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Thursday, 19 April 2012

Important basic concepts in Fluid Mechanics and machines (Mechanical Engineering) for GATE 2015 Part-2

This article (Part-2) gives important basic concepts in Fluid mechanics and fluid machines used in mechanical systems. This subject is very much important for GATE exam because future M. Tech or M. E specialization are based on the basics of this subject.


  • Neglecting the forces due to inertia, gravity and frictional resistance, the design of a channel can be made by comparing Froude’s number.
  •  For smooth turbulent flow the friction factor changes as Nr1/4.
  •  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.
  •  The continuity equation is applicable to conservation of mass.
  •  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.
  •  McLeod gauge used for low pressure measurement operates on the principle of Boyle’s law.
  •  Mass density of liquid (ρ ) is given by ρ = kg sec2/m4.
  •  Running away speed of a Pelton wheel gives no load speed when governor mechanism fails.
  • A Kaplan turbine is low head axial flow turbine.
  •  Vector difference of two velocities is relative velocity.
  •  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.
  •  For stable equilibrium of floating body its metacentre should lie above the center of gravity.
  •  Center of pressure on an inclined plane lies below the centroid.
  •  The line of action of the buoyant force always acts through the centroid of the displaced volume of the fluid.
  •  An equipotential line is one that has no velocity component tangent to it.