Three-dimensional computations of non-isothermal wall bounded complex flows

2008 ◽  
pp. 191-197 ◽  
Author(s):  
P. Dewagenaere ◽  
P. Esposito ◽  
F. Lana ◽  
P. L. Viollet
Keyword(s):  
Three Dimensional ◽  
Complex Flows ◽  
Bounded Complex ◽  
Isothermal Wall

Near-Wall Turbulent Pressure Diffusion Modeling and Influence in Three-Dimensional Secondary Flows

2006 ◽  
Vol 129 (5) ◽  
pp. 634-642 ◽  
Author(s):  
E. Sauret ◽  
I. Vallet
Keyword(s):  
Diffusion Model ◽  
Turbulent Diffusion ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Moment Closure ◽  
Complex Flows ◽  
Diffusion Term ◽  
Pressure Diffusion ◽  
Turbulent Pressure ◽  
Near Wall

The purpose of this paper is to develop a second-moment closure with a near-wall turbulent pressure diffusion model for three-dimensional complex flows, and to evaluate the influence of the turbulent diffusion term on the prediction of detached and secondary flows. A complete turbulent diffusion model including a near-wall turbulent pressure diffusion closure for the slow part was developed based on the tensorial form of Lumley and included in a re-calibrated wall-normal-free Reynolds-stress model developed by Gerolymos and Vallet. The proposed model was validated against several one-, two, and three-dimensional complex flows.

Three-dimensional direct numerical simulation of a turbulent lifted hydrogen jet flame in heated coflow: a chemical explosive mode analysis

2010 ◽  
Vol 652 ◽  
pp. 45-64 ◽  
Author(s):  
T. F. LU ◽  
C. S. YOO ◽  
J. H. CHEN ◽  
C. K. LAW
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Near Field ◽  
Three Dimensional ◽  
Mode Analysis ◽  
Scalar Dissipation ◽  
Complex Flows ◽  
Jet Flame ◽  
Auto Ignition ◽  
Grid Points

A chemical explosive mode analysis (CEMA) was developed as a new diagnostic to identify flame and ignition structure in complex flows. CEMA was then used to analyse the near-field structure of the stabilization region of a turbulent lifted hydrogen–air slot jet flame in a heated air coflow computed with three-dimensional direct numerical simulation. The simulation was performed with a detailed hydrogen–air mechanism and mixture-averaged transport properties at a jet Reynolds number of 11000 with over 900 million grid points. Explosive chemical modes and their characteristic time scales, as well as the species involved, were identified from the Jacobian matrix of the chemical source terms for species and temperature. An explosion index was defined for explosive modes, indicating the contribution of species and temperature in the explosion process. Radical and thermal runaway can consequently be distinguished. CEMA of the lifted flame shows the existence of two premixed flame fronts, which are difficult to detect with conventional methods. The upstream fork preceding the two flame fronts thereby identifies the stabilization point. A Damköhler number was defined based on the time scale of the chemical explosive mode and the local instantaneous scalar dissipation rate to highlight the role of auto-ignition in affecting the stabilization points in the lifted jet flame.

Calculations of three-dimensional viscous flow in a multiblade centrifugal fan by modelling blade forces

2003 ◽  
Vol 217 (3) ◽  
pp. 287-297 ◽  
Author(s):  
S-J Seo ◽  
K-Y Kim ◽  
S-H Kang
Keyword(s):  
Mathematical Model ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Fan ◽  
Complex Flows ◽  
Flow Through ◽  
Volume Method ◽  
The Mathematical Model

A numerical study is presented for Reynolds-averaged Navier-Stokes analysis of three-dimensional turbulent flows in a multiblade centrifugal fan. Present work aims at development of a relatively simple analysis method for these complex flows. A mathematical model of impeller forces is obtained from the integral analysis of the flow through the impeller. A finite volume method for discretization of governing equations and a standard k-ɛ model as turbulence closure are employed. For the validation of the mathematical model, the computational results for velocity components, static pressure, and flow angles at the exit of the impeller were compared with experimental data. The comparisons show generally good agreement, especially at higher flow coefficients.

scholarly journals WAVE-GENERATED FLOWS ON THE WATER SURFACE

2016 ◽  
Vol 42 ◽  
pp. 1660179
Author(s):  
MICHAEL SHATS ◽  
HORST PUNZMANN ◽  
NICOLAS FRANCOIS ◽  
HUA XIA
Keyword(s):  
Water Surface ◽  
Large Scale ◽  
Three Dimensional ◽  
Surface Flow ◽  
Theoretical Problem ◽  
Complex Flows ◽  
Localized Source ◽  
New Methods ◽  
Flow Generation ◽  
Surface Jets

Predicting trajectories of fluid parcels on the water surface perturbed by waves is a difficult mathematical and theoretical problem. It is even harder to model flows generated on the water surface due to complex three-dimensional wave fields, which commonly result from the modulation instability of planar waves. We have recently shown that quasi-standing, or Faraday, waves are capable of generating horizontal fluid motions on the water surface whose statistical properties are very close to those in two-dimensional turbulence. This occurs due to the generation of horizontal vortices. Here we show that progressing waves generated by a localized source are also capable of creating horizontal vortices. The interaction between such vortices can be controlled and used to create stationary surface flows of desired topology. These results offer new methods of surface flow generation, which allow engineering inward and outward surface jets, large-scale vortices and other complex flows. The new principles can be also be used to manipulate floaters on the water surface and to form well-controlled Lagrangian coherent structures on the surface. The resulting flows are localized in a narrow layer near the surface, whose thickness is less than one wavelength.

Three-Dimensional VOF Simulations of Laminar Fluid Flows in Micro-Pipes Containing Superhydrophobic Walls With Micro-Posts and Micro-Ridges

2016 ◽  
Author(s):  
Mohamed E. Eleshaky
Keyword(s):  
Reynolds Number ◽  
Solid Fraction ◽  
Three Dimensional ◽  
Fluid Flows ◽  
Complex Flows ◽  
Air Water Interface ◽  
Monotonically Decreasing Function ◽  
Frictional Performance ◽  
Flow Field Characteristics ◽  
Flow Enhancement

This paper investigates water flowfield characteristics inside micro-pipes containing superhydrophobic walls under laminar flow conditions. It also investigates the effects of solid fraction, wall pattern, and Reynolds number on both skin friction drag and flow field characteristics. A transient, incompressible, three-dimensional, volume-of-fluid (VOF) methodology has been employed to continuously track the air–water interface and to visualize the dynamic behavior of the complex flows inside micro-pipes containing different superhydrophobic wall features (square micro-posts and longitudinal micro-ridges). The results of the present simulations show that micro-pipes containing superhydrophobic walls with longitudinal micro-ridges features have a better frictional performance than those having square posts features. The predicted results also show that the frictional performance of micro-pipes is a monotonically decreasing function of Reynolds number for both patterns examined in the present study. In addition, as the solid fraction decreases, the flow enhancement of superhydrophobic micro-pipes increases and it seems, based on the studied cases, to reach an asymptotic value. However, a further study is needed to confirm this latter issue.

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