simulation of low-re flow over a modified naca 4415 airfoil with oscillating camber

159 Pages·2016·3.64 MB·English

by  Vamsidhar Katam

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University of Kentucky Master's Theses Graduate School
2005
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Vamsidhar Katam
University of Kentucky
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Katam, Vamsidhar, "SIMULATION OF LOW-RE FLOW OVER A MODIFIED NACA 4415 AIRFOIL WITH
OSCILLATING CAMBER" (2005). University of Kentucky Master's Theses. 339.
https://uknowledge.uky.edu/gradschool_theses/339
This Thesis is brought to you for free and open access by the Graduate School at UKnowledge. It has been
accepted for inclusion in University of Kentucky Master's Theses by an authorized administrator of UKnowledge.
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ABSTRACT OF THESIS

SIMULATION OF LOW-RE FLOW OVER A MODIFIED NACA 4415 AIRFOIL
WITH OSCILLATING CAMBER

Recent interest in Micro Aerial Vehicles (MAVs) and Unmanned Aerial Vehicles
(UAVs) have revived research on the performance of airfoils at relatively low Reynolds
numbers. A common problem with low Reynolds number flow is that separation is almost
inevitable without the application of some means of flow control, but understanding the
nature of the separated flow is critical to designing an optimal flow control system. The
current research presents results from a joint effort coupling numerical simulation and wind
tunnel testing to investigate this flow regime. The primary airfoil for these studies is a
modified 4415 with an adaptive actuator mounted internally such that the camber of the
airfoil may be changed in a static or oscillatory fashion. A series of simulations are
performed in static mode for Reynolds numbers of 25,000 to 100,000 and over a range of
angles of attack to predict the characteristics of the flow separation and the coefficients of
lift, drag, and moment. Preliminary simulations were performed for dynamic mode and it
demonstrates a definitive ability to control separation across the range of Re and AoA. The
earlier experimental work showed that separation reduction is gradual until a critical
oscillation frequency is reached, after which increases in frequency have little additional
impact on the flow. Present numerical simulation results were compared with the previous
experiments results which were performed on the airfoil in like flow conditions and these
comparisons allow the accuracy of both systems to be determined.

KEYWORDS: Low-Re Flow, Flow Separation, Adaptive Actuator, Flow Control, NACA
4415

Vamsidhar Katam

01/19/2005

Copyright © Vamsidhar Katam 2005
SIMULATION OF LOW-RE FLOW OVER A MODIFIED NACA 4415 AIRFOIL
WITH OSCILLATING CAMBER

By

Vamsidhar Katam

Dr. Raymond P LeBeau
Director of Thesis

Dr. George Huang
Director of Graduate Studies

01/19/2005
RULES FOR THE USE OF THESIS

Unpublished thesis submitted for the Master’s degree and deposited in the University of
Kentucky Library are as a rule open for inspection, but are to be used only with due regard
to the rights of the authors. Bibliographical references may be noted, but quotations or
summaries of parts may be published only with the permission of the author, and with the
usual scholarly acknowledgements.

Extensive copying or publication of the thesis in whole or in part also requires the consent
of the Dean of the Graduate School of the University of Kentucky.
THESIS

Vamsidhar Katam

The Graduate School

University of Kentucky

2005
SIMULATION OF LOW-RE FLOW OVER A MODIFIED NACA 4415 AIRFOIL
WITH OSCILLATING CAMBER

THESIS

A thesis submitted in partial fulfillment of the
requirements for the degree of Master of Science in Mechanical Engineering in the
College of Engineering at the University of Kentucky

By

Vamsidhar Katam

Lexington, Kentucky

Director: Dr. Raymond P LeBeau, Assistant Professor of Mechanical Engineering

Lexington, Kentucky
2005

Copyright © Vamsidhar Katam 2005
Dedication

To my family and friends
ACKNOWLEDGEMENTS

I would like to express my gratitude to my advisor Dr. Raymond P LeBeau, who
has been a constant source of encouragement and inspiration. He was always available to
discuss the problems at hand with my project. His invaluable suggestions and ingenious
ideas have taken the shape of this project. He was solicitous person not only in academic
affairs but also in other matters and it shall remain as reminiscence. I thank Dr. Jamey D
Jacob, for his assistance in providing me with experimental details along with useful
suggestions. In spite of his busy schedule, he always found time to help me out by allocating
suitable time slots to discuss about my project. I also express my gratitude to him for being
part of my defense committee. I also wish to express my gratefulness to Dr. George
Huang, for involving me into other projects. I am thankful to him for being part of my
thesis defense committee.
I also thank Dr.Yildirim Bora Suzen for helping me to understand the CFD code
used in this project.
I would like to acknowledge Kentucky NASA EPSCoR for providing financial
assistance for this project.

iii
TABLE OF CONTENTS

Acknowledgements………………………………………………………………..... iii
List of Tables……………………………………………………………………….. vii
List of Figures………………………………………………………………………. viii
List of Files…………………………………………………………………………. xv
Chapter
1. Introduction……………………………………………………………………. 1
1.1 Overview……………………………………………………………. 1
1.2 Background………………………………………………………… 2
1.3 Low Reynolds Number Effects……………………………………... 3
1.4 Flow Control………………………………………………………... 5
1.5 Wing Morphing……………………………………………………… 6
1.6 Code Validation……………………………………………………... 7
1.7 Organization of the Thesis………………………………………….. 8
2. Literature Survey and Previous Work…………………………………………. 9
2.1 Flow Control Previous Work……………………………………….. 9
2.2 Wing Construction of Munday and Jacob (2001)…………………… 14
2.3 Wind Tunnel Description…………………………………………… 16
2.4 Results by Munday and Jacob (2001 & 2002)………………………... 17
2.5 CFDVAL…………………………………………………………… 20
2.5.1 Previous Work………………………………………... 21
2.5.2 Experimental Description…………………………….. 22
2.5.3 Experimental Details………………………………… 25
3. Computational Tools…………………………………………………………… 26
3.1 Introduction………………………………………………………… 26
3.2 Description of GHOST…………………………………………….. 27
3.3 Description of UNCLE……………………………………………... 29
3.4 Hardware and Computation details…………………………………. 30
4. Validation of Codes Against a High-Re Test Case …………………………… 31
4.1 Introduction………………………………………………………… 31
4.2 Experimental Conditions…………………………………………… 32
iv
4.3 Quantities Calculated……………………………………………….. 32
4.4 Grid and Boundary Conditions……………………………………... 33
4.4.1 Inlet Boundary Conditions…………………………… 35
4.4.2 Grid Independence………………………………….... 35
4.5 Results……………………………………………………………… 36
4.5.1 Baseline Case…………………………………………. 37
4.5.2 Suction Case………………………………………….. 38
4.5.3 Figures Related to Baseline Case……………………… 41
4.5.3 Figures Related to Suction Case………………………. 46
4.6 Results of Other CFD codes in Comparison to GHOST…………… 51
4.7 Conclusions………………………………………………………… 53
5. Case Setup and Results for Non-Actuating Case……………………………. 55
5.1 Experimental Details………………………………………………... 56
5.2 Cases………………………………………………………………... 56
5.2.1 Static Actuator Case Setup……………………………. 57
5.2.2 Computation Domain………………………………… 58
5.3 Preliminary Studies…………………………………………………. 60
5.3.1 Study for the Effect of Wall…………………………… 60
5.3.2 Effect of Time Step…………………………………… 62
5.3.3 Effect of Transition Model……………………………. 63
5.4 Grid Study…………………………………………………………... 64
5.4.1 Variation in Airfoil Grid Density……………………… 65
5.4.2 Cylinder Cases………………………………………… 66
5.5 Validation of Numerical Simulations………………………………… 71
5.5.1 Experimental Results…………………………………… 71
5.5.2 Numerical Simulation results in Comparison with
Experimental Results………………………………………… 74
5.6 Variation with Reynolds Number and Angle of Attack………………. 76
5.7 Variation of Lift with Different Grids……………………………….. 79
5.8 Voriticity Distribution in Comparison with Lift and Pressure Plots for
Grid 1…………………………………………………………………… 84
5.9 Voricity Distribution for Grid 2 and Grid 3…………………………. 93
v