# Basic concepts of Fluid Mechanics | Gate Mechanical Notes

2. Density is defined in terms of viscosity as dynamic viscosity/kinematic viscosity.

3. The Reynolds number for pipe flow is given VDρ/µ.

4. SI unit of viscosity is 10 times poise.

5. Kinetic viscosity is not a dimensionless parameter.

6. The upper critical importance Reynolds’s number for pipe flow is of no practical importance to designers.

7. A liquid compressed in a cylinder has a volume of 1 liter at 1 MN/m2 and a volume of 995 cu cm at MN/m2. The bulk modulus of elasticity is 200 MPa.

8. The length of mercury column at a place at an altitude will change with respect to that at ground first slowly and then steeply.

9. The volumetric change of the fluid caused by a resistance is called adhesion.

10. Property of a fluid whereby its own molecules are attracted is known as cohesion.

11. The pressure at a point in a fluid will not be the same in all directions if the fluid is viscous and is in motion.

12. Pitot tube can be used to measure the flow of water in a pipe of diameter 3000mm.

13. An ideal fluid is one that is frictionless and incompressible.

14. Uniform flow takes place when at every point the velocity vector is identical in magnitude and direction for any given instant.

15. The continuity equation for an ideal fluid flow state that energy is constant everywhere in the fluid.

16. Neglecting the forces due to inertia, gravity and frictional resistance, the design of a channel can be made by comparing Froude’s number.

17. For smooth turbulent flow the friction factor changes as Nr1/4.

18. In order to avoid vaporization in the pipe line, the pipe line over the ridge is laid in such a way that it is not more than 6.4 m above the hydraulic gradient.

19. The continuity equation is applicable to conservation of mass.

20. The rise or fall of head ‘h’ in a capillary tube of diameter ‘d’ and liquid surface tension ‘ σ‘ and specific weight ‘w’ is given by 4σ/wd.

21. McLeod gauge used for low pressure measurement operates on the principle of Boyle’s law.

22. Mass density of liquid (ρ ) is given by ρ = kg sec2/m4.

23. Running away speed of a Pelton wheel gives no load speed when governor mechanism fails.

24. A Kaplan turbine is low head axial flow turbine.

25. Vector difference of two velocities is relative velocity.

26. A ship whose hull length is 100 m is to travel at 10 m/sec. For dynamic similarity, at 2 m/sec velocity a 1:25 model be towed through water.

27. For stable equilibrium of floating body its metacentre should lie above the center of gravity.

28. Center of pressure on an inclined plane lies below the centroid.

29. The line of action of the buoyant force always acts through the centroid of the displaced volume of the fluid.

30. An equipotential line is one that has no velocity component tangent to it.

31. Hydraulic jump is used to reduce the energy of flow.

32. The lowest portion to storage basin from where the water is not drawn, is dead storage.

33. The pitot tube is a device used for measurement of velocity.

34. Hydrometer is used to fine out specific gravity of liquids.

35. Mach number is signification is case of supersonics, as with projectiles and jet propulsion.

36. The fluid forces taken in to consideration in the Navier Stokes equation are gravity, pressure and viscosity.

37. Rocks having excessive internal stresses, producing spalling, are called stratified rocks.

38. Permissible velocity of water flowing through concrete tunnel, is generally 4-5 m/s.

39. The maximum continuous power available from a hydro-electric plant under the most adverse hydraulic conditions is called firm power.

40. The ratio of maximum load to the rated plant capacity is called utilization factor.

41. Orifice refers to n opening in hydraulic structure with regulation provision.

42. The value of coefficient of discharge in comparison to coefficient of velocity is found to be less.

43. Weir refer to an opening having partially full flow.

44. The pressure force, in Netwons, on the 15 cm dia head light of an automobile traveling at 25 m/s will be 6.8.

45. Power transmitted through a pipe is maximum when the loss of head due to friction is one-third of the total head supplied.

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