Journal of Hydraulic Engineering

Blockage detection using transient analysis has emerged as a promising technique because it requires measurements at only one location. This study proposes a modified reconstructive method of characteristics (RMOC) technique suitable for detecting multiple partial discrete and extended blockages in elastic and viscoelastic conduits. It is proposed that evaluating the steady-state (SS) head in a pipe can determine the discrete blockage parameters, and the pipe area reconstruction can be employed to estimate the multiple extended blockages. The pipe is discretized into several finite cells, and characteristic equations are derived for the inverse computation of SS flow parameters. The blockage is assumed to be at the interface of the cells. The blockage location and size predictions are more accurate than those using the techniques that use multiple signal cycles, because the short-duration signal (half-wave cycle) is used. The friction factor need not be known a priori in discrete blockage detection, and the need for the assumption of regular geometric blockages is eliminated in extended blockages. Prior knowledge of the number of blockages and the upstream reservoir boundary conditions also is not required. The paper discussed the significance of the inclusion of viscoelasticity in the model. The numerical and experimental validations showed excellent consistency between the actual and estimated fault parameters. The error in the estimation of the size of a discrete blockage from experimental data was less than 5% in all cases except one, which had an error of 8%. A sensitivity analysis was performed to determine the influence of the system parameters on the results.

A two-dimensional model of distributed vaporous cavitation is developed for transient flow in a low-density polyethylene pipeline. In this model, the governing equations of transient flow are solved with viscoelastic and cavitation equations simultaneously. The $k\text{-}\omega$ turbulence model is further combined with the model of transient flow to (1) simulate the energy dissipation during transient flow; and (2) investigate the effect of temperature and cavitation on turbulence behavior. Based on the results, the increase in flow velocity of cavitation significantly augments the intensity of turbulence production near the wall and the transport of turbulence in the inner layers. Higher temperatures result in higher power for the generation of turbulence near the wall. Cavitation significantly reduces the production of turbulence near the wall and intensifies the turbulence transport in the inner layers of the flow.

Previous studies have primarily focused on the estimation of equilibrium scour depths around weirs, while overlooking the details of the temporal evolution of the live bed scour process of submerged weirs at the equilibrium stage. This study aims to investigate the relationships between fluctuating frequencies of the approaching bedforms and live bed scour depths around submerged weirs. The average fluctuating frequencies of approaching bedforms, upstream scour depth, and downstream scour depth are quantified from measured topographic time-series data. The frequency of upstream scour depth variations is found to be almost the same as that of bedforms, while the fluctuating frequencies of the scour depth variations downstream of the weir are found to be 0.38–0.68 times the approaching bedform frequencies in the scour equilibrium stage. New empirical equations are proposed to predict the fluctuating frequencies of live bed scour depth variations in the scour equilibrium stage.