The effect of streamwise braid vortices on the particle dispersion in a plane mixing layer. I. Equilibrium points and their stability

1996 ◽  
Vol 8 (3) ◽  
pp. 715-733 ◽  
Author(s):  
B. Marcu ◽  
E. Meiburg
Keyword(s):  
Equilibrium Points ◽  
Mixing Layer ◽  
Particle Dispersion ◽  
Plane Mixing Layer ◽  
Layer I

Research on particle dispersion in a plane mixing layer with coherent structures

2003 ◽  
Vol 19 (6) ◽  
pp. 535-542 ◽  
Author(s):  
Lin Jonahing ◽  
Lin Jiang ◽  
Shao Xueming ◽  
Shi Xing
Keyword(s):  
Coherent Structures ◽  
Mixing Layer ◽  
Particle Dispersion ◽  
Plane Mixing Layer

Effect of Particle Residence Time on Particle Dispersion in a Plane Mixing Layer

1993 ◽  
Vol 115 (4) ◽  
pp. 751-759 ◽  
Author(s):  
Tsuneaki Ishima ◽  
Koichi Hishida ◽  
Masanobu Maeda
Keyword(s):  
Gas Phase ◽  
Residence Time ◽  
Time Scale ◽  
Characteristic Time ◽  
Mixing Layer ◽  
Particle Dispersion ◽  
Laser Doppler Velocimeter ◽  
Characteristic Time Scale ◽  
Two Phase ◽  
Particle Residence Time

A particle dispersion has been experimentally investigated in a two-dimensional mixing layer with a large relative velocity between particle and gas-phase in order to clarify the effect of particle residence time on particle dispersion. Spherical glass particles 42, 72, and 135 μm in diameter were loaded directly into the origin of the shear layer. Particle number density and the velocities of both particle and gas phase were measured by a laser Doppler velocimeter with modified signal processing for two-phase flow. The results confirmed that the characteristic time scale of the coherent eddy apparently became equivalent to a shorter characteristic time scale due to a less residence time. The particle dispersion coefficients were well correlated to the extended Stokes number defined as the ratio of the particle relaxation time to the substantial eddy characteristic time scale which was evaluated by taking account of the particle residence time.

Spanwise averaging of plane mixing layer properties

AIAA Journal ◽  
1992 ◽  
Vol 30 (3) ◽  
pp. 835-837 ◽  
Author(s):  
James H. Bell ◽  
Michael W. Plesniak ◽  
Rabindra D. Mehta
Keyword(s):  
Mixing Layer ◽  
Plane Mixing Layer

Streamwise vortex meander in a plane mixing layer

1993 ◽  
Vol 5 (8) ◽  
pp. 1983-1991 ◽  
Author(s):  
Richard L. LeBoeuf ◽  
Rabindra D. Mehta
Keyword(s):  
Mixing Layer ◽  
Streamwise Vortex ◽  
Plane Mixing Layer

scholarly journals Assumptions about footprint layer heights influence the quantification of emission sources: a case study for Cyprus

2017 ◽  
Vol 17 (18) ◽  
pp. 10955-10967 ◽  
Author(s):  
Imke Hüser ◽  
Hartwig Harder ◽  
Angelika Heil ◽  
Johannes W. Kaiser
Keyword(s):  
Mixing Layer ◽  
Particle Dispersion ◽  
Reasonable Assumption ◽  
Night Time ◽  
Meteorological Model ◽  
Source Contributions ◽  
Time Sensitivity ◽  
Tracer Particles ◽  
Constant Height ◽  
The Impact

Abstract. Lagrangian particle dispersion models (LPDMs) in backward mode are widely used to quantify the impact of transboundary pollution on downwind sites. Most LPDM applications count particles with a technique that introduces a so-called footprint layer (FL) with constant height, in which passing air tracer particles are assumed to be affected by surface emissions. The mixing layer dynamics are represented by the underlying meteorological model. This particle counting technique implicitly assumes that the atmosphere is well mixed in the FL. We have performed backward trajectory simulations with the FLEXPART model starting at Cyprus to calculate the sensitivity to emissions of upwind pollution sources. The emission sensitivity is used to quantify source contributions at the receptor and support the interpretation of ground measurements carried out during the CYPHEX campaign in July 2014. Here we analyse the effects of different constant and dynamic FL height assumptions. The results show that calculations with FL heights of 100 and 300 m yield similar but still discernible results. Comparison of calculations with FL heights constant at 300 m and dynamically following the planetary boundary layer (PBL) height exhibits systematic differences, with daytime and night-time sensitivity differences compensating for each other. The differences at daytime when a well-mixed PBL can be assumed indicate that residual inaccuracies in the representation of the mixing layer dynamics in the trajectories may introduce errors in the impact assessment on downwind sites. Emissions from vegetation fires are mixed up by pyrogenic convection which is not represented in FLEXPART. Neglecting this convection may lead to severe over- or underestimations of the downwind smoke concentrations. Introducing an extreme fire source from a different year in our study period and using fire-observation-based plume heights as reference, we find an overestimation of more than 60  % by the constant FL height assumptions used for surface emissions. Assuming a FL that follows the PBL may reproduce the peak of the smoke plume passing through but erroneously elevates the background for shallow stable PBL heights. It might thus be a reasonable assumption for open biomass burning emissions wherever observation-based injection heights are not available.

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