scholarly journals Three-dimensional numerical simulation of stepped dropshaft with different step shapes

2020 ◽  
Author(s):  
Jingkang Sun ◽  
Shangtuo Qian ◽  
Hui Xu ◽  
Xiaosheng Wang ◽  
Jiangang Feng
Keyword(s):  
Numerical Simulation ◽  
Energy Dissipation ◽  
Standing Wave ◽  
Flow Rate ◽  
Effective Means ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Deep Tunnel ◽  
Rate Distribution ◽  
Tunnel System

Abstract The deep tunnel system is increasingly used worldwide for stormwater conveyance and storage, providing a robust and effective means of preventing urban waterlogging. In the system, the dropshaft with the function of conveying stormwater to the deep tunnels underground, often runs under conditions of high falling head and large discharge. Based on the standard stepped dropshaft, a blade-shaped stepped dropshaft was proposed in order to control the potential standing wave and improve discharge capacity. Its hydraulic characteristics in respect of flow pattern, flow rate distribution, time-averaged pressure and energy dissipation were investigated by numerical simulation. Compared with the standard stepped dropshaft, the blade-shaped stepped dropshaft generated a more uniform flow rate distribution in the radial direction, therefore effectively decreasing the height of the standing wave near the external wall. The negative pressure areas that easily existed on the vertical wall of steps were well controlled. The energy dissipation of the blade-shaped stepped dropshaft was as high as that of the standard stepped dropshaft. Therefore, the blade-shaped stepped dropshaft could be a preferable design for the deep tunnel system.

Numerical Tests of Tunnel Reinforcing Influences on Zonal Disintegration within Rockmass around Deep Tunnel

2011 ◽  
Vol 261-263 ◽  
pp. 1282-1286
Author(s):  
Yu Jun Zuo ◽  
Yong Bin Zhang ◽  
Shu Cai Li ◽  
Yi Ping Zhang ◽  
Chun Chun Chen
Keyword(s):  
Failure Process ◽  
Vertical Wall ◽  
Three Dimensional ◽  
General Nature ◽  
Zonal Disintegration ◽  
Deep Tunnel ◽  
Tunnel Wall ◽  
Numerical Tests ◽  
Zonal Disintegration Phenomenon ◽  
The Stability

Nnumerical tests on three-dimensional failure process of rock samples containing vertical wall semi-arched tunnel with and without reinforcing are carried out with Mechsoft’s RFPA-Parallel system running on Lenovo 1800 Cluster, reproducing zonal disintegration phenomenon within rockmass around deep tunnels, and then the deep tunnel reinforcing influences on zonal disintegration within rockmass around tunnel is analyzed. Numerical results indicate that deep tunnel reinforcing does not change the general nature to form zonal disintegration phenomenon, but it can improve the stability of the tunnel wall.

Numerical Simulation on Internal Flows of Reducing Cross

2014 ◽  
Vol 945-949 ◽  
pp. 980-986
Author(s):  
Jian Ping Yuan ◽  
Wen Ting Sun ◽  
Yin Luo ◽  
Bang Lun Zhou
Keyword(s):  
Numerical Simulation ◽  
Flow Rate ◽  
Branch Pipe ◽  
Three Dimensional ◽  
Uniform Flow ◽  
Hydraulic Loss ◽  
Steady Flows ◽  
Internal Flows ◽  
Inlet Velocity ◽  
Main Pipe

In order to study the internal flows and hydraulic loss of reducing cross, numerical simulation was carried out on a horizontally installed reducing cross. Three schemes of pipe diameters were studied. The time-averaged N-S equations of three-dimensional steady flows in the reducing pipe were calculated by CFX 14.5 based on the standard - two equation turbulence model together with standard wall function. The results show that the higher the inlet velocity, the hydraulic loss become larger when the split ratios are same for the reducing cross. With the uniform inlet velocities the higher the inlet velocity, the quicker the increasing rate of the hydraulic loss in main pipe, as well as the branch pipe. The integral change rules of hydraulic loss are similar with the condition of uniform flow rate inflow when the flow patterns at inlet are uniform. But with the same spilt ratio, the hydraulic loss of uniform velocity inflow is markedly less than that of uniform flow rate inflow in both main pipe and branch pipe. The bigger the differences of the diameters between the main pipe and the branch pipe, the larger the hydraulic loss of the branch pipe.

scholarly journals Numerical Simulation of Full-Scale Three-Dimensional Fluid Flow in an Oscillating Reactor

2021 ◽  
Vol 9 ◽  
Author(s):  
Houjun Gong ◽  
Mengqi Wu
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Flow Field ◽  
Flow Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Full Scale ◽  
Variation Patterns ◽  
Oscillating Motion ◽  
Resistance Coefficients

Marine reactors are subjected to additional motions due to ocean conditions. These additional motions will cause large fluctuation of flow rate and change the coolant flow field, making the system unstable. Therefore, in order to understand the effect of oscillating motion on the flow characteristics, a numerical simulation of fluid flow is carried out based on a full-scale three-dimensional oscillating marine reactor. In this study, the resistance coefficients of the lattice, rod buddle and steam generator are fitted, and the distribution of flow rate, velocity as well as pressure in different regions is investigated through the standard model. After additional oscillation is introduced, the flow field in an oscillating reactor is presented and the effect of oscillating angle and elevation on the flow rate is investigated. Results show that the oscillating motion can greatly change the flow field in the reactor; most of the coolant circulates in the downcommer and lower head with only a small amount of coolant entering the core; the flow fluctuation period is consistent with the oscillating period, and the flow variation patterns under different oscillating conditions are basically the same; since the flow amplitude is related to oscillating speed, the amplitude of flow rate rises when decreasing the maximum oscillating angle; the oscillating elevation has little effect on the flow rate.

Numerical Simulation and Experimental Study on Hydraulic Performance of Centrifugal Pump's Impeller Based on FINE

2013 ◽  
Vol 444-445 ◽  
pp. 390-394
Author(s):  
Yong Shang ◽  
Xiao Bing Liu ◽  
Xue Jun Yu
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Hydraulic Performance ◽  
Test Results ◽  
Turbulent Model ◽  
Three Dimensional Flow ◽  
Dimensional Flow

By using the FINE software developed by NUMECA Company, the hydraulic performance of the impeller of a centrifugal pump with spatial guide vanes was numerically simulated. The S-A turbulent model was used to numerically calculate the three-dimensional flow field in the centrifugal pump under three different conditions. The flow analysis shows that the pressure gradient on the vane surface gradually reduces with the increasing of the flow rate; the position of axial vortex between vanes has nothing to do with the flow rate; the tangential flow gradient in the flow passage decreases with the increasing of the flow rate. Compared with the test results, it is obvious that this numerical simulation can accurately predicate the complicated three-dimensional flow and the hydraulic performance of the pump.

scholarly journals NUMERICAL SIMULATION OF WATER CIRCULATION IN A CYLINDRICAL HORIZONTAL THERMAL TANK

2009 ◽  
Vol 8 (1) ◽  
pp. 72
Author(s):  
D. L. Savicki ◽  
H. A. Vielmo
Keyword(s):  
Numerical Simulation ◽  
Flow Rate ◽  
Significant Variation ◽  
Thermal Stratification ◽  
Numerical Study ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Water Circulation ◽  
Numerical Code ◽  
Temperature And Velocity Fields

It is carried out a numerical study of the three-dimensional temperature and velocity fields in a cylindrical horizontal thermal tank during the process of water circulation. The numerical simulations were made using an academic Finite Volumes numerical code. This simulation considers that the thermal tank is connected to solar collectors. So, in the tank, the inlet jet temperature is higher than those inside the tank. This study aims to investigate the influence of the inlet jet on thermal stratification. The results show that for the mass flow rate studied, there is no significant variation on thermal stratification.

scholarly journals Three-Dimension Numerical Simulation of Scour Temporal Changes due to Flow in the Downstream of Combined Weirs and Gate Model

2017 ◽  
Vol 3 (11) ◽  
pp. 1111 ◽  
Author(s):  
Yaser Sadeghi Googheri ◽  
Mojtaba Saneie ◽  
Sirous Ershadi
Keyword(s):  
Numerical Simulation ◽  
Energy Dissipation ◽  
Numerical Model ◽  
Three Dimensional ◽  
Turbulent Energy ◽  
Temporal Changes ◽  
Three Dimension ◽  
Flow Conditions ◽  
Scour Hole ◽  
Static Water

Most of weirs create a region with relatively static water in upstream, which can be the place of sediments and wastes deposition in water. Sediments accumulation in upstream changes flow conditions.  In this case, combined weir and gate can be propounded as a useful solution. In the present paper, Flow3D was used to numerically simulate temporal changes of scour in combined free flow over weirs and below gates. Numerical modeling was run after fully preparing and the obtained data was analyzed under three-dimensional conditions. Comparing experimental and numerical results with data fitness revealed that determination coefficient (R2) of the numerical model results to the experimental model results is 0.94. Also, it was found that the relative error of the numerical model results relative to the experimental results equals 7.36%. Further, it was found that at the start of computations in the numerical model, compared to the end of running the model, the turbulent energy dissipation was decreased to 38% and decreasing the turbulent energy dissipation led to the creation of scour hole balance in the numerical model.

scholarly journals Hydraulic Characteristics and Numerical Simulation of the Entrance Section of Ladder-Shaped Spillway

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
X. B. Gu ◽  
Q. H. Wu ◽  
Y. Wang ◽  
H. X. Zhao
Keyword(s):  
Numerical Simulation ◽  
Energy Dissipation ◽  
Dissipation Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Energy Dissipation Rate ◽  
Numerical Results ◽  
Experimental Results ◽  
Flow State ◽  
Hydraulic Characteristics

The ladder-shaped spillway in a certain reservoir junction is set as the engineering background in the paper. The hydraulic similarly model experiment and three-dimensional numerical simulation of hydraulic characteristics of water flow are performed. The outflow capacity, flow state analysis, velocity distribution, water surface line, pressure, and the energy dissipation rate are analyzed, and experimental results are compared with the numerical results. The conclusions demonstrate that the numerical results of the flow characteristics are very proximate to actual experimental results, the changeable law is the same, and their energy dissipation rate is basically consistent; it shows the feasibility of three-dimensional numerical simulation; the conclusions can provide the basis for the optimization about the flow state of the ladder-shaped spillway in the future.

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