Bayram ÇELİK, Berkay PAMUK, Mehmet TAN, Ülgen GÜLÇAT

PROPULSIVE FORCE OF A HEAVING-PLUNGING RIGID AIRFOIL WITH THICKNESS

Heaving-plunging airfoils, which have been popular because of MAV applications can overcome drag and create net propulsiondepending on the relative values of two forcesgenerated by the leading edge suction and the shear stress.The two forces are in opposite directions and their values are highly dependent on Reynolds number, amplitude and frequencyof oscillation. In this study, flowsover a heaving-plunging NACA 0012 airfoilarenumerically solved using a developed MATLAB code. The code uses Blasius theorem and unsteady aerodynamics to predict leading edge suction and surface velocity distribution, respectively. The motions of the airfoil are modelled as a vertical oscillation ofa rigid platewith a thicknesscorrection for NACA0012. Critical values of Reynolds number, amplitude (h) and reduced frequency (k) that give zero net propulsive force are determinedfor 0 ≤ kh ≤0.4 and 0 ≤ Re≤4.5x104. A curve is fitted to obtained zero net propulsive force data. For comparison, the flows are also solved using a commercial CFD solver, FLUENT. The results obtained fromboth solvers are in good agreement. Computational time requirement of the developed codeis less than a minuteand beyond comparisonwith the commercial solver.

DÜŞEY EKSENDE SALINAN KALINLIKLI BİR RİGİD KANAT PROFİLİNİN İTKİ KUVVET

Mikro İnsansız Hava Aracı uygulamaları sebiyle popüler olan düşey eksende harmonik olarak salınan kanat profilleri, hücum kenarındaki emme ve kayma gerilmesininmeydana getirdiği kuvvetlerin görece büyüklüklerine bağlı olarak sürüklemeyi yenebilir ve net bir itki meydana getirebilir. Bu iki kuvvet birbirine zıt yöndedir ve aldıkları değerler; Reynolds sayısı, titreşim genliği ve frekansla değişmektedir. Bu çalışmada, akışa dik doğrultuda harmonik salınım yapan bir NACA 0012 kanat profili etrafındaki akış, geliştirilen bir MATLAB kodu ile sayısal olarak çözülmüştür. Geliştirilen kod, hücum kenarı emmesi ve yüzey hız dağılımı için sırasıyla Blasius teoremi ve daimi olmayan aerodinamik ilkelerini kullanmaktadır. Reynolds sayısı, titreşim genliği (h) ve indirgenmiş frekans (k) büyüklükleri için sıfır itki meydana getiren kritik değerler 0 ≤ kh ≤0.4 ve 0 ≤ Re≤4.5x104aralıkları için tespit edilmiştir. Elde edilen verilere bir eğri uydurulmuştur. Karşılaştırmayapmak için, modellenen akışlar ticari bir hesaplamalı akışkanlar dinamiği yazılımı olan FLUENT ile de çözülmüştür. Geliştirilen kod ve ticari programdan elde edilen sonuçlar iyi bir uyum içerisindedir. Geliştirilenkod için gereken hesaplama zamanı bir dakikadanaz olup ticari yazılımla kıyaslanamayacak ölçüde kısadır.

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