文档介绍：Chapter 1 Fluid statics 流体静力学
连续介质假定(Continuum assumption):The real fluid is considered as no-gap continuous media, called the basic assumption of continuity of fluid, or the continuum hypothesis of fluid. 流体是由连续分布的流体质点(fluid particle)所组成,彼此间无间隙。它是流体力学中最基本的假定,1755年由欧拉提出。在连续性假设之下,表征流体状态的宏观物理量在空间和时间上都是连续分布的,都可以作为空间和时间的函数。
流体质点(Fluid particle): A fluid element that is small enough with enough moles to make sure that the macroscopic mean density has definite value is defined as a Fluid Particle. 宏观上足够小,微观上足够大。
流体的粘性(Viscosity): is an internal property of a fluid that offers resistance to shear deformation. It describes a fluid's internal resistance to flow and may be thought as a measure of fluid friction. 流体在运动状态下抵抗剪切变形的性质,称为黏性或粘滞性。它表示流体的内部流动阻力,也可当做一个流体摩擦力量。The viscosity of a gas increases with temperature, the viscosity of a liquid decreases with temperature.
牛顿内摩擦定律(Newton’s law of viscosity):
The dynamic viscosity(动力黏度)is also called absolute viscosity(绝对黏度). The kinematic viscosity(运动黏度)is the ratio of dynamic viscosity to density.
Compressibility(压缩性):As the temperature is constant, the magnitude pressibility is expressed by coefficient of pressibility (体积压缩系数) к, a relative variation rate(相对变化率) of volume per unit pressure.
The bulk modulus of elasticity (体积弹性模量) E is the reciprocal of coefficient of pressibilityк.
流体的膨胀性(expansibility; dilatability):The coefficient of cubical expansion (体积热膨胀系数) αt is the relative variation rate of volume per unit temperature change.
表面张力Surface tension: A property resulting from the attractive forces between molecules. s-----单位长度所受拉力
表面力 Surface force——is the force exerted on the contact surface by the contacted fluid or other body. Its value is proportional to contact area.
作用在所研究流体外表面上与表面积大小成正比的力。Stress (应力) is the surface force on per unit area.
质量力Mass force——The force acting on every fluid mass particle within the control body. Its value is proportional to its mass. Mass force is also known as body force. 作