Optimization of a hydrodynamic separator using a
multiscale computational fluid dynamics approach
Vivien Schmitt, Matthieu Dufresne, Jose Vazquez, Martin Fischer
and Antoine Morin
ABSTRACT
This article deals with the optimization of a hydrodynamic separator working on the tangential
separation mechanism along a screen. The aim of this study is to optimize the shape of the device to
avoid clogging. A multiscale approach is used. This methodology combines measurements and
computational fluid dynamics (CFD). A local model enables us to observe the different phenomena
occurring at the orifice scale, which shows the potential of expanded metal screens. A global model
is used to simulate the flow within the device using a conceptual model of the screen (porous wall).
After validation against the experimental measurements, the global model was used to investigate
the influence of deflectors and disk plates in the structure.
Vivien Schmitt (corresponding author)
Matthieu Dufresne
Jose Vazquez
Martin Fischer
National School for Water and Environmental
Engineering of Strasbourg (ENGEES),
ICube (University of Strasbourg, CNRS, INSA of
Strasbourg, ENGEES),
Mechanics Department, Fluid Mechanics Team,
ENGEES 1 quai Koch BP 61039 67070 Strasbourg
cedex,
France.
E-mail: vivien.schmitt@engees.unistra.fr
Antoine Morin
Hydroconcept, ZA Trappes Elancourt,
46 avenue des frères Lumière 78190 Trappes,
France
Key words | computational fluid dynamics, experiments, hydrodynamic separator, multiscale
approach
INTRODUCTION
Hydrodynamic separators are structures currently used to
remove sediments from water to protect receiving water-
courses. Several types of hydrodynamic separators exist,
each having its own operating process (USEPA ). The
CycloneSep
®
works on the tangential separation mechan-
ism along the screen. After passing through the screen, the
effluent reaches the central part of the device and is then dis-
charged into the environment (Figure 1). The objective of
this structure is to maximize the retention of particles in
the part located around the screen. The main constraint is
to avoid the clog.
Measurements and numerical simulations are the two
main ways that can be used to get a better understanding
of the structure. The first approach is more direct to collect
information but it can be very costly if an optimization pro-
cedure is carried out. Indeed, a large number of layouts have
to be built. Presently, computational fluid dynamics (CFD) is
a good alternative to investigate hydrodynamics in such
structures (Andoh & Saul ). It has been successfully
used for storage tanks (Stovin & Saul ; Adamsson
et al. ; Dufresne et al. ; Lipeme-Kouyi et al. ),
lamella settlers (Morin et al. ; Vazquez et al. )
and hydrodynamic separators (Pathapati & Sansalone
; Lee et al. ).
The aim of this study is to optimize the structure to
avoid clogging. The novelty in this study is the appli-
cation of a multiscale methodology: two approaches are
followed. The first one consists in testing the shape of
the screen. Indeed, the local phenomena that occur
near the screen can be modified by the shape of the
screen. The idea is to investigate the pressure effects by
testing different characteristics (size, angle and shape of
the orifice). The second step is to study the global behav-
iour of the structure and to increase the velocity near the
screen with the insertion of deflectors in order to avoid
clogging.
METHODS
Experimental work
The experimental pilot consists of a circular tank, as illus-
trated in Figure 1. The dimensions of the pilot are similar
to real-life devices corresponding to a small catchment
area; the horizontal scale is about 1:1 and the vertical
scale is approximately 1:3. The diameter of the pilot is 2 m
and the height is 1.3 m. The characteristics of the screen
1574 © IWA Publishing 2013 Water Science & Technology | 68.7 | 2013
doi: 10.2166/wst.2013.404
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