Mathematical models for the numerical study of turbulent flows

1988 ◽  
Vol 11 (2) ◽  
pp. 121-136 ◽  
Author(s):  
Tom I‐Ping Shih
Keyword(s):  
Mathematical Models ◽  
Turbulent Flows ◽  
Numerical Study

scholarly journals A Review of Russian Snow Avalanche Models—From Analytical Solutions to Novel 3D Models

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 77 ◽  
Author(s):  
Margarita Eglit ◽  
Alexander Yakubenko ◽  
Julia Zayko
Keyword(s):  
Soviet Union ◽  
Mathematical Models ◽  
Turbulent Flows ◽  
Analytical Solutions ◽  
Numerical Study ◽  
3D Models ◽  
Snow Avalanches ◽  
The Soviet Union ◽  
Averaged Equations ◽  
Mass Entrainment

The article is a review of mathematical models of snow avalanches that have been proposed since the middle of the 20th century and are still in use. The main attention is paid to the work of researchers from the Soviet Union and Russia, since many of their works were published only in Russian and are not widely available. Mathematical models of various levels of complexity for avalanches of various types—from dense to powder-snow avalanches—are discussed. Analytical solutions including formulas for the avalanche front speed are described. The results of simulations of the movement of avalanches are given that were used to create avalanche hazard maps. The last part of the article is devoted to constructing models of a new type, in which avalanches are considered as laminar or turbulent flows of non-Newtonian fluids, using the full (not depth-averaged) equations of continuum mechanics. The results of a numerical study of the effect of non-Newtonian rheology and mass entrainment on the avalanche dynamics are presented.

scholarly journals Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1079
Author(s):  
Lena Mahl ◽  
Patrick Heneka ◽  
Martin Henning ◽  
Roman B. Weichert
Keyword(s):  
Boundary Conditions ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Free Water ◽  
Lateral Wall ◽  
Lateral Spreading ◽  
Propagation Length ◽  
Vertical Slot ◽  
Surface Jets

The efficiency of a fishway is determined by the ability of immigrating fish to follow its attraction flow (i.e., its jet) to locate and enter the fishway entrance. The hydraulic characteristics of fishway entrance jets can be simplified using findings from widely investigated surface jets produced by shaped nozzles. However, the effect of the different boundary conditions of fishway entrance jets (characterized by vertical entrance slots) compared to nozzle jets must be considered. We investigate the downstream propagation of attraction jets from the vertical slot of a fishway entrance into a quiescent tailrace, considering the following boundary conditions not considered for nozzle jets: (1) slot geometry, (2) turbulence characteristics of the approach flow to the slot, and (3) presence of a lateral wall downstream of the slot. We quantify the effect of these boundary conditions using three-dimensional hydrodynamic-numeric flow simulations with DES and RANS turbulence models and a volume-of-fluid method (VoF) to simulate the free water surface. In addition, we compare jet propagation with existing analytical methods for describing jet propagations from nozzles. We show that a turbulent and inhomogeneous approach flow towards a vertical slot reduces the propagation length of the slot jet in the tailrace due to increased lateral spreading compared to that of a jet produced by a shaped nozzle. An additional lateral wall in the tailrace reduces lateral spreading and significantly increases the propagation length. For highly turbulent flows at fishway entrances, the RANS model tends to overestimate the jet propagation compared to the transient DES model.

A numerical study on combined baffles quick-separation device

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ehsan Dehdarinejad ◽  
Morteza Bayareh ◽  
Mahmud Ashrafizaadeh
Keyword(s):  
Turbulent Flows ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Turbulence Models ◽  
Complete Separation ◽  
Solid Particles ◽  
Flow Rates ◽  
Separation Device ◽  
Coupling Technique ◽  
Laminar And Turbulent Flows

Abstract The transfer of particles in laminar and turbulent flows has many applications in combustion systems, biological, environmental, nanotechnology. In the present study, a Combined Baffles Quick-Separation Device (CBQSD) is simulated numerically using the Eulerian-Lagrangian method and different turbulence models of RNG k-ε, k-ω, and RSM for 1–140 μm particles. A two-way coupling technique is employed to solve the particles’ flow. The effect of inlet flow velocity, the diameter of the splitter plane, and solid particles’ flow rate on the separation efficiency of the device is examined. The results demonstrate that the RSM turbulence model provides more appropriate results compared to RNG k-ε and k-ω models. Four thousand two hundred particles with the size distribution of 1–140 µm enter the device and 3820 particles are trapped and 380 particles leave the device. The efficiency for particles with a diameter greater than 28 µm is 100%. The complete separation of 22–28 μm particles occurs for flow rates of 10–23.5 g/s, respectively. The results reveal that the separation efficiency increases by increasing the inlet velocity, the device diameter, and the diameter of the particles.

scholarly journals Numerical Study of Turbulent Flows and Heat Transfer in Coupled Industrial-Scale Tundish of a Continuous Casting Material in Steel Production

2018 ◽  
Author(s):  
Jose Adilson de Castro ◽  
Bruno Amaral Pereira ◽  
Roan Sampaio de Souza ◽  
Elizabeth Mendes de Oliveira ◽  
Ivaldo Leão Ferreira
Keyword(s):  
Heat Transfer ◽  
Continuous Casting ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Steel Production ◽  
Industrial Scale

scholarly journals A numerical study of the alpha model for two-dimensional magnetohydrodynamic turbulent flows

2005 ◽  
Vol 17 (3) ◽  
pp. 035112 ◽  
Author(s):  
Pablo D. Mininni ◽  
David C. Montgomery ◽  
Annick G. Pouquet
Keyword(s):  
Turbulent Flows ◽  
Numerical Study ◽  
Two Dimensional

Deposition of Small Particles From Turbulent Flows

2003 ◽  
Author(s):  
Z. Wu ◽  
J. B. Young
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
Channel Flow ◽  
Gas Turbines ◽  
Particle Deposition ◽  
Numerical Study ◽  
Turbulent Channel Flow ◽  
Brownian Diffusion ◽  
Small Particles ◽  
Two Fluid

This paper deals with particle deposition onto solid walls from turbulent flows. The aim of the study is to model particle deposition in industrial flows, such as the one in gas turbines. The numerical study has been carried out with a two fluid approach. The possible contribution to the deposition from Brownian diffusion, turbulent diffusion and shear-induced lift force are considered in the study. Three types of turbulent two-phase flows have been studied: turbulent channel flow, turbulent flow in a bent duct and turbulent flow in a turbine blade cascade. In the turbulent channel flow case, the numerical results from a two-dimensional code show good agreement with numerical and experimental results from other resources. Deposition problem in a bent duct flow is introduced to study the effect of curvature. Finally, the deposition of small particles on a cascade of turbine blades is simulated. The results show that the current two fluid models are capable of predicting particle deposition rates in complex industrial flows.

Numerical Study of Mass Dispersion in Laminar and Turbulent Flows Through a Pipeline

2002 ◽  
Author(s):  
Horacio Antonio Flo´rez Guzma´n
Keyword(s):  
Turbulent Flows ◽  
Molecular Diffusion ◽  
Numerical Study ◽  
Computer Code ◽  
Finite Difference Schemes ◽  
Entire Volume ◽  
Two Fluids ◽  
Mass Dispersion ◽  
Miscible Fluid ◽  
Domain Discretization

A computer code for solving the equations of mass diffusion has been developed and applied to study the molecular-level mixing between two fluids inside a pipe. First, one fluid occupies the entire volume within the pipe, and then a second miscible fluid is forced into the pipe, developing a mixing process through the interface between the fluids. This phenomenon occurs as the combination of molecular diffusion, variation of velocity over the cross-section and turbulence. The code developed for this study is based on the finite element method for domain discretization and standard finite difference schemes for temporal discretization. Comparison with experimental data shows that the code is able to reproduce the physical trends and gives good predictions for engineering applications. A grid independence analysis is presented for all computations.

The Reynold’s Number Effect in High Swirling Flow in Unconfined Burner

2015 ◽  
Vol 72 (4) ◽  
Author(s):  
Norwazan A. R. ◽  
Mohammad Nazri Mohd. Jaafar
Keyword(s):  
Turbulent Flows ◽  
Gas Turbines ◽  
Swirling Flow ◽  
Numerical Study ◽  
Isothermal Condition ◽  
Navier Stokes ◽  
Reacting Flow ◽  
Ansys Fluent ◽  
Inlet Velocity ◽  
Burner Exit

The numerical simulations of swirling turbulent flows in isothermal condition in combustion chamber of burner were investigated. The aim is to characterize the main flow structures and turbulence in a combustor that is relevant to gas turbines. Isothermal flows with different inlet flow velocities were considered to demonstrate the effect of radial velocity. The inlet velocity, Uo is varied from 30 m/s to 60 m/s represent a high Reynolds number up to 3.00 X 105. The swirler was located at the upstream of combustor with the swirl number of 0.895. A numerical study of non-reacting flow in the burner region was performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) approach method was applied with the standard k-ɛ turbulence equations. The various velocity profiles were different after undergoing the different inlet velocity up to the burner exit. The results of velocity profile showed that the high U0 give better swirling flow patterns.

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