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The hydraulic diameter, D H, is a commonly used term when handling flow in non-circular tubes and channels. Using this term, one can calculate many things in the same way as for a round tube. When the cross-section is uniform along the tube or channel length, it is defined as [1] [2] =, where
For example, it is used to calculate flow through circular and non-circular tubes in order to examine flow conditions (i.e., the Reynolds number). In those cases, the characteristic length is the diameter of the pipe or, in case of non-circular tubes, its hydraulic diameter D h {\displaystyle D_{h}} :
The hydraulic diameter is the equivalent circular configuration with the same circumference as the wetted perimeter. The area of a circle of radius R is π R 2 {\displaystyle \pi R^{2}} . Given the area of a non-circular object A , one can calculate its area-equivalent radius by setting
D o is the inside diameter of the outer pipe, D i is the outside diameter of the inner pipe. 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]
In this expression for Reynolds number, the characteristic length D is taken to be the hydraulic diameter of the pipe, which, for a cylindrical pipe flowing full, equals the inside diameter. In Figures 1 and 2 of friction factor versus Reynolds number, the regime Re < 2000 demonstrates laminar flow; the friction factor is well represented by ...
In fluid dynamics, the entrance length is the distance a flow travels after entering a pipe before the flow becomes fully developed. [1] Entrance length refers to the length of the entry region, the area following the pipe entrance where effects originating from the interior wall of the pipe propagate into the flow as an expanding boundary layer.
The length of line of the intersection of channel wetted surface with a cross sectional plane normal to the flow direction. The term wetted perimeter is common in civil engineering, environmental engineering, hydrology, geomorphology, and heat transfer applications; it is associated with the hydraulic diameter or hydraulic radius. Engineers ...
is the hydraulic diameter, is the frictional coefficient, is the axial coordinate in the manifold, ∆X = L/n. The n is the number of ports and L the length of the manifold (Fig. 2). This is fundamental of manifold and network models.