Numerical Investigation of Channel Flows with Emphasis on Coherent Structures and Turbulence Anisotropy

2016 ◽  
Author(s):  
Luiz Augusto C. Schiavo ◽  
William Wolf ◽  
Joao Luiz F. Azevedo
Keyword(s):  
Numerical Investigation ◽  
Coherent Structures ◽  
Channel Flows ◽  
Turbulence Anisotropy

Interactions of Flow Structure With Nano- and Micro-Particles in Turbulent Channel Flows

2018 ◽  
Author(s):  
Amir A. Mofakham ◽  
Goodarz Ahmadi ◽  
John McLaughlin
Keyword(s):  
Relaxation Time ◽  
Coherent Structures ◽  
Concentration Distribution ◽  
Channel Flows ◽  
Small Scale ◽  
Turbulence Structure ◽  
Micro Particles ◽  
Turbulent Channel Flows ◽  
Wide Range ◽  
Near Wall

This study is concerned with the effects of the flow structures including the near-wall coherent eddies in turbulent channel flows on the dispersion and deposition of nano- and micro-particles. A pseudo-spectral computational code was used for direct numerical simulations (DNS) of the Navier-Stokes equations and the corresponding time histories of the instantaneous fluid velocities were evaluated. Under the oneway coupling assumption, the trajectories of a wide range of particle sizes from 10 nm to 80 μm with dimensionless relaxation time of 2.2e−6 to 142 were obtained by solving the particle equation of motion including Stokes drag and Brownian excitations. Dispersion and deposition of particles in the turbulent flow were evaluated and the effects of turbulence structure on different size particles were studied. The simulation results showed that the concentration distribution of small particles that behave like fluid tracer particles were quite random. However, the preferential concentrations appeared as the dimensionless relaxation time increased to 2–20. In particular, the influence of coherent structures in the near-wall regions was clearly detectable on the concentration distribution of particles, as well as, in their deposition pattern. For τ+ = 20 particles due to the increase of relaxation time and inertia of particles, the small-scale turbulent features were filtered out and only the effect of large-scale turbulent eddies could be identified. For τ+ = 2–20 particles, the ensemble/time average of the position of the deposited particles showed specific spacing which was comparable to the size of the near-wall coherent structures.

NONLINEAR EVOLUTION OF TURBULENT COHERENT STRUCTURES IN CHANNEL FLOWS

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1539-1542
Author(s):  
ZHANG LI ◽  
DENGBIN TANG ◽  
LINLIN GUO
Keyword(s):  
Coherent Structures ◽  
Nonlinear Evolution ◽  
Three Dimensional ◽  
Channel Flows ◽  
Navier Stokes ◽  
Theoretic Model ◽  
Compact Difference Scheme ◽  
Navier Stokes Equation ◽  
Turbulent Coherent Structures ◽  
Dimensional Coupling

The generation and the development of turbulent coherent structures in channel flows are investigated by using numerical simulation of Navier-Stokes equation and the theoretic model of turbulent coherent structures built up by the flow stability theories. The three-dimensional coupling compact difference scheme with high accuracy and resolution developed can be applied to the calculative region including points near the boundary. The results computed show nonlinear evolution process and characteristics of Reynolds stress, stream-wise vortices and span-wise vorticities, especially the nonlinear interactions between different coherent structures.

Turbulence anisotropy and intermittency in open-channel flows on rough beds

2020 ◽  
Vol 32 (11) ◽  
pp. 115127
Author(s):  
F. Coscarella ◽  
N. Penna ◽  
S. Servidio ◽  
R. Gaudio
Keyword(s):  
Open Channel ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Turbulence Anisotropy ◽  
Rough Beds
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