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Laminar flow

 
Laminar Flow

 
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Laminar flow
 
 
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Laminar flow, sometimes known as streamline
Streamlines, streaklines and pathlines

Fluid flow is described in general by a vector field in three or four dimensions. Pathlines, streamlines, and streaklines are field lines of different vector field descriptions of the flow....
 flow, occurs when a fluid flows in parallel layers, with no disruption between the layers. In fluid dynamics
Fluid dynamics

In physics, fluid dynamics is the sub-discipline of fluid mechanics dealing with fluid flow — the natural science of fluids in motion....
, laminar flow is a flow regime characterized by high momentum
Momentum

In classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section Momentum#Modern definitions of momentum on this page....
 diffusion
Diffusion

Molecular diffusion, often called simply diffusion, is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion....
, low momentum convection
Convection

Convection in the most general terms refers to the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer....
, pressure
Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
 and velocity
Velocity

In physics, velocity is defined as the Derivative of Position vector. It is a vector physical quantity; both speed and direction are required to define it....
 independent from time
Time

Time is a component of the measurement used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects....
. It is the opposite of turbulent flow. In nonscientific terms laminar flow is "smooth," while turbulent flow is "rough."

The dimensionless Reynolds number
Reynolds number

In fluid mechanics and heat transfer, the Reynolds number is a dimensionless number that gives a measure of the ratio of inertial forces to viscosity forces and, consequently, it quantifies the relative importance of these two types of forces for given flow conditions....
 is an important parameter in the equations that describe whether flow conditions lead to laminar or turbulent flow.






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Laminar flow, sometimes known as streamline
Streamlines, streaklines and pathlines

Fluid flow is described in general by a vector field in three or four dimensions. Pathlines, streamlines, and streaklines are field lines of different vector field descriptions of the flow....
 flow, occurs when a fluid flows in parallel layers, with no disruption between the layers. In fluid dynamics
Fluid dynamics

In physics, fluid dynamics is the sub-discipline of fluid mechanics dealing with fluid flow — the natural science of fluids in motion....
, laminar flow is a flow regime characterized by high momentum
Momentum

In classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section Momentum#Modern definitions of momentum on this page....
 diffusion
Diffusion

Molecular diffusion, often called simply diffusion, is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion....
, low momentum convection
Convection

Convection in the most general terms refers to the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer....
, pressure
Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
 and velocity
Velocity

In physics, velocity is defined as the Derivative of Position vector. It is a vector physical quantity; both speed and direction are required to define it....
 independent from time
Time

Time is a component of the measurement used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects....
. It is the opposite of turbulent flow. In nonscientific terms laminar flow is "smooth," while turbulent flow is "rough."

The dimensionless Reynolds number
Reynolds number

In fluid mechanics and heat transfer, the Reynolds number is a dimensionless number that gives a measure of the ratio of inertial forces to viscosity forces and, consequently, it quantifies the relative importance of these two types of forces for given flow conditions....
 is an important parameter in the equations that describe whether flow conditions lead to laminar or turbulent flow. Reynolds numbers of less than 500 are generally considered to be of a laminar type. When the Reynolds number is much less than 1, Creeping motion or Stokes flow
Stokes flow

Stokes flow is a type of fluid flow where advection inertia forces are small compared with Viscosity forces. The Reynolds number is low, i.e. ....
 occurs. This is an extreme case of laminar flow where viscous (friction) effects are much greater than inertial forces.

For example, consider the flow of air over an airplane wing
Wing

A wing is a surface used to produce Lift for flight through the Earth's atmosphere or another gaseous or fluid medium. The wing shape is usually an airfoil....
. The boundary layer
Boundary layer

In physics and fluid mechanics, a boundary layer is that layer of fluid in the immediate vicinity of a bounding surface. In the Earth's atmosphere, the planetary boundary layer is the air layer near the ground affected by diurnal heat, moisture or momentum transfer to or from the surface....
 is a very thin sheet of air lying over the surface of the wing (and all other surfaces of the airplane). Because air has viscosity
Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
, this layer of air tends to adhere to the wing. As the wing moves forward through the air, the boundary layer at first flows smoothly over the streamlined shape of the airfoil
Airfoil

An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section.An airfoil-shaped body moved through a fluid produces a force perpendicular to the motion called lift ....
. Here the flow is called laminar and the boundary layer is a laminar layer
Boundary layer

In physics and fluid mechanics, a boundary layer is that layer of fluid in the immediate vicinity of a bounding surface. In the Earth's atmosphere, the planetary boundary layer is the air layer near the ground affected by diurnal heat, moisture or momentum transfer to or from the surface....
.

For a practical demonstration of laminar and non-laminar flow, one can observe the smoke
Smoke

File:Bling-Bling Skywriting David Shankbone.jpgSmoke is the collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrainment or otherwise mixed into the mass....
 rising off a cigarette
Cigarette

A cigarette is a product consumed through smoking and manufactured out of curing and finely cut tobacco leaves and reconstituted tobacco, often combined with other List of additives in cigarettes, then rolled or stuffed into a paper-wrapped cylinder ....
 in a place where there is no breeze
Breeze

Breeze can refer to:* Sea breeze, an onshore afternoon wind, caused by warm air rising over the land in sunny weather* Breeze or Breeze Card, a stored-value smart card used as part of an automated fare collection system in Atlanta, Georgia...
. The smoke from the cigarette will rise vertically and smoothly for some distance (laminar flow) and then will start undulating into a turbulent, nonlaminar flow.

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