Name and give definitions of two viscosity flow regimes.
Flow RegimesAll fluid flow is classified into one of two broad categories or regimes. These two flow regimesare laminar flow and turbulent flow. The flow regime, whether laminar or turbulent, is importantin the design and operation of any fluid system. The amount of fluid friction, which determinesthe amount of energy required to maintain the desired flow, depends upon the mode of flow.This is also an important consideration in certain applications that involve heat transfer to thefluid.
Laminar FlowLaminar flow is also referred to as streamline or viscous flow. These terms are descriptive ofthe flow because, in laminar flow, (1) layers of water flowing over one another at differentspeeds with virtually no mixing between layers, (2) fluid particles move in definite andobservable paths or streamlines, and (3) the flow is characteristic of viscous (thick) fluid or isone in which viscosity of the fluid plays a significant part.
Turbulent FlowTurbulent flow is characterized by the irregular movement of particles of the fluid. There is nodefinite frequency as there is in wave motion. The particles travel in irregular paths with noobservable pattern and no definite layers.
turbulent flow is a flow regime characterized by chaotic and stochastic[citation needed] property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time. Nobel Laureate Richard Feynman described turbulence as "the most important unsolved problem of classical physics."[1] Flow in which the kinetic energy dies out due to the action of fluid molecular viscosity is called laminar flow. While there is no theorem relating the non-dimensional Reynolds number (Re) to turbulence, flows at Reynolds numbers larger than 5000 are typically (but not necessarily) turbulent, while those at low Reynolds numbers usually remain laminar. In Poiseuille flow, for example, turbulence can first be sustained if the Reynolds number is larger than a critical value of about 2040; moreover, the turbulence is generally interspersed with laminar flow until a larger Reynolds number of about 3000. In turbulent flow, unsteady vortices appear on many scales and interact with each other. Drag due to boundary layer skin friction increases. The structure and location of boundary layer separation often changes, sometimes resulting in a reduction of overall drag. Although laminar-turbulent transition is not governed by Reynolds number, the same transition occurs if the size of the object is gradually increased, or the viscosity of the fluid is decreased, or if the density of the fluid is increased.
Give the definition of the boundary layer.
In physics and fluid mechanics, a boundary layer is the layer of fluid in the immediate vicinity of a bounding surface where the effects of viscosity are significant. 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. On an aircraft wing the boundary layer is the part of the flow close to the wing, where viscous forces distort the surrounding non-viscous flow. See Reynolds number.
Laminar boundary layers can be loosely classified according to their structure and the circumstances under which they are created. The thin shear layer which develops on an oscillating body is an example of a Stokes boundary layer, while the Blasius boundary layerrefers to the well-known similarity solution near an attached flat plate held in an oncoming unidirectional flow. When a fluid rotates and viscous forces are balanced by the Coriolis effect (rather than convective inertia), an Ekman layer forms. In the theory of heat transfer, a thermal boundary layer occurs. A surface can have multiple types of boundary layer simultaneously.
