气浮轴承的fluent 三维仿真

Large eddy simulation of vortex shedding and pressure

fluctuation in aerostatic bearings

Jincheng Zhu a,Han Chen a,b,Xuedong Chen a,n

a State Key Laboratory of Digital Manufacturing Equipment and Technology,Huazhong University of Science and Technology,

Wuhan430074,China

b Department of Mechanics,Huazhong University of Science and Technology,Wuhan430074,China

a r t i c l e i n f o

Article history:

Received21May2012

Accepted5March2013

Available online28April2013

Keywords:

Aerostatic bearing

Large eddy simulation

Vortex shedding

Pressure fluctuation

Vibration

a b s t r a c t

In aerostatic bearings,high speed air flow may induce small vibration,which has been

harmful to the improvement of moving and positioning accuracy of aerostatically

supported devices in ultra-precision applications.In this paper,the transient flow field

in the aerostatic bearing is numerically investigated using the large eddy simulation

method.Turbulent structures are studied and vortex shedding phenomenon is discovered

in the bearing recess.Our computational results demonstrate that vortex shedding causes

pressure fluctuation in the bearing clearance.Relationship between pressure fluctuation

and bearing vibration is established based on our simulation results and experimentally

measured vibration strength.

&2013Elsevier Ltd.All rights reserved.

1.Introduction

Aerostatic bearings have been widely used in ultra-precision moving and positioning equipments.Due to the merit of near-zero friction and low heat generation,applications of aerostatic bearings make it possible for supported devices to realize nanometer positioning accuracy.However,with the increasing demand of positioning accuracy,the inherent small vibration on the order of nanometers(Kawai et al.,2005)severely damages stability and precision of the bearing,especially in sub-nanometer positioning equipments.To understand and eventually suppress this harmful vibration,traditional design and analysis methods for mass flow rate and load carrying capacity do not suffice anymore,and lots of research efforts have been made on the air flow field in aerostatic bearings.

Recently,the relationship between the high speed air flow and the small vibration in aerostatic bearings has been realized by many researchers.Kawai et al.(2005)studied the nano-vibration in ultra-precision machine tools and attributed it to air turbulence due to bearing surface roughness.Chen and He(2006)found vortex flow structures in the bearing recess by computational fluid dynamics(CFD)simulation of the steady air flow field,and suggested that these air vortices are responsible for the instability of the aerostatic bearing.Aoyama et al.(2006)also observed this air vortex flow by CFD simulation and reached a similar conclusion,and accordingly proposed a new restrictor design to weaken the vibration. Zhang et al.(2007)analyzed the high Reynolds number(Re)flow in the bearing clearance,and reduced the vibration of aerostatic bearings by flow laminarization.In a recent work,Yoshimura et al.(2012)attributed nano-vibration of aerostatic bearings with surface restriction to pressure fluctuation at the bearing outlet due to atmospheric turbulence.Although the flow-induced nature of bearing vibration has generally been recognized,the previous works only assumed a steady flow

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Journal of Fluids and Structures

0889-9746/$-see front matter&2013Elsevier Ltd.All rights reserved.

/10.1016/j.jfluidstructs.2013.03.012

n Corresponding author.Tel./fax:+862787557325.

E-mail address:chenxd@(X.Chen).

Journal of Fluids and Structures40(2013)42–51