Fluid mechanics-2.ppt

NCWU Chapter 2 Fluid Statics Pressure at a point Basic equation for pressure field Pressure variation in fluid at rest Standard Atmosphere Measurement of pressure NCWU Fluid Statics Manometry 1) Piezometer tube 2) U-tube menometer 3) Inclined-tube manometer Hydrostatic force on plane surface Hydrostatic force on curved surface NCWU Characteres of Rest Fluid This chapter will consider fluid at rest or moving in such a manner that there is no relative motion between adjacent particles, namely there will be no shearing stresses in the fluid, and only force on the surface of particles will be pressure. NCWU Pressure at a Point the same in all directions 1. Direction of pressure at a point in fluid at rest: Vertical point to acted surface. 2. Size of pressure at a point in fluid at rest: The pressures from every direction are equal in size. NCWU 1) Direction of Pressure at a Point There are no shearing stresses in fluid at rest, only pressure. dy du ??? 0?? dy du ?? NCWU 2) Size of Pressure at a Point Forces on a particle of fluid at rest: * Surface forces: P x, P y, P z, P n* Mass forces: F x, F y, F z??0F ?),,(zyxppppp nzyx???? NCWU Basic Equation for Pressure Field NCWU Euler ’ s Equibrium Equation In 1775 Euler got the following equation: 0 1 0 1 0 1????????????z pZ y pY x pX??? NCWU Euler ’ s Equibrium Equation(2) ?p ?z ?p ?y X?Y?Z? dydy dzdz ??? dx dx ?p ?y? dp ?( ) Xdx Ydy Zdz ?? ? NCWU Physical Sense of Euler ’ s . 1) Isobaric surface is isobaric potential surface. 2)The work of unit mass forces is zero on isobaric surface. dU Zdz Ydy Xdx dp??????) (CUCp???0 0????? Zdz Ydy Xdx dp