Based on the extensive literature review provided in this chapter, it is noted that although numerous experiments had been conducted to understand the phenomenon of hydroplaning and the prediction of skid resistance, the analytical and numerical aspect of it is
research.
1. To identify skid resistance and hydroplaning mechanisms that could adequately explains the development of skid resistance and hydroplaning in tire-fluid- pavement interaction. A true appreciation of the various test methods in obtaining the coefficient of friction could never be achieved without understanding the underlying mechanisms of skid resistance under different testing conditions.
2. To propose a numerical model that could model hydroplaning by using the turbulent flow model and taking into consideration the tire deformation profile.
This is needed as it is noted that currently numerical modeling of hydroplaning using turbulent fluid flow model does not take into account the changes in tire deformation profile.
3. To re-assess the validity of the NASA hydroplaning equation. This equation is widely adopted by aircraft engineers, tire engineers and pavement researchers due to its simplicity. However, other factors that are known to affect hydroplaning are not reflected in this equation. It is therefore necessary to assess factors such as microtexture, macrotexture, pavement grooving, water-film thickness, load etc.
from an analytical and numerical point of view.
4. To assess the validity of current pavement engineering techniques used to improve skid resistance and reduce the risk of hydroplaning. Examples include pavement grooving, and surface treatment to improve microtexture or macrotexture. Current understanding of the effects of such measures is purely based on past experience and experimental evidence. There exists a need to model these effects and to explain them on an analytical or theoretical basis.
5. To propose a numerical model that could model hydroplaning and wet skidding and predict the skid resistance under these situations by using the turbulent flow model and taking into consideration coupled fluid-structure interaction. This is considered as a natural extension in the modeling of elasto-hydrodynamic
make use of potential flow theory of laminar flow model, which does not correctly represent the conditions at incipient hydroplaning.
The primary objective of this research is to develop numerical models that could simulate hydroplaning and skid resistance. The research would adopt a two-stage approach as shown in Figure 2.15 and the relevant chapters of each topic covered in this thesis are shown in Figure 2.15. The first stage would involve simulating the hydroplaning phenomenon numerically by assuming a hydroplaning tire profile while the second stage would relax the assumed hydroplaning tire profile assumption to develop a more generic model to simulate both hydroplaning and skid resistance. These models are applied to study major issues of concern to pavement researchers, such as the effect of different pavement-related, operational, loading and environmental parameters on hydroplaning and skid resistance, and the use of pavement grooving in hydroplaning prevention.
The scope of the work planned for this research can be stated as follows:
Stage I: Numerical Modeling of Hydroplaning using Computational Fluid Dynamics and Using the NASA Hydroplaning Tire Profile
1. To develop a numerical model for hydroplaning assuming a fixed tire deformation profile and to verify it with experimental results reported by past researchers.
Two-dimensional and three-dimensional forms of the model will be assessed for their suitability.
2. To apply the proposed numerical model to study the effects of tire pressure on hydroplaning and to verify the NASA hydroplaning equation.
3. To apply the proposed numerical model to study the effects of microtexture on hydroplaning and to study the validity of NASA hydroplaning equation in this context.
4. To apply the proposed numerical model to assess the effectiveness of transverse and longitudinal pavement grooving in reducing the risk of hydroplaning.
transverse and longitudinal pavement grooving against hydroplaning.
Stage II: Numerical Modeling of Hydroplaning and Skid Resistance using Fluid-Structure- Interaction (Solid Mechanics and Computational Fluid Dynamics) and relaxing the NASA Hydroplaning Tire Profile Assumption
1. To develop an improved numerical model for the prediction of skid resistance and hydroplaning speed with the consideration of fluid-structure interaction and to verify it with experimental results reported in past research and the NASA hydroplaning equation.
2. To apply the improved numerical model in hydroplaning simulation and to study the effects of tire pressure, water-film thickness, footprint aspect ratio and wheel load on hydroplaning.
3. To apply the improved numerical model in wet-pavement skid resistance simulation and to study the effects of vehicle speed, tire pressure, water-film thickness and wheel load on skid resistance.
2000) Locked-Wheel Methods Test Tire
Water Depth (nominal), mm
Country Skid resistance trailer
(ASTM E 274) Ribbed (ASTM E 501)
Blank (ASTM E 524) 0.5 United States, Canada, Taiwan Stuttgarter
Reibungsmesser SRM
PIARC (ribbed) 1 Germany
Skiddometer BV8 165-R15 (ribbed) 0.5 Switzerland
Polish SRT-3 Patterned 0.5 Poland
Japanese Skid Tester 165-SR13 0.5 Japan Slip Methods % Slip Test Tire Water
Depth, mm Country
Skiddometer BV 11 15 VTI 4.00-8 0.5 Sweden,
Slovakia
Skiddometer BV 12 0-50 Passenger car type 0.5 Sweden (VTI) Saab Friction Tester
(RST) 15 VTI 4.00-8 0.5 Sweden
DWW Trailer 86 165-R15 (PIARC
smooth) 0.5 Netherlands
Griptester 14.5 Griptester 0.5 Scotland, Canada Side Force Methods Low Angle,
degree Test Tire
Water Depth (nominal), mm
Country
Side-force coefficient road inventory machine (SCRIM)
20 3.00-20 (smooth) 0.5-1
United Kingdom, Australia, Belgium, France,
Ireland, Italy, Spain
Mu meter 7.5 Special External
United Kingdom United States (FAA), Norway Locked-Wheel Methods Low Angle,
degree Test Tire
Water Depth (nominal), mm
Country Stradograph 12 PIARC 165-R15
(smooth) 0.2 Denmark
Finnish 8 Nokia 165 SR15
(smooth) 1.1 Finland
Multifunction Systems Methods Country
Stradograph Locked-wheel, slip (0 to 15%), side force (0 to 15˚), locked-wheel side force
Belgium, France Penn State road friction
Tester Locked-wheel, transient slip (0 to100%), side force (0 to
12˚), locked-wheel side force United States (Penn State) Mobile tire traction
dynamometer (MTTD)
Locked-wheel, slip (0 to 100%), side force (0 to 25˚) United States (U.S. DOT)
Skid resistance measuring machine
Locked-wheel, slip (0 to 100%), side force (0 to 45˚) Japan
Skiddometer BV 8 Locked-wheel, slip (14%) Switzerland
Description of system* Schematic representation Hydrodynamic equation 1. Plane, smooth, rigid,
inclined surfaces. No vertical motion.
Wedge term:
3 6
d dp d
h U
dx⎛⎜⎝ dx⎞ =⎟⎠ μ dx h U2=U
U1=0
P W
x
h(x)
2. Plane, smooth, parallel surfaces.
Lower surface rigid and fixed. Upper surface flexible and held at one end.
Stretch term:
3 6
d dp d
h h
dx⎛⎜⎝ dx⎞ =⎟⎠ μ dx U
3. Plane, smooth, parallel, rigid surfaces. No side motion, lower surface fixed. Upper surface reciprocates
vertically.
Squeeze term:
3 12
d dp
h V
dx⎛⎜ dx⎞ =⎟ μ
⎝ ⎠
U1=0
U2=U W
P
h x
W P
h(t)
* Incompressible, iso-viscous liquid. Two-dimensional models.
x
U2=0 V
U1=0
Classification of support mechanism
Remarks Schematic representation
1. Directional effect Directional parameter negative.
Rigid, parallel surfaces, lower surface fixed.
2. Macro-elasto- hydrodynamic
Upper surface plane, smooth and rigid. Lower surface flexible with sinusoidal or symmetrical roughness. Elasto-hydrodynamic distortion produces net load support.
3. Cavitation Rigid, parallel surfaces. Upper surface smooth, lower has sinusoidal roughness. Cavitation destroys negative pressure, giving net load support.
4. Viscosity effects For sinusoidal roughness in lower surfaces (same conditions as 3 above), pressure effect increases viscosity and load support, temperature has opposite effect.
In all cases:
W p A p
W U
P
+ + + +
+
- - -
- -
h(x) x
W U
P
+ + + +
+
h(x) x
Distortion
- - -
+ -
P
h(x) x
+ -
+ -
+ -
+ -
W U
Cavitation effects
δ δA
+ −
≡∑ −∑
Texture Depth (m)
10-6 10-5 0.0001 0.001 0.01 0.1 1.0 10
Microtexture Macrotexture Mega-
texture
Unevenness
Wet Pavement Friction
Exterior Noise
Interior Noise Splash & Spray
Rolling Resistance
Tire Wear Tire Damage
Figure 2.1 Effect of texture depth on friction and noise (PIARC, 1987)
0 10 20 30 40 50 60 70 80
20 40 60 80 100 120 140
Vehicle Speed (km/h)
Skid Number
t = 0 mm (Dry Pavement
Surface)
t = 0.1 mm
t = 0.5 mm
t = 1 mm
t =1.5 mm
Note: t refers to the water film thickness
Figure 2.2 Influences of water film thickness and vehicle speed on skid resistance (Benedetto, 2002)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
20 30 40 50 60 70
Speed, mph
Friction Factor
6.50 x 15 Bias Ply
24 psi Inflation Pressure Test Method ASTM E274 Full Standard Tread
High Styrene Rubber
Ribbed Tire Synthetic Rubber Smooth Tire
Natural Rubber
Figure 2.3 Differences in locked wheel performance on interchangeable tires on the same wet pavement surface (fine cold asphalt) (Maycock, 1965)
Figure 2.4 British Pendulum Tester (Giles et al., 1964)
Figure 2.5 Rubber Sliding on a Hard Substrate of Short-ranged and Long ranged Surface Roughness (Persson, 1998)
Figure 2.6 Frictional performances of (a) adhesion-producing and (b) hysteresis producing surfaces (Kummer and Meyer, 1966)
TOTAL
ADHESION
HYSTERESIS
COEFFICIENT OF FRICTION
SLIDING SPEED
Figure 2.7 Generalized representation of the coefficient of friction between a steel sphere and rubber as a function of sliding speed (Highway Research Board, 1972)
dx
dy dz
p p + (∂p/∂x)dx
τzx + (∂τzx/∂z)dz
τzx
u + (∂u/∂z)dz
(x, y, z) u h
dh/dt
x y
z vb
wb
va
wa
l W
ua
ub
Figure 2.8 Schematic of fluid flow between two surfaces and stresses acting on fluid element and velocities in x-z plane
Assumed Film Thickness Distribution
Modified Film Thickness Distribution
Hydrodynamic Pressure Generation
Elastic Displacements
Initial Fina Reynolds Equation
Elastic Equation
l
Figure 2.9 General iterative procedures for elasto-hydrodynamic lubrication
F1 V1
Figure 2.10 Boundary layer lubricated frictional contact
P2
F2 V2
Figure 2.11 Hydrodynamic lubricated frictional contact (Partial)
Direction of movement Direction of movement
A B C
A B C
Zone A Zone B Zone C
Boundary of static tire- ground contact area
Low Speed
Zone A Zone B Zone C
Boundary of static tire- ground contact area
Low Speed
Zone A Zo
A: Sinkage Zone (Hydrodynamic Lubrication)
B: Transition Zone (Partial Hydrodynamic Lubrication) C: Actual Contact Zone (Boundary Layer Lubrication)
Figure 2.12 Tire sliding on wetted pavement surface - three-zone concept (Moore 1966)
ne B
Zone C
Boundary of static tire- ground contact area
High Speed
Zone A ne B
Zone C Zo
High Speed
Boundary of static tire- ground contact area
20 30 40 50 60 70 80
20 30 40 50 60
Speed, mph
SN, Calculated Skid Number
Simulated Rain Conditions Tread depth = 11/32 in.
Texture depth = 0.030 in.
Transverse Texture (WD = -0.02 in.)
Transverse Texture (WD = -0 in.)
Longitudinal Texture (WD = -0.02 in.)
Longitudinal Texture (WD = 0 in.)
Figure 2.13 Longitudinal pavement texture versus transverse pavement texture (Balmer and Gallaway, 1983)
Figure 2.14 Finite element model of the British pendulum tester developed by Liu et al. (2003)
Beam 1
Beam 2
Beam 3 Spring
Rubber slider
Numerical Modeling of Hydroplaning and Skid Resistancefor Sliding Locked Wheel Stage I: Numerical Modeling of Hydroplaning using Computational Fluid Dynamics and Using the NASA Hydroplaning Tire Profile Stage II: Numerical Modeling of Hydr Resistance using Fluid-Structure-Inter Mechanics and Computational Fluid D relaxing the NASA Hydroplaning Tire Pr
oplaning and Skid action (Solid ynamics) and ofile Assumption Assessing the validity of 2-D hydroplaning modeling of Browne’s experiment
Assessing the validity of 3-D hydroplaning modeling of Browne’s experiment
Modeling concepts and fundamentals 3-D modeling of hydroplaning using NASA hydroplaning tire profile
Verification 3-D hydroplaning modeling of Browne’s experiment Verification against NASA hydroplaning equation Effects of microtexture on hydroplaning Analysis of longitudinal and transverse pavement grooving against hydroplaning Comparison between longitudinal and transverse pavement grooving in hydroplaning control
Modeling concepts and fundamentals Design and evaluation of longitudinal and transverse pavement grooving against hydroplaning
Effect of longitudinal and transverse groove dimensions on hydroplaning Evaluation of current pavement grooving design practices Design of longitudinal and transverse pavement grooving dimensions using concept of risk Development of 3-D model using Fluid-Structure-Interaction (FSI)
Pneumatic tire and pavement modeling and calibration of model Fluid modeling -Phase I 3-D modeling of hydroplaning for the ASTM standard smooth tire
Verification against NASA hydroplaning equation Effect of water depth, load and tire inflation pressure on hydroplaning
Effect of footprint aspect ratio on hydroplaning Verification of simulation model 3-D modeling of skid resistance for the ASTM standard smooth tire
Chapter 3 Chapter 4 Chapter 5
Chapter 7 Effect of vehicle speed, water depth, tire pressure and load on skid resistance Figure 2.15 Scope of Research in Thesis
Chapter 8 Chapter 6