R. Verhoeven

Physical Model Study Of A Vortex SeparatorOverflow

A detailed research project is set up to validate a vortex separator overflow construction. In this vortex separator, collected sewer water enters radially from the sewer pipe in a cylindrical inner reservoir. The passage flow to the treatment plant is situated in the bottom centre, while the overflow passes a radial weir into an outer shell reservoir. In a laboratory model the removal efficiency of this overflow structure is identified for several hydrodynamic flow operation modes by recording sediment redistribution over the structure. As a result of these series of experiments on a model of a vortex separator overflow, the efficiency of this kind of construction is identified as a function of both hydrodynamic parameters and lay-out features. Doing so, the vortex separator is introduced as an alternative overflow construction to control and manage combined sewer overflow (CSO)-events, leading to a less negative operation impact of combined sewer systems on the receiving waters.

Numerical Modelling Of River Flo7Data Collection And Problem Solving

The discrepancy between the theoretical solution of the Saint-Venant equations for flood routing calculations and the problems encountered during practical implementation is often quite big. This paper tries to give an overview of the different bottle necks and the possibilities to cover the gap between theory and practice. After a brief overview of the equations used for steady and unsteady flow simulation, collection of topographical and hydraulic data is discussed. Then follows some practical considerations on the processing of input data on cross-sections, longitudinal profile and friction coefficient. Finally the impact of different approaches on the quality of the numerical simulation is illustrated by some practical examples.

Ecological evaluation for river meandering restoration. A case study on five Flemish rivers

Ecological data provide crucial information to evaluate the present status of vegetation, fish andor wildlife communities. The assessment of the success (or failure) of river restoration (or rehabilitation) is only possible when ecological information was gathered before implementation. This means that monitoring is a crucial step in the planning of restoration projects and that it has to start in a very early stage of the planning process. During this project it was not our intention to start an extensive monitoring campaign. We decided to do a pre-restoration evaluation of the selected sites to see if restoration will most likely lead to a significant increase of the ecological value of the river system. In this paper we evaluate the fish assemblage and the macro-invertebrate communities, mainly on population level. These results were used to indicate the need for restoration. In one case (the Kemmelbeek) the pre-evaluation showed that restoration at the present state would probably not result in a higher ecological value. In this case, restoring a good water quality will be of higher priority than restoring meanders. On the other hand, meander restoration of 4 other sites will result in a higher ecological value. So these sites were proposed for remeandering.

Design Of A Smart Sand Trap Construction As APart Of An Interregional Environmental Study

The Mark-Vliet river system transports bed material and heavily polluted suspended sediments to the Volkerak-Zoom lake. To protect the living, working and recreation areas in this catchment, a proper integrated water management is essential. A systematic control and sanitation of the polluted sediments in the river environment will help to stop the further degradation of the water system quality. Therefore, a transboundary collaboration between Belgian and Dutch authorities is set up to study and sanitate this interregional river catchment. To improve the water and river bed quality, an effect-oriented as well as source-oriented approach is followed. The inventory of pollution sources is translated into a sanitation plan for the competent authorities. The effect-oriented approach searches an optimum design and location of sand trap configurations in the catchment. As pollutants are mainly fixed to the fine suspended material, it is valuable to separate the relatively clean sand particles from the heavily polluted fine fraction. Hence, the amount of polluted (silt and mud) dredged material and consequently the treatment costs are reduced. Starting from an existing sand trap configuration, an adapted construction is designed through physical scale model tests taking into account the practical and economical issues of the project. The operation of the optimum sand trap configuration relies on three basic principles: an upstream bifurcation ensures a proper deflection of suspension transport in a parallel deviation; a downstream sill controls the flow distribution over the respective main and deviation branch for different regimes; an underwater sill at the entrance of the lateral deviation forces the transport of all sand material near the bottom into the sand trap. Transactions on Engineering Sciences vol 9,

Air Entrainment In Water Hammer Phenomena

In common waterhammer design, a detailed two-phase flow calculation is too demanding to preserve a handsome numerical tool. Nevertheless, implosion of gas or air bubbles in pressurized conduits introduces extra shock waves. As a result, possible fatigue corrosion or pipe instability strengthen the safety demands. Air inlet valves as a protection device enter air into a pipe system, by this reducing the transient wave celerity and the magnitude of the shock wave. Therefore, the impact of air entrainment on the waterhammer phenomena is studied to reveal its relative importance. Detailed calculations with an extended two-phase model reveal only small differences in absolute underpressure values in comparison with the traditional one-phase waterhammer design calculations.

Interactive control of hydraulic structures

In normalized or canalized rivers the waterlevel is kept within small limits by hydraulic control structures (weirs, gates,...). These structures ensure the protection of riparians from inundation, while at the same time optimal navigation conditions are created. In flood periods, many movements are needed to maintain the optimum waterlevel. Different hydraulic control structures on one river reach, has as consequence that control actions of one affect the others, resulting in an increase of movements of the downstream ones. In order to avoid this inconvenience, an interactive control procedure is developed and tested. A case study is presented.