Mixing at high Schmidt number in a complex porous structure

2016 ◽  
Vol 150 ◽  
pp. 74-84 ◽  
Author(s):  
Adrian Zenklusen ◽  
Saša Kenjereš ◽  
Philipp Rudolf von Rohr
Keyword(s):  
Porous Structure ◽  
Schmidt Number ◽  
High Schmidt Number

Simulation of high Schmidt number fluids with dissipative particle dynamics: Parameter identification and robust viscosity evaluation

2021 ◽  
Vol 33 (7) ◽  
pp. 073106 ◽  
Author(s):  
N. Lauriello ◽  
J. Kondracki ◽  
A. Buffo ◽  
G. Boccardo ◽  
M. Bouaifi ◽  
...  
Keyword(s):  
Parameter Identification ◽  
Schmidt Number ◽  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
High Schmidt Number

scholarly journals Lagrangian wall shear stress structures and near-wall transport in high-Schmidt-number aneurysmal flows

2016 ◽  
Vol 790 ◽  
pp. 158-172 ◽  
Author(s):  
Amirhossein Arzani ◽  
Alberto M. Gambaruto ◽  
Guoning Chen ◽  
Shawn C. Shadden
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Shear Stress ◽  
Vector Field ◽  
Wall Shear Stress ◽  
Residence Time ◽  
Vessel Wall ◽  
Schmidt Number ◽  
High Schmidt Number ◽  
Near Wall

The wall shear stress (WSS) vector field provides a signature for near-wall convective transport, and can be scaled to obtain a first-order approximation of the near-wall fluid velocity. The near-wall flow field governs mass transfer problems in convection-dominated open flows with high Schmidt number, in which case a flux at the wall will lead to a thin concentration boundary layer. Such near-wall transport is of particular interest in cardiovascular flows whereby haemodynamics can initiate and progress biological events at the vessel wall. In this study we consider mass transfer processes in pulsatile blood flow of abdominal aortic aneurysms resulting from complex WSS patterns. Specifically, the Lagrangian surface transport of a species released at the vessel wall was advected in forward and backward time based on the near-wall velocity field. Exposure time and residence time measures were defined to quantify accumulation of trajectories, as well as the time required to escape the near-wall domain. The effect of diffusion and normal velocity was investigated. The trajectories induced by the WSS vector field were observed to form attracting and repelling coherent structures that delineated species distribution inside the boundary layer consistent with exposure and residence time measures. The results indicate that Lagrangian WSS structures can provide a template for near-wall transport.

Self-similar decay and mixing of a high-Schmidt-number passive scalar in an oscillating boundary layer in the intermittently turbulent regime

2013 ◽  
Vol 726 ◽  
pp. 338-370 ◽  
Author(s):  
Carlo Scalo ◽  
Ugo Piomelli ◽  
Leon Boegman
Keyword(s):  
Boundary Layer ◽  
Scalar Field ◽  
Equilibrium State ◽  
Turbulent Mixing ◽  
Schmidt Number ◽  
Wall Region ◽  
Turbulent Regime ◽  
High Schmidt Number ◽  
Oscillating Boundary ◽  
Non Equilibrium

AbstractWe performed numerical simulations of dissolved oxygen (DO) transfer from a turbulent flow, driven by periodic boundary-layer turbulence in the intermittent regime, to underlying DO-absorbing organic sediment layers. A uniform initial distribution of oxygen is left to decay (with no re-aeration) as the turbulent transport supplies the sediment with oxygen from the outer layers to be absorbed. A very thin diffusive sublayer at the sediment–water interface (SWI), caused by the high Schmidt number of DO in water, limits the overall decay rate. A decomposition of the instantaneous decaying turbulent scalar field is proposed, which results in the development of similarity solutions that collapse the data in time. The decomposition is then tested against the governing equations, leading to a rigorous procedure for the extraction of an ergodic turbulent scalar field. The latter is composed of a statistically periodic and a steady non-decaying field. Temporal averaging is used in lieu of ensemble averaging to evaluate flow statistics, allowing the investigation of turbulent mixing dynamics from a single flow realization. In spite of the highly unsteady state of turbulence, the monotonically decaying component is surprisingly consistent with experimental and numerical correlations valid for steady high-Schmidt-number turbulent mass transfer. Linearly superimposed onto it is the statistically periodic component, which incorporates all the features of the non-equilibrium state of turbulence. It is modulated by the evolution of the turbulent coherent structures driven by the oscillating boundary layer in the intermittent regime, which are responsible for the violent turbulent production mechanisms. These cause, in turn, a rapid increase of the turbulent mass flux at the edge of the diffusive sublayer. This outer-layer forcing mechanism drives a periodic accumulation of high scalar concentration levels in the near-wall region. The resulting modulated scalar flux across the SWI is delayed by a quarter of a cycle with respect to the wall-shear stress, consistently with the non-equilibrium state of the turbulent mixing.

scholarly journals Experimental Study on the Mixing of High-Schmidt-Number Scalar in Regular/Fractal Grid Turbulence

2013 ◽  
Vol 79 (799) ◽  
pp. 304-316
Author(s):  
Koichi HOSHINO ◽  
Kouji NAGATA ◽  
Yasuhiko SAKAI ◽  
Hiroki SUZUKI ◽  
Ryota UKAI ◽  
...  
Keyword(s):  
Experimental Study ◽  
Schmidt Number ◽  
Grid Turbulence ◽  
High Schmidt Number
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