Authors

D A Egarr, MG Faram, T O’Doherty

Abstract

A hydrodynamic vortex separator (HDVS) has been studied under laboratory conditions by using a specifically designed rig. Pressure tapping points placed at eight locations, six external and two internal, have revealed an even radial pressure distribution on the outer walls and central shaft. The ability of the HDVS to separate particulates has been studied. The particulates have been characterized by measurements of particle diameter and settling velocity, which have allowed efficiency cusps to be plotted against dimensionless groups used by other researchers. Owing to an unsatisfactory reduction of the data to a single curve by plotting the efficiency against dimensionless groups, an efficiency law has been determined based on the logistic equation and describes the separation efficiency in terms of the inlet flowrate, volume of the separator, and particle diameter and density.

Authors

J. P. LeCornu, M. G. Faram, D. S. Jarman, and R. Y. G. Andoh

Abstract

Urban drainage networks require accurate, reliable flow control systems for their effective operation and minimisation of flood risk. Different types of flow control produce different hydraulic characteristics, having implications to system design in particular relating to upstream storage utilisation. Vortex flow controls (VFCs) present particular opportunities, producing desirable hydraulic characteristics while also having large clearances compared to other devices. This paper describes the implementation of advanced flow control characterisation procedures and techniques allowing VFCs in particular to be characterised within a period of a few hours. The results are shown to correspond with those collected using conventional methods. Work is also described relating to the development and application of a model to allow storm hydrograph response modelling of storage-flow control combinations. It is demonstrated how the use of a VFC can lead to significantly more efficient storage utilisation compared to when a simple orifice plate is used. Further to this, it is found that system recovery times can be significantly improved, with gains of in excess of 35% being obtained. Initial verification of the simulations shows a favourable correspondence with test outputs produced by others.

Authors

G P BOAKES, A STEPHENSON, J B LOWES, A C MORISON, A T USBORNE

Abstract

The Northamptonshire villages around Weedon in the upper River Nene valley, suffered disastrous flooding in 1947, 1992 and 1998, with Weedon Bec being particularly badly affected. The channel through the village is constricted by historic developments and the opportunity to enlarge the channels was not available. Restricted culverts under the railway embankments downstream compounded the flood situation.

Authors

R. Y.G. Andoh1, D. A. Egarr and M. G. Faram

Abstract

Hydrodynamic Vortex Separators (HDVSs) have been used extensively as solid-liquid separators throughout the water industry. In recent years their application scope has been extended through adaptation to allow unit processes such as solids separation, screening and disinfection to be accomplished within the same vessel. The paper reviews the current state of understanding of HDVS operation, focusing in particular on their use as Combined Sewer Overflow and wet-weather treatment systems for high-rate chemical disinfection. This includes a review of the role Computational Fluid Dynamics (CFD) has played in providing detailed insights into their operating mechanisms, which has lead to the generation of improved knowledge and provided scope for physical (e.g. configurational) and operational (e.g. chemical dosing) design optimisation. It is found that macro flow field behaviour has a key bearing on operational effectiveness, in terms of determining the efficiency with which chemical contacting can take place, and this is an area where CFD analysis offers particular promise. The paper also presents and discusses data from full scale monitoring and performance evaluations including those undertaken as part of regulatory compliance reporting for a full-scale installation in the United States, confirming the efficacy of these devices in practice.

Authors

D.A. Phipps, R.M.Alkhaddar, E. Loffill, R.Y.G Andoh and M.G. Faram

Abstract

The factors affecting the overall efficiency for the removal of a solid from an influent stream of water by an HDVS (Hydrodynamic Vortex Separator) have been examined using a combination of solids capture/washout experiments and dye tracer studies. The overall solids removal efficiency of the device is a function of loading rate (overall flow). The efficiency can be considered in terms of the balance between initial capture of the sediment and any subsequent re-entrainment. Tracer studies have shown that a well-designed device offers almost complete separation into a mobile and quiescent zone, with slow exchange between the two. This enhances both sediment capture and its subsequent retention.