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360. Online publications featuring online calculations [221112] |  |
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360. Online publications featuring online calculations [221112] | |
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ABSTRACT:
A study of the effect of cross-sectional shape on free-surface channel
hydrodynamic
instability is accomplished. At the outset, the rating exponent β, Froude number
F, and Vedernikov number V are identified
as the controlling variables.
A steep, lined channel is specified for the analysis.
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| ABSTRACT: The theoretical basis for Clark's original 1945 and Clark's Ponce 1989 methods of catchment routing are explained and compared. It is shown that Ponce's method consistently provides a somewhat longer time base and a correspondingly smaller peak discharge than Clark's original methodology. This is a direct consequence of Ponce's use of a continuous time-area derived unit hydrograph, in lieu of the discrete hyetograph used by Clark. However, the differences in peak discharge are consistent with the methodologies used and do not appear to be significant. |
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| ABSTRACT: The Lane et al. (1959) theory for the equilibrium shape of self-formed channels in noncohesive alluvium has been revisited, with all assumptions and derivations clearly stated. The results are used to estimate self-formed top-width/maximum-depth ratios as a function of: (1) the friction angle of the noncohesive material forming the bed, and (2) the lift-to-drag force ratio acting on the particles. The findings may be used as a point-of-start in the study of unsteady alluvial channel morphology. |
| ABSTRACT: The differential equation for the dissolved oxygen sag curve (DO sag curve) is derived. The solution of this differential equation can be shown to be essentially the same as that of the well known Streeter-Phelps equation (Streeter and Phelps, 1925). Unlike the latter, the differential equation derived herein can be solved numerically and, therefore, does not require integration. Moreover, the differential equation is valid for all deoxygenation and oxygenation constants, unlike the Streeter-Phelps equation, which is undefined when these constants are equal. Two online calculators: (a) single case, and (b) general case, round up the analysis. |
| ABSTRACT: A verification of the Muskingum-Cunge flood routing method is accomplished by comparing theoretically calculated peak outflow and travel time with those generated using the constant-parameter Muskingum-Cunge method. The remarkably close agreement between analytical and numerical results underscores the utility of Muskingum-Cunge routing as a viable and accurate method for practical applications in flood hydrology. |
| ABSTRACT:
The source of a large river system, for example, the Missouri river, is often taken
as the location of the uppermost spring in the farthest tributary.
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| ABSTRACT:
The design of a lined channel, with a steep slope, to be hydraulically
stable is governed by the well-known Vedernikov criterion. However,
it can be shown that this depends on the shape of the cross section,
whether trapezoidal, rectangular, or triangular. For a given section,
there is a unique relationship between the exponent β of the
rating curve Q - A (discharge vs flow area), and the value
of V /F,
in which V = Vedernikov number, and F =
Froude number. In this work we use the onlinechannel15b
calculator to calculate the value of β and the corresponding
Vedernikov number for a rectangular, trapezoidal, or triangular
cross section. Three series of tests are carried out in a hypothetical
channel, keeping constant
discharge Q, Manning's n,
and bottom slope S, and varying the value of
the side slope z: (a) 0.25; (b) 0.5, and (c) 1. It is
concluded that when the bottom width b is reduced, the
Vedernikov number V is reduced more quickly
to values less than 1 for the lower values of z in the range |
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ABSTRACT:
The theoretical foundations and relevant experience with open-channel flow instability are
examined with the objective of controlling roll waves.
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| ABSTRACT: The concepts of safe yield and sustainable yield of groundwater are analyzed and compared in the context of a hydrologic balance. It is surmised here that vertical recharge, i.e., the recharge originating in local precipitation, is the only recharge that may be tapped for capture by groundwater to avoid encroachment on established rights. A methodology to evaluate vertical recharge is developed and tested. The methodology is based on L'vovich's cybernetic hydrologic balance. This coefficient represents the fraction of precipitation that reaches the water table; therefore, it may be used to evaluate and assess sustainable groundwater yield. |
| ABSTRACT: A comparison between the conventional approach to the hydrologic balance and L'vovich's catchment wetting approach, referred herein as the cybernetic approach, reveals fundamental conceptual differences. The conventional approach is seen to be mostly suited to event hydrology, particularly for applications of flood hydrology and related urban hydrology. On the other hand, the cybernetic approach is suited to yield hydrology, i.e., for determinations of the availability of water resources on an annual basis. |
| ABSTRACT: An online calculator has been developed and tested using the Muskingum-Cunge method to solve the classical Thomas problem of flood routing. The calculator can vary peak inflow, time base, and channel length. The choice for peak inflow qp (cfs/ft) is: (a) 200, (b) 500, and (c) 1,000. The choice for time base Tb (hr) is: (a) 48, (b) 96, and (c) 192. The choice for channel length L (mi) is: (a) 200, and (b) 500. The results are in agreement with analytical results of the Thomas problem. |
| ABSTRACT: The inherently stable channel is reviewed, elucidated, and calculated online. Theoretically, such a channel will become neutrally stable when the Froude number reaches infinity. Thus, constructing an inherently stable channel provides an unrealistically high factor of safety against roll waves. This suggests the possibility of designing instead a conditionally stable cross-sectional shape, for a suitably high but realistic Froude number such as F = 25, for which the risk of roll waves would be so small as to be of no practical concern. |
| ABSTRACT:
A comprehensive review of the amplitude and phase portraits of the Muskingum-Cunge method of flood routing is accomplished.
Expressions for the
amplitude and phase convergence ratios are developed as a function of:
(a) spatial resolution L/Δx; (b) Courant number C; and (c) weighting factor X.
It is concluded that the Muskingum-Cunge routing model is a good representation of the physical prototype, provided:
(1) the spatial resolution is sufficiently high,
(2) the Courant number is around 1, and
(3) the weighting factor is high enough in the range |
| ABSTRACT: The hydraulic design of a channel transition is described and explained. The calculation of an inlet transition between canal and flume is shown by an example, originally presented by Hinds (1928) and subsequently cited by Chow (1959). The example is reproduced with detailed explanation and minor corrections for rounding accuracy. An online calculator is provided. |
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| ABSTRACT: The concept of runoff diffusion is reexamined. Diffusion is inherent to reservoirs and it is always produced in flow through reservoirs. In channel flow, diffusion is produced in the absence of kinematic wave conditions, i.e., under diffusion wave conditions, provided the Vedernikov number is less than 1. In catchment runoff, diffusion is produced: (1) for all wave types, when the time of concentration exceeds the effective rainfall duration, a condition which is usually associated with midsize and large basins, or (2) for all effective rainfall durations, when the wave is a diffusion wave, which is usually associated with a sufficiently mild catchment slope. |
| ABSTRACT: The concept of hydraulic diffusivity and its extensions to the dynamic regime are examined herein. Hayami (1951) originated the concept of hydraulic diffusivity in connection with the propagation of flood waves. Dooge (1973) extended Hayami's hydraulic diffusivity to the realm of dynamic waves. Subsequently, Dooge et al. (1982) expressed the dynamic hydraulic diffusivity in terms of the exponent of the discharge-area rating. Lastly, Ponce (1991) expressed it in terms of the Vedernikov number, further clarifying the mechanics of flood wave propagation. |
| ABSTRACT: Henderson's formulations of the energy-based and momentum-based limiting contraction ratios are reviewed (Henderson 1966). Henderson's explicit energy-based equation is found to be correct, however, his implicit momentum-based equation is found to be incorrect. A new explicit momentum-based equation is derived, rendering the implicit formulation unnecessary. An online calculator enables the calculation of the limiting contraction ratio for both energy and momentum formulations. |
ABSTRACT:
The Penman-Monteith combination method for the
calculation of evaporation is reviewed and clarified. Unlike the original Penman
model, in the Penman-Monteith model the mass-transfer evaporation rate
is calculated based on physical principles. An illustrative example is worked out to show the
computational procedure. An online calculation using
ONLINE PENMAN-MONTEITH gives the same
answer.
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| ABSTRACT: This document provides a tabular comparison of several sharp-crested weirs for discharge measurement in open-channel flow. The following weirs are considered: (1) V-notch, fully contracted; (2) V-notch, partially contracted; (3) Cipolletti; (4) rectangular; (5) standard contracted rectangular; and (6) standard suppressed rectangular. Descriptions follow the USBR Water Measurement Manual. |
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| ABSTRACT: An online calculator of the Shuttleworth-Wallace method for calculating evapotranspiration from sparse crops is developed. The method can be used to complement evapotranspiration calculations based on the Penman-Monteith method. |
| ABSTRACT: Gradually varied flow water-surface profiles are expressed in terms of the critical slope Sc. In this way, the flow-depth gradient dy/dx is shown to be strictly limited to values outside the range encompassed by Sc and So, in which So is the bed slope. This new approach improves and completes the definition of flow-depth-gradient ranges in the analysis of water-surface profiles. Online calculators are provided to round up the experience. |
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