Stream Tube

stream tube

[′strēm ‚tüb]
(fluid mechanics)
In fluid flow, an imaginary tube whose wall is generated by streamlines passing through a closed curve.

Tube, Stream

 

in hydromechanics, a tube composed of the stream lines that pass through the points of a small closed contour within a moving fluid. The tangents to the stream lines coincide with the direction in which the fluid particles located in the stream lines are moving. During unsteady motion of the fluid, the stream lines change from moment to moment, and therefore the stream tube also changes its shape. During steady motion of the fluid, the stream lines coincide with the particle trajectories and remain invariant; in this case the stream tube is similar to a tube with rigid walls in which the fluid flows at a constant rate through the tube’s cross section. If the density is constant, the stream tube will constrict or expand, depending on whether the flow speed increases or decreases. Such behavior of a stream tube also occurs when the density is variable—that is, in the case of a gas—but only until the speed of the steady gas flow exceeds the local speed of sound. After the local speed of sound is exceeded, a further increase in the speed of the gas flow is accompanied by expansion, and not constriction, of the stream tube.

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Effects of local-scale transport parameters on field-scale transport for a variety of boundary and initial conditions were investigated by Toride and Leij (1996) assuming the convection dispersion equation (CDE) in each stream tube.
Toride N, Leij FJ (1996) Convective-dispersive stream tube model for field-scale solute transport: 1.
Hypothetical parameter values for the stream tube model Case C represents fitted values [[sigma] [[sigma] [[rho] Case <v> <D> .
When the field is viewed as a set of homogeneous vertical stream tubes without exchange between the stream tubes, field-scale transport may be described by averaging local-scale concentrations over all stream tubes (Bresler and Dagan 1981; Simmons 1982).
the streamline tube theory (the water particles axial velocities distribution at entrance in the propeller disk can be configured favorably--homogenized-by comprising the radial corrugated stern sections in a stream tube that also comprises the propeller disk);
Models of this kind, which include parallel soil columns obeying local convection--dispersion, are called stochastic stream tube models (STM) (Dagan and Bresler 1979; Amoozegard-Fard et al.
The STM makes the following assumptions regarding the transport processes: (i) the hydraulic properties controlling solute transport vary horizontally across the field but not with depth; thus, (ii) we can divide the field into a number of vertical columns called 'stream tubes' within which the hydraulic properties are constant; (iii) each stream tube is independent of its nearest neighbours and does not interact with them (1-dimensional flow); and (iv) the local-scale transport or transport in each stream tube is described deterministically assuming convective--dispersive model (Jury and Roth 1990; Dagan 1993).
Deterministic (v, D, [lambda]) and stochastic ((v), (D), [lambda]) transport parameters determined from the concentration profiles Stream tube Convection--dispersion model model Time (h) D and drainage v ([cm.
Toride N, Leij FJ (1996a) Convective-dispersive stream tube model for field-scale solute transport: I.