Added Mass
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(or Virtual Mass) The inertia added to a system because an accelerating or decelerating body must move (or deflect) some volume of surrounding fluid as it moves through it.
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Barus Effect
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A viscoelastic effect. A phenomenon in which the diameter of fluid becomes larger than the diameter of a nozzle at its exit when the fluid is extruded through the nozzle.
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Basset Force
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The force due to the lagging boundary layer development with changing relative velocity (acceleration) of bodies moving through a fluid.
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Bingham Plastic
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A viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. A common example is toothpaste, which will not be extruded until a certain pressure is applied to the tube. It then is pushed out as a solid plug.
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Boundary Layer
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A boundary layer is that layer of fluid in the immediate vicinity of a bounding surface. The boundary layer effect occurs at the field region in which all changes occur in the flow pattern. The boundary layer distorts surrounding nonviscous flow.
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Bubble
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A globule of one substance in another, usually gas in a liquid. Due to the Marangoni effect, bubbles may remain intact when they reach the surface of the immersive substance.
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Coanda Effect
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The tendency of a fluid jet to stay attached to an adjacent suitably shaped curved surface. Also applies to powdered solids.
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Conservation of Momentum
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In a closed system (one that does not exchange any matter with the outside and is not acted on by outside forces) the total momentum is constant.
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Coriolis Force
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An apparent deflection, or force, experienced by moving objects when viewed from a rotating frame of reference. The Coriolis force is an example of a fictitious force (or pseudo force), because it does not appear when the motion is expressed in an inertial frame of reference. For example, freely moving objects on the surface of the Earth experience a Coriolis force, and appear to veer to the right in the northern hemisphere, and to the left in the southern.
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Diamagnetism
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The property of an object which causes it to create a magnetic field in opposition of an externally applied magnetic field, thus causing a repulsive effect. It is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field. Diamagnetism is generally a quite weak effect in most materials, although superconductors exhibit a strong effect.
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If a thin (under 0.5 cm) layer of water is placed on top of a powerful magnet (such as a super magnet) then the field of the magnet repels the water. This causes a slight dimple in the water's surface that may be seen by its reflection.
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Electric Field
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The space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field (that can also be equated to electric flux density). This electric field exerts a force on other electrically charged objects.
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If the liquid carries an electric charge.
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Electrohydrodynamics
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Includes the following types of particle and fluid transport mechanisms:Electrophoresis, electrokinesis, dielectrophoresis, electro-osmosis, and electrorotation. In general, the phenomena relate to the direct conversion of electrical energy into kinetic energy, and vice versa.
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Electrostatics
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The phenomena arising from stationary or slowly moving electric charges
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Electrowetting
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(or Electrocapillary Effect) The modification of the wetting properties of a hydrophobic surface with an applied electric field.
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Entrainment
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The movement of one fluid due to the motion of another.
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Faraday Wave
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(or Faraday Ripples) Nonlinear standing waves that appear on liquids enclosed by a vibrating receptacle. When the vibration frequency exceeds a critical value, the flat hydrostatic surface becomes unstable. The waves can take the form of stripes, close-packed hexagons, or even squares or quasiperiodic patterns.
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Ferromagnetism
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The mechanism by which certain materials (such as iron) form permanent magnets and/or exhibit strong interactions with magnets. Responsible for commonly observed magnetism phenomena, e.g. 'fridge magnets. A material is 'ferromagnetic' only if all its magnetic ions add a positive contribution to the net magnetisation. If some of them subtract from the net magnetisation (i.e. are partially anti-aligned), then the material is 'ferrimagnetic'.
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In the case of a ferrofluid.
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Flow Separation
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For a solid object travelling through a fluid (or alternatively a stationary object exposed to a moving fluid) flow separation occurs when the boundary layer travels far enough against an adverse pressure gradient that the speed of the boundary layer falls almost to zero.The fluid flow becomes detached from the surface of the object, and instead takes the forms of eddies and vortices.
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Flutter
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A dynamic instability of an elastic structure in a fluid flow, caused by positive feedback between the body's deflection and the force exerted by the fluid flow.
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Force
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That which can cause an object with mass to accelerate. Force has both magnitude & direction, i.e. it's a vector quantity. An object with constant mass will accelerate in proportion to the net force acting upon it and in inverse proportion to its mass (or the net force on an object is equal to the rate of change of momentum it experiences). Forces acting on objects may cause them to rotate or deform, or result in a change in pressure.
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Gravitation
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A natural phenomenon by which objects with mass attract one another. In everyday life, gravitation is most commonly thought of as the agency which lends weight to objects with mass.
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Hydraulic Jump
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When liquid at high velocity discharges into a zone of lower velocity, a rather abrupt rise (a step or standing wave) occurs in the liquid surface. The liquid is abruptly slowed and increases in height converting some of the flow's initial kinetic energy into an increase in potential energy, with some energy lost through turbulence to heat. In an open channel flow, this manifests as the fast flow rapidly slowing and piling up on top of itself.
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Kármán Vortex Street
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A repeating pattern of swirling vortices caused by the unsteady separation of flow of a fluid over bluff bodies. It is responsible for such phenomena as the 'singing' of suspended telephone or power lines, the vibration of a car antenna at certain speeds.
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Kaye Effect
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A property of complex liquids, common in shear-thinning liquids (liquids which thin under shear stress). While pouring one the liquid onto a surface, the surface suddenly spouts an upcoming jet of liquid which merges with the downgoing one. Common household liquids with this property are liquid hand soaps, shampoos and non-drip paint. The effect usually goes unnoticed, however, because it seldom lasts more than about 300ms.
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Magnetic Field
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A vector field which surrounds magnets and electric currents, and is detected by the force it exerts on moving electric charges and on magnetic materials. When placed in a magnetic field, magnetic dipoles tend to align their axes parallel to the magnetic field. Magnetic fields also have their own energy with an energy density proportional to the square of the field intensity.
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For example, in the case of a ferromagnetic liquid or one moved by a ferromanetic solid in contact with the liquid.
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Magnetism
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One of the phenomena by which materials exert attractive or repulsive forces on other materials. Some well-known materials that exhibit easily detectable magnetic properties (called magnets) are nickel, iron, cobalt, and their alloys; however, all materials are influenced to greater or lesser degree by the presence of a magnetic field.
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Magnetohydrodynamic Effect
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A magnetic field can induce currents in a moving conductive fluid, which create forces on the fluid, and also change the magnetic field itself.
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Pressure Drop
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Pressure is an effect which occurs when a force is applied on a surface. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point. Rapid pressure drop is a useful technique for applying force or breaking objects apart.
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Pressure Gradient
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A fluid (gas or liquid) subject to a pressure gradient results in a net force that is directed from high to low pressure (the 'pressure gradient force').
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Pressure Increase
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Pressure is an effect which occurs when a force is applied on a surface. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point.
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Suction
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The flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area.
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Surface Tension
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An attractive property of the surface of a liquid. It is what causes the surface portion of liquid to be attracted to another surface, such as that of another portion of liquid (as in connecting bits of water or as in a drop of mercury that forms a cohesive ball).
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Thermo-capillary Convection
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Mass transfer along an interface between two fluids due to a surface tension gradient, where the surface tension gradient is caused by a temperature gradient.
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Tidal Force
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A situation in which a body or material (for example, tidal water, or the Moon) is mainly under the gravitational influence of a second body (for example, the Earth), but is also perturbed by the gravitational effects of a third body (for example, by the Moon in the case of tidal water, or by the Sun in the case of the Moon).
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Triboelectric Effect
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A type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated (such as through rubbing). The polarity and strength of the charges produced differ according to the materials, surface roughness, temperature, strain, and other properties.
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For a liquid carrying an electric charge
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Turbulence
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A fluid regime characterised by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time (flow that is not turbulent is called laminar flow).
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Vortex Ring
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A torus shaped vortex in a fluid i.e. a region where the fluid mostly spins around an imaginary axis line that forms a closed loop. The dominant flow in a vortex ring is said to be toroidal, more precisely poloidal. Within a stationary body of fluid, a vortex ring can travel for relatively long distance, carrying the spinning fluid with it.
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