Modeling of Tarbela Reservoir and Water Flow Simulation Through Its Spillways

2010 ◽  
Author(s):  
Muhammad Abid ◽  
Muftooh Ur Rehman Siddiqi
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Discharge Rate ◽  
Flow Simulation ◽  
Maximum Velocity ◽  
Warming Trend ◽  
Height Distribution ◽  
Complex Flow ◽  
Local Flow ◽  
Buoyant Force

This numerical study is performed to predict the flow patterns and characteristics in Tarbela dam which is a multipurpose dam during the summer season the flow of the dam reaches to its design capacity or near flooding due to weather changes resulting from the global warming trend. A 3D model was made in Pro-Engineer® and meshed in ICEM CFD®. Commercially known software, ANSYS CFX®, was applied to numerically solve the Navier-Stokes equations for solution domain. The calculated results such as pressure, velocities, flow rate, surface height, and water buoyant force were compared with the actual data where available. The numerical calculations show uneven discharge through each gate due to the complex flow pattern just upstream of the weir. Maximum velocity was observed along the spillways outlet. In conclusion, the results from numerical simulation are generally well agreed with the existing data, the flow information such as flow field patterns at increased flow, local flow disturbances, discharge rate and surface height distribution obtained used for the behavior of existing dam and can be used for engineering design purpose of future dams.

Comparison of LBM and FVM in the estimation of LAD stenosis

2021 ◽  
pp. 095441192110169
Author(s):  
Jian Liu ◽  
Yong Yu ◽  
Chenqi Zhu ◽  
Yu Zhang
Keyword(s):  
Stokes Equations ◽  
Flow Simulation ◽  
Diagnostic Methods ◽  
Computational Time ◽  
Speed Ratio ◽  
Maximum Speed ◽  
Fractional Flow ◽  
Local Flow ◽  
Non Invasive ◽  
Flow Reserve

The finite volume method (FVM)-based computational fluid dynamics (CFD) technology has been applied in the non-invasive diagnosis of coronary artery stenosis. Nonetheless, FVM is a time-consuming process. In addition to FVM, the lattice Boltzmann method (LBM) is used in fluid flow simulation. Unlike FVM solving the Navier–Stokes equations, LBM directly solves the simplified Boltzmann equation, thus saving computational time. In this study, 12 patients with left anterior descending (LAD) stenosis, diagnosed by CTA, are analysed using FVM and LBM. The velocities, pressures, and wall shear stress (WSS) predicted using FVM and LBM for each patient is compared. In particular, the ratio of the average and maximum speed at the stenotic part characterising the degree of stenosis is compared. Finally, the golden standard of LAD stenosis, invasive fractional flow reserve (FFR), is applied to justify the simulation results. Our results show that LBM and FVM are consistent in blood flow simulation. In the region with a high degree of stenosis, the local flow patterns in those two solvers are slightly different, resulting in minor differences in local WSS estimation and blood speed ratio estimation. Notably, these differences do not result in an inconsistent estimation. Comparison with invasive FFR shows that, in most cases, the non-invasive diagnosis is consistent with FFR measurements. However, in some cases, the non-invasive diagnosis either underestimates or overestimates the degree of stenosis. This deviation is caused by the difference between physiological and simulation conditions that remains the biggest challenge faced by all CFD-based non-invasive diagnostic methods.

Numerical Flow Simulation in the Induction System of an Internal Combustion Engine

1992 ◽  
Author(s):  
S. Y. Ho ◽  
A. J. Przekwas
Keyword(s):  
Internal Combustion Engine ◽  
Stokes Equations ◽  
Combustion Engine ◽  
Flow Simulation ◽  
Internal Combustion ◽  
Flow Fields ◽  
The Body ◽  
Design Parameters ◽  
Complex Flow ◽  
Induction System

Abstract An advanced computational fluid dynamics package, REFLEQS, has been adapted to calculate the flow in the induction system of an internal combustion engine. Results of complex flow fields in multi-valve engine intake/exhaust ports and cylinders, including moving valves and piston, are calculated. The body-fitted structured grids generated with partial differential equations method have been applied to represent complex engine components configuration such as engine intake/exhaust ports, ducts, valves and cylinders. An upwind scheme combined with SIMPLEC method is employed to solve the Navier-Stokes equations. Several 2D and 3D flows in engine ports/cylinders are simulated. Complex flow fields involve separated flows near the entry of cylinder head, vortices near the corner and behind the valves and the valve/stem generated swirling and tumbling flows. The present work aims at establishing a generalized computational environment for analyzing the physical mechanisms and design parameters controlling internal flows in automotive air/fuel induction systems.

scholarly journals Numerical Study on Concrete Pumping Behavior via Local Flow Simulation with Discrete Element Method

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1415 ◽  
Author(s):  
Yijian Zhan ◽  
Jian Gong ◽  
Yulin Huang ◽  
Chong Shi ◽  
Zibo Zuo ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Fresh Concrete ◽  
Numerical Study ◽  
Flow Simulation ◽  
Discrete Element ◽  
Local Flow ◽  
Pumping System ◽  
Concrete Pumping ◽  
Pipe Geometry ◽  
Element Method

The use of self-consolidating concrete and advanced pumping system enables efficient construction of super high-rise buildings; however, risks such as clogging or even bursting of pipeline still exist. To better understand the fresh concrete pumping mechanisms in detail, the discrete element method is employed in this paper for the numerical simulation of local pumping problems. By modeling the coarse aggregates as rigid clumps and appropriately defining the contact models, the concrete flow in representative pipeline units is well revealed. Important factors related to the pipe geometry, aggregate geometry and pumping condition were considered during a series of parametric studies. Based on the simulation results, their impact on the local pumping performance is summarized. The present work demonstrates that the discrete element simulation offers a useful way to evaluate the influence of various parameters on the pumpability of fresh concrete.

Numerical Study of the Buoyancy Effect on Magnetohydrodynamic Three-Dimensional LiPb Flow in a Rectangular Duct

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Tigrine Zahia ◽  
Mokhtari Faiza ◽  
Bouabdallah Ahcène ◽  
Merah AbdelKrim ◽  
Kharicha Abdellah
Keyword(s):  
Magnetic Field ◽  
Hartmann Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Liquid Lead ◽  
Buoyancy Effect ◽  
Rectangular Duct ◽  
Buoyant Force ◽  
The Core

In this paper, the effect of transverse magnetic field on a laminar liquid lead lithium flow in an insulating rectangular duct is numerically solved with three-dimensional (3D) simulations. Cases with and without buoyancy force are examined. The stability of the buoyant flow is studied for different values of the Hartmann number from 0 to 120. We focus on the combined influence of the Hartmann number and buoyancy on flow field, flow structure in the vicinity of walls and its stability. Velocity and temperature distributions are presented for different magnetic field strengths. It is shown that the magnetic field damps the velocity and leads to flow stabilization in the core fluid and generates magnetohydrodynamic (MHD) boundary layers at the walls, which become the main source of instabilities. The buoyant force is responsible of the generation of vortices and enhances the velocities in the core region. It can act together with the MHD forces to intensify the flow near the Hartmann layers. Two critical Hartmann numbers (Hac1 = 63, Hac2 = 120) are found. Hac1 is corresponding to the separation of two MHD regimes: the first one is characterized by a core flow maximum velocity, whereas the second regime is featured by a maximum layer velocity and a pronounced buoyancy effect. Hac2 is a threshold value of electromagnetic force indicating the onset of MHD instability through the generation of small vortices close to the side layers.

2D numerical simulation of shallow water and bedload transport in channel confluences by considering the non-hydrostatic pressure

2021 ◽  
Author(s):  
Behnam Balouchi ◽  
Nils Rüther ◽  
Mahmood Shafaei Bejestan ◽  
Kordula Valerie Anne Schwarzwälder ◽  
Hans Bihs
Keyword(s):  
Hydrostatic Pressure ◽  
Shallow Water ◽  
Flow Pattern ◽  
Stokes Equations ◽  
Maximum Velocity ◽  
Bedload Transport ◽  
Water Model ◽  
Effective Parameters ◽  
Complex Flow ◽  
Channel Confluence

<p>Channel confluence is one of the important sections of channel networks which is also common encountered in nature. Six different zones exist at a channel confluence: 1) stagnation zone, 2) flow deflection zone, 3) flow separation zone, 4) maximum velocity zone, 5) flow recovery zone and 6) shear layers between combining flows zone. Due to the complexity of flow pattern at channel confluence, this location is always interesting among researchers. Although there are a number of studies on the flow and sediment pattern at confluences, there are still some gaps to be studied. Hence, a calibrated numerical model should be a good tool for evaluating the various effective parameters on flow and sediment patterns. The numerical 2D shallow-water model used in this paper is SFLOW which was developed by NTNU. Besides, the model calibration part of the current study is done by using a set of data from laboratory experiments.</p><p>This study attempt to simulate bed changes at channel confluences with a 2D shallow-water modeling under non-hydrostatic pressure, and show the applicability of the SFLOW model for this complex flow pattern. SFLOW solving the depth-averaged Navier-Stokes equations which is equipped with cutting-edge solvers. Besides, SFLOW modeled turbulency with depth-averaged two-equation RANS. In comparison with other codes, one of the interesting features of SFLOW is solving the non-hydrostatic pressure besides of hydrostatic part. This leads to a more realistic representation of the complex flow and sediment patterns of channel confluences, and consider less computational power than full 3D models.</p>

Experimental and Numerical Study of Orifice Discharge Coefficients in High-Speed Rotating Disks

1996 ◽  
Vol 118 (2) ◽  
pp. 400-407 ◽  
Author(s):  
S. Wittig ◽  
S. Kim ◽  
R. Jakoby ◽  
I. Weißert
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Tangential Velocity ◽  
Laser Doppler Velocimeter ◽  
Rotating Disks ◽  
Complex Flow ◽  
Local Flow ◽  
Discharge Coefficients

Experimental and numerical results of the flow through orifices in rotating disks are presented, with emphasis on basic physical phenomena. It is shown that rotational effects strongly influence the massflow discharged, a phenomenon that cannot be modeled by a stationary setup. The study includes the determination of discharge coefficients under variation of the length-to-diameter ratio, pressure ratio, and rotational speed. The pressure ratio covers low as well as critical values, the maximum rotational speed is 10,000 rpm, which is equivalent to a tangential velocity of 110 m/s. In order to understand the flow structure, local flow velocities were measured by means of a two-dimensional Laser-Doppler Velocimeter. Phase-resolved measurements have been carried out in front of and behind the orifices. A three-dimensional Finite-Volume Code with body-fitted coordinates in a rotating frame of reference is employed for the numerical analysis and the verification of its possibilities and limitations. The results reveal a very complex flow field, which is dominated by high velocity gradients in close vicinity to the orifices. The comparison of the computational solutions with the experimental data shows good agreement. Based on the measurements in combination with the numerical solution, a detailed insight into the physical properties of the flow is achieved.

Drag and Cavity Development of Two Slender Bodies: A Numerical Study

2015 ◽  
Author(s):  
Yong-Du Jun ◽  
Kang-Sik Bae ◽  
Seok-Soon Lee ◽  
Jong Soo Lee
Keyword(s):  
Drag Coefficient ◽  
Stokes Equations ◽  
Numerical Study ◽  
Phase Interface ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Slender Bodies ◽  
Cavity Development ◽  
Disk Cavitator

In the present study, an unsteady three-dimensional flow simulation based on the RANS (Reynolds Average Navier-Stokes) equations with k-ε turbulence model and Singhal et al.’s cavitation model is conducted to study the cavity development behavior of two slender bodies, that is, a flat-headed cylinder and a step-headed cylinder of 50 mm in length and 10 mm in diameter. Using so called VOF method to track the liquid-vapor phase interface, time dependent solutions with varying approach speed range from 10 m/s to 55 m/s are obtained and analyzed to provide key information such as cavity initiation speed, drag coefficient and the cavity shape and size (max. length and diameter). The implemented numerical model is validated for flows over a flat disk cavitator against the experimental correlation. According to the present simulation results, slender bodies with two different head shapes, that is, a flat cylinder and a stepped one, respectively, showed very close behavior in their cavity initiation speed, maximum developed cavity diameter and length, but consistently lower drag coefficient with the step-headed cylinder case, which suggests the possible advantage of seeking optimized cavitator shape.

Transonic aerofoils admitting anomalous behaviour of lift coefficient

2014 ◽  
Vol 118 (1202) ◽  
pp. 425-433 ◽  
Author(s):  
A. Kuzmin ◽  
A. Ryabinin
Keyword(s):  
Free Stream ◽  
Stokes Equations ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Small Perturbations ◽  
Navier Stokes Equations ◽  
Adverse Conditions ◽  
Abrupt Changes

Abstract Transonic flow past a Boeing 737 Outboard aerofoil and Whitcomb one with a defected aileron is studied. The flow simulation is based on the system of Reynolds-averaged Navier-Stokes equations. The numerical study demonstrates the existence of free-stream conditions in which small perturbations produce abrupt changes of the lift coefficient. Also the simulation reveals adverse conditions in which aileron deflections have no influence on the lift.

Numerical Analysis of Turbomachinery Flows With Transitional Boundary Layers

2002 ◽  
Author(s):  
P. De Palma
Keyword(s):  
Boundary Layers ◽  
Transonic Flow ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Boundary Layer Separation ◽  
Transition Model ◽  
Compressor Cascade ◽  
Complex Flow ◽  
Flow Through

This paper provides a numerical study of the flow through two turbomachinery cascades with transitional boundary layers. The aim of the present work is to validate some state-of-the-art turbulence and transition models in complex flow configurations. Therefore, the compressible Reynolds-averaged Navier–Stokes equations, with an Explicit Algebraic Stress Model (EASM) and k − ω turbulence closure, are considered. Such a turbulence model is combined with the transition model of Mayle for separated flow. The space discretization is based on a finite volume method with Roe’s approximate Riemann solver and formally second-order-accurate MUSCL extrapolation with minmod limiter. Time integration is performed employing an explicit Runge–Kutta scheme with multigrid acceleration. Firstly, the computations of the two- and three-dimensional subsonic flow through the T106 low-pressure turbine cascade are briefly discussed. Then, a more severe test case, involving shock-induced boundary-layer separation and corner stall is considered, namely, the three-dimensional transonic flow through a linear compressor cascade. In the present paper, calculations of such a transonic flow are presented, employing the standard k − ω model and the EASM, without transition model, and a comparison with the experimental data available in the literature is provided.

Experimental and Numerical Study of Orifice Discharge Coefficients in High Speed Rotating Disks

1994 ◽  
Author(s):  
S. Wittig ◽  
S. Kim ◽  
R. Jakoby ◽  
I. Weißert
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Tangential Velocity ◽  
Laser Doppler Velocimeter ◽  
Rotating Disks ◽  
Complex Flow ◽  
Local Flow ◽  
Discharge Coefficients

Experimental and numerical results of the flow through orifices in rotating disks are presented, with emphasis on basic physical phenomena. It is shown, that rotational effects strongly influence the massflow discharged, a phenomenon which cannot be modelled by a stationary setup. The study includes the determination of discharge coefficients under variation of the length to diameter ratio, pressure ratio and rotational speed. The pressure ratio covers low as well as critical values, the maximum rotational speed is 10000 rpm which is equivalent to a tangential velocity of 110 m/s. In order to understand the flow structure, local flow velocities were measured by means of a 2D Laser-Doppler-Velocimeter. Phase-resolved measurements have been carried out in front of and behind the orifices. A 3D Finite-Volume-Code with bodyfitted coordinates in a rotating frame of reference is employed for the numerical analysis and the verification of its possibilities and limitations. The results reveal a very complex flow field, which is dominated by high velocity gradients in close vicinity to the orifices. The comparison of the computational solutions with the experimental data shows good agreement. Based on the measurements in combination with the numerical solution, a detailed insight into the physical properties of the flow is achieved.

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