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I.To choose the correct answer (2 points for each question) 1. The right statement about the viscosity of a fluid is (A) Real fluid have no viscosity at rest; (B) Viscosity can both speed up and slow down the movement of fluid; (C) Viscosity of a fluid increases as the temperature increases; (D) In turbulence, the viscosity force doesn't have the effects on the flow. 2. The viscosity of gases_ _with increase in temperature. (A) decreases (B) increases (C) first decreases and then increases (D) first increases and then decreases 3. There is no relative motion between fluid particles close to a solid wall and the solid wall. This is called the _condition (A) slip (B) no-slip (C) initial (D) None of the above

4. A steady flow is one in which all conditions at any point in the stream remain constant with respect to (A) Time (B) Space (C) Temperature (D) pressure 5. According to the concept of continuum, fluid particle is (A) fluid molecule; (B) solid particle in fluid; (C) geometric point; (D) differential element which includes a large amount of molecules. 6. When a flow is characterized as hydraulically rough turbulent, which of the following statement is true? (A) Friction factor decreases with increasing Reynolds Number (B) Friction factor increases with increasing Reynolds Number (C) Friction factor is independent of Reynolds Number (D) Friction factor is independent of relative roughness 7. Inertia force belongs to force in fluid mechanics. (A) Surface (B) Body (C) Either of the above (D) Neither of the above 8. is the pressure head. 2ܐ (A)z (B) р pg (C) z+ P (D) pg 2g

9. Which one of these statements is true? (A) The shape and size of the system should be constant; (B) The mass of a given control volume is constant; (C) There exist the interchanges of mass, momentum and energy on the surfaces of system; (D) A control volume refers to a fixed region in space. 10. The working principle of Venturi meter is (A) Continuity equation (B) Momentum equation (C) Bernoulli's equation along a streamline (D) Bernoulli's equation for a total flow 11.An oil has a kinematic viscosity of 1.2*10* m²/s and a density of 900 kg/m? What is its dynamic (absolute) viscosity in kg/(m·s)? (A) 0.08 (B)0.108 (C) 0.125 (D) 0.10 12. The local head loss always happens in (A) Laminar flow (B) Turbulent flow (C) Gradually varied flow (D) Suddenly varied flow 13. Consider a steady incompressible flow in pipes (shown in the figure). If the ratio of diameters is dı:d=3:1, the mean velocities have the mathematical relationship of v/:VF (A) 1: 9 (B) 9: 1 (C) 1: 3 (D) Neither of the above di d.

14. Newton's viscosity law can be used in (A) Laminar flow (B) Turbulent flow (C) Gradually varied flow (D) Suddenly varied flow 15. Which of these is true? (A) Streamlines and pathlines are the same for any incompressible flow (B) Pathlines and streamlines are the same for any compressible flow (C) Streamlines and pathlines are the same for any steady flow (D) Pathlines and streamlines are the same for any unsteady flow