FLUID MECHANICS

 

INTRODUCTION:

• Fluid mechanics is the branch of science that deals with the behaviour of the flow of liquid and gas at rest or in motion.
• Study of fluid at rest----Fluid statics
• Study of fluid in motion-----Fluid dynamics
• Study of fluid in motion without considering force-----Fluid kinematics...

•                     FLUID MECHANICS QUESTIONS AND THEIR SOLUTIONS...
• Calculate the specific weight, density and specific gravity of one litre of a liquid that weighs 7N.
  
• Calculate the density, specific weight and weight of one litre of petrol of specific density=0.7
  
• If the velocity distribution over a plate is given by u=(2/3)y - (y^2) in which u is the velocity in m/s at a distance y m. Determine shear stress at y=0 and y=0.15 m. Dynamic viscosity is 8.63 poises.
  
• A plate 0.025 mm distant from a fixed plate, moves at 60 cm/s and requires a force of 2N per unit area (2N/m^2) to maintain this speed. Determine the fluid viscosity between the plates.
  
• A flat plate of area 1.5×10^6 mm^2 is pulled with a speed of 0.4 m/s relatives to another plate located at a distance of 0.15 mm from it. Find the force and power required to maintain this speed, if the fluid separating them is having a viscosity as 1 poise.
  
• Determine the intensity of shear of an oil having viscosity = 1 poise. The oil is used for lubricating the clearance between a shaft of diameter 10 cm and its journal bearing. The clearance is 1.5 mm and the shaft rotates at 150 r.p.m.
  
• Calculate the dynamic viscosity of an oil, in which size of a square plate is 0.8mm×0.8mm and the angle of inclination is 30°. The weight of the square plate is 300N with a velocity of 0.3 m/s. The thickness of oil film is 1.5mm.
  
• Two horizontal plates are placed 1.25 cm apart, the space between them being filled with oil of viscosity 14 poises. Calculate the shear stress in oil if upper plate is moved with a velocity of 2.5m/s.
  
• The space between two square plates is 12.5mm in which each of the sides is 60cm. The upper plates which moves at 2.5m/s requires a force of 98.1N. Determine 1) Dynamic viscosity 2) Kinematic viscosity if specific gravity is 0.95
  
• Find the kinematic viscosity of an oil having density 981 Kg/m^3. The shear stress at a point in oil is 0.2452 N/m^2 and velocity gradient at that point is 0.2/s.
  
• Determine the speicific gravity of a fluid having viscosity 0.05 poise and kinematic viscosity 0.035 stokes.
  
• Determine the viscosity of a liquid having kinematic viscosity 6 stokes and specific gravity 1.9.
  
• The velocity distribution for flow over a flat plate is given by u=3/4 y - y^2 in which u is the velocity in m/s. Determine the shear stress at y = 0.15m. Dynamic viscosity=8.6 poise.
  
• A Newtonian fluid is filled in the clearance between a shaft and a concentric sleeve. The sleeve attains a speed of 50 cm/s, when a force of 40N is applied to the sleeve parallel to the shaft. Determine the speed if a force of 200N is applied.
  
• Determine the bulk modulus of elasticity of a liquid, if the pressure of the liquid is increased from 70N/ cm^2 to 130 N/cm^2. The volume of the liquid decreases by 0.15 per cent.
  
• What is the bulk modulus of elasticity of a liquid which is compressed in a cylinder from a volume of 0.0125 m^3 at 80N/cm^2 pressure to a volume of 0.0124m^3 at 150N/cm^2 pressure?
  
• One litre of crude oil weighs 9.6N. Calculate its specific weight, density and specific gravity.
  
• The velocity distribution for flow over a flat plate is given by u= (3/2)y - y^(3/2), where u is the point velocity in m/s at a distance y metre above the plate. Determine the shear stress at y=9cm. Assume dynamic viscosity as 8 poise.
  
• Determine the intensity of shear of an oil having viscosity=1.2 poise and is used for lubrication in the clearance between a 10 cm diameter shaft and its journal bearing. The clearance is 1.0mm and shaft rotates at 200r.p.m