Pressure and partial wetting effects on superhydrophobic friction reduction in microchannel flow

2012 ◽  
Vol 24 (11) ◽  
pp. 112003 ◽  
Author(s):  
Tae Jin Kim ◽  
Carlos Hidrovo
Keyword(s):  
Friction Reduction ◽  
Microchannel Flow ◽  
Partial Wetting

Friction reduction by inlet temperature variation in microchannel flow

2021 ◽  
Vol 33 (6) ◽  
pp. 062003
Author(s):  
Dmitry S. Gluzdov ◽  
Elizaveta Ya. Gatapova
Keyword(s):  
Temperature Variation ◽  
Friction Reduction ◽  
Inlet Temperature ◽  
Microchannel Flow

Stability Analysis of Cassie-Baxter State Under Pressure Driven Flow

2010 ◽  
Author(s):  
Tae Jin Kim ◽  
Carlos H. Hidrovo
Keyword(s):  
Liquid Layer ◽  
Friction Reduction ◽  
Wetting Transition ◽  
Textured Surface ◽  
Microchannel Flow ◽  
Flow Conditions ◽  
Cassie State ◽  
The Stability ◽  
Gas Layer ◽  
Micro Cavity

The Cassie-Baxter state is a phenomenon in which a liquid rests on top of a textured surface with a gas layer trapped underneath the liquid layer. This gas layer introduces an effective shear free boundary that induces slip at the liquid-gas interface, allowing for friction reduction in liquid channel flows. Multiple studies have shown that different surface configurations result in different friction reduction characteristics, and most work is aimed at controlling the roughness factor and its shape in order to achieve an increased slip flow. This paper investigates the effects that different texturing geometries have on the stability of the Cassie state under pressurized microchannel flow conditions. To test the stability effects associated with the pressurized microchannel flow conditions, microfluidic channels with microstructures on the side walls were designed and fabricated. The microstructures were designed to induce the Cassie state with a liquid-air interface forming between the texturing trenches. The air trapped within the microstructure is treated as an ideal gas, with the compressibility induced pressure rise acting as a restrictive force against the Wenzel wetting transition. The model was validated against experimental flow data obtained using microchannel samples with microtextured boundaries. The microchannels were fabricated in PDMS (poly-dimethylsiloxane) using soft lithography and were baked on a hot plate to ensure the hydrophobicity of the microtexture. Pressure versus flow rate data was obtained using a constant gravitational pressure head setup and a flow meter. The liquid-gas interface layer in the microchannel was visualized using bright field microscopy that allowed measurement of the liquid penetration depth into the microtexturing throughout the microhannel. The experimental results indicate that air trapped in the pockets created by micro-cavity structures prevented the liquid layer from completely filling the void. As expected, the pressure drop in the micro-cavity textured channel showed a considerable decrease compared to that in the flat surfaced channel. These results also suggest that micro-cavities can maintain the Cassie state of a liquid meniscus, resting on top of the surface, in larger pressure ranges than open spaced micro-pillars arrays.

Effect of Wetted Microtexturing on Friction in Microchannel Flow

2020 ◽  
Author(s):  
Nastaran Rabiei ◽  
Carlos Hidrovo
Keyword(s):  
Aspect Ratio ◽  
Hydraulic Resistance ◽  
Open Space ◽  
Friction Reduction ◽  
Solid Boundary ◽  
Textured Surface ◽  
Microchannel Flow ◽  
Small Diffusion ◽  
Pressure Drag ◽  
Aspect Ratios

Abstract Microchannel flows are widely used in applications where small diffusion length scales are important. However, their inherent dimensional constrain also translates into high pumping power requirements. Inspired by nature, one possible method to reduce the large viscous pressure losses is to introduce textures in a microchannel. Depending on the interaction between the textured surface and the liquid, the microstructures can either be wetted or nonwetted. Less adhesion between solid and liquid in nonwetted state has made it popular in most of the friction reduction studies. However, in the nonwetted state, preventing liquid from penetrating into the grooves under pressurized conditions and the gas-liquid interface acting like a solid boundary open space to consider the wetted state for friction reduction as well. When dealing with the wetted state we should be aware that penetration of the flow inside the grooves can induce the pressure drag alongside the skin drag. Therefore, the wetted state will lead to a trade-off between skin and pressure drag. The aim of this work is to understand how different microtextures affect the total drag in a laminar microchannel flow. Textured microchannels with width-to-depth aspect ratios of 1, 10 and 50 and different width of the land region have been tested. In order to perform correct comparisons, the textured and baseline microchannels are designed to have the same volume. The results show that increasing the aspect ratio of the trenches introduces an extermum point in the hydraulic resistance of the microchannels. The optimum aspect ratio for the tested microchannels is 10, in which the trenches are not wide enough for streamlines to bend inside the trenches and increase the skin drag and they are not highly dense along the microchannel to reveal the negative effect of the pressure drag. On the whole, the hydraulic resistance of the textured channels is higher than the equivalent baseline for all the tested geometries.

Estimating Friction Reduction ForCasing Operations in High-Angle Wells in The Arctic Region - A Russia Case History

2011 ◽  
Author(s):  
Chimerebere Onyekwere Nkwocha ◽  
Evgeny Glebov ◽  
Alexey Zhludov ◽  
Sergey Galantsev ◽  
David Kay
Keyword(s):  
Case History ◽  
Arctic Region ◽  
Friction Reduction ◽  
The Arctic ◽  
High Angle ◽  
The Arctic Region

scholarly journals Dynamic Wetting of Molten Polymers on Cellulosic Substrates: Model Prediction for Total and Partial Wetting

2020 ◽  
Vol 7 ◽  
Author(s):  
Monica Francesca Pucci ◽  
Benoît Duchemin ◽  
Moussa Gomina ◽  
Joël Bréard
Keyword(s):  
Model Prediction ◽  
Dynamic Wetting ◽  
Partial Wetting ◽  
Molten Polymers

scholarly journals The Rotating Liner Engine (RLE) Diesel Prototype: Reducing Internal Engine Friction by about 40% under Idle Conditions

2021 ◽  
Vol 11 (2) ◽  
pp. 779
Author(s):  
Dimitrios Dardalis ◽  
Amiyo Basu ◽  
Matt J. Hall ◽  
Ronald D. Mattthews
Keyword(s):  
Internal Combustion Engines ◽  
Hydrodynamic Lubrication ◽  
Cylinder Liner ◽  
Friction Reduction ◽  
Contact Boundary ◽  
Metal Contact ◽  
Load Testing ◽  
Gas Leakage ◽  
Brake Mean Effective Pressure ◽  
Economy Benefit

The Rotating Liner Engine (RLE) concept is a design concept for internal combustion engines, where the cylinder liner rotates at a surface speed of 2–4 m/s in order to assist piston ring lubrication. Specifically, we have evidence from prior art and from our own research that the above rotation has the potential to eliminate the metal-to-metal contact/boundary friction that exists close to the piston reversal areas. This frictional source becomes a significant energy loss, especially in the compression/expansion part of the cycle, when the gas pressure that loads the piston rings and skirts is high. This paper describes the Diesel RLE prototype constructed from a Cummins 4BT and the preliminary observations from initial low load testing. The critical technical challenge, namely the rotating liner face seal, appears to be operating with negligible gas leakage and within the hydrodynamic lubrication regime for the loads tested (peak cylinder pressures of the order of 100 bar) and up to about 10 bar BMEP (brake mean effective pressure). Preliminary testing has proven that the metal-to-metal contact in the piston assembly mostly vanished, and a friction reduction at idle conditions of about 40% as extrapolated to a complete engine has taken place. It is expected that as the speed increases, the friction reduction percentage will diminish, but as the load increases, the friction reduction will increase. The fuel economy benefit over the US Heavy-Duty driving cycle will likely be of the order of 10% compared to a standard engine.

scholarly journals On the Microstructural, Mechanical and Tribological Properties of Mo-Se-C Coatings and Their Potential for Friction Reduction against Rubber

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1336
Author(s):  
Jorge Caessa ◽  
Todor Vuchkov ◽  
Talha Bin Yaqub ◽  
Albano Cavaleiro
Keyword(s):  
Carbon Content ◽  
Friction And Wear ◽  
Current Mode ◽  
Friction Reduction ◽  
Transition Metal Dichalcogenide ◽  
Butadiene Rubber ◽  
Wear Rates ◽  
Mechanical And Tribological Properties ◽  
The Coefficient Of Friction ◽  
Pin On Disk

Friction and wear contribute to high energetic losses that reduce the efficiency of mechanical systems. However, carbon alloyed transition metal dichalcogenide (TMD-C) coatings possess low friction coefficients in diverse environments and can self-adapt to various sliding conditions. Hence, in this investigation, a semi-industrial magnetron sputtering device, operated in direct current mode (DC), is utilized to deposit several molybdenum-selenium-carbon (Mo-Se-C) coatings with a carbon content up to 60 atomic % (at. %). Then, the carbon content influence on the final properties of the films is analysed using several structural, mechanical and tribological characterization techniques. With an increasing carbon content in the Mo-Se-C films, lower Se/Mo ratio, porosity and roughness appeared, while the hardness and compactness increased. Pin-on-disk (POD) experiments performed in humid air disclosed that the Mo-Se-C vs. nitrile butadiene rubber (NBR) friction is higher than Mo-Se-C vs. steel friction, and the coefficient of friction (CoF) is higher at 25 °C than at 200 °C, for both steel and NBR countersurfaces. In terms of wear, the Mo-Se-C coatings with 51 at. % C showed the lowest specific wear rates of all carbon content films when sliding against steel. The study shows the potential of TMD-based coatings for friction and wear reduction sliding against rubber.

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.

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