مطالعه آزمايشگاهي ساختار جريان آشفته در ميدان دو آبشكن با روشPIV

Experimental Study of Turbulent Flow Structures in Two Groyne Field using PIV Method

در اين پژوهش ميدان جريان بين دو آبشكن مستقيم واقع در جريان كم عمق يك كانال عريض با استفاده از روش سرعت سنجي تصويري ذرات سطحي اندازه گيري شده است. بدين منظور آبشكن هاي مستقيم به طول 25 سانتيمتر در دو فاصله نسبي 1 و 2 در ناحيه جريان توسعه يافته كانالي به عرض 1/8 قرار داده شده و اندازه گيري ميدان جريان، به منظور مطالعه الگوي جريانهاي چرخشي افقي، ساختار لايه اختلاطي و ناحيه چرخشي پايين دست انجام شده است. براي پردازش تصاوير از نرم افزار GPIV استفاده شده و از روش هاي وستِرويل و الگوريتم تكراري برِويس براي فيلتراسيون ميدان‌هاي سرعت استفاده شده است. نتايج بصورت توزيع مقادير متوسط سرعت، شدت‌هاي آشفتگي و تنش‌هاي رينولدز ارائه شده است. بر اساس نتايج حاصله، بواسطه كم عمق بودن ميدان، بخش عمده‌اي از ساختارهاي آشفتگي حالت دوبعدي داشته وشكل گيري يك جريان برگشتي از ناحيه پايين دست به داخل ميدان آبشكن باعث پيچيدگي ساختار لايه اختلاطي و در نتيجه پروسه تبادل جرم بين ناحيه چرخشي ميدان آبشكن و جريان آزاد مي‌شود.

In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration.enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration.