Numerical Simulation of Emergency Shutdown Process of Ring Gate in Hydraulic Turbine Runaway

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Juliang Xiao ◽  
Enqiang Zhu ◽  
Guodong Wang
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Hydraulic Turbine ◽  
Navier Stokes ◽  
Guide Vanes ◽  
Flow Models ◽  
Emergency Shutdown ◽  
Spiral Case ◽  
Dynamic Quality

A numerical model that considers the interaction between the ring gate and its neighboring components was used to simulate the emergency shutdown process of a ring gate in hydraulic turbine runaway. The three-dimensional, unsteady Navier–Stokes equations with renormalization group (RNG) k-ε turbulence models, multiphase flow models, dynamic mesh, and sliding mesh technology were applied to model the entire flow passage of the Francis hydraulic turbine, including the spiral case, stay vanes, ring gate, guide vanes, runner, and draft tube. We present a detailed analysis on the working conditions of the turbine during its runaway quitting process, the inside and outside surface pressure distributions of the ring gate, the pressure and velocity distributions of the spiral case, stay vanes, and guide vanes at different gate openings, and the loading condition of the ring gate during its closing process. The theoretical basis for improving the dynamic quality of the transient process and for hydraulic designing and optimization is provided by analyses.

An Assessment of Turbulence Models for Predicting the Fluid Flow in Spiral Casing of a Hydraulic Turbomachine Using SUPG-Finite Element Method

2013 ◽  
Author(s):  
N. Parameswara Rao ◽  
K. Arul Prakash
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Spatial Discretisation ◽  
High Reynolds ◽  
Spiral Casing ◽  
Element Method

Numerical simulation of complex three-dimensional flow through the spiral casing has been studied using a finite element method. An explicit Eulerian velocity correction scheme has been employed to solve the Reynolds averaged Navier-stokes equations. The simulation has been performed to describe the flow in high Reynolds number (106) regime and two k-ε turbulence models (standard k-ε and RNG k-ε) have been used for computing the turbulent flow. A streamline upwind Petrov Galerkin technique has been used for spatial discretisation. The velocity field and the pressure distribution inside the spiral casing has been studied. It has been observed that very strong secondary flow is evolved on the cross-stream planes.

scholarly journals Aerothermodynamic Effects and Modeling of the Tangential Curvature of Guide Vanes in an Axial Turbine Stage

2017 ◽  
Vol 2017 ◽  
pp. 1-16
Author(s):  
Tzong-Hann Shieh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Suction Side ◽  
Meridional Flow ◽  
Navier Stokes ◽  
Obtuse Angle ◽  
Turbine Stage ◽  
Navier Stokes Equations ◽  
Axial Turbine ◽  
Guide Vanes

By tangential curvature of the stacking line of the profiles guide vanes can be designed, which have on both ends an obtuse angle between suction side and sidewall. This configuration, according to literature, is capable of reducing secondary loss. This type of vanes develops considerable radial components of the blade force and effects a displacement of the meridional flow towards both sidewalls. In this paper we work with a finite-volume-code for computations of the three-dimensional Reynolds averaged Navier-Stokes equations for an axial turbine stage with radial and two types of tangentially curved guide vanes. With computational results, mathematical formulations are developed for a new flow model of deflection of such blades that are formally compatible with the assumption of a rotation-symmetrical flow and with the existing throughflow codes, in order to predict the deflection angle over the blade height for the tangential leaned and curved blades.

Multigrid Computation of Incompressible Flows Using Two-Equation Turbulence Models: Part II—Applications

1997 ◽  
Vol 119 (4) ◽  
pp. 900-905 ◽  
Author(s):  
X. Zheng ◽  
C. Liao ◽  
C. Liu ◽  
C. H. Sung ◽  
T. T. Huang
Keyword(s):  
Turbulent Flows ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Time Stepping ◽  
Grid Algorithm ◽  
High Reynolds

In this paper, computational results are presented for three-dimensional high-Reynolds number turbulent flows over a simplified submarine model. The simulation is based on the solution of Reynolds-Averaged Navier-Stokes equations and two-equation turbulence models by using a preconditioned time-stepping approach. A multiblock method, in which the block loop is placed in the inner cycle of a multi-grid algorithm, is used to obtain versatility and efficiency. It was found that the calculated body drag, lift, side force coefficients and moments at various angles of attack or angles of drift are in excellent agreement with experimental data. Fast convergence has been achieved for all the cases with large angles of attack and with modest drift angles.

Strongly Coupled Fluid-Structure Interactions via a New Navier-Stokes Method for Prediction of Vortex-Induced Vibrations

2005 ◽  
Author(s):  
Yannis Kallinderis ◽  
Hyung Taek Ahn
Keyword(s):  
Stokes Equations ◽  
Computational Cost ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Design Tool ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Vortex Induced Vibrations ◽  
Offshore Industry

Numerical prediction of vortex-induced vibrations requires employment of the unsteady Navier-Stokes equations. Current Navier-Stokes solvers are quite expensive for three-dimensional flow-structure applications. Acceptance of Computational Fluid Dynamics as a design tool for the offshore industry requires improvements to current CFD methods in order to address the following important issues: (i) stability and computation cost of the numerical simulation process, (ii) restriction on the size of the allowable time-step due to the coupling of the flow and structure solution processes, (iii) excessive number of computational elements for 3-D applications, and (iv) accuracy and computational cost of turbulence models used for high Reynolds number flow. The above four problems are addressed via a new numerical method which employs strong coupling between the flow and the structure solutions. Special coupling is also employed between the Reynolds-averaged Navier-Stokes equations and the Spalart-Allmaras turbulence model. An element-type independent spatial discretization scheme is also presented which can handle general hybrid meshes consisting of hexahedra, prisms, pyramids, and tetrahedral.

Calculation of Turbulent Flows in a Hydraulic Turbine Draft Tube

1990 ◽  
Vol 112 (3) ◽  
pp. 257-263 ◽  
Author(s):  
M. Agouzoul ◽  
M. Reggio ◽  
R. Camarero
Keyword(s):  
Turbulent Flows ◽  
Stokes Equations ◽  
Draft Tube ◽  
Three Dimensional ◽  
Hydraulic Turbine ◽  
Navier Stokes ◽  
Pressure Gradients ◽  
Navier Stokes Equations ◽  
Conservative Form ◽  
Hydraulic Turbine Draft Tube

A numerical method to simulate three-dimensional incompressible turbulent flows has been developed and applied to the calculation of various flow situations in a draft tube. The conservative form of the primitive-variable formulation of the Reynolds averaged Navier-Stokes equations, written for a general curvilinear co-ordinate system, is employed. An overlapping grid combined with opposed differencing for mass and pressure gradients is used. All the properties are stored at the center of the same computational cell which is used for mass and transport balances. The k–ε model is used to describe the turbulent flow. The boundary conditions for the turbulent properties are treated with a particular attention.

scholarly journals A Study of RANS Turbulence Models in Fully Turbulent Jets: A Perspective for CFD-DEM Simulations

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 271
Author(s):  
Dustin Weaver ◽  
Sanja Mišković
Keyword(s):  
Stokes Equations ◽  
Near Field ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Turbulent Jets ◽  
Navier Stokes ◽  
Straight Tube ◽  
Developed Turbulence ◽  
Similar Work ◽  
Tube Geometry

This paper presents an analysis of linear viscous stress Favre averaged turbulence models for computational fluid dynamics (CFD) of fully turbulent round jets with a long straight tube geometry in the near field. Although similar work has been performed in the past with very relevant solutions, considerations were not given for the issues and limitations involved with coupling between an Eulerian and Lagrangian phase, such as in fully two-way coupled CFD-DEM. These issues include limitations on solution domain, mesh cell size, wall modelling, and momentum coupling between the two phases in relation to the particles size. Therefore, within these considerations, solutions are provided to the Navier–Stokes equations with various turbulence models using a three-dimensional wedge long straight tube geometry for fully developed turbulence flow. Simulations are performed with a Reynolds number of 13,000 and 51,000 using two different tube diameters. It is found that a modified k-ε turbulence model achieved the most agreeable results for both the velocity and turbulent flow fields between these two flow regimes, while a modified k-ω SST/BSL also provided suitable results.

Flow Analysis of the M151 Aircraft Model Using the Academic CFD Code Galatea

2017 ◽  
Author(s):  
Dimitrios A. Inglezakis ◽  
Georgios N. Lygidakis ◽  
Ioannis K. Nikolos
Keyword(s):  
Turbulent Flows ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Research Association ◽  
Navier Stokes Equations ◽  
Aircraft Model ◽  
Short Period

CFD (Computational Fluid Dynamics) solvers have become nowadays an integral part of the aerospace manufacturing process and product design, as their implementation allows for the prediction of the aerodynamic behavior of an aircraft in a relatively short period of time. Such an in-house academic solver, named Galatea, is used in this study for the prediction of the flow over the ARA (Aircraft Research Association) M151/1 aircraft model. The proposed node-centered finite-volume solver employs the RANS (Reynolds-Averaged Navier-Stokes) equations, combined with appropriate turbulence models, to account for the simulation of compressible turbulent flows on three-dimensional hybrid unstructured grids, composed of tetrahedral, prisms, and pyramids. A brief description of Galatea’s methodology is included, while attention is mainly directed toward the accurate prediction of pressure distribution on the wings’ surfaces of the aforementioned airplane, an uncommon combat aircraft research model with forward swept wings and canards. In particular, two different configurations of M151/1 were examined, namely, with parallel and expanding fuselage, while the obtained results were compared with those extracted with the commercial CFD software ANSYS CFX. A very good agreement is reported, demonstrating the proposed solver’s potential to predict accurately such demanding flows over complex geometries.

Navier-Stokes Flow Analysis for Hydraulic Turbine Draft Tubes

1990 ◽  
Vol 112 (2) ◽  
pp. 199-204 ◽  
Author(s):  
T. C. Vu ◽  
W. Shyy
Keyword(s):  
Stokes Flow ◽  
Stokes Equations ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Hydraulic Turbine ◽  
Navier Stokes ◽  
Numerical Result ◽  
Wide Range ◽  
Draft Tubes

Three-dimensional turbulent viscous flow analyses for hydraulic turbine elbow draft tubes are performed by solving Reynolds averaged Navier-Stokes equations closed with a two-equation turbulence model. The predicted pressure recovery factor and flow behavior in the draft tube with a wide range of swirling flows at the inlet agree well with experimental data. During the validation of the Navier-Stokes flow analysis, particular attention was paid to the effect of grid size on the accuracy of the numerical result and the importance of accurately specifying the inlet flow condition.

scholarly journals Numerical Research on Flow Characteristics around a Hydraulic Turbine Runner at Small Opening of Cylindrical Valve

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Zhenwei Mo ◽  
Juliang Xiao ◽  
Gang Wang
Keyword(s):  
Flow Velocity ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydraulic Turbine ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Small Opening ◽  
Turbine Runner ◽  
Computational Fluid Dynamics Cfd

We use the continuity equation and the Reynolds averaged Navier-Stokes equations to study the flow-pattern characteristics around a turbine runner for the small-opening cylindrical valve of a hydraulic turbine. For closure, we adopt the renormalization-groupk-εtwo-equation turbulence model and use the computational fluid dynamics (CFD) software FLUENT to numerically simulate the three-dimensional unsteady turbulent flow through the entire passage of the hydraulic turbine. The results show that a low-pressure zone develops around the runner blades when the cylindrical valve is closed in a small opening; cavitation occurs at the blades, and a vortex appears at the outlet of the runner. As the cylindrical valve is gradually closed, the flow velocity over the runner area increases, and the pressure gradient becomes more significant as the discharge decreases. In addition, the fluid flow velocity is relatively high between the lower end of the cylindrical valve and the base, so that a high-velocity jet is easily induced. The calculation and analysis provide a theoretical basis for improving the performance of cylindrical-valve operating systems.

scholarly journals Numerical Simulation of Internal Flow and Performance Prediction of Tubular Pump with Adjustable Guide Vanes

2014 ◽  
Vol 6 ◽  
pp. 171504 ◽  
Author(s):  
Honggeng Zhu ◽  
Rentian Zhang
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Internal Flow ◽  
Design Flow ◽  
Navier Stokes ◽  
Impeller Blade ◽  
Flow Angle ◽  
Guide Vanes ◽  
Operation Conditions ◽  
Setting Angle

Aiming at the performance defect of tubular pump with fixed guide vanes, a design scheme of tubular pump with adjustable guide vanes is proposed, so that the inlet setting angle of guide vanes can be flexibly adjusted to coordinate with the operation conditions of pump, to ensure the inlet setting angle of guide vanes changing with the outlet flow angle of the impeller. The three-dimensional time-averaged incompressible Navier-Stokes equations are adopted to numerically simulate the internal flow field of a tubular pump with fixed and adjustable guide vanes, respectively. Computed results indicate that with the design of adjustable guide vanes and at off-design flow rates the flow conditions inside the diffuser of tubular pump can be improved effectively, and its hydraulic losses can be reduced. When the impeller blade angles are fixed the best efficiency points are within 0.51% while adjusting setting angles of guide vanes within a certain range. Under off-design conditions the hydraulic efficiency of tubular pump with adjustable guide vanes can be obviously improved by 1.70% at 0.75 Q0 and 2.19% at 1.20 Q0, when the blade angle is 0 degrees and the angle of guide vanes is adjusted to be 2 degrees smaller and larger, respectively.

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