[hi′drȯ·lik ′rād·ē·əs]
(fluid mechanics)
The ratio of the cross-sectional area of a conduit in which a fluid is flowing to the inner perimeter of the conduit.

a hydraulic characteristic of the cross section of a fluid flow, expressed by the ratio of the area of this cross section to its so-called wetted perimeter (that is, that part of the perimeter along which the flow comes in contact with solid walls). The value of the hydraulic radius changes according to the dimensions and shape of the channel’s cross section. For a filled pipe of round cross section, the hydraulic radius is equal to one-fourth of the diameter, and for open channels of large width the radius is assumed to be equal to the mean depth of flow. The hydraulic radius is widely used in hydraulic calculations.

The ratio of the cross-sectional area of fluid flow through a pipe to the wetted perimeter of the pipe.
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References in periodicals archive ?
Thus, understandably, few were able to grasp concepts in water-related geometry such as Hydraulic Radius and Rating Curve.
When unsaturated soils are considered as a set of simple capillary tubes, the flow can be defined by using flow medium rate, hydraulic gradient, hydraulic radius, and permeability.
where d is the characteristic length (hydraulic radius) of the idealized parallel smooth fracture.
In the indoor experiments we conducted, the hydraulic radius differed from the mud depth, which we used to accurately calculate the results.
width, depth, hydraulic radius, wetted perimeter, bed slope, side slope and velocity were determined using the selected approaches.
where: V is the cross-sectional average velocity (m/s); n is the Manning coefficient; R is the hydraulic radius (m); S is the slope of the water surface or the linear hydraulic head loss.
where G = mass velocity of fluid (weight/second divided by the cross-sectional area, or lb/s x [ft.sup.2]); [f.sub.m] = mean friction factor; p = pressure; [v.sub.m] = mean specific volume; L = length of the pipe; [r.sub.h] = hydraulic radius; and z = height.
Water flowing in an open channel runs in relatively complex manner due to various influencing factors, including slope steepness, surface roughness, and the so-called hydraulic radius. The Manning equation , which was introduced about a century ago, attempts to capture the essential features of these factors.
The hydraulic radius is the cross-sectional area of the flow divided by the channel wetted perimeter P (Figure 6-1).
The recent McGill research aimed to determine 3-D properties such as porosity, numerical density, pore shape, size, length, volume, hydraulic radius, tortuosity and interconnectivity of soil macropores in undisturbed soil columns using X-ray CAT scanning.
Analysis Procedures * Capillary and slit dies * Hydraulic radius and shape factors * Shape factors for various geometries * Computing shape factors for simple and composite geometries * Diverging and converging flows * Lubrication approximation * Numerical integration procedures * Extruder-die interaction
The approximation is that the steady-state pressure drop in a noncircular runner can be estimated by the pressure drop in a circular runner of the same length if the average velocities are the same and the hydraulic radius of the noncircular runner equals the radius of the circular runner.

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