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Orifice plate showing vena contracta. An orifice plate is a thin plate with a hole in it, which is usually placed in a pipe. When a fluid (whether liquid or gaseous) passes through the orifice, its pressure builds up slightly upstream of the orifice [1] but as the fluid is forced to converge to pass through the hole, the velocity increases and the fluid pressure decreases.
Most charts or tables indicate the type of friction factor, or at least provide the formula for the friction factor with laminar flow. If the formula for laminar flow is f = 16 / Re , it is the Fanning factor f, and if the formula for laminar flow is f D = 64 / Re , it is the Darcy–Weisbach factor f D.
Churchill equation [24] (1977) is the only equation that can be evaluated for very slow flow (Reynolds number < 1), but the Cheng (2008), [25] and Bellos et al. (2018) [8] equations also return an approximately correct value for friction factor in the laminar flow region (Reynolds number < 2300). All of the others are for transitional and ...
The coefficient of contraction is defined as the ratio between the area of the jet at the vena contracta and the area of the orifice. C c = Area at vena contracta/Area of orifice. The typical value may be taken as 0.611 for a sharp orifice (concentric with the flow channel). [2] [3] The smaller the value, the greater the effect the vena ...
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
The boundary layer thickness, , is the distance normal to the wall to a point where the flow velocity has essentially reached the 'asymptotic' velocity, .Prior to the development of the Moment Method, the lack of an obvious method of defining the boundary layer thickness led much of the flow community in the later half of the 1900s to adopt the location , denoted as and given by
Generally, the higher the flow rate required to produce a given pressure difference, the less airtight the building. [2] The fan pressurization technique is also described in many standard test methods, such as ASTM E779 - 10, [ 17 ] ASTM E1827 – 11, [ 18 ] CAN/CGSB-149.10-M86, [ 19 ] CAN/CGSB-149.15-96, [ 20 ] ISO 9972:2006 [ 13 ] (now ...
The Fanning friction factor (named after American engineer John T. Fanning) is a dimensionless number used as a local parameter in continuum mechanics calculations. It is defined as the ratio between the local shear stress and the local flow kinetic energy density: [1] [2]