"the meniscus. This means that any instrument is calibrated for a specific liquid, usually water. Menisci are a manifestation of capillary action, by which surface adhesion pulls a liquid up to form a concave meniscus or internal cohesion pulls the liquid down to form a convex meniscus. This phenomenon is important in transpirational pull in plants. When a tube of a narrow bore, often called a capillary tube, is dipped into a liquid and the liquid wets the tube (with zero contact angle), the liquid surface inside the tube forms a concave meniscus, which is a virtually spherical surface having"
"Crenation Crenation (from modern Latin ""crenatus"" meaning 'scalloped or notched', from popular Latin ""crena"" meaning 'notch') in botany and zoology, describes an object's shape, especially a leaf or shell, as being round-toothed or having a scalloped edge. The descriptor can apply to objects of different types, including cells, where one mechanism of crenation is the contraction of a cell after exposure to a hypertonic solution, due to the loss of water through osmosis. In a hypertonic environment, the cell has a lower concentration of solutes than the surrounding extracellular fluid, and water diffuses out of the cell by osmosis, causing"
"given by J. Willard Gibbs in his work ""On the Equilibrium of Heterogeneous Substances"" (1875-8). Since a liquid with a high surface tension pulls more strongly on the surrounding liquid than one with a low surface tension, the presence of a gradient in surface tension will naturally cause the liquid to flow away from regions of low surface tension. The surface tension gradient can be caused by concentration gradient or by a temperature gradient (surface tension is a function of temperature). As an example, wine may exhibit a visible effect called ""tears"", as shown in the photograph. The effect is"
"concave meniscus forms. Adhesion occurs between the fluid and the solid inner wall pulling the liquid column up until there is a sufficient mass of liquid for gravitational forces to overcome these intermolecular forces. The contact length (around the edge) between the top of the liquid column and the tube is proportional to the radius of the tube, while the weight of the liquid column is proportional to the square of the tube's radius. So, a narrow tube will draw a liquid column higher than a wider tube will, given that the inner water molecules cohere sufficiently to the outer"
"= 1,100.65. In case of a free liquid surface in contact with air, buoyancy and surface tension effects will also play a role in how the convection patterns develop. Liquids flow from places of lower surface tension to places of higher surface tension. This is called the Marangoni effect. When applying heat from below, the temperature at the top layer will show temperature fluctuations. With increasing temperature, surface tension decreases. Thus a lateral flow of liquid at the surface will take place, from warmer areas to cooler areas. In order to preserve a horizontal (or nearly horizontal) liquid surface, cooler"
"Convection cell In the field of fluid dynamics, a convection cell is the phenomenon that occurs when density differences exist within a body of liquid or gas. These density differences result in rising and/or falling currents, which are the key characteristics of a convection cell. When a volume of fluid is heated, it expands and becomes less dense and thus more buoyant than the surrounding fluid. The colder, denser part of the fluid descends to settle below the warmer, less-dense fluid, and this causes the warmer fluid to rise. Such movement is called convection, and the moving body of liquid"
"Surface tension Surface tension is the elastic tendency of a fluid surface which makes it acquire the least surface area possible. Surface tension allows insects (e.g. water striders), usually denser than water, to float and slide on a water surface. At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion). The net effect is an inward force at its surface that causes the liquid to behave as if its surface were covered with a stretched elastic membrane. Thus, the surface becomes"
"of the continuum. The upper-convected derivative is widely use in polymer rheology for the description of behavior of a viscoelastic fluid under large deformations. For the case of simple shear: Thus, In this case a material is stretched in the direction X and compresses in the directions Y and Z, so to keep volume constant. The gradients of velocity are: Thus, Upper-convected time derivative In continuum mechanics, including fluid dynamics, an upper-convected time derivative or Oldroyd derivative, named after James G. Oldroyd, is the rate of change of some tensor property of a small parcel of fluid that is written"
"is referred to as a ""convection cell"". This particular type of convection, where a horizontal layer of fluid is heated from below, is known as Rayleigh-Bénard convection. Convection usually requires a gravitational field, but in microgravity experiments, thermal convection has been observed without gravitational effects. Fluids are generalized as materials that exhibit the property of flow; however, this behavior is not unique to liquids. Fluid properties can also be observed in gases and even in particulate solids (such as sand, gravel, and larger objects during rock slides). A convection cell is most notable in the formation of clouds with its"
"Buoyancy In physics, buoyancy () or upthrust, is an upward force exerted by a fluid that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the"
"Taylor column A Taylor column is a fluid dynamics phenomenon that occurs as a result of the Coriolis effect. It was named after Geoffrey Ingram Taylor. Rotating fluids that are perturbed by a solid body tend to form columns parallel to the axis of rotation called Taylor columns. An object moving parallel to the axis of rotation in a rotating fluid experiences more drag force than what it would experience in a non rotating fluid. For example, a strongly buoyant ball (such as a pingpong ball) will rise to the surface slower than it would in a non rotating fluid."
"surface liquid will descend. This down-welling of cooler liquid contributes to the driving force of the convection cells. The specific case of temperature gradient-driven surface tension variations is known as thermo-capillary convection, or Bénard–Marangoni convection. Rayleigh–Bénard convection, whose effects are due solely to a temperature gradient, was first successfully analyzed by Lord Rayleigh; Rayleigh assumed boundary conditions in which the vertical velocity component and temperature disturbance vanish at the top and bottom boundaries (perfect thermal conduction). Those assumptions resulted in the analysis losing any connection with Henri Bénard's experiment. This resulted in discrepancies between theoretical and experimental results until Pearson"
"rises in a narrow space such as a thin tube, or in porous materials. This effect can cause liquids to flow against the force of gravity. It occurs because of inter-molecular attractive forces between the liquid and solid surrounding surfaces; If the diameter of the tube is sufficiently small, then the combination of surface tension and forces of adhesion between the liquid and container act to lift the liquid. The Marangoni effect is the convection of fluid along an interface between dissimilar substances because of variations in surface tension. Surface tension can vary because of inhomogeneous composition of the substances"
"Coandă effect The Coandă effect ( or ) is the tendency of a fluid jet to stay attached to a convex surface. As described by the eponymous Henri Coandă in different patents: ""the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to entrain fluid from the surroundings so that a region of lower pressure develops."" The pressure effect, which is usually not indicated, is fundamental for the comprehension of the Coandă effect. The principle was named after Romanian aerodynamics pioneer Henri Coandă, who was the first to recognize the"
"illumination, where the heating of the ground produces thermals, or where two winds converge forcing air upwards, or where winds blow over terrain of increasing elevation. The moisture carried upward cools into liquid drops of water due to lower temperatures at high altitude, which appear as ""cumulus"" clouds. As the water vapor condenses into liquid, latent heat is released, which warms the air, causing it to become less dense than the surrounding, drier air. The air tends to rise in an ""updraft"" through the process of convection (hence the term convective precipitation). This process creates a low-pressure zone within and"
"Mantle convection Mantle convection is the slow creeping motion of Earth's solid silicate mantle caused by convection currents carrying heat from the interior to the planet's surface. The Earth's surface lithosphere, which rides atop the asthenosphere (the two components of the upper mantle), is divided into a number of plates that are continuously being created and consumed at their opposite plate boundaries. Accretion occurs as mantle is added to the growing edges of a plate, associated with seafloor spreading. This hot added material cools down by conduction and convection of heat. At the consumption edges of the plate, the material"
"different spins couple has been analyzed in depth. Coandă effect The Coandă effect ( or ) is the tendency of a fluid jet to stay attached to a convex surface. As described by the eponymous Henri Coandă in different patents: ""the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to entrain fluid from the surroundings so that a region of lower pressure develops."" The pressure effect, which is usually not indicated, is fundamental for the comprehension of the Coandă effect. The principle was named after Romanian aerodynamics pioneer Henri"
"the volume of a liquid exactly matches the volume of its container, one or more surfaces are observed. The surface of a liquid behaves like an elastic membrane in which surface tension appears, allowing the formation of drops and bubbles. Surface waves, capillary action, wetting, and ripples are other consequences of surface tension. In a confined liquid, defined by geometric constraints on a nanoscopic scale, most molecules sense some surface effects, which can result in physical properties grossly deviating from those of the bulk liquid. A free surface is the surface of a fluid that is subject to both zero"
"liquid-vapor interface. Surface tension describes how difficult it is to extend the area of a surface. If surface tension is high, there is a large free energy required to increase the surface area. The surface of the bubbles will contract due to this increased surface tension. This contraction encourages the formation of a foam. Foam is a type of colloidal dispersion where gas is dispersed throughout a liquid phase. The liquid phase is also called the continuous phase because it is an uninterrupted, unlike the gas phase. As the foam is formed, it changes in structure. As the liquid foams"
"reworked the problem based on surface tension. This is what was originally observed by Bénard. Nonetheless in modern usage ""Rayleigh–Bénard convection"" refers to the effects due to temperature, whereas ""Bénard–Marangoni convection"" refers specifically to the effects of surface tension. Davis and Koschmieder have suggested that the convection should be rightfully called the ""Pearson–Bénard convection"". Rayleigh–Bénard convection is also sometimes known as ""Bénard–Rayleigh convection"", ""Bénard convection"", or ""Rayleigh convection"". Rayleigh–Bénard convection Rayleigh–Bénard convection is a type of natural convection, occurring in a plane horizontal layer of fluid heated from below, in which the fluid develops a regular pattern of convection cells"
"Convexity (finance) In mathematical finance, convexity refers to non-linearities in a financial model. In other words, if the price of an underlying variable changes, the price of an output does not change linearly, but depends on the second derivative (or, loosely speaking, higher-order terms) of the modeling function. Geometrically, the model is no longer flat but curved, and the degree of curvature is called the convexity. Strictly speaking, convexity refers to the second derivative of output price with respect to an input price. In derivative pricing, this is referred to as Gamma (Γ), one of the Greeks. In practice the"
"creep, crystal structures reorient into lower stress orientations. This does not happen under diffusional creep, thus observation of preferred orientations in samples lends credence to the dominance of dislocation creep. Mantle convection Mantle convection is the slow creeping motion of Earth's solid silicate mantle caused by convection currents carrying heat from the interior to the planet's surface. The Earth's surface lithosphere, which rides atop the asthenosphere (the two components of the upper mantle), is divided into a number of plates that are continuously being created and consumed at their opposite plate boundaries. Accretion occurs as mantle is added to the"
"the surface near the inside and flows towards the outside, forming the helical flow. The greater the curvature of the bend, and the faster the flow, the stronger is the cross-current and the sweeping. Due to the conservation of angular momentum the speed on the inside of the bend is faster than on the outside. Since the flow velocity is diminished, so is the centrifugal pressure. The pressure of the super-elevated column prevails, developing an unbalanced gradient that moves water back across the bottom from the outside to the inside. The flow is supplied by a counter-flow across the surface"
"flow develops singularities. Under the constraint that volume enclosed is constant, this is called surface tension flow. It is a parabolic partial differential equation, and can be interpreted as ""smoothing"". The most familiar example of mean curvature flow is in the evolution of soap films. A similar 2-dimensional phenomenon is oil drops on the surface of water, which evolve into disks (circular boundary). Mean curvature flow was originally proposed as a model for the formation of grain boundaries in the annealing of pure metal. The mean curvature flow extremalizes surface area, and minimal surfaces are the critical points for the"
"Thermal A thermal column (or thermal) is a column of rising air in the lower altitudes of Earth's atmosphere, a form of atmospheric updraft. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. The Sun warms the ground, which in turn warms the air directly above it. The warmer air nearer to the surface expands, becoming less dense than the surrounding air. The lighter air rises and cools due to its expansion in the lower pressure at higher altitudes. It stops rising when it has cooled to"
"means that it is difficult to achieve the static equilibrium as a pure liquid does. The most typical impurity to induce dynamic surface tension measurement is a surfactant molecule which has both of hydrophilic segment, generally called “head group” and hydrophobic segment, generally called “tail group” in a same molecule. Due to the characteristic molecular structure, surfactants migrate to the liquid surface bordering gas phase until an external force disperse the accumulated molecules from the interface or surface is fully occupied and thus cannot accommodate extra molecules. During this process, surface tension decrease as function of time and finally approach"
"are also seen on the solar, typically forming hexagonal prisms (Bénard cells). Thermal A thermal column (or thermal) is a column of rising air in the lower altitudes of Earth's atmosphere, a form of atmospheric updraft. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. The Sun warms the ground, which in turn warms the air directly above it. The warmer air nearer to the surface expands, becoming less dense than the surrounding air. The lighter air rises and cools due to its expansion in the lower"
"Entasis In architecture, entasis is the application of a convex curve to a surface for aesthetic purposes. Its best-known use is in certain orders of Classical columns that curve slightly as their diameter is decreased from the bottom upward. It also may serve an engineering function regarding strength. The word we apply to the design principle is used by the Roman architectural historian Vitruvius, and derives from the Greek word ""εντείνω"" (""enteino""), ""to stretch or strain tight"". Creating the illusion of greater strength or perception of height may have been an objective in the application of entasis. Examples of this"
"Ascent of sap The ascent of sap in the xylem tissue of plants is the upward movement of water and minerals from the root to the crown. Xylem is a complex tissue consisting of living and non-living cells. The conducting cells in xylem are typically non-living and include, in various groups of plants, vessels members and tracheids. Both of these cell types have thick, lignified secondary cell walls and are dead at maturity. Although several mechanisms have been proposed to explain the phenomenon, the cohesion-tension mechanism has the most evidence and support. Although cohesion-tension has received criticism, for example due"
"surface. Any protuberance that develops is accompanied by a steeper concentration gradients at its tip. This increases the diffusion rate to the tip. In opposition to this is the action of the surface tension tending to flatten the protuberance and setting up a flux of solute atoms from the protuberance out to the sides. However, overall, the protuberance becomes amplified. This process occurs again and again until a dendrite is produced. The term ""dendrite"" comes from the Greek word ""dendron (δενδρον)"", which means ""tree"". In paleontology, dendritic mineral crystal forms are often mistaken for fossils. These pseudofossils form as naturally"
"the surface is additionally known to be axisymmetric with formula_31, where formula_33 comes from the derivative of formula_34. The mean curvature of a surface specified by an implicit equation formula_35 can be calculated by using the gradient formula_36 and the Hessian matrix The mean curvature is given by: Another form is as the divergence of the unit normal. A unit normal is given by formula_39 and the mean curvature is An alternate definition is occasionally used in fluid mechanics to avoid factors of two: This results in the pressure according to the Young-Laplace equation inside an equilibrium spherical droplet being"
"under tension from the imbalanced forces, which is probably where the term ""surface tension"" came from. Because of the relatively high attraction of water molecules for each other through a web of hydrogen bonds, water has a higher surface tension (72.8 millinewtons per meter at 20 °C) compared to that of most other liquids. Surface tension is an important factor in the phenomenon of capillarity. Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent, but when referring to energy per unit of area, it is common to use the"
"have a purpose-made fan to ensure its operating temperature is kept within tolerable limits. A convection cell, also known as a Bénard cell is a characteristic fluid flow pattern in many convection systems. A rising body of fluid typically loses heat because it encounters a cold surface. In liquid, this occurs because it exchanges heat with colder liquid through direct exchange. In the example of the Earth's atmosphere, this occurs because it radiates heat. Because of this heat loss the fluid becomes denser than the fluid underneath it, which is still rising. Since it cannot descend through the rising fluid,"