Reduction of Hydraulic Friction in Confined Flows by Laser Texturing: Experiments and Theoretical Validation

2018 ◽  
Author(s):  
Avinash Kumar ◽  
Subhra Datta ◽  
Dinesh Kalyanasundaram
Keyword(s):  
Fluid Dynamic ◽  
Friction Reduction ◽  
Textured Surfaces ◽  
Nanosecond Pulsed Laser ◽  
Microfluidic Flow ◽  
Theoretical Predictions ◽  
Pressure Manometer ◽  
Hydraulic Friction ◽  
Pump Pressure ◽  
Titanium Alloy Ti6al4v

Hydraulic friction reduction in a microchannel due to superhydrophobic texturing of its walls was studied theoretically and experimentally. A modified Poiseuille equation formulated from an earlier-established semi-analytical approach to model texturing of slip lengths and the “gas cushion model” was used to predict the hydraulic conductance of a microchannel. An experimental setup with a microfluidic flow cell consisting of syringe pump, pressure manometer and tubing measured the pressure drop at different flow rates through a microchannel. The top and bottom walls of the microchannel was textured with micro-pits using nanosecond pulsed laser on the titanium alloy Ti6Al4V. A very high contact angle was observed on the textured surfaces suggesting entrapped gas bubbles. Liquid slippage leading to reduced hydraulic friction is attributable to the bubbles. The pressure-flow rate characteristics of the microchannels confirm friction reduction and also demonstrate a reasonable agreement with the theoretical predictions from the developed fluid dynamic model.

scholarly journals Fast laser surface texturing of spherical samples to improve the frictional performance of elasto-hydrodynamic lubricated contacts

Friction ◽  
2021 ◽  
Author(s):  
G. Boidi ◽  
P. G. Grützmacher ◽  
A. Kadiric ◽  
F. J. Profito ◽  
I. F. Machado ◽  
...  
Keyword(s):  
Surface Texturing ◽  
Hydrodynamic Pressure ◽  
Friction Reduction ◽  
Laser Surface Texturing ◽  
Textured Surfaces ◽  
Engineering Applications ◽  
Lubricated Contacts ◽  
Fluid Uptake ◽  
Direct Laser ◽  
Frictional Performance

AbstractTextured surfaces offer the potential to promote friction and wear reduction by increasing the hydrodynamic pressure, fluid uptake, or acting as oil or debris reservoirs. However, texturing techniques often require additional manufacturing steps and costs, thus frequently being not economically feasible for real engineering applications. This experimental study aims at applying a fast laser texturing technique on curved surfaces for obtaining superior tribological performances. A femtosecond pulsed laser (Ti:Sapphire) and direct laser interference patterning (with a solid-state Nd:YAG laser) were used for manufacturing dimple and groove patterns on curved steel surfaces (ball samples). Tribological tests were carried out under elasto-hydrodynamic lubricated contact conditions varying slide-roll ratio using a ball-on-disk configuration. Furthermore, a specific interferometry technique for rough surfaces was used to measure the film thickness of smooth and textured surfaces. Smooth steel samples were used to obtain data for the reference surface. The results showed that dimples promoted friction reduction (up to 20%) compared to the reference smooth specimens, whereas grooves generally caused less beneficial or detrimental effects. In addition, dimples promoted the formation of full film lubrication conditions at lower speeds. This study demonstrates how fast texturing techniques could potentially be used for improving the tribological performance of bearings as well as other mechanical components utilised in several engineering applications.

Liquid Slippage in Confined Flows: Effect of Periodic Micropatterns of Arbitrary Pitch and Amplitude

2016 ◽  
Author(s):  
Avinash Kumar ◽  
Subhra Datta ◽  
Dinesh Kalyanasundaram
Keyword(s):  
Slip Length ◽  
Fluid Dynamic ◽  
Low Cost ◽  
Slip Boundary Condition ◽  
Friction Reduction ◽  
Fourier Decomposition ◽  
Slip Boundary ◽  
Local Degree ◽  
Effective Slip Length ◽  
Effective Slip

The recently confirmed violation of the no-slip boundary condition in the flow of small-molecule liquids through microchannels and nanochannels has technological implications such as friction reduction. However, for significant friction reduction at low cost, the microchannel wall needs to be chemically inhomogeneous. The direct fluid dynamic consequence of this requirement is a spatial variation in the local degree of liquid slippage. In this work, the pressure-driven flow in a channel with periodically patterned slippage on the channel walls is studied using a spectrally accurate semi-analytical approach based on Fourier decomposition. The method puts no restrictions on the pitch (or wavelength) and amplitude of the pattern. The predicted effective slip length in the limits of small pattern amplitude and thick channels is found to be consistent with previously published results. The effective degree of slippage decreases with the patterning amplitude. Finer microchannels and longer pattern wavelengths promote slippage.

Friction Reduction by Micro-Textured Surfaces in Lubrication

2018 ◽  
Vol 12 (4) ◽  
pp. 603-610 ◽  
Author(s):  
Yue Sun ◽  
Keita Shimada ◽  
Shaolin Xu ◽  
Masayoshi Mizutani ◽  
Tsunemoto Kuriyagawa ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Contact Surface ◽  
Friction Reduction ◽  
Experimental Investigations ◽  
Textured Surface ◽  
Textured Surfaces ◽  
Diamond Cutting ◽  
Tribological Tests ◽  
Sliding Direction

Experimental investigations were carried out to verify if the friction reduction in lubrication can be expanded by a textured surface with sawtooth riblets. Sawtooth riblets were formed by ultraprecision diamond cutting, with a ridge angle of about 60°–90° and height of about 20–50 μm on the contact surface. Six types of textured surfaces with different ridge angles, heights, and sliding directions were tested and compared with the untextured surface. The tribological tests were conducted by a flat-on-flat tribometer in lubrication. The effects of the ridge angle, height, and relative sliding direction on the friction coefficient in lubrication were reported.

scholarly journals Surface Texture Influences on the Running-in Behavior and Friction Reduction

2018 ◽  
Vol 159 ◽  
pp. 02017
Author(s):  
Zhouyong Hou ◽  
Tomomi Honda
Keyword(s):  
Surface Texture ◽  
Internal Combustion Engines ◽  
Friction And Wear ◽  
Fuel Efficiency ◽  
Surface Profile ◽  
Friction Reduction ◽  
Profile Measurement ◽  
Textured Surface ◽  
Combustion Engines ◽  
Textured Surfaces

For improving automobile fuel efficiency, the internal combustion engines must be required to reduce the friction and wear. Changing viscosity of lubricant and surface pressure could succeed, but the seizure is easy to happen in engines. However, the surface texture can solve those problems. The running-in behavior affects friction and wear on whole combustion engines. If the running-in is not carefully designed, catastrophic accident can happen. This experiment investigates that the running-in behavior is influenced by textured surfaces and the tested materials are the cast iron and the different area ratio of dimple of aluminum alloy combination. The friction coefficient and the number and size of wear particles are measured by the friction sensor and particle counter. After the tests, the worn surfaces are measured through using surface profile measurement systems, and some significant phenomena are observed and analyzed. The textured surface verifies good consequence and tribological advantages.

PFPE Modified Silicon Nano-Textured Surfaces for Adhesion and Friction Reduction

2008 ◽  
Author(s):  
Ying Song ◽  
Hengyu Wang ◽  
Min Zou
Keyword(s):  
Amorphous Silicon ◽  
Silicon Surface ◽  
Surface Hydrophobicity ◽  
Friction Reduction ◽  
New Technique ◽  
Textured Surface ◽  
Textured Surfaces ◽  
Hydrophobic Surfaces ◽  
A New Technique ◽  
Induced Crystallization

This paper reports a new technique of producing hydrophobic surfaces with WCA as high as 147°. This technique consists of first generating nano-textures on a silicon surface via aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) and then applying perfluoropolyether (PFPE) on the nano-textured surface (NTS). The resulting PFPE-modified NTS showed significant improvement on both surface hydrophobicity and tribological performances compared to a PFPE-modified smooth silicon surface.

THE EFFECTS OF SURFACE ROUGHNESS ON FRICTION REDUCTION AS THE RESULT OF SURFACE TEXTURING BY ABRASIVE JET MACHINING

Tribologia ◽  
2016 ◽  
Vol 267 (3) ◽  
pp. 195-204
Author(s):  
Sławomir WOŚ ◽  
Waldemar KOSZELA ◽  
Paweł PAWLUS
Keyword(s):  
Surface Roughness ◽  
Friction Force ◽  
Surface Texturing ◽  
Frictional Resistance ◽  
Friction Reduction ◽  
Textured Surfaces ◽  
Sliding Surfaces ◽  
Abrasive Jet Machining ◽  
Oil Pockets

Various machining methods are currently used to obtain the best co-action of sliding surfaces. Application of two-process surfaces led to a decrease of frictional resistance. Textured surfaces after abrasive jest machining are practical examples of two-process topographies. The results of the application of textured discs with the same array of oil pockets of similar sizes, but with different roughness in areas free of dimples, are presented in this paper. It was determined that after this type of machining, the effect of the friction force decrease was caused by surface texturing.

CFD Analysis of Friction-Reduction Effect of Micro-Textured Surfaces in Lubricant

2018 ◽  
Vol 12 (2) ◽  
pp. 206-214 ◽  
Author(s):  
Yue Sun ◽  
Shaolin Xu ◽  
Tomoki Kyoizumi ◽  
Keita Shimada ◽  
Masayoshi Mizutani ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Lubricant Film ◽  
Friction Reduction ◽  
Navier Stokes ◽  
Orthogonal Experimental Design ◽  
Textured Surfaces ◽  
Navier Stokes Equations ◽  
Geometrical Features ◽  
Reduction Effect ◽  
Friction Surfaces

This paper investigates the effects of geometrical features of tailored textures on friction reduction of a surface with a lubricant-film thickness of several to several-tenths micrometers, using the Navier-Stokes equations and the orthogonal experimental design. The results indicate that the surface textured with the selected sawtooth riblets in lubricant can have up to 93.83% less friction than an untextured surface. The thickness of the lubricant film plays the most important role in friction reduction; the height and the ridge angle of the riblets are the secondary factors. The results and principles obtained can potentially be used in the designing of low-friction surfaces in precision machines with transmission parts.

Rapid Computations to Match Impellers With Inducers

2006 ◽  
Author(s):  
Kevin Kaupert
Keyword(s):  
Fluid Dynamic ◽  
Characteristic Curve ◽  
Centrifugal Impeller ◽  
Dynamic Design ◽  
Impeller Outlet ◽  
Rapid Calculation ◽  
Complete Calculation ◽  
Simulated Case ◽  
Pump Pressure ◽  
Pressure Boundary Conditions

Simplifying assumption are examined to quicken the fluid dynamic design of centrifugal pump impellers when an upstream inducer is applied. First a complete inducer with a complete impeller is computed. Second a more rapid calculation method is investigated which utilizes only one inducer passage and one impeller passage. Pitchwise averaging is performed at their interface. A third and even more rapid approach replaces the entire inducer with simulated velocity and pressure boundary conditions upstream of a single impeller passage. In all 3 computed cases a vaned channel diffuser is included at the impeller outlet. The 3 computed cases are compared to the measured pump pressure and efficiency characteristic. In terms of computational intensity the complete calculation presented here took 5 days to generate a 9 point characteristic curve. For the same number of points the averaged case took 2.5 days while the simulated case took 1.5 days to compute. In terms of the results the 3rd simulated method is reasonable until the final centrifugal impeller design phase is reached, when more accurate calculations are required.

Experimental and numerical studies of positive texture effect on friction reduction of sliding contact under mixed lubrication

2020 ◽  
pp. 135065012093091 ◽  
Author(s):  
P Venkateswara Babu ◽  
Syed Ismail ◽  
B Satish Ben
Keyword(s):  
Numerical Study ◽  
Mixed Lubrication ◽  
Friction Reduction ◽  
Asperity Contact ◽  
Textured Surfaces ◽  
Area Density ◽  
Surface Textures ◽  
Lubrication Regimes ◽  
Numerical Predictions ◽  
Pin On Disc

Textured surfaces have been remarkable in improving the frictional performance of sliding contacts, particularly at instances such as boundary or mixed lubrication regimes. This article reports the results of an experimental and numerical study carried out by introducing surface textures in the form of protrusions to investigate its effects on friction performance under a mixed lubrication regime. The surface textures produced by the chemical etching process are tested on the pin on disc test rig by varying area density and height of the texture. In numerical simulation, the modified Reynolds equation (Patir–Cheng flow model) and asperity contact model (Greenwood–Tripp model) are solved for hydrodynamic and asperity pressures, respectively. The results indicate that the experimental measurements are qualitatively in good agreement with numerical predictions. Furthermore, the simulations are performed for different texture shapes by varying texture area density, height, and sliding velocity. The results depict that a maximum friction reduction of 87% with elliptical textures compared to the un-textured case.

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