analysis of drag reduction using aerodynamic devices on commercial buses by computational fluid ...

131 Pages·2015·1.68 MB·English

by  Brown, Rachel R

ANALYSIS OF DRAG REDUCTION USING AERODYNAMIC
DEVICES ON COMMERCIAL BUSES BY COMPUTATIONAL FLUID
DYNAMIC SIMULATION
BY
RACHEL BROWN
A THESIS
SUBMITTED TO THE FACULTY OF
ALFRED UNIVERSITY
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF
MASTER OF SCIENCE
IN
MECHANICAL ENGINEERING
ALFRED, NEW YORK
September, 2015
Alfred University theses are copyright protected and
may be used for education or personal research only.
Reproduction or distribution in part or whole is
prohibited without written permission from the author.
Signature page may be viewed at Scholes Library,
New York State College of Ceramics, Alfred University,
Alfred, New York.
COMPUTATIONAL SIMULATION OF DRAG REDUCTION USING
AERODYNAMIC DEVICES ON COMMERCIAL BUSES
BY
RACHEL BROWN
B.S. UNION COLLEGE (2013)
SIGNATURE OF AUTHOR___________________________________
APPROVED BY____________________________________________
DR. SEONG-JIN LEE, ADVISOR
_______________________________________________
DR. WALLACE LEIGH, ADVISORY COMMITTEE
_______________________________________________
DR. JOE ROSICZKOWSKI, ADVISORY COMMITTEE
_______________________________________________
CHAIR, ORAL THESIS DEFENSE
ACCEPTED BY ____________________________________________
DOREEN D. EDWARDS, DEAN
KAZUO INAMORI SCHOOL OF ENGINEERING
ACKNOWLEDGMENTS
Foremost, the author of this study would like to express her sincere gratitude to her
advisor Dr. Seong-Jin Lee for the continuous support of her Master's study and research,
for his patience, motivation, and enthusiasm. His guidance helped her throughout all the
research and writing of this thesis. Research could also not have been completed without
the financial support of the Kazuo Inamori School of Engineering and Dean Edwards. The
author would also like to acknowledge her thesis committee members Dr. Wallace Leigh
and Dr. Joe Rosiczkowski in their time and support of this study. Lastly she would like to

acknowledge the continued support of her parents throughout her education.
iii
TABLE OF CONTENTS

Page
Acknowledgements ...................................................................................................... iii
Table of Contents ......................................................................................................... iv
List of Tables ............................................................................................................... vi
List of Figures ............................................................................................................ viii
Abstract ....................................................................................................................... xii
I INTRODUCTION....................................................................................................... 1
A. Aerodynamics of Commercial Buses .................................................................................. 3
1. Flow Field around a Bus ...................................................................................................... 3
2. Turbulence ........................................................................................................................... 5
B. Computational Fluid Dynamics (CFD) Software ............................................................... 7
C. Reynolds Averaged Navier-Stokes Equations (RANS) ...................................................... 9
1. Boundary-Layer Equations ................................................................................................ 13
D. Turbulence Models ........................................................................................................... 16
A. Previous Studies on Turbulence Modeling .................................................................... 16
B. Modeling Terminology .................................................................................................. 17
C. Two-Equation Turbulence Models ................................................................................ 18
E. Aerodynamic Drag Reduction Devices ............................................................................ 27
1. Airvane as a Drag Reduction Device ............................................................................. 29
II EXPERIMENTAL PROCEDURE.......................................................................... 34
A. SolidWorks Scaled-Down Model ..................................................................................... 34
B. Parameter Study to Reach Optimized Airvane Devices ................................................... 36
C. ANSYS Fluent Setup and Procedure ................................................................................ 41
1. Geometry Setup ............................................................................................................. 41
2. Meshing Procedure ........................................................................................................ 43
3. Fluent Procedure ............................................................................................................ 48
D. Calibration of Fluent Simulations ..................................................................................... 49
III RESULTS AND DISCUSSION ............................................................................... 50
A. Calibration of Fluent ......................................................................................................... 50
B. Bus Model without Airvane .............................................................................................. 55
C. Bus Model with Airvane ................................................................................................... 61
iv
1. Top Airvane Only .......................................................................................................... 62
2. Top and Side Airvanes ................................................................................................... 74
3. Different Configurations ................................................................................................ 85
IV CONCLUSION ......................................................................................................... 91
V FUTURE WORK ...................................................................................................... 93
REFERENCES ................................................................................................................ 94
APPENDIX A: Dimensions of Full Sized Bus and 1/35th Scale Model ..................... 97
APPENDIX B: Blueprint of Side View of MCI D4505 ................................................ 98
APPENDIX C: SolidWorks 1/35th Scaled Model of Commercial Bus ....................... 99
APPENDIX D: ANSYS Fluent Set-up and Procedure .............................................. 100
APPENDIX E: Calibration Raw Data ........................................................................ 106
APPENDIX F: Raw Data of Parameter Study Performed on Top Airvane ........... 108
APPENDIX G: Raw Data of Parameter Study Performed on Side Airvane .......... 113
APPENDIX H: Raw Data of Different Configurations, Bottom Airvane and
Deflection Plate.............................................................................................................. 118

v
LIST OF TABLES
Page
Table I: Model Constants for k-e Two Equation Turbulence Model ................................ 20
Table II: Closure Constants for Wilcox’s Standard k-ω Equation. .................................. 22
Table III: Model Constants for the RKE Turbulence Model ............................................ 23
Table IV: Model Constants for the Outer Layer for the SST Turbulence Model ............. 25
Table V: Model Constants for the Inner Layer for the SST Turbulence Model ............... 26
Table VI: Dimensions for Wind Tunnel Enclosure Designed in ANSYS Fluent............. 42
Table VII: Dimensions for Refinement Box. .................................................................... 42
Table VIII: A Set of Simulations was Run with Different Combinations. ....................... 86
Table IX: A Set of Simulations was Run with Different Configurations ......................... 87
Table X: Important Dimensions of MCI D4505 Commercial Bus ................................... 97
Table XI: First Run of the Calibration of the Fluent simulations. .................................. 106
Table XII: Second Run of the Calibration of the Fluent simulations. ............................ 107
Table XIII: Raw Data of Refined Angle Tests Run on the Top Airvane ....................... 108
Table XIV: Raw Data of General Expansion Ratio Tests Run on the Top Airvane ...... 108
Table XV: Raw Data of the Refined Expansion Ratios on the Top Airvane ................. 109
Table XVI: Data of the Radius of the Curved Portion of the Top Airvane. ................... 110
Table XVII: Raw Data of the Inlet Gap for the Top Airvane ......................................... 110
Table XVIII: Raw Data for the Angle of the Planar Portion of the Top Airvane........... 111
Table XIX: Raw Data of the Planar Length of the Top Airvane .................................... 112
Table XX: Raw Data of the General Angle of the Side Airvane .................................... 113
Table XXI: Raw Data of the Refined Angle of the Side Airvane .................................. 114
Table XXII: Raw Data of the General Expansion Ratio of the Side Airvane ................ 114
vi
Table XXIII: Raw Data of the Refined Expansion Ratio of the Side Airvane ............... 115
Table XXIV: Raw Data Radius of Curvature of the Side Airvane ................................. 115
Table XXV: Raw Data of the Inlet Gap of the Side Airvane ......................................... 116
Table XXVI: Raw Data of the Angle of the Inlet of the Side Airvane ........................... 117
Table XXVII: Raw Data of the Planar Length of the Side Airvane ............................... 117
Table XXVIII: Raw Data of the Different Combinations .............................................. 118

Table XXIX: Raw Data of Different Configurations. .................................................... 118
vii
LIST OF FIGURES
Page
Figure 1: Relation of aerodynamic and rolling drag to velocity of a bluff body ............... 2
Figure 2: Flow around a bluff body .................................................................................... 4
Figure 3: Relationship between time-averaged variables, fluctuations and average: (a)
steady flow and (b) unsteady flow ..................................................................... 10
Figure 4: Boundary layer notation and coordinate system on a flat plate ........................ 13
Figure 5: Visual representation of the SST turbulence model .......................................... 25
Figure 6: Aivane kit created by Kirsch with important aspects numbered ....................... 29
Figure 7: Different configurations of airvanes that were mounted on the top leeward
corner of the body .............................................................................................. 31
Figure 8: SolidWorks 1/35th scaled CAD model of commercial bus ............................... 36
Figure 9: Optimized airvane attached to the top horizontal edge ..................................... 39
Figure 10: Optimized airvane attached to the side vertical edges .................................... 40
Figure 11: Different element types for three-dimensional meshes ................................... 44
Figure 12: Cutcell mesh created in ANSYS for the bus model without a drag reduction
device attached ................................................................................................... 46
Figure 13: Enhanced view of CutCell mesh created in ANSYS. ..................................... 47
Figure 14: Polyhedral mesh created in ANSYS Fluent .................................................... 47
Figure 15: Calibration tests run for the Realizable k-ε turbulence model utilizing a
polyhedral mesh ................................................................................................. 51
Figure 16: Calibration tests run for the Realizable k-ε turbulence model utilizing a
CutCell mesh ...................................................................................................... 52
viii
Figure 17: Calibration tests run for the SST k-ω turbulence model utilizing a polyhedral
mesh ................................................................................................................... 53
Figure 18: Graph of calibration tests run for the SST k-ω turbulence model utilizing a
CutCell mesh ...................................................................................................... 54
Figure 19: Velocity contour of bus model without an airvane employed ......................... 55
Figure 20: Pressure contour found for the bus without an airvane employed .................. 57
Figure 21: Contour of turbulence kinetic energy .............................................................. 58
Figure 22: Velocity contour of the bus model without an airvane employed ................... 59
Figure 23: Pressure contour found for the bus without an airvane ................................... 60
Figure 24: Contour of turbulence kinetic energy .............................................................. 61
Figure 25: Percent reduction in the drag coefficients versus the general angles .............. 63
Figure 26: Percent reduction in the drag coefficients versus the more refined angles ..... 64
Figure 27: Percent reduction in the drag coefficients versus the general expansion ratios
tested .................................................................................................................. 65
Figure 28: Percent reduction in the drag coefficients versus the more refined expansion
ratios ................................................................................................................... 67
Figure 29: Percent reductions in the drag coefficient versus the radius of curvatures ..... 68
Figure 30: Percent reduction in the drag coefficients versus the inlet gaps ...................... 69
Figure 31: Percent reduction in the drag coefficients versus the angles of the planar
portion of the airvane ......................................................................................... 70
Figure 32: Percent reduction in the drag coefficients versus the lengths of the planar
portion ................................................................................................................ 71
Figure 33: Velocity contour of the wake of the bus model with a top airvane ................. 72
ix