scholarly journals Modeling and simulation of transitional Taylor-Green vortex flow with partially averaged Navier-Stokes equations

2021 ◽  
Vol 6 (5) ◽  
Author(s):  
F. S. Pereira ◽  
F. F. Grinstein ◽  
D. M. Israel ◽  
R. Rauenzahn ◽  
S. S. Girimaji
Keyword(s):  
Modeling And Simulation ◽  
Vortex Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations

scholarly journals Dynamics of laminar flows with coaxial oppositely-rotating layers

Vestnik MGSU ◽  
2019 ◽  
pp. 332-346
Author(s):  
Andrey L. Zuikov
Keyword(s):  
Reynolds Number ◽  
Active Zone ◽  
Vortex Flow ◽  
Stokes Equations ◽  
Laminar Flows ◽  
Radial Velocities ◽  
Navier Stokes ◽  
Recirculation Region ◽  
Vortex Flows ◽  
Navier Stokes Equations

Introduction. The work relates to the scientific foundations of hydraulic and energy construction and is devoted to the study of laminar flows with coaxial oppositely-rotating layers. In the literature, such flows are called counter-vortex. In the turbulent range, counter-vortex flows are characterized by intensive mixing of the medium, which is widely used in the technologies of mixing non-natural and multi-phase media in thermal and atomic energy, in systems of mass- and heat transfer, in chemistry and microbiology, ecology, engine and rocket production. The aim of the theoretical study is to study the physical laws of the hydrodynamics of counter-vortex flows. Research methods. The theoretical Navier-Stokes equations and continuity equation are the basis of the theoretical model of the laminar counter-vortex flow. Results. Assuming the radial velocities are much less than the azimuthal and axial velocities and taking the Oseen approximation, the solution of the Navier - Stokes equations is obtained as Fourier - Bessel series or products of Fourier - Bessel series. In particular, the following were obtained: formulas for calculating the radial-longitudinal distributions of the normalized azimuthal, axial and radial velocities in the flow under study, the velocities are presented graphically in the form of radial profiles; equations for the calculation of current lines and viscous vortex fields, which are also presented in the form of graphs, were obtained. The two-layer and four-layer counter-vortex flows are considered. The analysis of the obtained theoretical results is performed. Conclusions. On the axis at the beginning of the active zone, the formation of a return flow with significant negative velocities is characteristic. This leads to the formation of a recirculation region, the mass exchange between which and the external flow is absent. Cascades of concentric vortexes of such high intensity that are not found in streams of a different nature are generated in the active zone. Calculation formulas include exp (-λ2x/Re) exponent multiplied by Reynolds number in degree b = 0 or b = -1, therefore increasing Reynolds number when b = 0 leads to proportional transfer of arbitrary characteristic counter-vortex flow down the pipe; and at b = -1, the bias of characteristic is accompanied by a proportional decrease in its scale.

Research of Tubular Pumping Systems on Dual-Directional Operation

2009 ◽  
Author(s):  
Long Li ◽  
Wang Ze ◽  
Xuelin Yang ◽  
Dan Li
Keyword(s):  
Fluid Flow ◽  
Vortex Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Experiment Data ◽  
Navier Stokes Equations ◽  
Diffuse Flow ◽  
Pumping Station ◽  
Pumping System

The tubular pumping system on dual-directional operation is used extensively for drainage and feedwater pumping stations of the cities and towns. The performance of the dual-directional operation of pumping systems is different with that of simple-way operation. The article described the three-dimensional fluid flow and the predicted performance of the numerical investigation inside a tubular pumping station on dual-directional operation, based on the Reynolds time-averaged Navier-Stokes equations and the realizable k-ε turbulent flow model, applied the law-of-wall and sliding mesh technique, and comparing with the experiment data. The main phenomena existing in pressure contours, velocity contours, velocity vectors and flow lines is showed. The disturbance of fluid flow from the pump outlet to pumping station channel is researched. The axial-whirling flow, circulation-vortex flow is discovered inside discharge diffuser of tubular pumping station on feed-directional operation. The axial-whirling flow is strengthened as a result of diffuse flow. The circulation-vortex flow of the impeller outlet is enhanced in the radius and reduced in the middle of discharge diffuser without guide vanes. There is more loss of head in discharge diffuser of the channel, comparing with that of the suction reducer. It was a close predicted performance of numerical simulation with that of the experiment in the best efficiency point. There was a more difference between the predicted performances with that of the experiment data on the feedwater-directional operation, comparing that of the drainagewater -directional operation.

scholarly journals Comparison between the Lagrangian and Eulerian Approach in Simulation of Free Surface Air-Core Vortices

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 726
Author(s):  
Maryam Azarpira ◽  
Amir Reza Zarrati ◽  
Pouya Farrokhzad
Keyword(s):  
Vortex Flow ◽  
Stokes Equations ◽  
Computational Cost ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Eulerian Approach ◽  
Advantages And Disadvantages ◽  
Air Core ◽  
Image Velocimetry ◽  
The Difference

The problematic consequences regarding formation of air-core vortices at the intakes and the drastic necessity of a thorough investigation into the phenomenon has resulted in particular attention being placed on Computational Fluid Dynamics (CFD) as an economically viable method. Two main approaches could be taken using CFD, namely the Eulerian and Lagrangian methods each of which is characterized by specific advantages and disadvantages. Whereas many researchers have used the Eulerian approach for vortex simulation, the Lagrangian approach has not been found in the literature. The present study dealt with the comparison of the Lagrangian and Eulerian approaches in the simulation of vortex flow. Simulations based on both approaches were carried out by solving the Navier–Stokes equations accompanied by the LES turbulence model. The results of the numerical model were evaluated in accordance with a physical model for steady vortex flow using particle image velocimetry (PIV), revealing that both approaches are sufficiently capable of simulating the vortex flow but with the difference that the Lagrangian method has greater computational cost with less accuracy.

scholarly journals Modeling and simulation of transitional Rayleigh–Taylor flow with partially averaged Navier–Stokes equations

2021 ◽  
Vol 33 (11) ◽  
pp. 115118
Author(s):  
F. S. Pereira ◽  
F. F. Grinstein ◽  
D. M. Israel ◽  
R. Rauenzahn ◽  
S. S. Girimaji
Keyword(s):  
Modeling And Simulation ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Taylor Flow

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

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