The forebay of pumping stations is an important hydraulic structure that connects the channel with the inlet channel. Actual test observations and theoretical studies have shown that poor precursors produce backflow, vortex, and water flow disturbances in the forebay water. In this paper, taking a lateral inlet pump station as an example, we study the nonmeasures and five rectification measures—“Y” type diversion pier, “T” shaped diversion pier, narrow bottom hole, high and wide bottom, and diversion wall—through adopting the method of numerical simulation and model test. For the numerical simulation, the corresponding threedimensional model is established by UG solid modeling software, and then the computational fluid is simulated numerically with CFX. Based on the analysis and comparison of the results during the test of numerical simulation and model test, the stability of the rectification measures is considered after taking into consideration the results of the uniformity test of the velocity distribution of the surface layer, the bottom layer, and the front section of each scheme. The proposed scheme
To operate the pump safely, the water flow in the foreland is a very important factor. It is very important for the pump station to be stable and safe to operate. In many pumping stations during operation, many phenomena are related to poor water flow, such as severe vibration, low efficiency, and serious cavitation. We studied the influencing factors of the flow regime of the forebay and the causes of the bad flow. After that, the corresponding rectification measures were put forward, and various engineering measures of the geometric parameters were adjusted to change its influence on the improvement of the flow regime. Setting the bottom and the columns in the forebay can improve the flow, and then we can prepare the brewing in the pool before the whirlpool and swing and other bad flow [
CFD technology has become mature, and numerical simulation for pumping stations has also emerged, so the flow of the former pool and its impact were predicted and evaluated through using numerical simulation technology. Adopting the method of the Fluent software to analyze the geometrical parameters of the Y shaped diversion piers and analyzing the rectification effect, it is shown that the Y shaped diversion piers have a good effect on the whole dispersion water flow. At the same time, the diversion of the tail will appear after the whirlpool, adjusting the Y shaped diversion pier position, height, angle, and length to adjust the flow [
In this paper, at one side of the inlet pump station, if the 4 900ZLB70 axial flow pump is set up in the pump station, flow will be 10 m^{3}/s. As for the lateral water of the station, to get a good water flow and ensure a safe economical operation of the pump station, we carried out a study on the station before the pool flow model test and numerical simulation. There are no measures but five rectification measures: “Y” type diversion pier, “T” shaped diversion pier, narrow bottom, high and wide bottom, and diversion wall (Table
Layout plan of the pump station.
In the study of a part of the hydraulic structure of the water flow, the local model can be used; the scale should not be less than 1 : 50 [
Scale for physical model test and hydraulic volume conversion ratio.
Hydraulic conversion ratio  Conversion formula  Model scale 

Horizontal length scale 

25 
Vertical length scale 

25 
Area ratio 

625 
Velocity ratio 

5 
Flow ratio 

3125 
Slope ratio 

625 
Roughness coefficient ratio 

0.585 
List of test schemes for flow pattern of pumping station.
Program number  Plan description  Action description (prototype in parentheses) 

1  Original plan  Without any action (Figure 


2  “Y” type diversion pier  The “Y” type diversion pier top elevation is equal to the lowest water level. Side length: 10 cm (2.5 m) (Figure 


3  “T” shaped diversion pier  The “T” type diversion pier top elevation is equal to the lowest water level. Side length: 10 cm (2.5 m). The edges of the diversion piers have changed (Figure 


4  4 cm narrow bottom  Bottom hole height: 4 cm ( 


5  High and wide bottom  High and wide bottom width of 6 cm (1.5 m); top width: 3 cm (0.75 m); bucket top elevation: 6 cm (1.5 m) (Figure 


6  Diversion wall  The diversion wall elevation is equal to the minimum water level. Length: 30 cm (7.5 m) (Figure 
The flow pattern of the forebay of the pumping station includes the river, the front tank, the inlet, and the inlet pipe (including the horn tube). The overall layout of the flow pattern of the forebay of the pumping station is shown in Figure
Overall layout of the flow pattern of the forebay of the pumping station.
Panorama of the pumping station forebay flow model test.
“Y” type guide pier position and shape diagram.
“T” type guide pier position and shape diagram.
Narrow bottom position and shape diagram.
Highwidth bottom position and shape diagram.
Guide wall location and shape diagram.
During the operation of pumping, the flow of water in the front tank can be regarded as a complex threedimensional incompressible turbulent flow. The unsteady continuous equations and the instantaneous Navier–Stokes equations are suitable for turbulence applications [
Continuous equation:
Momentum equation:
The RNG
The first step in numerical simulation is the modeling of threedimensional entities. It is an important factor affecting the lattice division and the accuracy of the final research results whether the model is accurate or not [
Pump design water level calculation fluid model.
Pump station water intake details.
In this paper, meshes are used to divide the tetrahedron unstructured meshes with the method of RNG
Velocity uniformity under different grid numbers.
Number of grids  757355  852241  950476  1196985  1285549  1070463 
Flow rate uniformity %  82.54648  86.55  84.66543  82.13911  83.20061  84.10678 
Pump station forebay grid map
Flow velocity uniformity for different grid numbers
Mesh sensitivity verification, that is, changing the mesh density several times, after calculating the results, compares the changes in the calculated results. If the variation range is within the allowable error range, it is considered that the grid density has reached the expected accuracy of calculation. It can also be said that the degree of grid density is suitable. In this paper, due to the cross section of the inlet basin for the flow rate uniformity test, when the velocity uniformity changes within a reasonable range, the grid density becomes reasonable. The verification results are shown in Table
When the grid reaches 852241, 950476, and 1196985, the error of the corresponding velocity uniformity becomes −2.1% and −2.9% under the condition of no rectification measures. It can be considered that the calculation result of the grid with the number 950476 is irrelevant to the degree of grid density. Therefore, other models calculated in this paper adopt this grid density.
The results of numerical simulation and model test are almost impossible to be identical. The analysis errors are as follows.
(1) If the surface of free water is of steel cover and symmetrical boundary conditions, that is to say, the free water is always completely level, the surface layer of flow cannot accurately be described, and steel cover assumptions ignore the impact of air resistance.
(2) With the floating plastic particles, to characterize the surface layer of fluid, the interaction among particles will also affect the conditions of the water surface movement (Figure
Surface flow tracer.
(3) The influence of refractive index: in drawing the flow diagram of the surface layer, the center and scope of the vortex are measured by the naked eye. Actually, this way, it is difficult to ensure that the viewing angle has been perpendicular to the surface to locate the whirlpool in the grid line position.
In view of the two cases, these existing errors are basically similar to the flow chart, including the location of the whirlpool and its size.
Model test of streamlines
Numerical simulation of streamlines
Model test of streamlines
Numerical simulation of streamlines
Model test of streamlines
Numerical simulation of streamlines
Model test of streamlines
Numerical simulation of streamlines
Model test of streamlines
Numerical simulation of streamlines
Model test of streamlines
Numerical simulation of streamlines
From Figures
As we can see in Figure
Model test and numerical simulation section flow velocity distribution (original plan).
Water flows through the “Y” shaped rectifier, and the rectification effect is better, as the right whirlpool is also greatly reduced. The comparative analyses of the velocity distribution of the model test and the numerical simulation are roughly the same. After the diversion, the main body of water flows to both sides, and the flow velocity from the surface layer to the bottom is gradually reduced, when reaching the inlet position becomes relatively uniform (Figure
Model test and numerical simulation section flow velocity distribution (“Y” type diversion pier).
The velocity distribution of the section is similar to that of scheme “Y” type diversion pier. As a result of the adjustment of the “T” type diversion pier and the inlet channel distance, diversion of water can quickly be achieved. The whirlpool after the diversion pier can also be dissipated by the two streams’ diversion flow (Figure
Model test and numerical simulation section flow velocity distribution (“T” type diversion pier).
The comparative analyses of the velocity distribution of the model test and the numerical simulation are roughly the same. The high velocity area is above the narrow bottom, and the flow velocity on both sides is relatively high. Numerical simulation in the narrow bottom will produce a roll; the flow rate will be negative. In the model test, when the flow velocity of the bottom water flow is measured, the flow pattern is chaotic and the flow direction changes quickly, and it is difficult to achieve a relatively stable state. Therefore, the two flow rate distributions have certain differences. After the diversion, the flow velocity from the surface layer to the bottom is gradually reduced, when reaching the inlet position becomes relatively uniform. After the water flows through the narrow bottom, when the water reaches the AB section, the cross section flow rate is quite uniform. But at both sides of the forebay, due to the curved wing wall contraction, both sides of the velocity exhibit a little change (Figure
Model test and numerical simulation section flow velocity distribution (narrow bottom).
The velocity distribution of the section is similar to that of scheme narrow bottom. Because of the slope set on the bottom, rotating water will be controlled. Therefore, the crosssectional flow from E to C to AB also achieves uniform flow faster. The main body of water in the E section is in the right side of the surface; with the flow of water forward, the mainstream tends to the left and eventually to the pumping station (Figure
Model test and numerical simulation section flow velocity distribution (high and wide bottom).
After diversion of the diversion wall, the water flow is mainly distributed to both sides. Both velocity profiles (Figure
Model test and numerical simulation section flow velocity distribution (diversion wall).
From Figures
The flow rate distribution uniformity calculation was carried out for the three sections of AB, C, and E before the inlet.
The velocity distribution uniformity is calculated as follows:
The results of the flow velocity uniformity are shown in Table
Section velocity uniformity.
Program number  Condition  Velocity distribution uniformity  

AB  C  E  
1  Model test  82.13  62.26  57.18 
Numerical simulation  77.91  61.63  55.28  


2  Model test  85.27  65.35  59.90 
Numerical simulation  79.08  59.04  52.51  


3  Model test  82.82  67.58  62.33 
Numerical simulation  79.06  64.91  59.02  


4  Model test  90.56  81.32  54.26 
Numerical simulation  73.54  54.8  39.34  


5  Model test  87.75  80.49  62.57 
Numerical simulation  77.38  51.36  42.88  


6  Model test  80.92  62.35  60.84 
Numerical simulation  73.79  63.95  59.54 
As can be seen from Figure
Section velocity uniformity.
In the absence of any engineering measures (Figures
In order to optimize the flow pattern of the forebay, five kinds of rectification measures are set up in the front of the pumping station: “Y” type diversion pier, “T” shaped diversion pier, narrow bottom, high and wide bottom, and diversion wall. The surface and bottom flow modes of these five optimization measures were simulated by the model test, and the velocity uniformity of the characteristic cross section was calculated. Finally, the results show that the uniformity of flow and velocity distribution before the station can be improved.
The change of the position, the range, and the number of the vortices in the bottom layer of the scheme and the uniformity of the velocity distribution of each section of the pump foreground are comprehensively compared with each other. Program 3 (“T” shaped diversion pier) is recommended as the pumping station flow control measures. Due to the positive water blocking effect of the “T” shaped diversion piers, the water flow will be separated from the sides of the diversion piers, leading to a sudden change in the flow direction on the left side, so that the vortex range on the left side becomes smaller. The diversion pier can effectively reduce the shunt after the resulting vortex, so as to achieve uniform flow of water into the pumping station. The improvement of water flow in the pumping station can effectively improve the running performance of the pump, reduce the sedimentation, improve the reliability and economy of the pumping station, reduce the cost, and improve the efficiency.
The authors declare that they have no conflicts of interest.
This research was supported by the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, the National Water Pollution Control and Treatment Science and Technology Major Project (Grant no. 2014ZX07405002), and Postgraduate Research & Practice Innovation Program of Jiangsu Province (Grant no. KYCX17_0417). The authors would like to thank the Nanjing Environmental Protection Bureau, Nanjing, for providing monitoring data and associated information.