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Stable Stratification
Stable stratification of fluids occurs when each layer is less dense than the one below it. Unstable stratification is when each layer is denser than the one below it. Buoyancy forces tend to preserve stable stratification; the higher layers float on the lower ones. In unstable stratification, on the other hand, buoyancy forces cause convection. The less-dense layers rise though the denser layers above, and the denser layers sink though the less-dense layers below. Stratifications can become more or less stable if layers change density. The processes involved are important in many science and engineering fields. Destablization and mixing Stable stratifications can become unstable if layers change density. This can happen due to outside influences (for instance, if water evaporates from a freshwater lens, making it saltier and denser, or if a pot or layered beverage is heated from below, making the bottom layer less dense). However, it can also happen due to internal diffusio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Immiscible
Miscibility () is the property of two chemical substance, substances to mix in all mixing ratio, proportions (that is, to fully dissolution (chemistry), dissolve in each other at any concentration), forming a homogeneity and heterogeneity, homogeneous mixture (a Solution (chemistry), solution). Such substances are said to be wikt:miscible, miscible (etymologically equivalent to the common term "wikt:mixable, mixable"). The term is most often applied to liquids but also applies to solids and gases. An example in liquids is the miscibility of water and ethanol as they mix in all proportions. By contrast, substances are said to be wikt:immiscible, immiscible if the mixture does not form a solution for certain proportions. For one example, oil is not soluble in water, so these two solvents are immiscible. As another example, butanone (methyl ethyl ketone) is immiscible in water: it is soluble in water up to about 275 grams per liter, but will separate into two Phase (matter), phases b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temperature Inversion
In meteorology, an inversion (or temperature inversion) is a phenomenon in which a layer of warmer air overlies cooler air. Normally, air temperature gradually decreases as altitude increases, but this relationship is reversed in an inversion. An inversion traps air pollution, such as smog, near the ground. An inversion can also suppress convection by acting as a "cap". If this cap is broken for any of several reasons, convection of any humidity can then erupt into violent thunderstorms. Temperature inversion can cause freezing rain in cold climates. Normal atmospheric conditions Usually, within the lower atmosphere (the troposphere) the air near the surface of the Earth is warmer than the air above it, largely because the atmosphere is heated from below as solar radiation warms the Earth's surface, which in turn then warms the layer of the atmosphere directly above it, e.g., by thermals ( convective heat transfer). Air temperature also decreases with an increase in al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Passive Cooling
Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption. This approach works either by preventing heat from entering the interior (heat gain prevention) or by removing heat from the building (natural cooling). Natural cooling utilizes on-site energy, available from the natural environment, combined with the architectural design of building components (e.g. building envelope), rather than mechanical systems to dissipate heat. Therefore, natural cooling depends not only on the architectural design of the building but on how the site's natural resources are used as heat sinks (i.e. everything that absorbs or dissipates heat). Examples of on-site heat sinks are the upper atmosphere (night sky), the outdoor air (wind), and the earth/soil. Passive cooling is an important tool for design of buildings for climate change adaptationreducing dependency ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underfloor Heating
Underfloor heating and cooling is a form of Heating, ventilation, and air conditioning, central heating and cooling that achieves indoor climate control for thermal comfort using hydronics, hydronic or electrical heating elements embedded in a floor. Heating is achieved by Conduction (heat), conduction, radiation and convection. Use of underfloor heating dates back to the Neoglacial and Neolithic periods. History Underfloor heating has a long history back into the Neoglacial and Neolithic periods. Archeological digs in Asia and the Aleutian islands of Alaska reveal how the inhabitants drafted smoke from fires through stone covered trenches which were excavated in the floors of their subterranea (geography), subterranean dwellings. The hot smoke heated the floor stones and the heat then radiated into the living spaces. These early forms have evolved into modern systems using fluid filled pipes or electrical cables and mats. Below is a chronological overview of under floor heating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UFAD Air Stratification Example Diagram
Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings as part of the design of a HVAC system. UFAD systems use an underfloor supply plenum located between the structural concrete slab and a raised floor system to supply conditioned air to supply outlets (usually floor diffusers), located at or near floor level within the occupied space. Air returns from the room at ceiling level or the maximum allowable height above the occupied zone. The UFAD system takes advantage of the thermal plume and stratification phenomenon: the conditioned air is supplied directly to the occupied zone (OZ). The thermal plumes generated by the occupants and other heat sources introduce the conditioned air to absorb the heat and humidity and then bring the contaminated air to the upper zone (UZ). At a certain plane in the room, the airflow rate returned to the upper zone is equal to the supply air. The plane divides the room into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strait Of Gibraltar
The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Europe from Africa. The two continents are separated by 7.7 nautical miles (14.2 kilometers, 8.9 miles) at its narrowest point. Ferries cross between the two continents every day in as little as 35 minutes. The Strait's depth ranges between . The strait lies in the territorial waters of Morocco, Spain, and the British overseas territory of Gibraltar. Under the United Nations Convention on the Law of the Sea, foreign vessels and aircraft have the freedom of navigation and overflight to cross the strait of Gibraltar transit passage, in case of continuous transit. Names and etymology The name comes from the Rock of Gibraltar, which in turn originates from the Arabic (meaning "Tariq's Mount"), named after Tariq ibn Ziyad. It is also known as the Straits of Gibraltar, the Gut (coastal geography), Gut of Gibraltar (although this is mostly archaic), the STROG (STRait Of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratified Flows
The flow in many fluids varies with density and depends upon gravity. The fluid with lower density is always above the fluid with higher density (stable stratification). Stratified flows are very common such as the Earth's ocean and its atmosphere. Stratified fluid A stratified fluid may be defined as the fluid with density variations in the vertical direction. For example, air and water; both are fluids and if we consider them together then they can be seen as a stratified fluid system. Density variations in the atmosphere profoundly affect the motion of water and air. Wave phenomena in air flow over the mountains and occurrence of smog are the examples of stratification effect in the atmosphere. When a fluid system having a condition in which fluid density decreases with height, is disturbed, then the gravity and friction restore the undisturbed conditions. If however the fluid tends to be stable if density decreases with height. Upstream motions in stratified flow It is kno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermohaline Circulation
Thermohaline circulation (THC) is a part of the large-scale Ocean current, ocean circulation driven by global density gradients formed by surface heat and freshwater fluxes. The name ''thermohaline'' is derived from ''wikt:thermo-, thermo-'', referring to temperature, and ', referring to salinity, salt content—factors which together determine the Water (molecule)#Density of saltwater and ice, density of sea water. Wind-driven surface currents (such as the Gulf Stream) travel Polar regions of Earth, polewards from the equatorial Atlantic Ocean, cooling and sinking en-route to higher latitudes - eventually becoming part of the North Atlantic Deep Water - before flowing into the ocean basins. While the bulk of thermohaline water upwelling, upwells in the Southern Ocean, the oldest waters (with a transit time of approximately 1000 years) upwell in the North Pacific; extensive mixing takes place between the ocean basins, reducing the difference in their densities, forming the Worl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Circulation
Atmospheric circulation is the large-scale movement of Atmosphere of Earth, air and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth. The Earth's atmospheric circulation varies from year to year, but the large-scale structure of its circulation remains fairly constant. The smaller-scale weather systems – middle latitudes, mid-latitude low-pressure area, depressions, or tropical convective cells – occur chaotically, and long-range weather predictions of those cannot be made beyond ten days in practice, or a month in theory (see chaos theory and the butterfly effect). The Earth's weather is a consequence of its illumination by the Sun and the laws of thermodynamics. The atmospheric circulation can be viewed as a heat engine driven by the Sun's energy and whose heat sink, energy sink, ultimately, is the blackness of space. The work produced by that engine causes the motion of the masses of air, and in that process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Stratification
The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes), all retained by Earth's gravity. The atmosphere serves as a protective buffer between the Earth's surface and outer space, shields the surface from most meteoroids and ultraviolet solar radiation, keeps it warm and reduces diurnal temperature variation (temperature extremes between day and night) through heat retention (greenhouse effect), redistributes heat and moisture among different regions via air currents, and provides the chemical and climate conditions allowing life to exist and evolve on Earth. By mole fraction (i.e., by quantity of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other trace gases (see Composition below ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Instability
Atmospheric instability is a condition where the Earth's atmosphere is considered to be unstable and as a result local weather is highly variable through distance and time. Atmospheric instability encourages vertical motion, which is directly correlated to different types of weather systems and their severity. For example, under unstable conditions, a lifted air parcel, parcel of air will find cooler and denser surrounding air, making the parcel prone to further ascent, in a positive feedback loop. In meteorology, instability can be described by various indices such as the Bulk Richardson Number, lifted index, K-index (meteorology), K-index, convective available potential energy, convective available potential energy (CAPE), the Showalter, and the Vertical totals. These indices, as well as atmospheric instability itself, involve temperature changes through the troposphere with height, or lapse rate. Effects of atmospheric instability in moist atmospheres include thunderstorm d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Stratification
Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers: the epilimnion, comprising the top warm layer; the thermocline (or metalimnion), the middle layer, whose depth may change throughout the day; and the colder hypolimnion, extending to the floor of the lake. Every lake has a set mixing regime that is influenced by lake morphometry and environmental conditions. However, changes to human influences in the form of land use change, increases in temperature, and changes to weather patterns have been shown to alter the timing and intensity of stratification in lakes around the globe. Rising air temperatures have the same effect on lake bodies as a physical shift in geographic location, with tropical zones being particularly sensitive. These changes can further alter the fish, zooplankton, and phytoplankton community composition, in addition to creating gradients that alter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
