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The peak expiratory flow (PEF), also called peak expiratory flow rate (PEFR) and peak flow measurement, [1] is a person's maximum speed of expiration, as measured with a peak flow meter, a small, hand-held device used to monitor a person's ability to breathe out air.
The flow coefficient of a device is a relative measure of its efficiency at allowing fluid flow. It describes the relationship between the pressure drop across an orifice valve or other assembly and the corresponding flow rate. Mathematically the flow coefficient C v (or flow-capacity rating of valve) can be expressed as
MMEF or MEF stands for maximal (mid-)expiratory flow and is the peak of expiratory flow as taken from the flow-volume curve and measured in liters per second. It should theoretically be identical to peak expiratory flow (PEF), which is, however, generally measured by a peak flow meter and given in liters per minute.
The variance per unit length of the column is taken as the ratio of the column length to the column efficiency in theoretical plates. The van Deemter equation is a hyperbolic function that predicts that there is an optimum velocity at which there will be the minimum variance per unit column length and, thence, a maximum efficiency. The van ...
Peak discharge the highest point on the hydrograph when the rate of discharge is greatest. Recession (or falling) limb The recession limb extends from the peak flow rate onward. The end of stormflow (a.k.a. quickflow or direct runoff) and the return to groundwater-derived flow is often taken as the point of inflection of the recession limb. The ...
U = flow rate, A = peak-to-peak oscillation amplitude. In animal flight or swimming, propulsive efficiency is high over a narrow range of Strouhal constants, generally peaking in the 0.2 < St < 0.4 range. [10] This range is used in the swimming of dolphins, sharks, and bony fish, and in the cruising flight of birds, bats and insects. [10]
A computer simulation of high velocity air flow around the Space Shuttle during re-entry A simulation of the Hyper-X scramjet vehicle in operation at Mach-7. The fundamental basis of almost all CFD problems is the Navier–Stokes equations, which define many single-phase (gas or liquid, but not both) fluid flows.
[4] [5] [6] A generalized model of the flow distribution in channel networks of planar fuel cells. [6] Similar to Ohm's law, the pressure drop is assumed to be proportional to the flow rates. The relationship of pressure drop, flow rate and flow resistance is described as Q 2 = ∆P/R. f = 64/Re for laminar flow where Re is the Reynolds number.