Types of Fluid Flows Prepared By : VINOD DAHIYA LECTURER MECHANICAL ENGG. RGGGPNARWANA

Types of Flows Steady and unsteady flow. Uniform and non-uniform flow. Laminar and turbulent flow. Compressible and incompressible flow. Rotational and irrotational flow One, two and three-dimensional flow.

Steady and Unsteady Flow : The flow in which fluid characteristics like velocity, pressure, density etc. at a point does not changes with time is called as steady flow. Eg flow of water with constant discharge through a pipeline is as steady flow. ∂v / ∂t = 0 ∂ρ / ∂t = 0 ∂ρ / ∂t = 0 The flow in which fluid characteristics like velocity, pressure, density etc. at a point changes with time is called as unsteady flow. E.g flow of water with varying discharge though a pipe is as unsteady flow. ∂v / ∂t ≠ 0 ∂ρ / ∂t ≠ 0 ∂ρ / ∂t ≠ 0

Uniform and Non-uniform Flow : The flow in which velocity at a given time does not change with respect to space (length of direction of flow is called as uniform flow. E.g flow through a long straight pipe of uniform diameter is considered as uniform flow. ∂v / ∂s = 0 The flow in which velocity at a given time changes with respect to space (length of direction of flow) is called as non- uniform flow. E.g flow through a long pipe with varying cross section is consider as non-uniform flow. ∂v / ∂s ≠ 0 Uniform velocity (b) Non – uniform velocity

Laminar and Turbulent Flow : The flow in which the adjacent layer do not cross to each other and move along the well defined path is called as laminar flow. E.g. flow of blood in small veins, flow of ail in bearings, flow in porous media, flow of highly. The flow in which the adjacent layers cross each other and do not move along the well define path is called as turbulent flow. E.g. flow through a river or canal, smoke from chimney, smoke from a cigarette.

If Reynolds’s number is less than 2000, then the flow is laminar. If Reynolds’s number is more than 4000, then the flow is turbulent. If Reynolds’s number is between 2000 to 4000, then the flow is transit.

Compressible and Incompressible Flow : The flow in which the density does not remain constant for the fluid flow is called as compressible flow. E.g. problems involving flight of rockets, aircrafts, flow fo air in problems concerned with tubomachines, compressor blades, flow of gases through openings like nozzles. The flow in which the density is constant for the fluid flow is called as incompressible flow. E.g. problems involving liquids i.e. hydraulics problems, flow of gases in machines like fans and blowers.

Rotational and Irrigational Flow : The flow in which the fluid particle while flowing along stream lines, also rotate about their own axis is called as rotational flow. E.g. motion of liquid in a rotating cylinder (forced vortex) as rotational flow. The flow in which the fluid particle while flowing along streamlines, do not rotate about their own axis is called as irrigational flow. E.g. flow of liquid in an emptyi vortex) as a rotational flow. ng wash-basin (free

One, Two and Three-dimensional Flow : The flow in which the velocity is the function of time and one space co-ordinate (x) is called as One-dimensional flow. E.g. flow through the pipe is consider as a one dimensional flow. u = f(x), v = 0, w = 0 The flow in which the velocity is the function of time and to space co-ordinate (x,y) is called as two-dimensional flow.

Eg viscous flow between parallel plates of large extent, flow at the middle part of airplane wing, flow over a long spillway, flow below long weirs are consider as two-dimensional flow. u = f1(x,y), v = f2 (x,y), w = 0 The flow is converging or diverging pipes or open channels are as three dimensional flow. Flow in a river, flow at a inlet of a nozzle etc. are the example of three-dimensional flow. u = f1 (x,y,z), v = f2 (x,y,z), w = f3 (x,y,z) 0