• Title/Summary/Keyword: Slip Velocity

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Numerical Analysis of the Slip Velocity and Temperature-Jump in Microchannel Using Langmuir Slip Boundary Condition (미소채널내의 Langmuir 미끄럼 경계조건을 통한 미끄럼 속도 및 급격한 온도변화에 관한 수치해석)

  • Kim, Sang-Woo;Kim, Hyun-Goo;Lee, Do-Hyung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.3
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    • pp.164-169
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    • 2009
  • The slip velocity and the temperature jumps for low-speed flow in microchannels are investigated using Langmuir slip boundary condition. This slip boundary condition is suggested to simulate micro flow. The current study analyzes Langmuir slip boundary condition theoretically and it analyzed numerically micro-Couette flow, micro-Poiseuille flow and grooved microchannel flow. First, to prove validity for Langmuir slip condition, an analytical solution for micro-Couette flow is derived from Navier-Stokes equations with Langmuir slip conditions and is compared with DSMC and an analytical solution with Maxwell slip boundary condition. Second, the numerical analysis is performed for micro-Poiseuille flow and grooved microchannel flow. The slip velocity and temperature distribution are compared with results of DSMC or Maxwell slip condition and those are shown in good agreement.

Anti-Slip Control for Wheeled Robot Based on Disturbance Observer (외란 관측기를 이용한 이동 로봇의 슬립 제어)

  • Kwon, Sun-Ku;Huh, Uk-Youl;Kim, Jin-Whan;Kim, Hak-Il
    • Proceedings of the KIEE Conference
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    • 2004.05a
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    • pp.50-52
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    • 2004
  • Mobility of an indoor wheeled robot is affected by adhesion force that is related to various floor conditions. When the adhesion force between driving wheels and the floor decreases suddenly, the robot has slip state. First of all, this paper models adhesion characteristics and slip in wheeled robot. Secondly, the paper proposes estimation method of adhesion force coefficient according to slip velocity. In oder to overcome this slip problem, optimal slip velocity must be decided for stable movement of wheeled robot. The paper proposes an anti-slip control system based on an ordinary disturbance observer, that is, the anti-slip control is achieved by reducing the driving torque enough to give maximum adhesion force coefficient. These procedure is implemented using a Pioneer 2-DXE parameter.

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Stability Analysis of the Optimal Semi-Trailer Vehicles

  • Mongkolwongrojn, M.;Campanyim, P.
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.248-251
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    • 2004
  • Stability of truck and trailer are the most significance in Thai automotive industry. This paper presents the mathematical model of a six-degree-of-freedom semi-trailer vehicle. Search method was implemented to obtain the optimum design variables of the trailer which are the distance from the fifth wheel to the centroid of the trailer and the distance from the centroid of the trailer to the trailer axel. The objective function is to minimize the steady side slip velocity, steady-state yawing velocity and steady-state angle between the tractor and the trailer. From the calculation , the optimum distance from the fifth wheel to the centroid of the trailer and the optimum distance from the centroid of the trailer to the trailer axle are 5.50 and 3.25 meters respectively. The stability of the optimal semi-trailer vehicle was also examined in steady state. The steady side slip velocity, yawing velocity and the angle between tractor and trailer are also obtained using linearization technique under unit step disturbance of the tractor front wheel steering angle.

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Mixing in a Microchannel by using Induced-charge Electro-osmosis (마이크로 채널 내 유도-전하 전기삼투에 의한 혼합)

  • Jeon, Young-Hun;Heo, Young-Gun;Jung, Won-Hyuk;Alapati, Suresh;Suh, Yong-Kweon
    • Journal of the Korean Society of Visualization
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    • v.8 no.4
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    • pp.13-18
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    • 2010
  • This paper presents an experimental study on the performance of a micro-mixer using AC electro-osmotic flow. The microchannel is made of PDMS for the side and top walls and glass patterned with ITO for the bottom wall. We first investigated the effect of the applied potential as well as the frequency on the slip velocity. We have found that the slip velocity is roughly proportional to the applied voltage in line with the Helmholtz-Smoluchowski equation and there is an optimum frequency at which the slip velocity becomes maximized. To find the optimum parameters for mixing device we tested our device for various design parameters. It turned out that the best mixing effect is obtained approximately when the electrode angle is $30^{\circ}$, electrode width $200\;{\mu}m$, and the frequency of power supply 700 Hz.

Holdup and Flow Behavior of Fluidized Solid Particles in a Liquid-Solid Circulating Fluidized Bed

  • Lim, Dae Ho;Lim, Ho;Jin, Hae Ryong;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.52 no.3
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    • pp.371-377
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    • 2014
  • Characteristics of holdup and flow behavior of fluidized solid particles were investigated in a liquid-solid circulating fluidized bed ($0.102m{\times}3.5m$). Effects of liquid velocity ($U_L$), particle size ($d_P$) and solid circulation rate ($G_S$) on the solid holdup, overall particle rising velocity, slip velocity between liquid and particles and hydrodynamic energy dissipation rate in the riser were examined. The particle holdup increased with increasing $d_P$ or $G_S$ but decreased with increasing $U_L$. The overall particle rising velocity increased with increasing $U_L$ or $G_S$ but decreased with increasing $d_P$. The slip velocity increased with increasing $U_L$ or $d_P$ but did not change considerably with $G_S$. The energy dissipation rate, which was found to be closely related to the contacting frequency of micro eddies, increased with increasing $d_P$, $G_S$ or $U_L$. The solid particle holdup was well correlated with operating variables such as $U_L$, $d_P$ and $G_S$.

EFFECT OF ASPECT RATIO ON SLIP FLOW IN RECTANGULAR MICROCHANNELS

  • Islam, Md.Tajul;Lee, Yeon-Won
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2803-2810
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    • 2007
  • Three dimensional numerical studies were carried out to investigate the effect of aspect ratio on gas slip flow in rectangular microchannels. We focused on aspect ratio effect on slip velocity, pressure distribution and mass flow rate. As aspect ratio decreases the wall slip velocity also decreases. As a result nonlinearity of pressure distribution increases. The slip velocities on sides and top/bottom walls are different and this difference decreases with increasing aspect ratio. These two velocities are equal when aspect ratio is 1. The ratios of slip mass flow rate over noslip mass flow rate increases with increasing aspect ratios.

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Processing parallel-disk viscometry data in the presence of wall slip

  • Leong, Yee-Kwong;Campbell, Graeme R.;Yeow, Y. Leong;Withers, John W.
    • Korea-Australia Rheology Journal
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    • v.20 no.2
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    • pp.51-58
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    • 2008
  • This paper describes a two-step Tikhonov regularization procedure for converting the steady shear data generated by parallel-disk viscometers, in the presence of wall slip, into a shear stress-shear rate function and a wall shear stress-slip velocity functions. If the material under test has a yield stress or a critical wall shear stress below which no slip is observed the method will also provide an estimate of these stresses. Amplification of measurement noise is kept under control by the introduction of two separate regularization parameters and Generalized Cross Validation is used to guide the selection of these parameters. The performance of this procedure is demonstrated by applying it to the parallel disk data of an oil-in-water emulsion, of a foam and of a mayonnaise.

Analytical Approach of Polymer Flow in Thermal Nanoimprint Lithography (열-나노임프린트 리소그래피 공정에서의 폴리머 유동에 대한 해석적 접근)

  • Kim, Kug-Weon;Kim, Nam-Woong
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.3
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    • pp.20-26
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    • 2008
  • Nanoimprint lithography(NIL) is becoming next generation lithography of significant interest due to its low cost and a potential patterning resolution of 10nm or less. Success of the NIL relies on the adequate conditions of pressure, temperature and time. To have the adequate conditions for NIL, one has to understand the polymer flowing behavior during the imprinting process. In this paper, an analytical approach of polymer flow in thermal NIL was performed based on the squeeze flow with partial slip boundary conditions. Velocity profiles and pressure distributions of the polymer flow were obtained and imprinting forces and residual thickness were predicted with the consideration of the slip velocity between the polymer and the mold/substrate. The results show that the consideration of the slip is very important for investigating the polymer flow in Thermal NIL.

Effects of slip velocity on air gap membrane distillation process

  • Loussif, Nizar;Orfi, Jamel
    • Membrane and Water Treatment
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    • v.5 no.1
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    • pp.57-71
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    • 2014
  • In this study, a theoretical model for the transport phenomena in an Air Gap Membrane Distillation used for desalination was developed. The model is based on the conservation equations for the mass, momentum, energy and species within the feed water solution as well as on the mass and energy balances on the membrane sides. The rarefaction impacts are taken into consideration showing their effects on process parameters particularly permeate flow and thermal efficiency. The theoretical model was validated with available data and was found in good agreement especially when the slip condition is introduced. The rarefaction impact was found considerable inducing an increase in the permeate flux and the thermal efficiency.

Re-adhesion Control for Wheeled Robot Using Fuzzy Logic (퍼지 제어기를 이용한 이동 로봇의 재점착 제어)

  • Kwon, Sun-Ku;Huh, Uk-Youl;Kim, Hak-Il
    • Proceedings of the KIEE Conference
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    • 2004.07d
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    • pp.2423-2425
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    • 2004
  • Mobility of an indoor wheeled robot is affected by adhesion force that is related to various floor conditions. When the adhesion force between driving wheels and the floor decreases suddenly, the robot has slip state. First of all, this paper models adhesion characteristics and slip in wheeled robot. Secondly, the paper proposes estimation method of adhesion force coefficient(AFC) according to slip velocity. In order to overcome this slip problem, optimal slip velocity must be decided for stable movement of wheeled robot. The paper proposes an anti-slip control system based on an ordinary disturbance observer, that is, the re-adhesion control is achieved by reducing the driving torque enough to give maximum adhesion force coefficient. fuzzy logic controller(FLC) is petty useful with slip through that compare fuzzy with PI control for the controller performance. These procedure is implemented using a Pioneer 2-DXE parameter.

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