigation of Breakup Characteristics of Elliptical, Rectangular and Circular Water Jets

نویسندگان [English]

  • Amin Jaberi
  • Mehran Tadjfar
  • Armin Sheidani
Amirkabir University of Technology
چکیده [English]

In this study, the instabilities of elliptical, rectangular and circular water jets were experimentally investigated. Shadowgraph technique was employed to capture the jet column status instantaneously. Jet parameters such as disintegration length and axis switching wavelength were quantitatively studied. The results showed that due to the similar characteristics of rectangular and elliptical jets, their breakup length in the second wind-induced regime is nearly equal, while the breakup length of circular jet is perceptibly shorter. Both rectangular and elliptical jets are affected by aerodynamic forces sooner and thus enter the first wind induced regime at lower velocities. Furthermore, it was revealed that the axis switching wavelength is not dependent upon the jet geometry at low Weber numbers and remains equal for both elliptical and rectangular jets. However, at high Weber numbers, the axis switching wavelength of rectangular jet become larger than the elliptical one. Based on the obtained results, a semi-empirical relation was proposed to predict the axis switching wavelength of rectangular and elliptical jets.

کلیدواژه‌ها [English]

  • Water jet breakup
  • axis switching phenomenon
  • elliptical jet
  • rectangular jet
  • multiphase flows
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