laminar flow | GTU

GUJARAT TECHNOLOGICAL UNIVERSITY

VISHWAKARMA GOVERNMENT ENGINEERING COLLEGE ,CHANDKHEDA

Mechanical Semester-IVEnrollment No.- 140170119036 to 40

Laminar flowAlso known as

streamline flowOccurs when

the fluid flows in parallel layers, with no disruption between the layers

The opposite of turbulent flow (rough)

Laminar flowIn fluid dynamics (scientific study of

properties of moving fluids), laminar flow is:A flow regime characterized by high

momentum diffusion, low momentum convection, pressure and velocity independent from time.

*momentum diffusion refers to the spread of momentum (diffusion) between particles of substances, usually liquids

Laminar flowLaminar flow over a flat

and horizontal surface can be pictured as consisting of parallel and thin layers

Layers slide over each other, thus the name ‘streamline’ or smooth.

The paths are regular and there are no fluctuations

Laminar Flow

TurbulentFlow

Laminar flow3 Conditions

fluid moves slowlyviscosity is relatively highflow channel is relatively small

Blood flow through capillaries is laminar flow, as it satisfies the 3 conditions

Most type of fluid flow is turbulentThere is poor transfer of heat energy!

Turbulent flowUsually occurs when the

liquid is moving fastThe flow is ‘chaotic’ and

there are irregular fluctuations

Includes:Low momentum diffusionhigh momentum convectionrapid variation of pressure

and velocity of the fluidGood way to transfer

thermal energy

Turbulent FlowThe speed of the fluid at a point is

continuously undergoing changes in both magnitude and direction.

Examples of turbulenceOceanic and atmospheric layers and ocean

currentsExternal flow of air/water over vehicles such as

cars/ships/submarinesIn racing cars, e.g. leading car causes

understeer at fast cornersTurbulence during air-plane’s flightMost of terrestrial atmospheric circulationFlow of most liquids through pipes

Reynold’s numberA dimensionless number in fluid mechanicsDynamic Pressure : Shearing StressThus, it quantifies the relative importance of these

two types of forces for given flow conditions.

Arises when performing analysis of fluid dynamics Can be used to determine dynamic similitude in

such cases. Concept used in the testing of models, e.g. testing miniature airplanes/submarines

Dynamic Pressure + Shearing StressDynamic Pressure

The pressure of a fluid which results from its motion

Formula:

Shearing StressMeasure of the

force of friction from a fluid acting on a body in the path of that fluid

Formula: Fluid Density

Fluid Velocity

Weight Density of Water

Average water depth

WaterSurfaceSlope

Reynold’s numberFlow in a pipe or liquid

μ  is the dynamic viscosity of the fluid

v is the kinematic velocity of the fluid

A is the pipe cross-sectional area.

p is the density of the fluid V is the mean fluid velocity D is the diameterQ is the volumetric flow

rate

Dynamic Pressure

Shearing Stress

Reynold’s numberThe Reynold’s number can be used to

determine if a flow is laminar, transient or turbulent

Laminar when Re < 2300 Turbulent when Re > 4000Transient when 2300 < Re < 4000

Spermatozoa 1×10−4 Blood flow in brain 1×102 Blood flow in aorta 1×103