Direct numerical simulation of turbulent scalar transport in a channel with wall injection

2004 ◽  
Vol 18 (4) ◽  
pp. 597-605
Author(s):  
Yang Na
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Scalar Transport ◽  
Wall Injection

Direct numerical simulation of scalar transport in turbulent flows over progressive surface waves

2017 ◽  
Vol 819 ◽  
pp. 58-103 ◽  
Author(s):  
Di Yang ◽  
Lian Shen
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Viscous Sublayer ◽  
Wall Turbulence ◽  
Scalar Transport ◽  
Wave Age ◽  
Wave Surface ◽  
Scalar Flux ◽  
Flat Wall

The transport of passive scalars in turbulent flows over progressive water waves is studied using direct numerical simulation. A combined pseudo-spectral and finite-difference scheme on a wave-surface-fitted grid is used to simulate the flow and scalar fields above the wave surface. Three representative wave ages (i.e. wave-to-wind speed ratios) are considered, corresponding to slow, intermediate and fast wind-waves, respectively. For each wave condition, four Schmidt numbers are considered for the scalar transport. The presence of progressive surface waves is found to induce significant wave-phase-correlated variation to the scalar field, with the phase dependence varying with the wave age. The time- and plane-averaged profiles of the scalar over waves of various ages exhibit similar vertical structures as those found in turbulence over a flat wall, but with the von Kármán constant and effective wave surface roughness for the mean scalar profile exhibiting considerable variation with the wave age. The profiles of the root-mean-square scalar fluctuations and the horizontal scalar flux exhibit good scaling in the viscous sublayer that agrees with the scaling laws previously reported for flat-wall turbulence, but with noticeable wave-induced variation in the viscous wall region. The profiles of the vertical scalar flux in the viscous sublayer exhibit apparent discrepancies from the reported scaling law for flat-wall turbulence, due to a negative vertical flux region above the windward face of the wave crest. Direct observation and quadrant-based conditional averages indicate that the wave-dependent distributions of the scalar fluctuations and fluxes are highly correlated with the coherent vortical structures in the turbulence, which exhibit clear wave-dependent characteristics in terms of both shape and preferential location.

Investigation of Scalar Transport Closures Using Direct Numerical Simulation

2003 ◽  
pp. 787-788 ◽  
Author(s):  
Anthony Keating ◽  
Matthew Bilson ◽  
Klaus Bremhorst ◽  
Srdjan Nesic
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Scalar Transport

Direct numerical simulation of passive scalar transport in transverse jets

2008 ◽  
Vol 598 ◽  
pp. 335-360 ◽  
Author(s):  
SUMAN MUPPIDI ◽  
KRISHNAN MAHESH
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Near Field ◽  
Eddy Diffusivity ◽  
Passive Scalar ◽  
Scalar Transport ◽  
Transverse Jets ◽  
Downstream Side ◽  
Gradient Diffusion ◽  
Passive Scalar Transport

Direct numerical simulation is used to study passive scalar transport and mixing in a round turbulent jet, in a laminar crossflow. The ratio of the jet velocity to that of the crossflow is 5.7, the Schmidt number of the scalar is 1.49, and the jet-exit Reynolds number is 5000. The scalar field is used to compute entrainment of the crossflow fluid by the jet. It is shown that the bulk of this entrainment occurs on the downstream side of the jet. Also, the transverse jet entrains more fluid than a regular jet even when the jet has not yet bent into the crossflow. The transverse jet's enhanced entrainment is explained in terms of the pressure field around the jet. The acceleration imposed by the crossflow deforms the jet cross-section on the downstream side, which sets up a pressure gradient that drives downstream crossflow fluid toward the jet. The simulation results are used to comment on the applicability of the gradient–diffusion hypothesis to compute passive scalar mixing in this flow field. Computed values of the eddy diffusivity show significant scatter, and a pronounced anisotropy. The near field also exhibits counter gradient diffusion.

Sign in / Sign up

Export Citation Format

Share Document