The flow around passenger cars is characterized by many different separation structures, typically leading to vortices and areas of reversed flow. The flow phenomena in these patches show a strong interaction and the evolution of flow structures is difficult to understand from a physical point of view. Analyzing surface properties, such as pressure, vorticity, or shear stress, helps to identify different phenomena, but still it is not well understood how these are created. This paper investigates the crossflow separation (CFS) on the A-pillar of a passenger car using numerical simulations. It is discussed how the CFS and the resulting A-pillar vortex can be identified as well as how it is created. Additionally, the vortex strength is determined by its circulation to understand and discuss how the vortex preserves until it merges with the rear wake of the vehicle.

References

References
1.
Chapman
,
G. T.
, and
Yates
,
L. A.
,
1991
, “
Topology of Flow Separation on Three-Dimensional Bodies
,”
ASME Appl. Mech. Rev.
,
44
(
7
), pp.
329
345
.
2.
Wu
,
J.-Z.
,
Ma
,
H.-Y.
, and
Zhou
,
M.-D.
,
2006
,
Vorticity and Vortex Dynamics
,
Springer, Berlin
.
3.
Leder
,
A.
,
1992
,
Abgelöste Strömungen: Physikalische Grundlagen. Grundlagen Und Fortschritte Der Ingenieurwissenschaften
,
Vieweg
,
Braunschweig and Wiesbaden, Germany
.
4.
Maskell
,
E.
,
1955
,
Flow Separation in Three Dimensions, Ministry of Supply
,
Royal Aircraft Establishment, RAE Farnborough
, Farnborough, UK.
5.
Tobak
,
M.
, and
Peake
,
D. J.
,
1982
, “
Topology of Three-Dimensional Separated Flows
,”
Annu. Rev. Fluid Mech.
,
14
(
1
), pp.
61
85
.
6.
Han
,
T.
, and
Patel
,
V. C.
,
1979
, “
Flow Separation on a Spheroid at Incidence
,”
J. Fluid Mech.
,
92
(
4
), p.
643
.
7.
Patel
,
V. C.
,
1993
, “
Three-Dimensional Flow Separation
,”
Sadhana
,
18
(
3–4
), pp.
553
574
.
8.
Chesnakas
,
C. J.
, and
Simpson
,
R. L.
,
1994
, “
Full Three-Dimensional Measurements of the Cross-Flow Separation Region of a 6:1 Prolate Spheroid
,”
Exp. Fluids
,
17
(
1–2
), pp.
68
74
.
9.
Chesnakas
,
C. J.
, and
Simpson
,
R. L.
,
1996
, “
Measurements of the Turbulence Structure in the Vicinity of a 3D Separation
,”
ASME J. Fluids Eng.
,
118
(
2
), pp.
268
275
.
10.
Gregory
,
P. A.
,
Joubert
,
P. N.
, and
Chong
,
M. S.
,
2007
, “
Measurements of Turbulent Crossflow Separation Created by a Curved Body of Revolution
,”
J. Fluid Mech.
,
589
, pp.
353
374
.
11.
Wang
,
K.
,
1972
, “
Separation Patterns of Boundary Layer Over an Inclined Body of Revolution
,”
AIAA J.
,
10
(
8
), pp.
1044
1050
.
12.
Hucho
,
W.-H.
, ed.,
2005
,
Aerodynamik Des Automobils: Strömungsmechanik, Warmetechnik, Fahrdynamik, Komfort
,
5th ed.
,
Vieweg
,
Berlin
.
13.
Carr
,
G. W.
,
1974
,
Influence of Rear Body Shape on the Aerodynamic Characteristics of Saloon Cars
,
Motor Industry Research Association
, Warwickshire, UK.
14.
Morel
,
T.
,
1978
, “
The Effect of Base Slant on the Flow Pattern and Drag of Three-Dimensional Bodies With Blunt Ends
,”
Aerodynamic Drag Mechanisms of Bluff Bodies and Road Vehicles
,
G.
Sovran
,
T.
Morel
, and
W. T.
Mason
, eds.,
Springer
,
Boston, MA
, pp.
191
226
.
15.
Levy
,
B.
,
Brancher
,
P.
, and
Giovannini
,
A.
,
2008
, “
Experimental Characterization of the Velocity and Wall Pressure Fields of an A-Pillar Vortex
,”
AIAA
Paper No. 2008-2903.
16.
Levy
,
B.
, and
Brancher
,
P.
,
2013
, “
Topology and Dynamics of the A-Pillar Vortex
,”
Phys. Fluids
,
25
(
3
), p.
037102
.
17.
Levy
,
B.
, and
Brancher
,
P.
,
2015
, “
Experimental Investigation of the Wall Dynamics of the A-Pillar Vortex Flow
,”
J. Fluids Struct.
,
55
, pp.
540
545
.
18.
Krajnović
,
S.
, and
Davidson
,
L.
,
2005
, “
Flow around a Simplified Car, Part 1: Large Eddy Simulation
,”
ASME J. Fluids Eng.
,
127
(
5
), pp.
907
918
.
19.
Bonitz
,
S.
,
Löfdahl
,
L.
,
Larsson
,
L.
, and
Broniewicz
,
A.
,
2014
, “
Investigation of Three-Dimensional Flow Separation Patterns and Surface Pressure Gradients on a Notchback Vehicle A2—Park, Holywell
,”
The International Vehicle Aerodynamics Conference
, Loughborough, UK, Oct. 14–15, pp.
55
65
.
20.
Bonitz
,
S.
,
2015
,
Separation Phenomena on a Passenger Car
,
Department of Applied Mechanics, Vehicle Engineering and Autonomous Systems, Chalmers University of Technology
, Gothenburg, Sweden.
21.
Bonitz
,
S.
,
Larsson
,
L.
,
Lofdahl
,
L.
, and
Broniewicz
,
A.
,
2015
, “
Structures of Flow Separation on a Passenger Car
,”
SAE Int. J. Passenger Cars-Mech. Syst.
,
8
(
1
), pp. 177–185.
22.
Krajnović
,
S.
, and
Davidson
,
L.
,
2005
, “
Flow around a Simplified Car—Part 2: Understanding the Flow
,”
ASME J. Fluids Eng.
,
127
(
5
), pp.
919
928
.
23.
Strangfeld
,
C.
,
Wieser
,
D.
,
Schmidt
,
H.-J.
,
Woszidlo
,
R.
,
Nayeri
,
C.
, and
Paschereit
,
C.
,
2013
, “
Experimental Study of Baseline Flow Characteristics for the Realistic Car Model Drivaer
,”
SAE
Paper No. 2013-01-1251.
24.
Wieser
,
D.
,
Schmidt
,
H.-J.
,
Müller
,
S.
,
Strangfeld
,
C.
,
Nayeri
,
C.
, and
Paschereit
,
C.
,
2014
,
Experimental Comparison of the Aerodynamic Behavior of Fastback and Notchback DrivAer Models
,
SAE International
,
Warrendale, PA
.
25.
Lopez Mejia
,
O. D.
,
Ardila Gómez
,
S. A.
,
Blanco Otero
,
D. E.
, and
Muñoz Camargo
,
L. E.
,
2017
, “
Analysis of the Vorticity in the Near Wake of a Station Wagon
,”
ASME J. Fluids Eng.
,
139
(
2
), p.
021105
.
26.
Lucas
,
J.-M.
,
Cadot
,
O.
,
Herbert
,
V.
,
Parpais
,
S.
, and
Délery
,
J.
,
2017
, “
A Numerical Investigation of the Asymmetric Wake Mode of a Squareback Ahmed Body—Effect of a Base Cavity
,”
J. Fluid Mech.
,
831
, pp.
675
697
.
27.
Janssen
,
L. J.
, and
Hucho
,
W. H.
,
1974
, “
Aerodynamische Formoptimierung Von Vw Golf Und Vw Scirocco
,”
Automobiltechn Z
,
77
(
11
), pp. 49–70.
28.
Howell
,
J.
,
Fuller
,
J. B.
, and
Passmore
,
M.
,
2009
, “
The Effect of Free Stream Turbulence on A-Pillar Airflow
,”
SAE
Paper No. 2009-01-0003.
29.
Larsson
,
L.
,
Raven
,
H. C.
, and
Paulling
,
J. R.
,
2010
,
Ship Resistance and Flow
(Principles of Naval Architecture), Society of Naval Architects and Marine Engineers
,
Jersey City, NJ
.
30.
Hunt
,
J. C.
,
Wray
,
A.
, and
Moin
,
P.
,
1988
, “
Eddies, Stream, and Convergence Zones in Turbulent Flows
,” Center for Turbulence Research, Stanford University, Stanford, CA, Report No. CTR-S88.
31.
Wu
,
J. Z.
,
Tramel
,
R. W.
,
Zhu
,
F. L.
, and
Yin
,
X. Y.
,
2000
, “
A Vorticity Dynamics Theory of Three-Dimensional Flow Separation
,”
Phys. Fluids
,
12
(
8
), p.
1932
.
32.
AhmedBaumert
,
W.
,
1979
, “
The Structure of Wake Flow Behind Road Vehicles
,”
Joint ASME-CSME Applied Mechanics, Fluids Engineering, and Bioengineering Conference: Aerodynamics of Transportation
, Niagara Falls, NY, June 18–20, pp.
93
103
.
33.
Ahmed
,
S. R.
,
1981
, “
Wake Structure of Typical Automobile Shapes
,”
ASME J. Fluids Eng.
,
103
(
1
), pp.
162
169
.
34.
Ivanic
,
T.
, and
Gilliéron
,
P.
,
2005
, “
Aerodynamic Drag and Ways to Reduce It
,”
Lecture Ser.-Von Karman Inst. Fluid Dyn.
,
5
, p.
2
.
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