Elastic liquid jet impaction on a high‐speed moving surface

Abstract

In the railroad industry a friction‐modifying non‐Newtonian liquid, showing elastic behavior, may be applied to the rail in the form of a liquid jet. The interaction of this elastic liquid jet and the moving surface—specifically whether it splashes or adheres without splash—is important in this industrial application. Twelve different elastic liquids with widely varying relaxation times were tested to isolate the effect of elasticity from other fluid properties. Using high‐speed imaging, the interaction between the impinging jet and the moving surface could be captured and analyzed. Although similar to Newtonian jets, for which the Reynolds number plays a major role, the Deborah number was also salient to the splash of elastic liquids. At the elevated Weber numbers of the testing, the Weber number had a much smaller impact on splash than did the Reynolds or Deborah numbers. The ratio of the surface velocity to the jet velocity has only a small effect on the splash. © 2012 American Institute of Chemical Engineers AIChE J, 2012

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

“…In Figure 3A jet deposition occurs on the surface, which has an average roughness height of 0.51 µm, but jet splash occurs when the average roughness height is 0.016 µm (Figure 3C). This dependence on roughness is opposite to that observed by Keshavarz et al 10,11 , who studied impingement on much rougher surfaces, where the surface roughness is significantly larger than the lamella thickness.…”

“…Although some simple theories of splash have been proposed [10][11][12] , there is currently no comprehensive explanation of the phenomenon. Lamella liftoff, which is usually a precursor to splash 12 , is believed to be a function of lamella geometry.…”

“…In this, comparatively rare, regime the lamella remains attached to the surface, as for "deposition", but fine droplets are ejected from near the leading edge of the lamella. In a subsequent study of non-Newtonian fluid effects, Keshavarz et al concluded that the splash/deposition threshold is mainly determined by the Reynolds and Deborah numbers, whereas the jet impingement angle and jet velocity to surface velocity ratios only have a minor effect 11 . In experiments conducted under variable ambient air pressures, Moulson et al discovered that the splash/deposition threshold Reynolds number dramatically increases with decreasing ambient air pressure (i.e., higher ambient pressures make jets more prone to splash), while decreasing ambient air pressure below a certain threshold suppresses splash completely 12 .…”

Free surface lubrication of rotating cylinders by impacting Newtonian liquid jet

“…In the last decade, there has been a growing interest in phenomena of jet‐surface impaction with nonzero tangential velocity due to novel industrial applications such as liquid friction modifiers in rail transport 15 . The mechanism of jet deposition was investigated for both Newtonian 4,16–18 and non‐Newtonian liquids 17,19 . In Newtonian liquids, the most decisive parameters for occurrence of splash are the jet and substrate velocity, substrate surface roughness to jet diameter ratio, 4 as well as ambient air pressure 17 .…”

Smooth printing of viscoelastic microfilms with a flow focusing ejector

“…The impingement water-based suspension of polymers can also be used to reduce the friction in rails. In this case, the liquid is usually applied onto the rail top surface with sprayers mounted on maintenance vehicles [27]. Viscoelastic flow focusing can constitute an advantageous technology in these fields too.…”