Wall proximity effects on flow over cylinders with different cross sections

2014 ◽  
Vol 92 (10) ◽  
pp. 1141-1148 ◽  
Author(s):  
Seyfettin Bayraktar ◽  
Sedat Yayla ◽  
Alparslan Oztekin ◽  
Haolin Ma
Keyword(s):  
Cross Sections ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Proximity Effects ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Navier Stokes Equations ◽  
Finite Volume Discretization ◽  
Wall Proximity

This paper presents the results of a numerical study on flow characteristics over circular, square, and diamond cross-sectional cylinders. Investigations are performed in a two-dimensional domain using the finite volume discretization method solver for Reynolds number, Re = 20 000. Unsteady Reynolds averaged Navier–Stokes equations with Spalart–Allmaras turbulence model have been used as a turbulence closure. After the validation of the simulations with the available experimental data from the open literature, global characteristics of the flow field around different shaped cylinders near the wall have been presented. Effects of wall proximity on cylinders are investigated for four different gap width (G) to cylinder width (D) ratios.

Numerical Study of Wave Slamming on an Oscillating Flap

2014 ◽  
Author(s):  
Yanji Wei ◽  
Alan Henry ◽  
Olivier Kimmoun ◽  
Frederic Dias
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Numerical Studies ◽  
Wave Slamming ◽  
Volume Method

Bottom hinged Oscillating Wave Surge Converters (OWSCs) are efficient devices for extracting power from ocean waves. There is limited knowledge about wave slamming on such devices. This paper deals with numerical studies of wave slamming on an oscillating flap to investigate the mechanism of slamming events. In our model, the Navier–Stokes equations are discretized using the Finite Volume method with the Volume of Fluid (VOF) approach for interface capturing. Waves are generated by a flap-type wave maker in the numerical wave tank, and the dynamic mesh method is applied to model the motion of the oscillating flap. Basic mesh and time step refinement studies are performed. The flow characteristics in a slamming event are analysed based on numerical results. Various simulations with different flap densities, water depths and wave amplitudes are performed for a better understanding of the slamming.

Numerical Study on the Flow Characteristics of the Francis Turbine With Various Blade Profiles

2013 ◽  
Author(s):  
J.-H. Jeon ◽  
S.-S. Byeon ◽  
Y.-J. Kim
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Sst Turbulence Model

The Francis turbine is a kind of reaction turbines, which means that the potential energy of water converted to rotational kinetic energy. In this study, the flow characteristics have been investigated numerically in a Francis turbine on the 15 MW hydropower generation with various blade profiles (NACA 65 and NACA 16 series) and discharge angles (14°, 15°, 17°, and 18°), using the commercial code, ANSYS CFX. The k-ω SST turbulence model is employed in the Reynolds averaged Navier-Stokes equations. The computing domain includes the spiral casing, guide vanes, and draft tube, which are discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The results showed that the change of blade profiles and discharge angles significantly influenced the performance of the Francis turbine.

A Numerical Examination of the Inkjet Refilling

2004 ◽  
Author(s):  
Kai-Shing Yang ◽  
Ing-Young Chen ◽  
Chi-Chuan Wang
Keyword(s):  
Dynamic Viscosity ◽  
Bubble Growth ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Plane Boundary ◽  
Navier Stokes Equations ◽  
Numerical Examination

A numerical study is conducted to examine the flow characteristics of the inkjet print-head with special attentions on the refilling process. By solving the full set of three-dimensional transient Navier-Stokes equations and considering the process of bubble growth and collapse as a movable membrane, it is found that the double refilling channels can reduce the flow surge phenomenon considerably due to the imposed friction. However, for the additional cylinder obstacle placed at the filling channel, the flow surge phenomenon is still present. This is because of the jet-like flow along the cylinder leading to a collision and eruption of fluid angled towards the plane boundary with the presence of cylinder. The calculated results also indicated the flow surge can be moderately suppressed for fluid having larger dynamic viscosity.

scholarly journals The 3D Numerical Study on Flow and Sediment Properties of a River with Grouped Spur Dikes

2018 ◽  
Vol 40 ◽  
pp. 05056 ◽  
Author(s):  
Xun Han ◽  
Pengzhi Lin ◽  
Gary Parker
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Flume Experiments ◽  
Navier Stokes Equations ◽  
Sediment Properties ◽  
Eddy Simulation ◽  
Flow Motion ◽  
Spur Dikes

A 3D numerical model named NEWTANK is employed to investigate the flow motion and sediment transport in grouped spur dikes system. This model is based on the Navier-Stokes equations, adopting the Volume of Fluid (VOF) method to track the free surface motion, while the solid is described by using the Porous Media Method (PMM). The Large Eddy Simulation (LES) is applied to capture turbulence. In sediment calculation parts, the suspended load and bedload are treated separately but combined together to update bed variation eventually. The finite difference form and Two-step Projection Method are employed in the process of discretizing the governing equation. Several carefully selected flume experiments are introduced to verify this model's reliability before its application on the simulation of grouped spur dike case, and detailed flow characteristics and sediment properties are analyzed afterwards.

A numerical study of inkjet refilling

2004 ◽  
Vol 218 (12) ◽  
pp. 1481-1497
Author(s):  
K-S Yang ◽  
I-Y Chen ◽  
C-C Wang
Keyword(s):  
Fluid Flow ◽  
Bubble Growth ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Channel Design ◽  
Navier Stokes Equations ◽  
Inkjet Printer

A numerical study is conducted to examine the flow characteristics of the inkjet printer head with special attention made to the refilling process. By solving the full set of three-dimensional transient Navier-Stokes equations and considering the process of bubble growth and collapse as a movable membrane, the fluid flow inside the channel and the ejected droplet from the nozzle can be modelled. The calculated results indicate that the single refilling channel design provides the fastest refilling rate but also reveals pronounced flow surge/overshot phenomena. By using a double refilling channel design, the flow surge/overshot phenomenon can be reduced considerably owing to the imposed friction. Moreover, the flooding phenomenon is much less pronounced. However, placing an additional cylinder obstacle in the single filling channel will not reduce the flow surge/overshot phenomenon.

scholarly journals AERODYNAMICS OF A TURBULENT FLOW IN A ROTATING SEMI-CLOSED CYLINDER

2021 ◽  
pp. 114-126
Author(s):  
O.V. Matvienko ◽  
◽  
V.A. Arkhipov ◽  
N.N. Zolotorev ◽  
◽  
...  
Keyword(s):  
Mathematical Model ◽  
Stokes Equations ◽  
Swirling Flow ◽  
Numerical Study ◽  
Control Volume ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Grid Refinement ◽  
Navier Stokes Equations ◽  
Turbulent Air Flow

The mathematical model and results of a numerical study of swirling turbulent air flow characteristics in a semi-closed cylinder rotating around a symmetry axis are presented. A physical and mathematical model is used to describe aerodynamics of the stationary isothermal axisymmetric swirling flow, which includes the Navier-Stokes equations in cylindrical coordinates. The study of turbulence characteristics is carried out using the composite model Menter SST (Shear Stress Transport). The numerical solution is obtained using a chess grid. Nodes for axial and radial velocity components are located in the middle of the control volume faces for scalar quantities. Calculations are performed on a grid with 2000 and 1700 nodes in the axial and radial directions, respectively. The grid refinement is performed near the walls and in the areas with large velocity gradients. The calculated results show that the main grid refinement by 2 times in the axial and radial coordinates leads to a change in the values of the main variables by less than 1%. It is shown that the flow structure is determined by the rotational speed and cylinder height. Analyzing the calculated results, the ratio of the cylinder height to the angular velocity of the cylinder rotation is obtained, which ensures the formation of a quasi-solid rotation zone in the near-edge region.

Analysis of the Manifold Area Change in a Flat Solar Collector

2013 ◽  
Author(s):  
N. C. Uzarraga-Rodriguez ◽  
A. Gallegos-Muñoz ◽  
Luis A. Payan-Rodriguez ◽  
Juan M. Belman-Flores
Keyword(s):  
Water Flow ◽  
Solar Collector ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flow Distribution ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Navier Stokes Equations ◽  
Area Change ◽  
Uniform Flow Distribution

A numerical analysis of the characterization of the water flow through a flat solar collector is presented. The manifold area change for minimizing the water flow variation in the solar collector is analyzed. The area ratio in the inlet and outlet of the manifolds were modified in a range of Am/Ao = 1 to 4, where Am and Ao are the cross-sectional area modified and original of the manifolds, respectively. The solar collector investigated is equipped with six riser tubes, which are attached to the manifolds pipe. The numerical study was developed in a commercial Computational Fluid Dynamics (CFD) using FLUENT®. This code allows to solve the Reynolds averaged Navier-Stokes equations and the transport equations of the turbulence quantities. The results shown that increasing the inlet and outlet area of the manifolds allow a more uniform flow distribution compared to the original configuration of the solar collector. It also shows that the overall pressure drop in the solar collector is reduced.

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

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