Mulleners K. On the Coherent Structures behind the Phenomenon of Dynamic Stall / Deutsche Zentrum für Luft- und Raumfahrt Institut für Aerodynamik und Strömungstechnik: Dissertation. - Köln: DLR, Bibliotheks- und Informationswesen, 2010. - 125 p.: ill. - (Forschungsbericht; 2010-22). - Bibliogr.: p.115-125. - ISSN 1434-8454  Место хранения:   061 | Институт оптики атмосферы CO РАН | Томск | Библиотека

Оглавление / Contents

LIST OF FIGURES ................................................ XV LIST OF TABLES ................................................ XXI NOMENCLATURE ................................................. XXII ACRONYMS ...................................................... XXV 1 INTRODUCTION ................................................. 1 1.1 Motivation .............................................. 1 1.2 Literature Survey ....................................... 2 1.2.1 Dynamic Stall Phenomenology ...................... 2 1.2.2 Vorticity Concepts ............................... 5 1.2.3 Unsteady Separation Process ..................... 10 1.2.4 Dynamic Stall Parameters ........................ 14 1.3 Approach and Objectives ................................ 21 1.4 Overview ............................................... 22 2 COHERENT STRUCTURE ANALYSIS ................................. 23 2.1 Definition and Practical Importance .................... 23 2.2 Identification of Coherent Structures .................. 24 2.2.1 Eulerian Methods ................................ 25 2.2.2 The Lagrangian Approach ......................... 32 2.2.3 Proper Orthogonal Decomposition ................. 37 3 EXPERIMENTAL METHODS AND SET-UP ............................. 45 3.1 Experimental Facility .................................. 45 3.1.1 Wind Tunnel ..................................... 45 3.1.2 Airfoil Geometry and Kinematics ................. 46 3.2 Unsteady Surface Pressure Measurements ................. 47 3.3 Particle Image Velocimetry Measurements ................ 48 4 RESULTS AND DISCUSION ....................................... 51 4.1 Dynamic Stall Life Cycle ............................... 51 4.2 Dynamic Stall Onset and Delay .......................... 57 4.2.1 Triggering Mechanism ............................ 57 4.2.2 Primary Instability Stage ....................... 62 4.2.3 Vortex Formation Stage .......................... 69 4.3 Stalled Stage .......................................... 77 4.3.1 Vortex Shedding ................................. 78 4.3.2 Cycle-to-Cycle Variations ....................... 80 4.3.3 Three Dimensionality ............................ 85 5 CONCLUSION AND FUTURE WORK .................................. 99 A ON THE ROLE OF THE LAMINAR SEPARATION BUBBLE A.1 Laminar Separation Bubbles ............................ 103 A.1.1 Origin ......................................... 103 A.1.2 Bubble bursting ................................ 105 A.2 It Wasn't the Butler, Was it? ......................... 106 В DYNAMIC STALL ON A SCALED HELICOPTER MODEL ................. 113 BIBLIOGRAPHY .................................................. 115 CURRICULUM VITAE