What are the velocity thermal and concentration boundary layers under what conditions do they develop?
The boundary layer thickness is by convention defined as the distance from the surface at which the velocity is 99% of the free stream velocity. The concentration boundary layer develops when there is a difference in concentration of a component between the free stream and the surface.
What is a boundary layer under what conditions do they occur?
Boundary layer, in fluid mechanics, thin layer of a flowing gas or liquid in contact with a surface such as that of an airplane wing or of the inside of a pipe. The fluid in the boundary layer is subjected to shearing forces.
How high is the boundary layer?
The planetary boundary layer (PBL) is the lowest part of the atmosphere, ranging anywhere between 100 and 2000 m above the surface of the ground. Its behavior and properties are directly influenced by the topography of the earth’s surface.
What is Navier slip condition?
The Navier slip condition is derived as the effective boundary condition, in the limit as the roughness becomes small; it is the first order corrector to the no-slip condition on the limiting smooth surface.
What does no slip mean?
no-velocity-offset boundary condition
What is slip flow?
Rarefied gas flow with a mean free path of the molecules commensurate with the dimensions of the region in which the flow being studied occurs (the boundary layer thickness, pipe radius, etc.), when the gas can still be considered as a continuum, but the velocity of the gas on the surface of the solid body differs from …
How is slip length calculated?
In such techniques, the velocity profile of the liquid can be measured with high accuracy, and the slip length can be extracted from the equation [24] b=vs/∂vs/∂z, where vs and ∂vs/∂z are the velocity and the shear rate close to the surface.
How is slip length measured?
Slip lengths (full and half slips) are measured from the waist down – nightgowns and sleepshirts are measured from the shoulder down.
How should a slip dress fit?
The first rule with shopping for a slip dress is to find one that is the right length and fit – shapeless: good / clingy or too short: bad. The tighter/thinner/softer the dress, especially of the slip variety, the likelier it is to border on unflattering.
What is interstitial velocity?
Interstitial velocity is defined as the upward velocity of the air through the open area between the filter bags inside a dust collector. Upward velocity occurs when a hopper inlet is used on a pulse-jet baghouse.
Why is superficial velocity used?
Superficial velocity is used in many engineering equations because it is the value which is usually readily known and unambiguous, whereas real velocity is often variable from place to place.
What is discharge velocity and seepage velocity?
Discharge velocity is the volume of water flowing in unit time across the unit cross section perpendicular to the direction of flow. Seepage flow is the volume of of water flowing in unit time across the unit surface area of available voids. seepage velocity is the real velocity of water through the soil.
What is fluidization and its types?
Fluidization (or fluidisation) is a process similar to liquefaction whereby a granular material is converted from a static solid-like state to a dynamic fluid-like state. This process occurs when a fluid (liquid or gas) is passed up through the granular material.
What is minimum fluidisation velocity?
Minimum fluidization velocity. The minimum fluidization velocity can be calculated by equating the pressure–drop across the fixed packed–bed, calculated from Ergun’s equation to that from the expression for fluidized bed under particulate (smooth) conditions.
What are the types of fluidization?
Based on different Geldart particle groups and gas velocities, several different fluidization regimes can be observed: fixed bed, homogeneous fluidization, bubbling fluidization, slugging fluidization, turbulent fluidization, and entrainment process.
What is bed voidage?
Voidage, e, is defined as the fraction of the total volume which is free space available for the flow of fluids, and thus the fractional volume of the bed occupied by solid material is (1 − ε). Depending upon the nature of the porous medium, the voidage may range from near zero to almost unity.
What does the minimum fluidization velocity in the bed depends on?
Excessive moisture content of particles may affect the behavior of particles during fluidization. (10.20) The minimum fluidization velocity depends on particle moisture content; increasing moisture content increases the minimum fluidization velocity.
Why fluidization is required?
The resulting phenomenon is called fluidization. Fluidized beds are used for several purposes, such as fluidized bed reactors (types of chemical reactors), solids separation, fluid catalytic cracking, fluidized bed combustion, heat or mass transfer or interface modification, such as applying a coating onto solid items.
What is the purpose of fluidized bed?
Fluidized beds are a very important and common process technology used for everything from roasting coffee beans and drying agricultural grains to fluid catalytic cracking and pharmaceutical granulation.