Hydraulic Manual Consisting of Working Tables and Explanatory Text Intended as a Guide in Hydraulic Calculations and Field Operations

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Crosby, Lockwood and Company, 1883 - 491 من الصفحات
 

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الصفحة 4 - Second, velocity of issue. — The velocity of a fluid issuing from an orifice in the bottom of a vessel kept constantly full, is equal to that which a heavy body would acquire in falling through a space equal to the depth of the orifice below the surface of the fluid, which is called the head on the orifice ; or by way of formula where 7f=the head and g = force of gravity.
الصفحة 97 - Upon this evidence the important conclusion is drawn (ib.~) that — ' The ratio of the mid-depth velocity to the mean velocity in any vertical plane is practically independent of the depth and the width of the stream, of the mean velocity of the river, of the mean velocity of the vertical curve, and of the locus of its maximum velocity. In other words, it is a sensibly constant quantity for practical purposes.
الصفحة 83 - ... to a parabola. This approximation is quite sufficient to admit of its use in determining an approximate value of mean velocity. And first, it is clear that, as three data suffice to determine the velocity-parabola completely, velocitymeasurements at three distinct points on the same vertical will of course suffice to determine the mean velocity. [The three points must of course be suitably situa-.c to give a tolerably accurate determination.] The first step is to find an expression for the mean...
الصفحة 89 - Z > $H, both roots are+ , which shows that there are in this case two lines of mean velocity equidistant from the axis (as is evident from the symmetry of the parabola). It may be shown also that the larger root is always greater than ±H, for writing the larger root of (25) in form — so that h0=Z + a.
الصفحة 182 - That the greatest current is always at the surface, and the smallest at the bottom ; and that as the depth increases, or the surface current becomes greater, they become more equal, until in great depths and strong currents they practically become substantially alike.
الصفحة 92 - ... and -211, and one between -667 and 789, with mean values of about -105 and 728. The former is the better for practical velocity-measurements on account of the greater accuracy of work near the surface. Now the velocity corresponding to the value...
الصفحة 94 - ... depth (by definition) ; so that the middle ordinate always > the mean ordinate ; also, when the curve is very flat, it is clear that the excess of the former over the latter must be a small quantity.] This is fully borne out by the Roorkee Experiments : the value of the quantity (v\B— IT) is given for every series in Abstr.
الصفحة 4 - ... orifice. In the construction of water works, it is customary to conduct the stream, or such a part of it as is required, into a cubical cistern, and to let it issue from the side of this, near to the bottom, and thus fall upon the main wheel.

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