Application of an Angular Momentum Balance Method for Investigating Numerical Accuracy in Swirling Flow

2003 ◽  
Vol 125 (4) ◽  
pp. 723-730
Author(s):  
H. Nilsson ◽  
L. Davidson
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Angular Momentum ◽  
Swirling Flow ◽  
Linear Momentum ◽  
Correct Solution ◽  
Momentum Balance ◽  
Numerical Accuracy ◽  
Water Turbine ◽  
Water Turbines

This work derives and applies a method for the investigation of numerical accuracy in computational fluid dynamics. The method is used to investigate discretization errors in computations of swirling flow in water turbines. The work focuses on the conservation of a subset of the angular momentum equations that is particularly important to swirling flow in water turbines. The method is based on the fact that the discretized angular momentum equations are not necessarily conserved when the discretized linear momentum equations are solved. However, the method can be used to investigate the effect of discretization on any equation that should be conserved in the correct solution, and the application is not limited to water turbines. Computations made for two Kaplan water turbine runners and a simplified geometry of one of the Kaplan runner ducts are investigated to highlight the general and simple applicability of the method.

scholarly journals Computational fluid dynamics calculus and analysis for gas and water turbines

2018 ◽  
Vol 145 ◽  
pp. 03014
Author(s):  
Valeriu Vilag ◽  
Ivanka Zheleva ◽  
Jenia Popescu ◽  
Krasimir Tujarov
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Practical Applications ◽  
Water Turbine ◽  
Flow Through ◽  
Similarities And Differences ◽  
The Many ◽  
Water Turbines

The paper presents the utilization of Computational Fluid Dynamics for calculating the flow through turbines. The first and most extended part of the paper is focused on gas turbines where the simulations are very precise and can be successfully used even for optimization of blade geometry. Flow details and results for an axial turbine are presented along with a proposal of optimization algorithm. The second part of the paper is dedicated to water turbines and there is presented the calculus realized for a kinetic water turbine. I this case, the flow around the turbine blades is presented and some data about the predicted performances along with many ways for improving the simulations. The conclusions of the paper are related to similarities and differences between the two types of simulations and to the many ways of using these simulations for practical applications.

scholarly journals Morphological and Hemodynamic Changes during Cerebral Aneurysm Growth

2021 ◽  
Vol 11 (4) ◽  
pp. 520
Author(s):  
Emily R. Nordahl ◽  
Susheil Uthamaraj ◽  
Kendall D. Dennis ◽  
Alena Sejkorová ◽  
Aleš Hejčl ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Swirling Flow ◽  
Morphological Changes ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Aneurysm Wall ◽  
Aneurysm Growth ◽  
Computational Fluid Dynamics Cfd

Computational fluid dynamics (CFD) has grown as a tool to help understand the hemodynamic properties related to the rupture of cerebral aneurysms. Few of these studies deal specifically with aneurysm growth and most only use a single time instance within the aneurysm growth history. The present retrospective study investigated four patient-specific aneurysms, once at initial diagnosis and then at follow-up, to analyze hemodynamic and morphological changes. Aneurysm geometries were segmented via the medical image processing software Mimics. The geometries were meshed and a computational fluid dynamics (CFD) analysis was performed using ANSYS. Results showed that major geometry bulk growth occurred in areas of low wall shear stress (WSS). Wall shape remodeling near neck impingement regions occurred in areas with large gradients of WSS and oscillatory shear index. This study found that growth occurred in areas where low WSS was accompanied by high velocity gradients between the aneurysm wall and large swirling flow structures. A new finding was that all cases showed an increase in kinetic energy from the first time point to the second, and this change in kinetic energy seems correlated to the change in aneurysm volume.

Development of SIMPLE-Like Algorithms for Incompressible Navier-Stokes Equations in Liquid Processing of Materials

2012 ◽  
Vol 184-185 ◽  
pp. 944-948 ◽  
Author(s):  
Hai Jun Gong ◽  
Yang Liu ◽  
Xue Yi Fan ◽  
Da Ming Xu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Simple Algorithm ◽  
Navier Stokes ◽  
Incompressible Fluid Flow ◽  
Numerical Accuracy ◽  
Simple Scheme ◽  
Navier Stokes Equations ◽  
Computational Fluid Dynamics Cfd

For a clear and comprehensive opinion on segregated SIMPLE algorithm in the area of computational fluid dynamics (CFD) during liquid processing of materials, the most significant developments on the SIMPLE algorithm and its variants are briefly reviewed. Subsequently, some important advances during last 30 years serving as increasing numerical accuracy, enhancing robustness and improving efficiency for Navier–Stokes (N-S) equations of incompressible fluid flow are summarized. And then a so-called Direct-SIMPLE scheme proposed by the authors of present paper introduced, which is different from SIMPLE-like schemes, no iterative computations are needed to achieve the final pressure and velocity corrections. Based on the facts cited in present paper, it conclude that the SIMPLE algorithm and its variants will continue to evolve aimed at convergence and accuracy of solution by improving and combining various methods with different grid techniques, and all the algorithms mentioned above will enjoy widespread use in the future.

scholarly journals The Aerodynamics of a Diabolo

2021 ◽  
Author(s):  
Darren Jia
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Angular Momentum ◽  
Flow Pattern ◽  
High Spin ◽  
Angular Speed ◽  
Geometric Shape ◽  
Cfd Simulations ◽  
Resistive Torque ◽  
Computational Fluid Dynamics Cfd

Diabolo is a popular game in which the object can be spun at up to speeds of 5000 rpm. This high spin velocity gives the diabolo the necessary angular momentum to remain stable. The shape of the diabolo generates an interesting air flow pattern. The viscous air applies a resistive torque on the fast spinning diabolo. Through computational fluid dynamics (CFD) simulations it's shown that the resistive torque has an interesting dependence on the angular speed of the diabolo. Further, the geometric shape of the diabolo affects the dependence of torque on angular speed.

Experimental and numerical study of vortex gripper with a diversion body

2011 ◽  
Vol 226 (6) ◽  
pp. 1526-1534 ◽  
Author(s):  
Q Wu ◽  
Q Ye ◽  
G X Meng
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Swirling Flow ◽  
Numerical Study ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Lifting Force ◽  
Handling Device ◽  
Simulation Results

This article introduces a new vortex gripper with a diversion body. Vortex gripper, as a pneumatic non-contact handling device, can generate lifting force to hold a workpiece without any contact. In order to predict the characteristics of this new vortex gripper, including pressure distribution on the upper surface of the workpiece, lifting force, supporting stiffness, and flowrate, a computational fluid dynamics study has been carried out. In the vortex cup, air swirling flow is a complex turbulent one; so Reynolds stress model (RSM) was used to describe internal air swirling flow. In addition, an experiment was carried out to study the characteristics of the vortex gripper. When compared with the experimental results, the reliability of numerical simulation results by RSM was verified. The vortex gripper with a diversion body could generate greater lifting force when compared with those designed by Xin et al. with the same air consumption. Therefore, the efficiency of the vortex gripper is improved.

scholarly journals Computational Fluid Dynamics Study of Wake Recovery for Flow Across Hydrokinetic Turbine at Different Depth of Water

CFD letters ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 62-76
Author(s):  
Hew Wei Ren ◽  
Fatimah Al Zahrah Mohd Saat ◽  
Fadhilah Shikh Anuar ◽  
Mohd Arizam Abdul Wahap ◽  
Ernie Mat Tokit ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Low Cost ◽  
Water Channel ◽  
Pressure Change ◽  
Good Choice ◽  
Green Energy ◽  
Flow Depth ◽  
Hydrokinetic Turbine ◽  
Water Turbine

Depletion of fossil fuel caused mankind to look for sustainable and green energy resources. The characteristic of hydrokinetic turbine with ability to operate at low head stream and at low cost made it a good choice for use to harness hydro source of energy. As hydrokinetic turbine gain attention from the industry player, many experimental and Computational Fluid Dynamics (CFD) studies related to hydrokinetic turbine have been carried out. Yet the relationship of flow depth variation and wake recovery behind the turbine is still not fully understood. There is limited study about the effects of flow depth variations on the wake recovery behind the turbine. In this paper, a CFD model investigation was done based on published experimental work. A hydrokinetic water turbine was drawn using the MHKF1-180 and NACA4418 foils dimensions. The transient CFD study was conducted using SST k-w turbulence model and dynamic mesh method. The results showed that in near wake region, the wake at deeper depth will recover faster seemingly due to pressure change at that depth and the faster rate of momentum transfer of the fluid. It can be concluded that the deeper the placement of the turbine inside the water channel, the faster the wake recovers. The wake recovery results as presented in this paper should be considered when placing set of turbines especially in array arrangement to obtain a more efficient energy conversion.

scholarly journals Structural improvements on hydrodynamic separators: a computational fluid dynamics approach

2016 ◽  
Vol 74 (12) ◽  
pp. 2898-2908
Author(s):  
Joseph Albert Mendoza ◽  
Dong Hoon Lee ◽  
Sang-Il Lee ◽  
Joo-Hyon Kang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fine Particles ◽  
Swirling Flow ◽  
Particle Removal ◽  
Gravity Settling ◽  
Large Particles ◽  
Removal Efficiencies ◽  
Structural Configurations ◽  
Plate Type

Hydrodynamic separators (HDSs) have been used extensively to reduce stormwater pollutants from urbanized areas before entering the receiving water bodies. They primarily remove particulates and associated pollutants using gravity settling. Two types of HDSs with different structural configurations of the inner vortex-inducing components were presented in this study. One configuration consisted of a dip cylindrical plate with a center shaft while the other one has a hollow screen inside. With the help of computational fluid dynamics, the performance of these different types of HDSs have been evaluated and comparatively analyzed. The results showed that the particle removal efficiency was better with the cylindrical plate type HDSs than the screen type HDSs because of the larger swirling flow regime formed inside the device. Plate type HDSs were found more effective in removing fine particles (∼50 μm) than the screen type HDSs that were only efficient in removing large particles (≥250 μm). Structural improvements in a HDS such as increase in diameter and angle of the inlet pipe can enhance the removal efficiencies by up to 20% for plate type HDS while increase in the screen diameter can increase removal efficiencies of the screen type HDS.

Similarity in swirling wakes and jets

1962 ◽  
Vol 14 (2) ◽  
pp. 241-243 ◽  
Author(s):  
A. J. Reynolds
Keyword(s):  
Angular Momentum ◽  
Swirling Flow ◽  
Turbulent Wake ◽  
Linear Momentum ◽  
Length Scale ◽  
Mean Velocity ◽  
Swirl Velocity ◽  
Velocity Scale ◽  
Zero Momentum ◽  
The Mean

Both the net linear momentum and the net angular momentum of a developing swirling flow can play important parts in determining its ultimate form. To illustrate this the turbulent wake with both axial and swirl components of mean velocity is discussed, in particular for the two limiting cases of domination by linear momentum and domination by angular momentum. The dual conservation of axial and angular momentum implies that in general the mean swirl component decreases more rapidly downstream than does the defect in the mean axial velocity. Hence wakes with non-zero momentum flux ultimately have the familiar length scale $\sim Z^{\frac{1}{3}$ and velocity defect scale $\sim Z^{-\frac{2}{3}$. But in the wake of a self-propelled body the net drag is negligible and a swirl-dominated development can persist with length scale $\sim Z^{\frac{1}{4}$ and swirl velocity scale $\sim Z^{-\frac{3}{4}$.

Swirling Flow Through Venturi Tubes of Convergent Angle 10.5° and 21°

2006 ◽  
Author(s):  
Jeff Gibson ◽  
Michael Reader-Harris
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Swirling Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Good Agreement

Computational Fluid Dynamics (CFD) was used to compute the effect of two bends in perpendicular planes on the performance of 4-inch Venturi tubes with β = 0.4, 0.6 and 0.75 for water at a Reynolds number of 350,000 and at various distances from the bend. Two types of Venturi tubes were analysed, the first having a standard convergent angle of 21°, the second having a non-standard convergent angle of 10.5°. Good agreement with experiment was obtained. Swirling axisymmetric flows were computed to help interpret experimental data.

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