1. Multiple-choice Questions (24 points) (1) The relationship between the shear stress and shear rate of a Newtonian fluid is A) a straight line passing through the origin B) linearity but has a threshold shear stress C) a non-linear curve passing through the origin D) a concave line upward at low shear (2) For an inviscid liquid flows from a tube, now you increase the tube length, the fluid friction energy will A) increase as well B) decrease as well C) be negligible D) be a given value much higher that that of an actual fluid (3) The average velocity of a Newtonian fluid flowing in a horizontal straight tube is 0.8 m/s. Now we know the flow is laminar, the maximum velocity is A) 0.4 m/s B) 0.8 m/s C) 1.2 m/s D) 1.6 m/s (4) In metering of fluids, the velocity obtained by using Pitot tube is A) the average velocity at the cross-section of the streamline B) the local velocity along the streamline C) the maximum velocity along the streamline D) the minimum velocity at the direction of the streamline (5) From Moody diagram, one knows that the friction factor for a complete turbulence flow with the increasing of Reynolds number. A) increases B) decreases C) is unchanged D) increases and then decreases (6) The essential difference between laminar flow and turbulence is that A) the flow velocity of laminar flow is lager than that of turbulence. B) laminar flow occurs in large tubes, while turbulence occurs in small pipes. C) the Reynolds number of laminar is smaller than that of turbulence. D) laminar flow is characterized as "regularity" flow streams, while turbulence is characterized as "irregularity" or "randomicity" streams with lowing erratically, mixing as well as cross-currents and eddies. (7) The vacuum pressure in a tank is 395 mmHg and the local atmospheric pressure is 745 mmHg. The absolute pressure in a tank is A) 350mmHg B)-410mmHg C) 395mmHg D) 410mmHg (8) According to the Prandtl boundary layer theory, A) the flow friction is dominant in the thin boundary layer, but the viscous effects can be neglected, and not as important as inertia B) the fluid velocity in the boundary layer is constant C) the thickness of the boundary layer is approximately defined as the distance from the solid wall to the points where the local velocity is 99% of the bulk fluid velocity D) the boundary layer regions include the bulk region, laminar, turbulence, buffer, and viscous sub-layers. 2. Short Answer Questions (26 points) 1) Please derive the hydrostatic equilibrium equation based on the volume element of fluid. (10 points)