The formation of the steady and unsteady air-entrained vortices in pump sump

Meshing of domain in CFD is an important step to ensure accuracy of the solution. In the past, hexahedral or tetrahedral mesh systems were commonly used, and both have their merits and demerits. For large and complex geometry, polyhedral is another option but its accuracy is claimed to be lacking. In this paper, the use of polyhedral mesh system by past researchers are reviewed. Evaluation on the application of polyhedral mesh system for the study of the vortex formation with a simple single pump sump model is made. Validation was made through the comparison of the results from hexahedral, tetrahedral and polyhedral mesh sizes and the experimental data from published data. The polyhedral mesh system was found to perform satisfactorily and was able to match the results from the hexahedral mesh system as well as the experimental data.

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Bellmouth Shape Optimization for the Suppression of Flow Instability in a Pump Sump Model

The KSFM Journal of Fluid Machinery ◽

10.5293/kfma.2021.24.4.049 ◽

2021 ◽

Vol 24 (5) ◽

pp. 49-57

Author(s):

Ujjwal Shrestha ◽

Young-Do Choi

Keyword(s):

Shape Optimization ◽

Flow Instability ◽

Pump Sump

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Avoiding Sedimentation and Air Entrainment in Pump Sump for Wet Pit Pumping Stations

Volume 1A: Symposia, Part 2 ◽

10.1115/ajkfluids2015-33761 ◽

2015 ◽

Author(s):

Raja Abou Ackl ◽

Andreas Swienty ◽

Flemming Lykholt-Ustrup ◽

Paul Uwe Thamsen

Keyword(s):

Physical Model ◽

Air Entrainment ◽

Flow Patterns ◽

Operating Conditions ◽

Design Criteria ◽

Flow Conditions ◽

Pumping Station ◽

Pumping Stations ◽

Pump Sump ◽

Pump Stations

In many places lifting systems represent central components of wastewater systems. Pumping stations with a circular wet-pit design are characterized by their relatively small footprint for a given sump volume as well as their relatively simple construction technique [1]. This kind of pumping stations is equipped with submersible pumps. These are located in this case directly in the wastewater collection pit. The waste water passes through the pump station untreated and loaded with all kind of solids. Thus, the role of the pump sump is to provide an optimal operating environment for the pumps in addition to the transportation of sewage solids. Understanding the effects of design criteria on pumping station performance is important to fulfil the wastewater transportation as maintenance-free and energy efficient as possible. The design of the pit may affect the overall performance of the station in terms of poor flow conditions inside the pit, non-uniform und disturbed inflow at the pump inlet, as well as air entrainment to the pump. The scope of this paper is to evaluate the impact of various design criteria and the operating conditions on the performance of pump stations concerning the air entrainment to the pump as well as the sedimentation inside the pit. This is done to provide documentation and recommendations of the design and operating of the station. The investigated criteria are: the inflow direction, and the operating submergence. In this context experiments were conducted on a physical model of duplex circular wet pit wastewater pumping station. Furthermore the same experiments were reproduced by numerical simulations. The physical model made of acrylic allowed to visualize the flow patterns inside the sump at various operating conditions. This model is equipped with five different inflow directions, two of them are tangential to the pit and the remaining three are radial in various positions relative to the pumps centerline. Particles were used to enable the investigation of the flow patterns inside the pit to determine the zones of high sedimentation risk. The air entrainment was evaluated on the model test rig by measuring the depth, the width and the length of the aerated region caused by the plunging water jet and by observing the air bubbles entering the pumps. The starting sump geometry called baseline geometry is simply a flat floor. The tests were done at all the possible combinations of inflow directions, submergence, working pump and operating flow. The ability of the numerical simulation to give a reliable prediction of air entrainment was assessed to be used in the future as a tool in scale series to define the scale effect as well as to analyze the flow conditions inside the sump and to understand the air entrainment phenomenon. These simulations were conducted using the geometries of the test setup after generating the mesh with tetrahedral elements. The VOF multiphase model was applied to simulate the interaction of the liquid water phase and the gaseous air phase. On the basis of the results constructive suggestions are derived for the design of the pit, as well as the operating conditions of the pumping station. At the end recommendations for the design and operating conditions are provided.

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Simulation of the Flow Condition Near the Intake of a Pump Sump

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2006-98258 ◽

2006 ◽

Cited By ~ 1

Author(s):

Shuhong Liu ◽

Yong Li ◽

Xianwu Luo ◽

Yulin Wu

Keyword(s):

Flow Condition ◽

Water Surface ◽

Free Water ◽

Internal Flow ◽

Free Water Surface ◽

Pump Station ◽

Vof Model ◽

Calculation Results ◽

Pump Sump ◽

Steady Simulation

It is known that the flow condition in the pump sump is very complicated, which usually performs as several types of vortex, water wave of free surface, vibration, noise, and etc. To make clear the flow condition experimentally and numerically is very important to develop the performance and operating stability of the pump station. As one of the projects with Hitachi Industries ltd. Co., Japan, the investigation experimentally on the internal flow condition of the pump sump has been carried out in Tsinghua University. In this paper, we introduce the simulation results, which can show more detail information near the intake of the pump sump. The simulation is focused on the area near the intake, together with the extension of up-stream and down-stream. The calculation research includes two parts: steady simulation and unsteady simulation by VOF model, which is provided by the commercial software of Fluent. Through the steady simulation, the distribution of free water surface (water height) near the intake, as well as the flow condition inside the intake, were obtained. Comparing with the experimental data, a good agreement was observed. After analyzing the unsteady calculation results by VOF, four stages of the development of air-entraining vortex, and the wave characteristic of free water surface, were obtained, which were in accord with the experiment visualizing.

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