Detection of memory loss of symmetry in the blockage of a turbulent flow within a duct

2017 ◽  
Vol 28 (06) ◽  
pp. 1750079 ◽  
Author(s):  
F. Rodrigues Santos ◽  
G. da Silva Costa ◽  
A. T. da Cunha Lima ◽  
M. P. de Almeida ◽  
I. C. da Cunha Lima
Keyword(s):  
Turbulent Flow ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Memory Loss ◽  
Point Of View ◽  
Navier Stokes ◽  
Turbulent Model ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Large Eddy

This paper aims to detect memory loss of the symmetry of blockades in ducts and how far the information on the asymmetry of the obstacles travels in the turbulent flow from computational simulations with OpenFOAM. From a practical point of view, it seeks alternatives to detect the formation of obstructions in pipelines. The numerical solutions of the Navier–Stokes equations were obtained through the solver PisoFOAM of the OpenFOAM library, using the large Eddy simulation (LES) for the turbulent model. Obstructions were placed near the duct inlet and, keeping the blockade ratio fixed, five combinations for the obstacles sizes were adopted. The results show that the information about the symmetry is preserved for a larger distance near the ducts wall than in mid-channel. For an inlet velocity of 5[Formula: see text]m/s near the walls the memory is kept up to distance 40 times the duct width, while in mid-channel this distance is reduced almost by half. The maximum distance in which the symmetry breaking memory is preserved shows sensitivity to Reynolds number variations in regions near the duct walls, while in the mid channel that variations do not cause relevant effects to the velocity distribution.

Turbulent Flow Velocity Between Rotating Co-Axial Disks of Finite Radius

1989 ◽  
Vol 111 (3) ◽  
pp. 333-340 ◽  
Author(s):  
J. F. Louis ◽  
A. Salhi
Keyword(s):  
Turbulent Flow ◽  
Turbulence Model ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Finite Radius ◽  
Navier Stokes Equations ◽  
Rotating Cavity ◽  
Tangential Wall ◽  
Frictional Forces

The turbulent flow between two rotating co-axial disks is driven by frictional forces. The prediction of the velocity field can be expected to be very sensitive to the turbulence model used to describe the viscosity close to the walls. Numerical solutions of the Navier–Stokes equations, using a k–ε turbulence model derived from Lam and Bremhorst, are presented and compared with experimental results obtained in two different configurations: a rotating cavity and the outflow between a rotating and stationary disk. The comparison shows good overall agreement with the experimental data and substantial improvements over the results of other analyses using the k–ε models. Based on this validation, the model is applied to the flow between counterrotating disks and it gives the dependence of the radial variation of the tangential wall shear stress on Rossby number.

Numerical and scalability analysis of an unstructured Cartesian flow solver

2011 ◽  
Vol 225 (9) ◽  
pp. 2138-2148 ◽  
Author(s):  
Y H Yau ◽  
A Badarudin ◽  
P A Rubini
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Source Codes ◽  
Scalability Analysis ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Parallel Code

This article describes a systematic approach in building a flow solver for large eddy simulation (LES). Finite volume discretizations of the filtered, incompressible, Navier–Stokes equations were explained. The theory progresses to the description of the step-by-step process (mainly in increasing functionality or capability) in developing a three-dimensional, unstructured Cartesian mesh, parallel code after evaluating numerical factors, and available options carried out earlier. This was followed by a presentation of results produced from the simulations of laminar flow, related to the validation of the source codes, which indicates that the flow solver is behaving satisfactorily.

Large Eddy Simulation of Turbulent-Cavitation Interactions in a Venturi Nozzle

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Nagendra Dittakavi ◽  
Aditya Chunekar ◽  
Steven Frankel
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Small Scale ◽  
Navier Stokes Equations ◽  
Vapor Cavity ◽  
Eddy Simulation ◽  
Downstream Region ◽  
Large Eddy ◽  
Venturi Nozzle

Large eddy simulation of turbulent cavitating flow in a venturi nozzle is conducted. The fully compressible Favre-filtered Navier–Stokes equations are coupled with a homogeneous equilibrium cavitation model. The dynamic Smagorinsky subgrid-scale turbulence model is employed to close the filtered nonlinear convection terms. The equations are numerically integrated in the context of a generalized curvilinear coordinate system to facilitate geometric complexities. A sixth-order compact finite difference scheme is employed for the Navier–Stokes equations with the AUSM+-up scheme to handle convective terms in the presence of large density gradients. The stiffness of the system due to the incompressibility of the liquid phase is addressed through an artificial increase in the Mach number. The simulation predicts the formation of a vapor cavity at the venturi throat with an irregular shedding of the small scale vapor structures near the turbulent cavity closure region. The vapor formation at the throat is observed to suppress the velocity fluctuations due to turbulence. The collapse of the vapor structures in the downstream region is a major source of vorticity production, resulting into formation of hair-pin vortices. A detailed analysis of the vorticity transport equation shows a decrease in the vortex-stretching term due to cavitation. A substantial increase in the baroclinic torque is observed in the regions where the vapor structures collapse. A spectra of the pressure fluctuations in the far-field downstream region show an increase in the acoustic noise at high frequencies due to cavitation.

Large Eddy Simulation of Flow Past Circular Cylinder Based on the Least Square Meshless Method

2013 ◽  
Vol 394 ◽  
pp. 128-133
Author(s):  
Yuan Ding Wang ◽  
Jun Jie Tan ◽  
Xiao Wei Cai ◽  
Deng Feng Ren
Keyword(s):  
Circular Cylinder ◽  
Large Eddy Simulation ◽  
Meshless Method ◽  
Stokes Equations ◽  
Least Square ◽  
Scale Model ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Large Eddy

Large Eddy Simulation (LES) based on the least square meshless method was proposed in the present paper to simulate the classical turbulent flow around a stationary 2D circular cylinder. The subgrid scale model of Smagorinsky-Lily was employed to close the Navier-Stokes equations filtered by Favre filter. The Reynolds number is 3900 which means that the flow is subcritical and the wake is fully turbulent but the cylinder boundary is still laminar. Results obtained in this paper were evaluated by comparison with published experimental results and other numerical results. The results obtained in the present work show better agreement with the experimental values than other two-dimensional LES results .

LARGE EDDY SIMULATION OF SEDIMENT-LADEN TURBULENT FLOW IN AN OPEN CHANNEL

2008 ◽  
Vol 22 (16) ◽  
pp. 2517-2527 ◽  
Author(s):  
ZHANHONG WAN ◽  
ZHILIN SUN ◽  
ZHENJIANG YOU ◽  
QIYAN ZHANG
Keyword(s):  
Large Eddy Simulation ◽  
Open Channel ◽  
Stokes Equations ◽  
Sediment Concentration ◽  
Continuous Phase ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Concentration Equation

Sediment transport in fully developed turbulent open channel flow has been investigated using large eddy simulation (LES) of the incompressible Navier–Stokes equations. The scalar transport equation of the sediments concentration, which is based on the continuous-phase approach, is adopted. The settling process is taken into account with a modified settling velocity appearing in the sediment concentration equation. A Smagorinsky model allowing for the interaction between the fluid flow and the suspended sediment is used to simulate the unresolved, subgrid scale terms. The LES results are compared with the experimental data, and good general agreement is achieved.

Large-Eddy Simulation of Shallow Water Langmuir Turbulence Using Isogeometric Analysis and the Residual-Based Variational Multiscale Method

2011 ◽  
Vol 79 (1) ◽  
Author(s):  
Andrés E. Tejada-Martínez ◽  
Ido Akkerman ◽  
Yuri Bazilevs
Keyword(s):  
Large Eddy Simulation ◽  
Isogeometric Analysis ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Variational Multiscale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Coastal Shelf ◽  
Current Interaction

We develop a residual-based variational multiscale (RBVMS) method based on isogeometric analysis for large-eddy simulation (LES) of wind-driven shear flow with Langmuir circulation (LC). Isogeometric analysis refers to our use of NURBS (Non-Uniform Rational B-splines) basis functions which have been proven to be highly accurate in LES of turbulent flows (Bazilevs, Y., et al. 2007, Comput. Methods Appl. Mech. Eng., 197, pp. 173–201). LC consists of stream-wise vortices in the direction of the wind acting as a secondary flow structure to the primary, mean component of the flow driven by the wind. LC results from surface wave-current interaction and often occurs within the upper ocean mixed layer over deep water and in coastal shelf regions under wind speeds greater than 3 m s−1. Our LES of wind-driven shallow water flow with LC is representative of a coastal shelf flow where LC extends to the bottom and interacts with the sea bed boundary layer. The governing LES equations are the Craik-Leivobich equations (Tejada-Martínez, A. E., and Grosch, C. E., 2007, J. Fluid Mech., 576, pp. 63–108; Gargett, A. E., 2004, Science, 306, pp. 1925–1928), consisting of the time-filtered Navier-Stokes equations. These equations possess the same structure as the Navier-Stokes equations with an extra vortex force term accounting for wave-current interaction giving rise to LC. The RBVMS method with quadratic NURBS is shown to possess good convergence characteristics in wind-driven flow with LC. Furthermore, the method yields LC structures in good agreement with those computed with the spectral method in (Thorpe, S. A., 2004, Annu. Rev. Fluids Mech., 36, pp. 584 55–79) and measured during field observations in (D’Alessio, S. J., et al., 1998, J. Phys. Oceanogr., 28, pp. 1624–1641; Kantha, L., and Clayson, C. A., 2004, Ocean Modelling, 6, pp. 101–124).

Numerical Estimation of Aerodynamic Characteristics of Footbridge Deck

2014 ◽  
Vol 617 ◽  
pp. 291-295
Author(s):  
Robert Šoltýs ◽  
Michal Tomko
Keyword(s):  
Fluid Flow ◽  
Stokes Equations ◽  
Boundary Layer Separation ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Parameters

For estimation of aerodynamic characteristics of cable-stayed footbridge deck a computational fluid dynamics (CFD) has been used. An incompressible fluid flow with Navier-Stokes equations has been applied. An adequate numerical model has been created to obtain accurate values of aerodynamic characteristics. Preliminary determination of simulation parameters have been estimated using laminar fluid flow model. Subsequently, Smagorinsky large-eddy simulation (LES) turbulent model has been applied with different simulation parameters to obtain converged values. The boundary layer separation regions and downwind vortex shedding has been observed.

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