軸封在旋轉機械上的主要應用為控制洩漏量，流體經過軸封時，轉軸兩側流道出入口端壓降（pressure drop）分佈不同，會對轉子產生徑向作用力（radialforce）將轉子推回軸封中心位置，影響旋轉機械系統動態特性，此現象為Lomakin效應。影響Lomakin效應的幾何因素有：軸封的幾何外形，軸封間隙與半徑比，軸封表面粗糙度，轉子偏心量。過去文獻中Lomakin效應對於動態係數影響的分析上，均著重在主勁度係數的影響，此外影響Lomakin效應的各個因素也沒有完整的討論。本文利用CFD 軟體Fluent 來分析Lomakin 效應以求得更精準的動態係數，並針對幾何因素之影響作一詳細討論。

The major applications of seals in rotating machinery are to control
the leakage of fluids. When the fluid passes through the seals, Lomakin
effects are caused by the different distributions of pressure drop between
the opposite sides of the rotor, generating radial forces exerted on the
rotor and affecting the dynamic characteristics of the rotating machines.
The geometric factors that may affect the Lomakin effects include ratio
of seal length and shaft diameter, ratio of seal clearance to shaft radius,surface roughness, and eccentricity of the rotor. Previous research was conducted mainly on the direct stiffness coefficients affected by the Lomakin effects, without detailed investigation on the influence of various geometric factors. In this paper, the influence of geometric factors on the Loamkin effects and the dynamic coefficients are examined by Fluent, a CFD software.