第二章流体静力学ppt.ppt

1 2—6 A rotating container (cylindrical ) is filled with some water. If D=300 mm , H=500 mm and h=300 mm are given , ask that what the rotate speed n is when the surface of water just reaches the upper margin ? Figure for exercise 2—6 from height solution：When solve the questions about relative equilibrium of rotation the key knowledge point that the volume surrounded by the spinning paraboloidal is the half of its circumscribing cylindrical should be clear. the al paraboloid the forming after that suppose r/min 4 . 178 2 60 1/s 68 . 18 m/s 8 . 2 2 2 z is al paraboloid of surface free of equation the is container of top the to vertex the 2 = = = = = = = p w w n r V gz V g V mm 400 ) ( 2 = - = h H z , ) ( 4 4 2 1 2 2 - = p p h H D z D z 2—6 一旋转容器（圆柱形），装部分水，若已知 D=300 mm , H=500 mm , h=300 mm , 求转速 n 为多少时，水面恰好达到容器的上缘？ 解：这类求旋转相对平衡问题时，应知道形成的旋转抛物面所围成的体积是其外接圆柱形体积的一半这个知识点。 题 2—6 附图 2—7 A cylindrical container which is filled with water . A open manometric tube is installed on the center of its coping . Ask that when the container rotates as how much is the upward total pressure of liquid acting on the coping ？ solution： Figure for exercise 2—7 ) 2 ( p is coping on the pressure of regulation d distribute the zero. is coping on the point each of z Because , ) 2 ( is result the , it for integral and equation difference total the into them substitute , , formula n the ) ( equation difference total by the decided be can container of coping on the acting pressure the 2 2 2 2 2 2 h g r c gz r p g f y f x f i dz f dy f dx f dp z y x z y x + = 0 r = , 0 z = + - = - = = = + + = w g c h p = = g w r w w r 时， when 2—7 一圆柱容器装满水，顶盖中心装敞口测压管，当以 旋转时，顶盖受到多大的向上液体总压力？ 解： 题 2—7 附图 一、总压力的大小和方向 故总压力的水平分