Comparing Spray from Tires Rolling on a Wet Surface
Tire spray generated as automobile or truck tires roll over a wet roadway is a familiar hazard to all drivers. Past efforts to mitigate the effects of tire spray have focused on inventing and testing add-on devices to suppress, redirect, or contain spray. These devices have had only limited success in controlling spray. An alternate approach would be to examine tire spray at the source—the tire and wet roadway. This article describes a device designed to simulate tire spray in a laboratory setting, allowing a careful examination of spray in a controlled environment. The device limits the spray to that produced from water passing through a tire groove and then carried away from the roadway by the rotating tire. The spray pattern downstream of the tire patch is captured with high-speed video and stored on disk. The video images are then processed as desired by computer. A concept “time-to-drain” is introduced to characterize the angle at which spray leaves the tire. Time-to-drain is then used to compare the spray patterns of different tires.ABSTRACT
Devices for aerodynamic improvement. The belly pan is a shaped sheet metal panel fastened to the bottom of the vehicle. Adapted from [6].
Reference, sine, and Teflon-coated grooves.
The tire spray apparatus. The right and left tire-loading devices are shown moved away from their normal positions (bolted to the vertical pillars) for clarity.
Cross section of tire groove.
Spray illuminated by a sheet of laser light.
Two-dimensional channel draining under acceleration.
A frame from video for
.
The averaged background image and path 𝒫.
Average background b(θ) along path 𝒫 and the corrected gray level f(θ) along 𝒫 from a single image from video taken at 
. N.b., θ is the angular location of 
on 𝒫, so 
.
Probability
of finding a dark region at θ. For
with the average taken over nine runs. The location of
, determined from the spline fit to
, is marked.
as a function of
for the reference (straight, rubber) groove. Empty circles represent results from individual data sequences, while the filled circles represent averages of three data individual sequences. The error bars extend one standard deviation on either side of the mean.
as a function of
for the Teflon-coated groove. Filled diamonds represent averages of three data sequences.
as a function of
for the sine wave groove. Filled triangles at 3.66 m/s, 6.00 m/s, and 12.0 m/s represent averages of three data sequences, while the filled triangle at 18.0 m/s is the result of the average of four data sequences. The dash-dot line is the fit to data at all speeds. The dashed line is fit to the data at the lower three speeds, ignoring
.
Comparison of the mean breakaway angles for the straight groove (circles and solid line), the Teflon-coated groove (diamonds and dotted line), and the sine wave groove (triangles and dashed line) as functions of
and of We1/2.
Contributor Notes