Abstract




 
   

IJE TRANSACTIONS B: Applications Vol. 28, No. 2 (February 2015) 305-313   

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  NUMERICAL STUDY ON IMPROVEMENT OF HYDROFOIL PERFORMANCE USING VORTEX GENERATORS (RESEARCH NOTE)
 
A. Ashrafi, M. Ketabdari and H. Ghassemi
 
( Received: August 08, 2014 – Accepted: November 13, 2014 )
 
 

Abstract    In this paper the effects of rigid triangular passive vortex generators on a hydrofoil were investigated numerically. In the first step using the Finite Volume Method the bare hydrofoil were modeled and the results of lift and drag coefficients were validated using experimental data. In the next step the hydrofoil armed with vortex generators was modeled and its effect on the hydrofoil performance was examined. In the next step by introducing a source term into the momentum equation the vortex generators effect was considered. However their geometry was completely removed. The results showed that this can significantly decrease the computational memory and calculation time. The results also revealed that the use of vortex generators can delay the stall conditions by increase the stall angle leading to a higher lift coefficient in new stall angle and decreasing the drag coefficient. In a case study on NACA 0012 section profile results showed that the use of vortex generators increases the stall angle by 4 degrees and the lift coefficient at this point by 37%.

 

Keywords    Hydrofoil, Drag Reduction, Vortex Generators, Finite Volume Method, Source Term

 

چکیده    در این مقاله اثرات نصب یک تولید کننده گردابه غیر فعال مثلثی شکل روی هیدرو فویل به روش عددی مورد یررسی قرار گرفته است. در قدم اول هیدروفویل بدون تولید کننده گردابه به روش حجم محدود مدل شد و و نتایج مدلسازی عددی به کمک نتایج آزمایشگاهی معتبر گردید. در قدم دوم تولید کننده گردابه مدل شده و اثر آن روی هیدرو فویل مورد مطالعه قرار گرفت. در قدم بعد با استفاده از روش ترم چشمه و اضافه کردن آن به معادله مومنتوم اثر تولید کننده گردابه منظور شد اما هندسه از روی هیدروپلن بطور کامل حذف شد. نتایج نشان داد که با اینکار حافظه لازم و زمان محاسباتی برای مدلی که در نظر گرفته شده به اندازه قابل توجهی کاهش می یابد. نتایج همچنین نشان داد که استفاده از تولید کننده گردابه برروی هیدروفویل باعث تاخیر حالت توقف و در واقع افزایش این زاویه می گردد. این به نوبه خود باعث افزایش ضریب برا در زاویه حمله جدید هیدروفویل و کاهش ضریب پسا می گردد. در یک مطالعه موردی روی هیدروفویلی با مقطع NACA 0012 این افزایش برای زاویه استال هیدروفویل برابر 4 درجه و برای صریب برا 37% بدست آمد.

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