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Darcy–Weisbach equation. In fluid dynamics, the Darcy–Weisbach equation is an empirical equation that relates the head loss, or pressure loss, due to friction along a given length of pipe to the average velocity of the fluid flow for an incompressible fluid. The equation is named after Henry Darcy and Julius Weisbach.
Round cement plant duct stiffeners are sometimes about 5% duct plate weight. Rectangular cement plant duct stiffeners are 15 to 20% times duct plate weight. Power plant ductwork is often larger. Power plant ductwork is usually rectangular, with stiffener weights of 50% (or more) times duct plate weight.
For calculation involving flow in non-circular ducts, the hydraulic diameter can be substituted for the diameter of a circular duct, with reasonable accuracy, if the aspect ratio AR of the duct cross-section remains in the range 1 / 4 < AR < 4. [11]
Hagen–Poiseuille equation. In nonideal fluid dynamics, the Hagen–Poiseuille equation, also known as the Hagen–Poiseuille law, Poiseuille law or Poiseuille equation, is a physical law that gives the pressure drop in an incompressible and Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section.
Darcy friction factor formulae. In fluid dynamics, the Darcy friction factor formulae are equations that allow the calculation of the Darcy friction factor, a dimensionless quantity used in the Darcy–Weisbach equation, for the description of friction losses in pipe flow as well as open-channel flow. The Darcy friction factor is also known as ...
In those cases, the characteristic length is the diameter of the pipe or, in case of non-circular tubes, its hydraulic diameter : Where is the cross-sectional area of the pipe and is its wetted perimeter. It is defined such that it reduces to a circular diameter of D for circular pipes. For flow through a square duct with a side length of a ...
Ducted fans are used for propulsion or direct lift in many types of vehicle including aeroplanes, airships, hovercraft, and powered lift VTOL aircraft. The high-bypass turbofan engines used on many modern airliners is an example of a very successful and popular use of ducted fan design. The duct increases thrust efficiency by up to 90% in most ...
Nusselt number. In thermal fluid dynamics, the Nusselt number (Nu, after Wilhelm Nusselt [1]: 336 ) is the ratio of total heat transfer to conductive heat transfer at a boundary in a fluid. Total heat transfer combines conduction and convection. Convection includes both advection (fluid motion) and diffusion (conduction).