Fluids which are in motion has four basic characteristics which include volume, density, pressure and velocity. Based on how these parameters change there are six types of fluid flow in hydrodynamics.
1.Uniform & Non Uniform Fluid Flow
In an uniform flow, the velocity of fluid at any given time does not change with respect to space and in non uniform flow velocity varies from point to point.
When an open channel is
considered, its flow is uniform if the depth, mean velocity and discharge rate
do not change along the length of the channel at a given instant of time.
Non uniform flow takes
place due to gradual or sudden changes in the cross sectional area and the flow
through a pipeline of constant diameter is said to be uniform.
2.Steady & Unsteady Flow
Source (mechanicalwalkings.com)
Steady flow is a flow in
which the velocity, pressure and density of liquid is constant at any point
with respect to time and where those parameters change results an unsteady
flow.
Flow of a liquid through
a pipeline of variable diameter at a constant pressure head is steady.
Flow of a liquid through
a pipe of variable diameter under variable pressure due to changing water level
of a reservoir or by the opening or closure of a valve connected to the pipe.
3.Laminar & Turbulent Flow
(Source: Theconstructor.org) (Left- Laminar Right –Turbulent )
In laminar flow fluid particles move in straight paths and they are parallel to each other with no disruption between the layers. Blood flowing throughout the body follows laminar flow.In turbulent flow fluid particles do not move in straight paths and move in zig zag paths excluding straight and parallel condition. In here, rapid variation of pressure and flow velocity in space and time takes place.
When a flow is considered it can be turbulent, laminar or in between which is measured by Reynolds number. Laminar flow occurs at high viscosity and lower velocity.
(Source: Chegg.com)
In compressible flow the
density of fluid is not constant from point to point and it keeps on changing.
Any fluid flow which exceeds Mach
number 0.8 is treated as compressible. Compressible flows can be transonic
(0.8-1.2) or supersonic (1.2-3.0).
In incompressible flow,
the density is constant from point to point. Incompressible flow modelling is
being used widely in computational fluid dynamics including simulation of
liquid flow.
5.Rotational & Irrotational Fluid Flow
Irrotational Flow ( trekearth.com)
In rotational flow the fluid particles show streamline
motion and the fluid particles rotate about its own axis. In irrotational flow
also, the fluid particles show streamline motion but particles does not rotate
about its own axis.
Consider water flowing down a drain:
Rotational Flow (The journal.ie)
It flows clockwise in southern hemisphere and anticlockwise in northern hemisphere due to rotation of individual water molecules as a result of acceleration due to gravity.
The flow of water over a dam where water falls straight down is an example of irrotational flow.
6.1D,2D &3D Fluid Flow
Source-biomedical-Engineering-online.biomedcentral.com
In 1D flow the fluid is moving only in one dimension either x, y or z. In here, all the flow parameters are expressed as function of time and one space coordinate only. The space implies the distance measured along the centre line in which the fluid is flowing.
Under practical scenarios the flow is never 1D as the viscosity of fluids causes the velocity to decrease to zero at solid boundaries.
In 2D flow the fluid is moving in two dimensions either xy, zx or yx. Flow parameters are functions of time and two space coordinates. Similar streamline patterns can be seen in all planes at right angles to z direction at any moment.
In 3D flow, the fluid is moving in three dimensions either xyz, zyx or yzx.
Compiled by: G.M.D.V.D.Somarathna & P.A.D.E. Kulathilaka
References:themechanicalengineering.com
:globalnodes.org
:www.trekearth.com
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