Journal of Hydraulic Engineering

Weak, free surface vortices at vertical intakes with a headrace channel are defined by the first observance of a persistent dye core upon dye injection. Dimensionless parameters describing free surface vortex flows are used in an analysis of experimental data. The experimental results indicate that a large dimensionless submergence is required to avoid weak vortices at vertical intakes. Most vertical intakes will therefore require some type of antivortex device if weak vortices are to be avoided. The required dimensionless submergence is also highly dependent upon approach flow angle and headrace length/width ratio.

A one‐dimensional model for a steady inflow of a Newtonian, incompressible fluid to a horizontal pipe perforated with circular orifices along the entire length is considered. Experiments show that perforated pipes have a greater equivalent sand roughness height of the wall compared to nonperforated pipes. At a certain spacing of the orifices, the Darcy‐Weisbach friction factor depends on the Reynolds number, wall permeability, and wall roughness height. In some cases the friction factor in perforated pipes was found to be 80% higher than in nonperforated pipes. The equation of motion includes both the effect of the discontinuity of inflow along the perforated pipe and the effect of the lateral inflow angle on the total energy loss in the main stream. The maximum value of the coefficient ${\nu }_p\text{,}$ which describes this influence, is 0.77 and is lower than the theoretical maximum value 1.0.

The optimal design of closed hydraulic networks with pumping stations and different flow rate conditions is considered. The main difficulties in determination of optimal solutions for such problems are related to: (1) Nonlinearity of objective functions and constraints equations; and (2) heterogeneity between construction costs and management costs. In fact it is not easy to consider in the objective function both initial construction costs, which are related to the pipe weight, and management costs, which arise later and are essentially related to the pumping energy. Therefore it appears to be more reasonable to use multiobjective techniques. These techniques are used in order to define the optimal Pareto set in the space of the objective functions: each step of the sequence is analyzed by reduced gradient methods, with pipe diameters chosen in a range of standard values. The constraints are related to: (1) Minimum values of piezometric head at the nodes; and (2) maximum values of velocities in the branches.

Turbulent boundary layer flow past a bluff body placed on a boundary is characterized by the formation of a standing eddy just downstream of the separation point and reattachment and redevelopment of the flow downstream of the reattachment point. Atmospheric boundary layer flow past buildings and shelter belts (used in agriculture), the spread of polluted air in the vicinity of buildings, evaporation, and other exchange processes near vegetation cover are some of the practical problems in which the knowledge of the characteristics of a redeveloping boundary layer would be extremely useful. The present study was undertaken to study the mean flow characteristics of the turbulent boundary layer disturbed by the presence of an obstacle on a flat surface. The experiments reported in this paper are restricted to the redeveloping boundary layer flow past two‐dimensional, sharp‐edged fences placed over a flat boundary. Data on redeveloping boundary layer flow past obstacles of other shapes, collected by other investigators, are also used in the analysis.

Estimates of peak flood discharge on ungauged watersheds are often determined from regional relationships. This approach, however, ignores sitespecific information that might be available from sources such as historic high water marks, etc. A systematic procedure to estimate a given quantile flood, employing the limited at‐site historic data, is developed for the ungauged watershed. In this procedure, the estimates of discharge based upon historic sitespecific evidence are combined with independent regional estimates by inverse variance weighting, to obtain weighted estimates at the ungauged site. The variance of flow determined by the regional method is shown to be adequately represented by the square of the standard error of regression. The variance of flow determined on the basis of historic evidence is represented by the square of the regional standard error determined for gauged sites within the study region. The methodology based on inverse variance weighting appears to give better results than either independent estimate by itself, when compared to the station values at gauged sites within the study region. The simple inverse variance weighting procedure has also been shown to offer computational advantages over the optimal variance weighting scheme, with no sacrifice in accuracy.

Thermal change in lake storage between beginning‐of‐month (BOM) dates was calculated from joint volumetric and mass balances. Thermal change in storage was important in May and July because published data (5) indicate no change in lake storage during these months in 1976. For the remaining months, thermal change in storage peaked during the period of thermal stratification, when it accounted for over 10% of the change in storage. Thermal corrections to net basin supply (NBS) ranged from 30% to more than 100% when the NBS was less than $400m^3/s;$ thermal corrections to NBS when greater than $400m^3/s$ were between 1% and 30%, and they averaged 8.5%. An error analysis indicated that a 0.4 °C error along the entire BOM temperature profile yielded an average error of 27% in the monthly thermal change in storage.