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Model of a water distribution system (WDS), containing old pipes, requires calibration to estimate the roughness of old pipes. Pipe roughness increases with age. In some cases the estimated roughness of old pipes, using optimization procedures based on measurements in operational WDS, can be quite high. Therefore it would be proper to use real diameters of the old pipes instead of high roughness values. The aim of the paper is to compare different approaches of calibration in such case. Five different calibration methods are analysed changing pipe roughness, diameter or both. Calculations have been conducted for an operational WDS. Measurements in the WDS indicated that there are quite large differences in the dynamics of demands (even for the same customer categories) in different zones of the system. It is shown that this has strong influence on the calibration results. [ABSTRACT FROM AUTHOR]

Abstract: The high frequency (0.1kHz) pressure and velocity measurements of two-phase unsteady flow are used to determine the hydraulic-grade-line (HGL) along the pipeline with a complex layout. The semi-empirical method is applied to estimate the pressure drop for the outflow, and thus determine the pipe downstream-end conditions for the modeling purposes. A Control- Volume (CV) model coefficient β, representing residual motion due to the pressurized water-column stratification is specified. Pressurized two-phase unsteady flow phases in a 250mm diameter and 275 meters long PVC pipeline with steel inlet and outlet counterparts are considered for the evaluation of this method. [Copyright &y& Elsevier]

A uniformly accelerated laminar flow in a pipe, initially at rest, is analyzed. One-dimensional unsteady flow equations for start-up flow were derived from the Navier-Stokes and continuity equations. The dynamical boundary layer in a pipe is described theoretically with the Laplace transformation method for small values of time. A mathematical model describing the development of the velocity profile for accelerating flow starting from rest up to the point of transition to turbulence is given. The theoretical results are compared with experimental findings gained in a large-scale pipeline. Particle image velocimetry (PIV) technique is used to deduce the development of accelerating pipe flow starting from rest. The measured values of the axial velocity component are found to be in a good agreement with the analytical values. [ABSTRACT FROM AUTHOR]

A uniformly accelerated laminar flow in a pipe, initially at rest, is analyzed. The acceleration increases the critical Reynolds number remarkably. New experimental findings are used to describe the transitional process in accelerating pipe flow. The results are shown to validate the previously suggested transition parameters obtained on the basis of results on small diameter pipes. The influence of the transition process on mean values is studied. The relationships between flow parameters and transition time were derived from the experimental results for data available. The time from the start of the flow to the initiation of turbulence can be predicted by an empirical formula. [ABSTRACT FROM AUTHOR]

Wideband excitation is used to perform the fast spectroscopy - to cover the wide frequency range within short timeframe. Power spectrum of the chirp excitation pulse can cover tailored frequency range within given duration in the time domain. Linear chirp is a well-known wideband excitation waveform, where the instantaneous frequency varies linearly with time. Chirps with nonlinear relationship between time and frequency are also well known. This group of waveforms shape the power spectrum differently from its linear counterpart. The paper describes the results of the study of spectral properties of the nonlinearly modulated chirp signals, where the frequency of the signal varies according to multi-slope nonlinear relationship over the time. The advantage of this type of chirp signals is that the power spectrum of these signals has substantially steeper slope above the cut-off frequency, compared to its common linear and nonlinear counterparts. [ABSTRACT FROM AUTHOR]

The article examines the eating disorder expectancy theory contention that expectancies for reinforcement from thinness play a causal role in body dissatisfaction and eating disorder symptoms by manipulating expectancies in two studies. Participants were exposed to either a psychoeducational intervention or an experimental manipulation of thinness and restricting expectancies. It showed that in two samples, the thinness expectancy manipulation produced greater declines in thinness expectancies and body dissatisfaction than did the psychoeducational intervention.