Showing papers on "Slip ratio published in 2012"
TL;DR: In this article, three different observers are developed for the estimation of slip ratios and longitudinal tire forces, based on the types of sensors available, including engine torque, brake torque, and GPS measurements.
Abstract: It is well recognized in the automotive research community that knowledge of the real-time tire-road friction coefficient can be extremely valuable for active safety applications, including traction control, yaw stability control and rollover prevention. Previous research results in literature have focused on the estimation of average tire-road friction coefficient for the entire vehicle. This paper explores the development of algorithms for reliable estimation of independent friction coefficients at each individual wheel of the vehicle. Three different observers are developed for the estimation of slip ratios and longitudinal tire forces, based on the types of sensors available. After estimation of slip ratio and tire force, the friction coefficient is identified using a recursive least-squares parameter identification formulation. The observers include one that utilizes engine torque, brake torque, and GPS measurements, one that utilizes torque measurements and an accelerometer and one that utilizes GPS measurements and an accelerometer. The developed algorithms are first evaluated in simulation and then evaluated experimentally on a Volvo XC90 sport utility vehicle. Experimental results demonstrate the feasibility of estimating friction coefficients at the individual wheels reliably and quickly. The sensitivities of the observers to changes in vehicle parameters are evaluated and comparisons of robustness of the observers are provided.
301 citations
TL;DR: In this paper, the effects of slip boundary condition in the presence of dynamic effects of nano particles have not been investigated yet, and the results of the present paper show the flow velocity and the surface shear stress on the stretching sheet and also reduced Nusselt number and reduced Sherwood number are strongly influenced by the slip parameter.
251 citations
TL;DR: In this paper, a state-of-the-art review on convective heat transfer in microchannels is presented, focusing on rarefaction effects in the slip flow regime.
Abstract: Accurate modeling of gas microvection is crucial for a lot of MEMS applications (microheat exchangers, pressure gauges, fluidic microactuators for active control of aerodynamic flows, mass flow and temperature microsensors, micropumps, and microsystems for mixing or separation for local gas analysis, mass spectrometers, vacuum, and dosing valves…). Gas flows in microsystems are often in the slip flow regime, characterized by a moderate rarefaction with a Knudsen number of the order of 10 � 2 ‐10 � 1 . In this regime, velocity slip and temperature jump at the walls play a major role in heat transfer. This paper presents a state of the art review on convective heat transfer in microchannels, focusing on rarefaction effects in the slip flow regime. Analytical and numerical models are compared for various microchannel geometries and heat transfer conditions (constant heat flux or constant wall temperature). The validity of simplifying assumptions is detailed and the role played by the kind of velocity slip and temperature jump boundary conditions is shown. The influence of specific effects, such as viscous dissipation, axial conduction and variable fluid properties is also discussed. [DOI: 10.1115/1.4005063]
137 citations
TL;DR: In this article, the effect of the slip ratio on the RCF strength of railway wheel steel was evaluated using two cylindrical contact specimens under water lubrication at a slip ratio of 0.0-1.0%.
109 citations
TL;DR: In this article, the effects of an anisotropic Navier slip-length boundary condition on turbulent channel flow were investigated by direct numerical simulations, where the slip length boundary condition was made direction dependent by specifying the value of the slip lengths independently for the streamwise and spanwise direction.
Abstract: The effects of an anisotropic Navier slip-length boundary condition on turbulent channel flow are investigated parametrically by direct numerical simulations. The slip-length boundary condition is made direction dependent by specifying the value of the slip length independently for the streamwise and spanwise direction. The change in drag is mapped versus a wide range of streamwise and spanwise slip-length combinations at two different friction Reynolds numbers, Re?0 = 180 and Re?0 = 360. For moderate slip lengths both drag-reducing and drag-increasing slip-length combinations are found. The percentage drag increase saturates at approximately 60% for high spanwise slip. Once a threshold value for the streamwise slip length is exceeded, drag is reduced in all cases irrespective of the value of the spanwise slip length. The Reynolds number appears to have only little influence on the change in drag for the moderate Reynolds numbers studied here. A detailed comparison with the implicit theoretical formula of Fukagata et al. [Phys. Fluids 18, 051703 (2006)], which relates the change in drag with the streamwise and spanwise slip length, has been made. In general, this formula gives a fair representation of the change in drag; a modified version of this relation is presented, which improves the prediction for the change in drag for small slip length values and reduces the number of free parameters contained in the model. The effects of the slip-length boundary condition on the flow are further investigated using mean flow and turbulence statistics. For drag-neutral slip-length combinations the level of turbulent fluctuations is approximately unchanged. The presence of a slip-length boundary condition affects both the level of wall-shear stress fluctuations and the degree of intermittency of the wall-shear stress probability density function. The correlation statistics of the velocity field show that a high spanwise slip length causes a disruption of the near-wall streaks, while high streamwise slip favours an increasing streak regularity.
99 citations
TL;DR: A new technique is proposed to avoid the so called “secular” terms and to improve the computation efficiency of the HAM to arrive at the convergence results by a third order iterative, which is better than that of a twenty-fifth order iteratives in the literature obtained by classical HAM.
97 citations
TL;DR: In this paper, the magnetohydrodynamic slip flow of an electrically conducting, non-Newtonian fluid past a shrinking sheet is studied and the physical pure exponential type solutions are targeted to investigate whether they are unique or multiple under the influence of slip flow conditions.
94 citations
TL;DR: In this paper, the effects of slip velocity on the flow and heat transfer for an electrically conducting micropolar fluid over a permeable stretching surface with variable heat flux in the presence of heat generation (absorption) and a transverse magnetic field are investigated.
88 citations
TL;DR: Sliding-mode-observer (SMO)-based adaptive sliding mode control (SMC) and neural network (NN) control for effective tracking of the slip ratio applicable to electric vehicles (EVs) and hybrid EVs (HEVs), where electric motors are used to achieve braking in addition to propulsion.
Abstract: This paper presents sliding-mode-observer (SMO)-based adaptive sliding mode control (SMC) and neural network (NN) control for effective tracking of the slip ratio applicable to electric vehicles (EVs) and hybrid EVs (HEVs), where electric motors are used to achieve braking in addition to propulsion. The proposed SMO alleviates the difficulty in choosing its gains. To adapt the road condition parameter for better performance, a Lyapunov-based adaptation is integrated with the sliding-mode controller. The resulting adaptive controller performs very well in achieving slip tracking in the face of parameter uncertainties. Furthermore, to cope up with the uncertainties and unknown nonlinearity involved with the vehicle slip dynamics, a nonmodel-based NN controller is developed using the function approximation properties of the multilayer perceptrons.
82 citations
TL;DR: In this paper, the effects of texture/slip configuration on improvement in load capacity and reduction in coefficient of friction for partially textured slip slider and journal bearing were evaluated using one dimensional analysis of modified classical Reynolds equation.
59 citations
TL;DR: In this paper, the surface prediction and control methods are based on a half car model to simulate high speed braking performance and the performance of the controller developed in this paper has been compared with four different ABS control algorithms reported in the literature.
Abstract: Anti-lock brake system (ABS) has been designed to achieve maximum deceleration by preventing the wheels from locking. The friction coefficient between tyre and road is a nonlinear function of slip ratio and varies for different road surfaces. In this paper, methods have been developed to predict these different surfaces and accordingly control the wheel slip to achieve maximum friction coefficient for different road surfaces. The surface prediction and control methods are based on a half car model to simulate high speed braking performance. The prediction methods have been compared with the results available in the literature. The results show the advantage of ABS with surface prediction as compared to ABS without proper surface identification. Finally, the performance of the controller developed in this paper has been compared with four different ABS control algorithms reported in the literature. The accuracy of prediction by the proposed methods is very high with error in prediction in a range of 0.17-2.4%. The stopping distance is reduced by more than 3% as a result of prediction for all surfaces.
TL;DR: In this paper, a study of the flow kinematics in a capillary rheometer was performed with a two-dimensional particle image velocimetry (PIV) system.
Abstract: An analysis of the yielding and flow behavior of a model yield-stress fluid, 0.2 wt% Carbopol gel, in a capillary with slip at the wall has been carried out in the present work. For this, a study of the flow kinematics in a capillary rheometer was performed with a two-dimensional particle image velocimetry (PIV) system. Besides, a stress-controlled rotational rheometer with a vane rotor was used as an independent way to measure the yield stress. The results in this work show that in the limit of resolution of the PIV technique, the flow behavior agrees with the existence of a yield stress, but there is a smooth solid–liquid transition in the capillary flow curve, which complicates the determination of the yield stress from rheometrical data. This complication, however, is overcome by using the solely velocity profiles and the measured wall shear stresses, from which the yield-stress value is reliably determined. The main details of the kinematics in the presence of slip were all captured during the experiments, namely, a purely plug flow before yielding, the solid–liquid transition, as well as the behavior under flow, respectively. Finally, it was found that the slip velocity increases in a power-law way with the shear stress.
TL;DR: In this paper, the peristaltic hemodynamic flow of couple-stress fluids through a porous medium under the influence of wall slip condition was investigated, and analytical solutions for axial velocity, pressure gradient, frictional force, stream function and mechanical efficiency were obtained.
Abstract: The present investigation deals with a theoretical study of the peristaltic hemodynamic flow of couple-stress fluids through a porous medium under the influence of wall slip condition. This study is motivated towards the physiological flow of blood in the micro-circulatory system, by taking account of the particle size effect. Reynolds number is small enough and the wavelength to diameter ratio is large enough to negate inertial effects. Analytical solutions for axial velocity, pressure gradient, frictional force, stream function and mechanical efficiency are obtained. Effects of different physical parameters reflecting couple-stress parameter, permeability parameter, slip parameter, as well as amplitude ratio on pumping characteristics and frictional force, streamlines pattern and trapping of peristaltic flow pattern are studied with particular emphasis. The computational results are presented in graphical form. This study puts forward an important observation that pressure reduces by increasing the magnitude of couple-stress parameter, permeability parameter, slip parameter, whereas it enhances by increasing the amplitude ratio.
TL;DR: In this paper, the authors consider the spreading of a thin two-dimensional droplet on a planar substrate as a prototype system to compare the contemporary model for contact line motion based on interface formation of Shikhmurzaev [Int. J. Multiphas. 1991] to the more commonly used continuum fluid dynamical equations augmented with the Navier-slip condition.
Abstract: We consider the spreading of a thin two-dimensional droplet on a planar substrate as a prototype system to compare the contemporary model for contact line motion based on interface formation of Shikhmurzaev [Int. J. Multiphas. Flow 19, 589 (1993)], to the more commonly used continuum fluid dynamical equations augmented with the Navier-slip condition. Considering quasistatic droplet evolution and using the method of matched asymptotics, we find that the evolution of the droplet radius using the interface formation model reduces to an equivalent expression for a slip model, where the prescribed microscopic dynamic contact angle has a velocity dependent correction to its static value. This result is found for both the original interface formation model formulation and for a more recent version, where mass transfer from bulk to surface layers is accounted for through the boundary conditions. Various features of the model, such as the pressure behaviour and rolling motion at the contact line, and their relevance, are also considered in the prototype system we adopt.
TL;DR: In this paper, a coordinated cascade control method with two sliding-mode variable structure controllers is presented, where the engine torque is tuned to achieve the maximum driving acceleration and then the active brake pressure is applied to the slipped wheel for further modification of the wheel slip ratio.
Abstract: Vehicle traction control system has been developed to enhance the traction capability and the direction stability of the driving wheels through the tyre slip ratio regulation. Under normal situations, if the tyre slip ratio exceeds a certain threshold, the slip ratio of the driving wheel is regulated by the coupled interaction of the engine torque and the active brake pressure. In order to obtain the best driving performance on a road under complicated friction conditions, the driving torque and the active brake pressure, need to be decoupled and adjusted to avoid penalisation of each other. In this paper, a coordinated cascade control method with two sliding-mode variable structure controllers is presented. In this control method, the driving wheel slip ratio is regulated by adjusting the engine torque and the wheel brake pressure. Through the sliding-mode controller, the engine torque is tuned to achieve the maximum driving acceleration and then the active brake pressure is applied to the slipped wheel for further modification of the wheel slip ratio. The advantage of this control method is that through proper regulation, the conflict between the two control inputs could be avoided. Finally, the simulation results validate the effectiveness of the proposed method.
TL;DR: In this paper, the relative motion between large particles and a turbulent flow is described by a stochastic slip velocity, which is defined as the probability distribution of fluctuating velocities for particle and fluid phases.
Abstract: We discuss possible definitions for a stochastic slip velocity that describes the relative motion between large particles and a turbulent flow. This definition is necessary because the slip velocity used in the standard drag model fails when particle size falls within the inertial subrange of ambient turbulence. We propose two definitions, selected in part due to their simplicity: they do not require filtration of the fluid phase velocity field, nor do they require the construction of conditional averages on particle locations. A key benefit of this simplicity is that the stochastic slip velocity proposed here can be calculated equally well for laboratory, field and numerical experiments. The stochastic slip velocity allows the definition of a Reynolds number that should indicate whether large particles in turbulent flow behave (a) as passive tracers; (b) as a linear filter of the velocity field; or (c) as a nonlinear filter to the velocity field. We calculate the value of stochastic slip for ellipsoidal and spherical particles (the size of the Taylor microscale) measured in laboratory homogeneous isotropic turbulence. The resulting Reynolds number is significantly higher than 1 for both particle shapes, and velocity statistics show that particle motion is a complex nonlinear function of the fluid velocity. We further investigate the nonlinear relationship by comparing the probability distribution of fluctuating velocities for particle and fluid phases.
TL;DR: In this article, the dispersion of a neutral non-reacting solute due to electro-osmotic flow through a circular channel under the combined effects of longitudinal non-uniformity of potential and hydrodynamic slippage on the channel wall is analyzed.
Abstract: An analysis using the lubrication approximation is performed for the dispersion of a neutral non-reacting solute due to electro-osmotic flow through a circular channel under the combined effects of longitudinal non-uniformity of potential and hydrodynamic slippage on the channel wall. The wall is periodically patterned for the charge and slip distributions, with a wavelength much longer than the channel radius. It is shown that the presence of slip can greatly amplify the increased dispersion caused by induced pressure gradient brought about by the non-uniformity of wall potential. Non-uniform wall potential interacting with non-uniform slip can give rise to effects much different from those when the potential and slip are both uniformly distributed and equal to the averages of the non-uniform distributions. Mobility and dispersion associated with recirculating flow resulting from oppositely charged slipping region is also examined.
TL;DR: In this article, the statistical moments of the slip velocity were evaluated considering particles with Stokes number, defined as the ratio between the particle response time and the viscous time scale of the flow, in the range 1 < St < 100.
Abstract: The particle slip velocity is adopted as an indicator of the behavior of heavy particles in turbulent channel flow. The statistical moments of the slip velocity are evaluated considering particles with Stokes number, defined as the ratio between the particle response time and the viscous time scale of the flow, in the range 1 < St < 100. The slip velocity fluctuations exhibit a monotonic increase with increasing particle inertia, whereas the fluid-particle velocity covariance is gradually reduced for St ⩾ 5. Even if this covariance equals the particle turbulence intensity, a substantial amount of particle slip may occur. Relevant to two-fluid modeling of particle-laden flows is the finding that the standard deviation of the slip velocity fluctuations is significantly larger than the corresponding mean slip velocity.
TL;DR: In this article, the authors consider the effects of thermal pressurization of pore fluid within a low-permeability fault core may play the key role in the development of earthquake slip.
Abstract: [1] There are several lines of evidence that suggest that thermal pressurization (TP) of pore fluid within a low-permeability fault core may play the key role in the development of earthquake slip. To elucidate effects of TP on spontaneous fault slip, we consider solutions for a steadily propagating slip pulse on a fault with a constant sliding friction, the level of which may reflect other thermally-activated processes at the rupture front (such as the flash heating on asperities). Upon arrival of the pulse front, essentially undrained-adiabatic TP takes place during the initial slip acceleration from the locked state with a corresponding reduction of the fault strength. With passage of time, the diminishing rate of heating (due to the reduced fault strength) and increasing rate of hydrothermal diffusion from the shear zone offset TP and result in partial recovery of the strength, slip deceleration and eventual locking and healing of the slip. We show that the rupture speedvr decreases with thickness hof the principal shear zone. For lab-constrained values of fault-gouge parameters, the TP-pulse solution predicts seismic (vr∼ km/s) slip on a millimeter-to-cm thin principal shear zone; and aseismic slip withvr ∼ 10 km/day and slip rates 1–2 orders above the plate rate on a relatively thick (h∼ 1 m) shear zone. These and other predictions of the TP-pulse model are consistent with the independent sets of observational constraints for large crustal and subduction interplate earthquakes, and slow slip transients (North Cascadia), respectively. Locking of the slip soon after the diffusive transport of the heat and pore fluid becomes efficient significantly limits the maximum co-seismic temperature rise to values well below previous theoretical estimates. As a result, the onset of macroscopic melting and some of thermal decomposition reactions, recently suggested to explain strong co-seismic fault weakening, are precluded over much of the seismogenic zone.
TL;DR: In this paper, the flow and heat transfer of a non-Newtonian power-law fluid over a nonlinearly stretching surface has been studied numerically under conditions of constant heat flux and thermal radiation and evaluated for the effect of wall slip.
Abstract: The flow and heat transfer of a non-Newtonian power-law fluid over a non-linearly stretching surface has been studied numerically under conditions of constant heat flux and thermal radiation and evaluated for the effect of wall slip. The governing partial differential equations are transformed into a set of coupled non-linear ordinary differential equations which are using appropriate boundary conditions for various physical parameters. The remaining set of ordinary differential equations is solved numerically by fourth-order Runge–Kutta method using the shooting technique. The effects of the viscosity, the slip velocity, the radiation parameter, power-law index, and the Prandtl number on the flow and temperature profiles are presented. Moreover, the local skin friction and Nusselt numbers are presented. Comparison of numerical results is made with the earlier published results under limiting cases.
01 Oct 2012
TL;DR: In this article, a four-wheel driving force distribution method based on driving stiffness and slip ratio estimation is proposed, which is applied to improve the distribution method, and the effectiveness of the improved method is verified by experiments.
Abstract: In this paper, a four-wheel driving force distribution method based on driving stiffness and slip ratio estimation is proposed. In previously proposed distribution method, vehicle velocity is measured by an expensive optical sensor and moreover the response speed of distribution is limited by that of Driving Force Control (DFC), the traction control proposed by the authors' research group. Therefore, driving stiffness and slip ratio estimation is applied to improve the distribution method. Due to the slip ratio estimation, vehicle velocity sensor is not needed and the distribution speed depends on that of driving stiffness estimation, which is faster than DFC. If the length of a slippery surface is shorter than the vehicle's wheel base, the total driving force is retained by distributing the shortage of driving force to the wheels that still have traction. On the other hand, when either the left or right side run on a slippery surface, yaw-moment is suppressed. The effectiveness of the improved method is verified by experiments.
TL;DR: In this article, the influence of partial-slip boundary conditions on the laminar flow properties past a circular cylinder was examined by using the finite element method accommodating SU/PG scheme and four Reynolds numbers (20, 40, 80, and 100) and six slip lengths were considered in numerical simulation to investigate the effects of slip length and Reynolds number on characteristic parameters such as wall vorticity, drag coefficient, separation angle, wake length, velocity distributions on and behind the cylinder, lift coefficient, and Strouhal number.
Abstract: SUMMARY
The no-slip condition is an assumption that cannot be derived from first principles and a growing number of literatures replace the no-slip condition with partial-slip condition, or Navier-slip condition. In this study, the influence of partial-slip boundary conditions on the laminar flow properties past a circular cylinder was examined. Shallow-water equations are solved by using the finite element method accommodating SU/PG scheme. Four Reynolds numbers (20, 40, 80, and 100) and six slip lengths were considered in the numerical simulation to investigate the effects of slip length and Reynolds number on characteristic parameters such as wall vorticity, drag coefficient, separation angle, wake length, velocity distributions on and behind the cylinder, lift coefficient, and Strouhal number. The simulation results revealed that as the slip length increases, the drag coefficient decreases since the frictional component of drag is reduced, and the shear layer developed along the cylinder surface tends to push the separation point away toward the rear stagnation point so that it has larger separation angle than that of the no-slip condition. The length of the wake bubble zone was shortened by the combined effects of the reduced wall vorticity and wall shear stress which caused a shift of the reattachment point closer to the cylinder. The frequency of the asymmetrical vortex formation with partial slip velocity was increased due to the intrinsic inertial effect of the Navier-slip condition. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this article, the effects of hydrodynamic slip on entropy generation in the boundary layer flow over a vertical sur- face with convective boundary condition are reported. And the expressions for the entropy generation number and the Bejan number are presented and the results are discussed graphically and quantitatively for the slip parameter, the local Grashof number, the Prandtl number, local convective heat transfer parameters, the group parameter and the local Reynolds number.
Abstract: The present article aims to report the effects of hydrodynamic slip on entropy generation in the boundary layer flow over a vertical sur- face with convective boundary condition. Suitable similarity transformations are used to transform the fundamental equations of hydro- dynamic and thermal boundary layer flow into ordinary differential equations. The governing equations are then solved numerically us- ing the shooting method and the velocity and the temperature profiles are obtained for various values of parameters involved in the gov- erning equations. The expressions for the entropy generation number and the Bejan number are presented and the results are discussed graphically and quantitatively for the slip parameter, the local Grashof number, the Prandtl number, the local convective heat transfer parameter, the group parameter and the local Reynolds number. It is observed that due to the presence of slip, entropy production in a thermal system can be controlled and reduced.
TL;DR: In this article, a simple analytical model with second-order slip boundary conditions for a normalized Poiseuille number is proposed, which can be applied to either rarefied gas flows or apparent liquid slip flows.
Abstract: This paper significantly extends previous studies to the transition regime by employing the second-order slip boundary conditions. A simple analytical model with second-order slip boundary conditions for a normalized Poiseuille number is proposed. The model can be applied to either rarefied gas flows or apparent liquid slip flows. The developed simple models can be used to predict the Poiseuille number, mass flow rate, tangential momentum accommodation coefficient, pressure distribution of gaseous flow in noncircular microchannels and nanochannels by the research community for the practical engineering design of microchannels and nanochannels. The developed second-order models are preferable since the difficulty and “investment” is negligible compared with the cost of alternative methods such as molecular simulations or solutions of Boltzmann equation. Navier–Stokes equations with second-order slip models can be used to predict quantities of engineering interest such as the Poiseuille number, tangential momentum accommodation coefficient, mass flow rate, pressure distribution, and pressure drop beyond its typically acknowledged limit of application. The appropriate or effective second-order slip coefficients include the contribution of the Knudsen layers in order to capture the complete solution of the Boltzmann equation for the Poiseuille number, mass flow rate, and pressure distribution. It could be reasonable that various researchers proposed different second-order slip coefficients because the values are naturally different in different Knudsen number regimes. It is analytically shown that the Knudsen’s minimum can be predicted with the second-order model and the Knudsen value of the occurrence of Knudsen’s minimum depends on inlet and outlet pressure ratio. The compressibility and rarefaction effects on mass flow rate and the curvature of the pressure distribution by employing first-order and second-order slip flow models are analyzed and compared. The condition of linear pressure distribution is given.
TL;DR: The obtained results show that the flow is appreciably influenced by the presence of Knudsen number of slip condition, permeability parameter of porous medium, Hartmann number of magnetic field, and frequency of periodic body acceleration.
Abstract: Unsteady pulsatile flow of blood through porous medium in an artery has been studied under the influence of periodic body acceleration and slip condition in the presence of magnetic field considering blood as an incompressible electrically conducting fluid. An analytical solution of the equation of motion is obtained by applying the Laplace transform. With a view to illustrating the applicability of the mathematical model developed here, the analytic explicit expressions of axial velocity, wall shear stress, and fluid acceleration are given. The slip condition plays an important role in shear skin, spurt, and hysteresis effects. The fluids that exhibit boundary slip have important technological applications such as in polishing valves of artificial heart and internal cavities. The effects of slip condition, magnetic field, porous medium, and body acceleration have been discussed. The obtained results, for different values of parameters into the problem under consideration, show that the flow is appreciably influenced by the presence of Knudsen number of slip condition, permeability parameter of porous medium, Hartmann number of magnetic field, and frequency of periodic body acceleration. The study is useful for evaluating the role of porosity and slip condition when the body is subjected to magnetic resonance imaging (MRI).
TL;DR: In this paper, the stability of steady slip and homogeneous shear is studied for rate-hardening materials undergoing chemical reactions that produce weaker materials (reaction-weakening process), in drained conditions.
Abstract: The stability of steady slip and homogeneous shear is studied for rate-hardening materials undergoing chemical reactions that produce weaker materials (reaction-weakening process), in drained conditions. In a spring- slider configuration, a linear perturbation analysis provides analytical expressions of the critical stiffness below which unstable slip occurs. In the framework of a frictional constitutive law, numerical tests are performed to study the effects of a nonlinear reaction kinetics on the evolution of the instability. Slip instabilities can be stopped at relatively small slip rates (only a few orders of magnitude higher than the forcing velocity) when the reactant is fully depleted. The stability analysis of homogeneous shear provides an independent estimate of the thickness of the shear localization zone due to the reaction weakening, which can be as low as 0.1 m in the case of lizardite dehydration. The potential effect of thermo-chemical pore fluid pressurization during dehydration is discussed, and shown to be negligible compared to the reaction-weakening effect. We finally argue that the slip instabilities originating from the reaction-weakening process could be a plausible candidate for intermediate depth earthquakes in subduction zones.
TL;DR: In this paper, peristaltic flow of an incompressible six constant Jeffrey's fluid model has been discussed and the flow has been analyzed in a wave frame of reference moving with the wave speed c.
TL;DR: In this paper, a molecular dynamics simulation of slip boundary for fluid flow past a solid surface incorporating roughness effect as characterized by fractal geometry has been conducted with a focus on the origin of slip, fluid structure, and slip boundary flow.
Abstract: A molecular dynamics simulation of slip boundary for fluid flow past a solid surface incorporating roughness effect as characterized by fractal geometry has been conducted with a focus on the origin of slip, fluid structure, and slip boundary flow. The results indicate that interfacial slip develops provided that the wall is effectively uncorrugated. Compared with the atomically smooth surface, extra viscous dissipation is induced for shear flow past a rough surface and leading to a reduction in boundary slip. In particular, we find that a more irregular topography decreases the boundary slip even for the same statistical roughness height.
TL;DR: In this article, the influence of surface slip on the physics of laminar jet impingement on a flat horizontal surface is explored, showing that at a given radial location, the boundary layer growth and thin film thickness decrease, while the surface velocity of the thin film increases with increasing slip at the surface.
Abstract: This paper explores the influence surface slip, uniform in all directions with constant slip length, exerts on the physics of laminar jet impingement on a flat horizontal surface. Slip exists on superhydrophobic surfaces, and due to the relatively thin film dynamics associated with the growth of the laminar jet after impingement, its influence on the fluid physics is significant. An analysis based on momentum considerations is presented that allows prediction of the relevant thin film parameters as a function of radial position from the impingement point, jet Reynolds number, and constant relative slip length of the surface. Further, the analysis allows determination of the hydraulic jump location in terms of laminar jet characteristics and imposed downstream liquid depth. The results reveal that at a given radial location, the boundary layer growth and thin film thickness decrease, while the surface velocity of the thin film increases with increasing slip at the surface. The departure from classical no-s...
TL;DR: In this article, the effects of Knudsen number (Kn) and slip boundary condition have been addressed on the viscosity of a nano flow passing through a nano-tube, as compared to a purely continuum and size-free formulation.