Abstract
Sewage water is typically made up of complex liquid mixtures carrying a wide range of suspended solids and
materials. Handling of such mixtures can present a significant challenge for hydraulic equipment and pumps in
particular. A computational model has been developed to simulate the transport and deformation of immersed thin
flexible structures in response to transient fluid loading and interactions with moving and static surfaces in confined
domains. The numerical solution is based on an Eulerian-Lagrangian formulation. The Navier-Stokes equations are
solved using a segregated approach relying on an iterative form of the PISO pressure-velocity coupling implemented
in the OpenFOAM®. The dynamic deformation of the solid are solved using a Finite Difference resolution of the
variational derivative of the deformation energy for the solid modelled as a thin flexible two-dimensional membranes
with the coupling based on a diffused Immersed Boundary Method (IBM). Turbulence is modelled with a hybrid RANS
LES approach which has been shown to better resolve the turbulent eddy structures within the volute than a pure
RANS method. The methods and solvers have been detailed and validated in recent publications, but this article is
the first detailed characterisation of rag dynamics under varying conditions. The case studies presented will focus on
a single blade impeller (SBI) and a two blade impeller (TBI) radial pump. Impeller eye and volute recirculation
blockage have been captured giving useful insight into the dynamics of the rag and its interaction with the impeller
and volute. The study also highlighted the limitation of the approximate solid-solid interaction model in more sensitive
leading edge blockage. Sensitivity analysis on rag length, rag ratio, rag stiffness and flows rate revealed that generally
the probability of the blockage increases with the rag length and aspect ratio and decreases with the rag stiffness and
flow rate. The complexity of the volute and impeller geometry has a significant impact on the possibility of clogging.
materials. Handling of such mixtures can present a significant challenge for hydraulic equipment and pumps in
particular. A computational model has been developed to simulate the transport and deformation of immersed thin
flexible structures in response to transient fluid loading and interactions with moving and static surfaces in confined
domains. The numerical solution is based on an Eulerian-Lagrangian formulation. The Navier-Stokes equations are
solved using a segregated approach relying on an iterative form of the PISO pressure-velocity coupling implemented
in the OpenFOAM®. The dynamic deformation of the solid are solved using a Finite Difference resolution of the
variational derivative of the deformation energy for the solid modelled as a thin flexible two-dimensional membranes
with the coupling based on a diffused Immersed Boundary Method (IBM). Turbulence is modelled with a hybrid RANS
LES approach which has been shown to better resolve the turbulent eddy structures within the volute than a pure
RANS method. The methods and solvers have been detailed and validated in recent publications, but this article is
the first detailed characterisation of rag dynamics under varying conditions. The case studies presented will focus on
a single blade impeller (SBI) and a two blade impeller (TBI) radial pump. Impeller eye and volute recirculation
blockage have been captured giving useful insight into the dynamics of the rag and its interaction with the impeller
and volute. The study also highlighted the limitation of the approximate solid-solid interaction model in more sensitive
leading edge blockage. Sensitivity analysis on rag length, rag ratio, rag stiffness and flows rate revealed that generally
the probability of the blockage increases with the rag length and aspect ratio and decreases with the rag stiffness and
flow rate. The complexity of the volute and impeller geometry has a significant impact on the possibility of clogging.
Original language | English |
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Title of host publication | 4th international rotating equipment conference (Wiesbaden – Germany) |
Publication status | Published - 2019 |