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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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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> .sub.v] .sub.D] .sub.v,D] A 1.01 66.3 0.38 0 n/a B 1.01 66.3 0.38 0.38 +1 C 1.01 66.3 0.38 0.61 0.74 D 1.01 6.63 0.38 0 n/a E 1.01 0.66 0.38 0 n/a
For instance, the stream-tube model (STM) regards the field as a series of independent vertical stream tubes. The model parameters for each tube are viewed as realisations of a stochastic process.
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);
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.sup.2] [lambda] (v) (mm) (cm/h) /h]) (cm) [r.sup.2] (cm/h) 4.8 (26.0) 2.75 3.15 1.15 1.000 2.10 9.8 (53.0) 2.94 2.31 0.79 0.999 2.94 17.8 (96.3) 2.95 1.12 0.38 0.982 3.00 27.5 (148.8) 2.40 3.01 1.25 0.950 2.40 37.0 (200.2) 2.15 2.60 1.21 0.995 2.16 46.5 (251.6) 1.70 7.96 4.68 0.804 1.74 56.0 (303.0) 1.89 4.61 2.44 0.971 1.89 66.0 (357.1) 1.96 2.79 1.42 0.778 2.00 77.0 (416.6) 1.85 5.27 2.85 0.989 1.88 96.0 (519.4) 1.84 1.96 1.07 0.961 1.84 Stream tube model Time (h) D and drainage ([cm.sup.2] [lambda] [[sigma].
Toride N, Leij FJ (1996a) Convective-dispersive stream tube model for field-scale solute transport: I.
Toride N, Leij FJ (1996b) Convective-dispersive stream tube model for field-scale solute transport: II.
, where: [??]-is volumic flow rates, [??]-masic flow rates, [[rho].sub.1][[rho].sub.2][[rho].sub.0]-fluids densities, that for non-compressible mediums are constant ([[rho].sub.1] = [[rho].sub.2] = [[rho].sub.0]), and [v.sub.1] [v.sub.2][v.sub.0]-fluid speeds within sections- [A.sub.1], [A.sub.2], [A.sub.0] of a narrow stream tube.