A zonal flow regime is the meteorological term meaning that the general flow pattern is west to east along the Earth's latitude lines, with weak shortwaves embedded in the flow. The use of the word "zone" refers to the flow being along the Earth's latitudinal "zones". This pattern can buckle and thus become a meridional flow.
Zonal flow
Troposphere
Troposphere | Zonal flow
Yes, Zonal flow, Meridional flow and Atmospheric flow Yes. It can be understood by the three-cell model of the atmosphere. This describes the actual flow of the Earth's atmosphere as a whole. It divides the Earth into the tropical, mid-latitude and polar regions, to describe energy flow and global atmospheric circulation. Yes, zonal and meridional flow. Yes, a zonal flow regime is the meteorological term meaning that the general flow pattern is west to east along the Earth's latitude lines, with weak shortwaves embedded in the flow
what are the alternating dark and light bands in jupiter’s atmosphere called
user
Lightly colored "zones" and relatively dark "belts."
assistant
what is the atmosphere like in jupiter?
user
It is mostly made of molecular hydrogen and helium in roughly solar proportions; other chemical compounds are present only in small amounts and include methane, ammonia, hydrogen sulfide, and water.
assistant
how can you describe its structure vertically?
user
The atmosphere of Jupiter is classified into four layers, by increasing altitude: the troposphere, stratosphere, thermosphere and exosphere
assistant
what is the definition of the first mentioned layer?
user
The troposphere is the lowest layer of Earth's atmosphere, and is also where nearly all weather conditions take place.
assistant
what is the flow here like?
user
The flow of the atmosphere generally moves in a west to east direction.
assistant
are there different types of flow?
user
The flow of the atmosphere generally moves in a west to east direction. This, however, can often become interrupted, creating a more north to south or south to north flow. These scenarios are often described in meteorology as zonal or meridional. These terms, however, tend to be used about localized areas of the atmosphere (at a synoptic scale). A fuller explanation of the flow of atmosphere around the Earth as a whole can be found in the three-cell model.
Troposphere | Atmospheric flow
When the zonal flow buckles, the atmosphere can flow in a more longitudinal (or meridional) direction, and thus the term "meridional flow" arises. Meridional flow patterns feature strong, amplified troughs of low pressure and ridges of high pressure, with more north–south flow in the general pattern than west-to-east flow.
Troposphere | Meridional flow
A zonal flow regime is the meteorological term meaning that the general flow pattern is west to east along the Earth's latitude lines, with weak shortwaves embedded in the flow. The use of the word "zone" refers to the flow being along the Earth's latitudinal "zones". This pattern can buckle and thus become a meridional flow.
Troposphere | Zonal flow
In meteorological term regarding atmospheric circulation, zonal flow brings a temperature contrast along the Earth's longitude. Extratropical cyclones in zonal flows tend to be weaker, moving faster and producing relatively little impact on local weather. Extratropical cyclones in meridional flows tend to be stronger and move slower. This pattern is responsible for most instances of extreme weather, as not only are storms stronger in this type of flow regime, but temperatures can reach extremes as well, producing heat waves and cold waves depending on the equator-ward or poleward direction of the flow.
Zonal and meridional flow | Introduction
Zonal and meridional flow are directions and regions of fluid flow on a globe. Zonal flow follows a pattern along latitudinal lines, latitudinal circles or in the west–east direction. Meridional flow follows a pattern from north to south, or from south to north, along the Earth's longitude lines, longitudinal circles (meridian) or in the north–south direction. These terms are often used in the atmospheric and earth sciences to describe global phenomena, such as "meridional wind", or "zonal average temperature". In the context of physics, zonal flow connotes a tendency of flux to conform to a pattern parallel to the equator of a sphere.
Zonal and meridional flow | Introduction
In toroidally confined fusion plasma experiments the term zonal flow means a plasma flow within a magnetic surface primarily in the poloidal direction. This usage is inspired by the analogy between the quasi-two-dimensional nature of large-scale atmospheric and oceanic flows, where zonal means latitudinal, and the similarly quasi-two-dimensional nature of low-frequency flows in a strongly magnetized plasma. Zonal flows in the toroidal plasma context are further characterized by
Zonal flow (plasma) | Introduction
The flow in many fluids varies with density and depends upon the gravity. Due to which the fluid with lower density is always above the fluid with higher density. Stratified flows are very common such as the Earth's ocean and its atmosphere.
Stratified flows | Introduction
Different flow regimes have been categorized over the years including twisted Taylor vortices and wavy outflow boundaries. It has been a well researched and documented flow in fluid dynamics.
Taylor–Couette flow | Introduction
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Carton flow | References
Even if air columns are homogeneous with height, the density of each column can change from location to location, firstly since air masses have different temperatures and moisture content depending on their origin; and then since air masses modify their properties as they flow over Earth's surface. For example, in extra-tropical cyclones the air circulating around a pressure low typically comes with a sector of warmer temperature wedged within colder air. The gradient-flow model of cyclonic circulation does not allow for these features. Balanced-flow schematisations can be used to estimate the wind speed in air flows covering several degrees of latitude of Earth's surface.
Balanced flow | Horizontal differences of air properties
As the secondary flow is drawn upward the air cools and its pressure falls, causing extremely heavy rainfall over several days.
Secondary flow | Tropical cyclones
Other geological flows that can be described as debris flows are typically given more specific names. These include:
Debris flow | Types
Inflow is the flow of a fluid into a large collection of that fluid. Within meteorology, inflow normally refers to the influx of warmth and moisture from air within the Earth's atmosphere into storm systems. Extratropical cyclones are fed by inflow focused along their cold front and warm fronts. Tropical cyclones require a large inflow of warmth and moisture from warm oceans in order to develop significantly, mainly within the lowest of the atmosphere. Once the flow of warm and moist air is cut off from thunderstorms and their associated tornadoes, normally by the thunderstorm's own rain-cooled outflow boundary, the storms begin to dissipate.
Inflow (meteorology) | Introduction
Flow volumes range from a few hundred cubic meters (yards) to more than 1,000 cubic kilometres (~240 cubic miles). Larger flows can travel for hundreds of kilometres (miles), although none on that scale has occurred for several hundred thousand years. Most pyroclastic flows are around 1 to 10 km (about ¼ to 2½ cubic miles) and travel for several kilometres. Flows usually consist of two parts: the "basal flow" hugs the ground and contains larger, coarse boulders and rock fragments, while an extremely hot ash plume lofts above it because of the turbulence between the flow and the overlying air, admixing and heating cold atmospheric air causing expansion and convection.
Pyroclastic flow | Size and effects
constant) term of the expansion. This flow pattern is also both irrotational and incompressible flow.
Elementary flow | Two Dimensional line source
In particular, if is equipped with a topology, then is usually required to be continuous. If is equipped with a differentiable structure, then is usually required to be differentiable. In these cases the flow forms a one parameter subgroup of homeomorphisms and diffeomorphisms, respectively.
Flow (mathematics) | Formal definition
Mathematical equations and concepts Fields of study Types of fluid flow Fluid properties Fluid phenomena
Pipe flow | See also
The Jovian bands are bounded by zonal atmospheric flows (winds), called "jets". The eastward (prograde) jets are found at the transition from zones to belts (going away from the equator), whereas westward (retrograde) jets mark the transition from belts to zones. Such flow velocity patterns mean that the zonal winds decrease in belts and increase in zones from the equator to the pole. Therefore, wind shear in belts is cyclonic, while in zones it is anticyclonic. The EZ is an exception to this rule, showing a strong eastward (prograde) jet and has a local minimum of the wind speed exactly at the equator.
Atmosphere of Jupiter | Zones, belts and jets
In the case of upstream air pressure at atmospheric pressure and vacuum conditions downstream of an orifice, both the air velocity and the mass flow rate becomes choked or limited when sonic velocity is reached through the orifice.
Choked flow | Vacuum conditions
It thus permits visualization of this kind of flow in two dimensions.
Hele-Shaw flow | Introduction
Like any fluid, air may exhibit both laminar and turbulent flow patterns. Laminar flow occurs when air can flow smoothly, and exhibits a parabolic velocity profile; turbulent flow occurs when there is an irregularity (such as a disruption in the surface across which the fluid is flowing), which alters the direction of movement. Turbulent flow exhibits a flat velocity profile. The Reynolds number, a ratio indicating the relationship between viscous and inertial forces in a fluid, can be used to predict the transition from laminar to turbulent flow. This number and related concepts can be applied to studying flow in systems of all scales.
Airflow | Types of airflow
There are two kinds of flow structures: bidirectional (multiple directions, back-and-forth) and unidirectional. Flow regimes in single-direction (typically fluvial) flow, which at varying speeds and velocities produce different structures, are called bedforms. In the "lower flow regime", the natural progression is from a flat bed, to some sediment movement (saltation etc.), to ripples, to slightly larger dunes. Dunes have a vortex in the lee side of the dune. As the "upper flow regime" forms, the dunes become flattened out, and then produce antidunes. At higher still velocity, the antidunes are flattened and most sedimentation stops, as erosion takes over as the dominant process.
Sedimentary structures | Flow structures
The most common class of multiphase flows are two-phase flows, and these include Gas-Liquid Flow, Gas-Solid Flow, Liquid-Liquid Flow and Liquid-Solid Flow. These flows are the most studied, and are of most interest in the context of industry. Different patterns of multiphase flow are known as flow regimes.
Multiphase flow | Types
In general, winds are strongest immediately under the tropopause (except locally, during tornadoes, tropical cyclones or other anomalous situations). If two air masses of different temperatures or densities meet, the resulting pressure difference caused by the density difference (which ultimately causes wind) is highest within the transition zone. The wind does not flow directly from the hot to the cold area, but is deflected by the Coriolis effect and flows along the boundary of the two air masses. All these facts are consequences of the thermal wind relation. The balance of forces acting on an atmospheric air parcel in the vertical direction is primarily between the gravitational force acting on the mass of the parcel and the buoyancy force, or the difference in pressure between the top and bottom surfaces of the parcel.
Jet stream | Cause
In advection-dominated flows, "μn" is greater than "αnh", and most of the incoming photons reach the ionization front and ionize fresh gas. In other flows, most photons fail to reach the ionization front, and instead balance recombinations in the flow.
Cometary knot | Relation to other photoevaporation flows
This type of flow is named in honor of Maurice Couette, a Professor of Physics at the French University of Angers in the late 19th century.
Couette flow | Introduction
Due to symmetry, pressure of the fluid can depend only on radial and axial coordinate formula_9. Then the continuity equation and the incompressible Navier–Stokes equations reduce to
Von Kármán swirling flow | Flow description
Pipe flow, a branch of hydraulics and fluid mechanics, is a type of liquid flow within a closed conduit (conduit in the sense of a means of containment). The other type of flow within a conduit is open channel flow. These two types of flow are similar in many ways, but differ in one important aspect. Pipe flow does not have a free surface which is found in open-channel flow. Pipe flow, being confined within closed conduit, does not exert direct atmospheric pressure, but does exert hydraulic pressure on the conduit. Not all flow within a closed conduit is considered pipe flow.
Pipe flow | Introduction
Whereas frequently the internal flow involves a single fluid phase (albeit often of a complex biological fluid such as blood), in many instances the presence of two or more distinct flowing phases is of primary importance (as is the case for air-liquid flows in peripheral lung airways, for example).
Collapsible flow | Introduction
To start with, a zonal mean flow, "U", can be considered to be perturbed where "U" is constant in time and space. Let formula_1 be the total horizontal wind field, where "u" and "v" are the components of the wind in the "x"- and "y"- directions, respectively. The total wind field can be written as a mean flow, "U", with a small superimposed perturbation, "u′" and "v′". The perturbation is assumed to be much smaller than the mean zonal flow. Relative vorticity "η", "u and "v can be written in terms of the stream function formula_5 (assuming non-divergent flow, for which the stream function completely describes the flow):
Rossby wave | Free barotropic Rossby waves under a zonal flow with linearized vorticity equation
In the real atmosphere, highs and lows have rarely the same strength and thus equal wind flow pattern around them. Thus the advection of warm or cold air is rarely equal. Furthermore, their shape and position are rarely as perfect as in the illustration quadrants either. There are thus 3 types of saddles or cols: the symmetrical, the cyclonic and anticyclonic. In the symmetrical saddle area, cyclonic and anticyclonic flows are in balance. This type is the least prevalent, since usually one of these two influences prevails. In the anticyclonic col, the curvature of the high pressure area isobars is greater than that of the cyclonic flow.
Col (meteorology) | Types
rotating), and bounded (influenced by wall effects) or unbounded (not influenced by wall effects). According to this classification the Taylor–Couette flow is an example of a flow pattern forming in a closed, bounded flow system.
Taylor–Couette flow | Gollub–Swinney circular Couette experiment
Collapsible flow is a phenomenon that occurs in steady flow in tubes with significant distensibility, or the capability of swelling or stretching, under conditions of lower internal pressure relative to pressure outside the tube. Such conditions occur rarely in industrial applications but are very common in biological studies such as blood flow in veins and air flow in lungs. When a flow is driven through a deformable channel or tube, interactions between fluid-mechanical and elastic forces can lead to a variety of biologically significant phenomena, including nonlinear pressure-drop/flow-rate relations, wave propagation, and the generation of instabilities. Understanding the physical origin and nature of these phenomena remains a significant experimental, analytical, and computational challenge, involving unsteady flows at low or high Reynolds numbers, large-amplitude fluid-structure interactions, free-surface flows, and intrinsically 2D or 3D motion.
Collapsible flow | Introduction
There are several mechanisms that can produce a pyroclastic flow:
Pyroclastic flow | Causes
In magnetic confinement fusion the zonal direction primarily connotes the poloidal direction (i.e. the short way around the torus), the corresponding coordinate being denoted by "y" in the slab approximation or "θ" in magnetic coordinates. However, in the fusion context, usage is restricted to the context of zonal plasma flows and there will in general be a toroidal component in such flows as well. Thus, although the term zonal has come into use in plasma physics to emphasize an analogy with zonal flows in geophysics, it does not uniquely identify the direction of flow, unlike the case in geophysics.
Zonal and poloidal | Introduction
There are many different styles of flow, with different terminology used by different people – stic.man of Dead Prez uses the following terms – Alternatively, music scholar Adam Krims uses the following terms –
Rapping | Styles
The surface conductances, formula_23 and formula_24 are approximated by either the Manning or Chezy equation.
HydroGeoSphere | Surface water flow
Von Kármán swirling flow is a flow created by a uniformly rotating infinitely long plane disk, named after Theodore von Kármán who solved the problem in 1921. This problem is used as a model for centrifugal fans or compressors. This flow is classified under the category of steady flows in which vorticity generated at a solid surface is prevented from diffusing far away by an opposing convection, the other examples being the Blasius boundary layer with suction, stagnation point flow etc.
Von Kármán swirling flow | Introduction
Hence, the flow is referred to as quasi-viscous.
Taylor–Culick flow | Introduction
Jet streak dynamics through the imbalance of Coriolis and pressure gradient forces, causing subgeostrophic and supergeostrophic flows, can also create upward vertical velocities. There are numerous other atmospheric setups in which upward vertical velocities can be created.
Atmospheric convection | Boundaries and forcing
These are the Taylor vortices. While the fluid mechanics of the original flow are unsteady when formula_16, the new flow, called "Taylor–Couette flow", with the Taylor vortices present, is actually steady until the flow reaches a large Reynolds number, at which point the flow transitions to unsteady "wavy vortex" flow, presumably indicating the presence of non-axisymmetric instabilities.
Taylor–Couette flow | Taylor vortex
High-pressure systems form due to downward motion through the troposphere, the atmospheric layer where weather occurs. Preferred areas within a synoptic flow pattern in higher levels of the troposphere are beneath the western side of troughs. On weather maps, these areas show converging winds (isotachs), also known as confluence, or converging height lines near or above the level of non-divergence, which is near the 500 hPa pressure surface about midway up through the troposphere. On weather maps, high-pressure centers are associated with the letter H placed within the isobar with the highest pressure value. On constant pressure upper level charts, it is located within the highest height line contour.
Anticyclogenesis | Process
Energy equation for the steady flow:
Isentropic nozzle flow | Flow analysis
This is the case of a vortex filament rotating at constant speed, there is a cylindrical symmetry and the problem can be solved in the orthogonal plane. Dual to the case above of line sources, Vortex lines play the role of monopoles for irrotational flows. Also in this case the flow is also both irrotational and incompressible and therefore a case of Potential flow.
Elementary flow | Two Dimensional vortex line
Gradient Flow is useful in studying atmospheric flow rotating around high and low pressures centers with small Rossby numbers. This is the case where the radius of curvature of the flow about the pressure centers is small, and geostrophic flow no longer applies with a useful degree of accuracy.
Balanced flow | Application
Even though the wind speed near the center of a tropical cyclone is very fast, at any point on the Earth's surface it is not as fast as it is above that point away from the retarding influence of the Earth's surface. The slower speed of the air at the earth's surface prevents the barometric pressure from falling as low as would be expected from the barometric pressure at mid altitudes. This is compatible with Bernoulli's principle. The secondary flow at the Earth's surface is toward the center of the cyclone but is then drawn upward by the significantly lower pressure at mid and high altitudes.
Secondary flow | Tropical cyclones
The equations were said to apply to parcels of air moving on horizontal planes. Indeed, when one considers a column of atmosphere, it is seldom the case that the air density is the same all the height up, since temperature and moisture content, hence density, do change with height. Every parcel within such a column moves according to the air properties at its own height. Homogeneous sheets of air may slide one over the other, so long as stable stratification of lighter air on top of heavier air leads to well-separated layers. If some air happens to be heavier/lighter than that in the surroundings, though, vertical motions do occur and modify the horizontal motion in turn.
Balanced flow | Vertical differences of air properties
Relatively intermediate albedos and smooth, several hundred meter flows typify these materials. Contact with surrounding terrain not as sharp as observed with bright and dark flow material. Origin of flows is often hard to tell. It is difficult to distinguish individual flows in a group. It is believed to have origin in sulfur/silicate-rich effusive eruptions.
Chaac-Camaxtli region | Undivided flow
Below convergence zones narrow jets of downward flow form and the magnitude of the current will be comparable to the horizontal flow. The downward propagation will typically be in the order of meters or tenths of meters and will not penetrate the pycnocline. The upwelling is less intense and takes place over a wider band under the divergence zone. In wind speeds ranging from the maximum vertical velocity ranged from with a ratio of down-welling to wind velocities ranging from −0.0025 to −0.0085.
Langmuir circulation | Observations
155–78).
Space of flows | Theoretic
There is another receiver pressure substantially below that of curve C that also results in isentropic flow throughout the nozzle, represented by curve D; after the throat the flow is supersonic. Pressures in the receiver in between those of curve C and curve D result in non-isentropic flow (a shock wave occurs in the flow) and will be considered in the next section. If pr is below that of curve D, the exit pressure pe is greater than pr. Once again, for receiver pressures below that of curve C, the mass flux remains constant since the conditions at the throat remain unchanged.
Isentropic nozzle flow | Converging nozzle
Extratropical cyclones are generally driven, or "steered", by deep westerly winds in a general west to east motion across both the Northern and Southern hemispheres of the Earth. This general motion of atmospheric flow is known as "zonal". Where this general trend is the main steering influence of an extratropical cyclone, it is known as a "zonal flow regime". When the general flow pattern buckles from a zonal pattern to the meridional pattern, a slower movement in a north or southward direction is more likely. Meridional flow patterns feature strong, amplified troughs and ridges, generally with more northerly and southerly flow.
Extratropical cyclone | Motion
Beside the flow maps in cartography there are several other kind of flow maps:
Flow map | Other types of flow maps
Open-channel flow can be classified and described in various ways based on the change in flow depth with respect to time and space. The fundamental types of flow dealt with in open-channel hydraulics are:
Open-channel flow | Classifications of flow
Inflow can originate from mid-levels of the atmosphere too. When thunderstorms are able to organize into squall lines, a feature known as a rear inflow jet develops to the south of the mid-level circulation associated with its northern bookend vortex. This leads to an erosion of rain within the broad rain shield behind the squall line, and may lead to acceleration of the squall line itself.
Inflow (meteorology) | Thunderstorms
The vorticity will be zero on the axis, and maximum near the walls, where the shear is largest. Conversely, a flow may have zero vorticity even though its particles travel along curved trajectories. An example is the ideal irrotational vortex, where most particles rotate about some straight axis, with speed inversely proportional to their distances to that axis. A small parcel of continuum that does not straddle the axis will be rotated in one sense but sheared in the opposite sense, in such a way that their mean angular velocity "about their center of mass" is zero.
Vorticity | Examples
Transonic, supersonic, and hypersonic flows are all compressible flows.
Aerodynamics | Compressible aerodynamics
Fluids or gases with controlled velocity pass through a laminar flow reactor in a fashion of laminar flow. That is, streams of fluids or gases slide over each other like cards. When analyzing fluids with the same viscosity ("thickness" or "stickiness") but different velocity, fluids are typically characterized into two types of flows: laminar flow and turbulent flow. Compared to turbulent flow, laminar flow tends to have a lower velocity and is generally at a lower Reynolds number. Turbulent flow, on the other hand, is irregular and travels at a higher speed. Therefore the flow velocity of a turbulent flow on one cross section is often assumed to be constant, or "flat".
Laminar flow reactor | Flow velocity in LFR
The speed at which a fluid flows past an object varies with distance from the object's surface. The region surrounding an object where the air speed approaches zero is known as the boundary layer. It is here that surface friction most affects flow; irregularities in surfaces may affect boundary layer thickness, and hence act to disrupt flow.
Airflow | Types of airflow
For instance, the thermal wind associated with pole-to-equator temperature gradients is the primary physical explanation for the jet stream in the upper half of the troposphere, which is the atmospheric layer extending from the surface of the planet up to altitudes of about 12-15 km. Mathematically, the thermal wind relation defines a vertical wind shear – a variation in wind speed or direction with height. The wind shear in this case is a function of a horizontal temperature gradient, which is a variation in temperature over some horizontal distance. Also called baroclinic flow, the thermal wind varies with height in proportion to the horizontal temperature gradient.
Thermal wind | Introduction
In hydrology, throughflow, a subtype of interflow (percolation), is the lateral unsaturated flow of water in the soil zone, typically through a highly permeable geologic unit overlying a less permeable one. Water thus returns to the surface, as return flow, before or on entering a stream or groundwater. Once water infiltrates into the soil, it is still affected by gravity and infiltrates to the water table or if permeabliity varies laterally travels downslope. Throughflow usually occurs during peak hydrologic events (such as high precipitation). Flow rates are dependent on the hydraulic conductivity of the geologic medium.
Throughflow | Introduction
Compressible flow accounts for varying density within the flow. Subsonic flows are often idealized as incompressible, i.e. the density is assumed to be constant. Transonic and supersonic flows are compressible, and calculations that neglect the changes of density in these flow fields will yield inaccurate results. Viscosity is associated with the frictional forces in a flow. In some flow fields, viscous effects are very small, and approximate solutions may safely neglect viscous effects. These approximations are called inviscid flows. Flows for which viscosity is not neglected are called viscous flows. Finally, aerodynamic problems may also be classified by the flow environment.
Aerodynamics | Flow classification
HydroGeoSphere assumes that the subsurface flow equation in a porous medium is always solved during a simulation, either for fully saturated or variably saturated flow conditions. The subsurface flow equation can be expanded to incorporate discrete fractures, a second interacting porous continuum, wells, tile drains and surface flow. The following assumptions are made for subsurface flow: The Richards’ equation is used to describe three-dimensional transient subsurface flow in a variably saturated porous medium: The fluid flux, formula_2, is represented by the Darcy's law shown as:
HydroGeoSphere | Groundwater Flow
The case of a vertical line emitting at a fixed rate a constant quantity of fluid Q per unit length is a line source. The problem has a cylindrical simmetry and can be treated in two dimension on the orthogonal plane. Line sources and line sinks (below) are important elementary flows because they play the role of monopole(s) for incompressible fluids (which can also be considered examples of solenoidal fields i.e. divergence free fields). Generic flow patterns can be also de-composed in terms of multipole expansions, in the same manner as for electric and magnetic fields where the monopole is essentially the first non trivial (e.g.
Elementary flow | Two Dimensional line source
Given a uniform velocity of a fluid at any position in space: This flow is incompressible because the velocity is constant, the first derivatives of the velocity components are zero, and the total divergence is zero: formula_2 Given the circulation is always zero the flow is also irrotational, we can derive this from the Kelvin's circulation theorem and from the explicit computation of the Vorticity:
Elementary flow | Two Dimensional uniform flow
When a fluid is flowing through a closed channel such as a pipe or between two flat plates, either of two types of flow may occur depending on the velocity and viscosity of the fluid: laminar flow or turbulent flow. Laminar flow occurs at lower velocities, below a threshold at which the flow becomes turbulent. The velocity is determined by a dimensionless parameter characterizing the flow called the Reynolds number, which also depends on the viscosity and density of the fluid and dimensions of the channel. Turbulent flow is a less orderly flow regime that is characterized by eddies or small packets of fluid particles, which result in lateral mixing.
Laminar flow | Introduction
Any fluid, including water in a stream, can only flow around a bend in vortex flow. In vortex flow the speed of the fluid is fastest where the radius of the flow is smallest, and slowest where the radius is greatest. (Tropical cyclones, tornadoes, and the spinning motion of water as it escapes down a drain are all visible examples of vortex flow.) In the case of water flowing around a bend in a stream the secondary flow in the boundary layer along the floor of the stream does not flow parallel to the banks of the stream but flows partly across the floor of the stream toward the inside of the stream (where the radius of curvature is smallest).
Point bar | Formation
However, in this case assuming a constant Coriolis parameter is unrealistic, and the balanced-flow speed can be applied locally. See Rossby waves as an example of when changes of latitude are dynamically effective.
Balanced flow | Horizontal differences of air properties
For an isentropic flow, entropy density can vary between different streamlines. If the entropy density is the same everywhere, then the flow is said to be homentropic.
Isentropic process | Isentropic flow
Taylor vortices (also named after Sir Geoffrey Ingram Taylor) are vortices formed in rotating Taylor–Couette flow when the Taylor number (formula_11) of the flow exceeds a critical value formula_12. For flow in which instabilities in the flow are not present, i.e. perturbations to the flow are damped out by viscous forces, and the flow is steady. But, as the formula_11 exceeds formula_12, axisymmetric instabilities appear. The nature of these instabilities is that of an exchange of stabilities (rather than an overstability), and the result is not turbulence but rather a stable secondary flow pattern that emerges in which large toroidal vortices form in flow, stacked one on top of the other.
Taylor–Couette flow | Taylor vortex
Hydrodynamic behaviour of flow in a confluence can be divided into six distinct features which are commonly called confluence flow zones (CFZ). These include
Confluence | River confluence flow zones
See image of de Laval Nozzle.
Compressible flow | Converging-diverging Laval nozzles
At an initial time a blocking-type circulation pattern establishes in the troposphere. This blocking pattern causes Rossby waves with zonal wavenumber 1 and/or 2 to grow to unusually large amplitudes. The growing wave propagates into the stratosphere and decelerates the westerly mean zonal winds. Thus the polar night jet weakens and simultaneously becomes distorted by the growing planetary waves. Because the wave amplitude increases with decreasing density this easterly acceleration process is not effective at fairly high levels. If the waves are sufficiently strong the mean zonal flow may decelerate sufficiently so that the winter westerlies turn easterly. At this point planetary waves may no longer penetrate into the stratosphere ).
Sudden stratospheric warming | Dynamics
return to its initial position). So, such a process is a reversible process. According to the Second Law of Thermodynamics, whenever there is a reversible and adiabatic flow, constant value of entropy is maintained. Engineers classify this type of flow as an "isentropic" flow of fluids. Isentropic is the combination of the Greek word "iso" (which means - same) and entropy. When the change in flow variables is small and gradual, isentropic flows occur. The generation of sound waves is an isentropic process. A supersonic flow that is turned while there is an increase in flow area is also isentropic.
Isentropic nozzle flow | Overview
This flow of air across the isobars near ground level is a "secondary flow". It does not conform to the primary flow, which is parallel to the isobars. At heights well above ground level there is a balance between the Coriolis effect, the local pressure gradient, and the velocity of the wind. This is balanced flow. Closer to the ground the air is not able to accelerate to the speed necessary for balanced flow. Interference by the surface of the ground or water, and by obstructions such as terrain, waves, trees and buildings, cause drag on the atmosphere and prevent the air from accelerating to the speed necessary to achieve balanced flow.
Secondary flow | Wind near ground level
Like for natural convection, the nature of a mixed convection flow is highly dependent on heat transfer (as buoyancy is one of the driving mechanisms) and turbulence effects play a significant role.
Combined forced and natural convection | Characterization
a more zonally symmetric jet).
Thermal wind | Jet stream
As a result, the wind direction near ground level is partly parallel to the isobars in the region, and partly across the isobars in the direction from higher pressure to lower pressure. As a result of the slower wind speed at the earth's surface, in a region of low pressure the barometric pressure is usually significantly higher at the surface than would be expected, given the barometric pressure at mid altitudes, due to Bernoulli's principle. Hence, the secondary flow toward the center of a region of low pressure is also drawn upward by the significantly lower pressure at mid altitudes.
Secondary flow | Wind near ground level
Flow velocity is used to classify flows according to speed regime. Subsonic flows are flow fields in which the air speed field is always below the local speed of sound. Transonic flows include both regions of subsonic flow and regions in which the local flow speed is greater than the local speed of sound. Supersonic flows are defined to be flows in which the flow speed is greater than the speed of sound everywhere. A fourth classification, hypersonic flow, refers to flows where the flow speed is much greater than the speed of sound. Aerodynamicists disagree on the precise definition of hypersonic flow.
Aerodynamics | Flow classification
Cyclostrophic flow describes a steady-state flow in a spatially varying pressure field when Trajectories do bend. The name 'cyclostrophic' stems from the Greek words 'kyklos' (circle) and 'strephein' (to turn).
Balanced flow | Cyclostrophic flow
The mechanisms are as follows: The pressure flow mechanism depends upon:
Pressure flow hypothesis | Mechanisms
The three-cell model of the atmosphere attempts to describe the actual flow of the Earth's atmosphere as a whole. It divides the Earth into the tropical (Hadley cell), mid-latitude (Ferrel cell), and polar (polar cell) regions, to describe energy flow and global atmospheric circulation (mass flow). Its fundamental principle is that of balance – the energy that the Earth absorbs from the sun each year is equal to that which it loses to space by radiation. This overall Earth energy balance, however, does not apply in each latitude due to the varying strength of the sun in each "cell" as a result of the tilt of the Earth's axis concerning its orbit.
Troposphere | Three-cell model
Helmholtz flow is a term used in fluid mechanics for flow with free streamlines or vortex sheets.
Helmholtz flow | Introduction
Unidirectional water flow is the key factor in lotic systems influencing their ecology. Stream flow can be continuous or intermittent, though. Stream flow is the result of the summative inputs from groundwater, precipitation, and overland flow. Water flow can vary between systems, ranging from torrential rapids to slow backwaters that almost seem like lentic systems. The speed or velocity of the water flow of the water column can also vary within a system and is subject to chaotic turbulence, though water velocity tends to be highest in the middle part of the stream channel (known as the thalveg). This turbulence results in divergences of flow from the mean downslope flow vector as typified by eddy currents.
River ecosystem | Water flow
Cometary knots are one type of ionized photoevaporation flow, which is characteristically associated with planetary nebulae, but several other types of photoevaporation flows (proplyds, cometary globules, elephant trunks, and champagne flows) are known from H II regions such as the Orion Nebula. Cometary knots are described as more advection-dominated than the other varieties, which are recombination-dominated or dust-dominated. The distinction can be made in terms of the formula for the "dynamic ionization balance within a photoevaporation flow", F ≈ "μn + αnh". Here F is the "ionizing photon flux incident on the outside of the flow", μ is the "initial velocity of the flow", α is the "recombination coefficient", n is the "peak ionized density in the flow", and h, which is approximately 0.1 r, is the "effective thickness of the flow".
Cometary knot | Relation to other photoevaporation flows
A radially symmetrical flow field directed outwards from a common point is called a source flow. The central common point is the line source described above. Fluid is supplied at a constant rate formula_15 from the source. As the fluid flows outward, the area of flow increases. As a result, to satisfy continuity equation, the velocity decreases and the streamlines spread out. The velocity at all points at a given distance from the source is the same. The velocity of fluid flow can be given as - We can derive the relation between flow rate and velocity of the flow.
Two-dimensional flow | Uniform source flow
A recirculating air flow path resulted from the warm (less-dense) air rising in a south-side solarium, and cooler (denser) air falling on the north side to create pressure differentials that automatically moved excess solar thermal gain from the south to the north side of the building without forced convection systems. Air flow was proportional to the differences in temperature between the two convection paths.
Double envelope house | Design and theory
Despite this, much of the atmosphere outside the tropics is close to geostrophic flow much of the time and it is a valuable first approximation. Geostrophic flow in air or water is a zero-frequency inertial wave.
Geostrophic wind | Introduction
The Walker circulation, also known as the Walker cell, is a conceptual model of the air flow in the tropics in the lower atmosphere (troposphere). According to this model, parcels of air follow a closed circulation in the zonal and vertical directions. This circulation, which is roughly consistent with observations, is caused by differences in heat distribution between ocean and land. It was discovered by Gilbert Walker. In addition to motions in the zonal and vertical direction the tropical atmosphere also has considerable motion in the meridional direction as part of, for example, the Hadley Circulation. The term "Walker circulation" was coined in 1969 by the Norwegian-American meteorologist Jacob Bjerknes.
Walker circulation | Introduction
Basically, Flow in pipes can be classified as follows –
Flow conditioning | Types of flow
The circulation in Venus's troposphere follows the so-called cyclostrophic flow. Its windspeeds are roughly determined by the balance of the pressure gradient and centrifugal forces in almost purely zonal flow. In contrast, the circulation in the Earth's atmosphere is governed by the geostrophic balance. Venus's windspeeds can be directly measured only in the upper troposphere (tropopause), between 60–70 km, altitude, which corresponds to the upper cloud deck. The cloud motion is usually observed in the ultraviolet part of the spectrum, where the contrast between clouds is the highest. The linear wind speeds at this level are about 100 ± 10 m/s at lower than 50° latitude.
Atmosphere of Venus | Circulation
Tornadoes and dust devils display localised vortex flow. Their fluid motion is similar to tropical cyclones but on a much smaller scale so that the Coriolis effect is not significant. The primary flow is circular around the vertical axis of the tornado or dust devil. As with all vortex flow, the speed of the flow is fastest at the core of the vortex. In accordance with Bernoulli's principle where the wind speed is fastest the air pressure is lowest; and where the wind speed is slowest the air pressure is highest. Consequently, near the center of the tornado or dust devil the air pressure is low.
Secondary flow | Tornadoes and dust devils
Steady-flow routing represents the simplest type of routing possible (actually no routing) by assuming that within each computational time step flow is uniform and steady. Thus it simply translates inflow hydrographs at the upstream end of the conduit to the downstream end, with no delay or change in shape. The normal flow equation is used to relate flow rate to flow area (or depth). This type of routing cannot account for channel storage, backwater effects, entrance/exit losses, flow reversal or pressurized flow. It can only be used with dendritic conveyance networks, where each node has only a single outflow link (unless the node is a divider in which case two outflow links are required).
Storm Water Management Model | Routing options
Vortices need not be steady-state features; they can move and change shape. In a moving vortex, the particle paths are not closed, but are open, loopy curves like helices and cycloids. A vortex flow might also be combined with a radial or axial flow pattern. In that case the streamlines and pathlines are not closed curves but spirals or helices, respectively. This is the case in tornadoes and in drain whirlpools. A vortex with helical streamlines is said to be solenoidal. As long as the effects of viscosity and diffusion are negligible, the fluid in a moving vortex is carried along with it.
Vortex | Evolution
This slow, widespread ascent of the air in a region of low pressure can cause widespread cloud and rain if the air is of sufficiently high relative humidity.
Secondary flow | Wind near ground level
Flow control methods are divided into passive, which require no auxiliary power and no control loop, and active, which require energy expenditure. Passive techniques include geometric shaping, the use of vortex generators, and the placement of longitudinal grooves or riblets on airfoil surfaces. Examples of active flow control methods include steady suction or blowing, unsteady suction or blowing, and the use of synthetic jets.
Flow control (fluid) | Active control
The flow in these regions is the secondary flow. These regions are usually in the vicinity of the boundary of the fluid adjacent to solid surfaces where viscous forces are at work, such as in the boundary layer. In engineering secondary flow also identifies an additional flow path.
Secondary flow | Introduction
A vortex is a region where the fluid flows around an imaginary axis. For an irrotational vortex, the flow at every point is such that a small particle placed there undergoes pure translation and does not rotate. Velocity varies inversely with radius in this case. Velocity will tend to formula_27 at formula_28 that is the reason for center being a singular point. The velocity is mathematically expressed as – Since the fluid flows around an axis, The stream function for irrotational vortices is given by –
Two-dimensional flow | Irrotational vortex
These flows are darker in color and are usually hotter according to NIMS observations. The length is generally greater than their width. The height of them tend to be larger based on the shadows they create. The Chaac Patera hot spot is a good example of this type of flow. Lava composition varies, but usually it is low-viscosity, mafic to ultramafic in composition.
Chaac-Camaxtli region | Dark flow
There is a pressure gradient toward the center of the vortex. This gradient, coupled with the slower speed of the air near the earth's surface, causes a "secondary flow" toward the center of the tornado or dust devil, rather than in a purely circular pattern. The slower speed of the air at the surface prevents the air pressure from falling as low as would normally be expected from the air pressure at greater heights. This is compatible with Bernoulli's principle. The secondary flow is toward the center of the tornado or dust devil, and is then drawn upward by the significantly lower pressure several thousands of feet above the surface in the case of a tornado, or several hundred feet in the case of a dust devil.
Secondary flow | Tornadoes and dust devils