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Slowing Down (or Stopping) occurs when the force of kinetic friction is greater than that of the external force. This also follows Newton's first law of motion as there exists a net force on the object. Constant Velocity occurs when there is no net force on the object, that is the external force is equal to force of kinetic friction.
Separation occurs in flow that is slowing down, with pressure increasing, after passing the thickest part of a streamline body or passing through a widening passage, for example. Flowing against an increasing pressure is known as flowing in an adverse pressure gradient .
Bernoulli's principle states that an increase in the speed of a parcel of fluid occurs simultaneously with a decrease in either the pressure or the height above a datum. [1]: Ch.3 [ 2 ] : 156–164, § 3.5 The principle is named after the Swiss mathematician and physicist Daniel Bernoulli , who published it in his book Hydrodynamica in 1738. [ 3 ]
An everyday example is the slow, smooth and optically transparent flow of shallow water over a smooth barrier. [ 8 ] When water leaves a tap without an aerator with little force, it first exhibits laminar flow, but as acceleration by the force of gravity immediately sets in, the Reynolds number of the flow increases with speed, and the laminar ...
An object moving downward faster than the terminal velocity (for example because it was thrown downwards, it fell from a thinner part of the atmosphere, or it changed shape) will slow down until it reaches the terminal velocity. Drag depends on the projected area, here represented by the object's cross-section or silhouette in a horizontal plane.
For certain geometries freely sinking through a column of water, hydrodynamic added mass associated with the sinking body can be much larger than the mass of the object. This situation can occur, for instance, when the sinking body has a large flat surface with its normal vector pointed in the direction of motion (downward).
Wave resistance (ship hydrodynamics) occurs when a solid object is moving along a fluid boundary and making surface waves. Last, in aerodynamics the term "parasitic drag" is often used. Parasitic drag is the sum of form drag and skin friction drag and is entirely negative to an aircraft, in contrast with lift-induced drag which is a consequence ...
The local acceleration (a) can also be thought of as the "unsteady term" as this describes some change in velocity over time. The convective acceleration (b) is an acceleration caused by some change in velocity over position, for example the speeding up or slowing down of a fluid entering a constriction or an opening, respectively.