An experimental trace gas investigation of fluid transport and mixing in a circular-to-rectangular transition duct

Abstract. We present airborne in-situ trace gas measurements which were performed on eight campaigns between November 2001 and July 2003 during the SPURT-project (SPURenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region). The measurements on a quasi regular basis allowed an overview of the seasonal variations of the trace gas distribution in the tropopause region over Europe from 35°-75°N to investigate the influence of transport and mixing across the extratropical tropopause on the lowermost stratosphere. From the correlation of CO and O3 irreversible mixing of tropospheric air into the lowermost stratosphere is identified. The CO distribution indicates that transport and subsequent mixing of tropospheric air across the extratropical tropopause predominantly affects a layer, which closely follows the shape of the local tropopause. In addition, the seasonal cycle of CO2 illustrates the strong coupling of that layer to the extratropical troposphere. Both, horizontal gradients of CO on isentropes as well as the CO-O3-distribution in the lowermost stratosphere reveal that the influence of quasi-horizontal transport and subsequent mixing weakens with distance from the local tropopause. The mixing layer extends to about 25 K in potential temperature above the local tropopause exhibiting only a weak seasonality. However, at large distances from the tropopause a significant influence of tropospheric air is still evident. The relation between N2O and CO2 indicates that a significant contribution of air originating from the tropical tropopause contributes to the background air in the extratropical lowermost stratosphere.

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Numerical Study on Fluid Transport and Mixing by Electrothermal Flow in a Microchannel

Transactions of the Korean Society of Mechanical Engineers B ◽

10.3795/ksme-b.2019.43.8.565 ◽

2019 ◽

Vol 43 (8) ◽

pp. 565-578

Author(s):

Jae-Sung Kwon ◽

Minsub Han ◽

Young-Eun Yun

Keyword(s):

Fluid Transport ◽

Numerical Study ◽

Transport And Mixing ◽

Electrothermal Flow

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Mixing and transport by ciliary carpets: a numerical study

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.36 ◽

2014 ◽

Vol 743 ◽

pp. 124-140 ◽

Cited By ~ 42

Author(s):

Yang Ding ◽

Janna C. Nawroth ◽

Margaret J. McFall-Ngai ◽

Eva Kanso

Keyword(s):

Fluid Transport ◽

Numerical Study ◽

Mixing Time ◽

Three Dimensional ◽

Chemical Diffusion ◽

Metachronal Wave ◽

Mixing Rates ◽

Infinite Array ◽

Transport Region ◽

Transport And Mixing

AbstractWe use a three-dimensional computational model to study the fluid transport and mixing due to the beating of an infinite array of cilia. In accord with recent experiments, we observe two distinct regions: a fluid transport region above the cilia and a fluid mixing region below the cilia tip. The metachronal wave due to phase differences between neighbouring cilia is known to enhance the fluid transport above the ciliary tip. In this work, we show that the metachronal wave also enhances the mixing rates in the sub-ciliary region, often simultaneously with the flow rate enhancement. Our results suggest that this simultaneous enhancement in transport and mixing is due to an enhancement in shear flow. As the flow above the cilia increases, the shear rate in the fluid increases and this shear enhances stretching, which is an essential ingredient for mixing. Estimates of the mixing time scale indicate that, compared to diffusion, the mixing due to the cilia beat may be significant and sometimes dominates chemical diffusion.

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Seasonality and extent of extratropical TST derived from in-situ CO measurements during SPURT

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-4-1691-2004 ◽

2004 ◽

Vol 4 (2) ◽

pp. 1691-1726 ◽

Cited By ~ 3

Author(s):

P. Hoor ◽

C. Gurk ◽

D. Brunner ◽

M. I. Hegglin ◽

H. Wernli ◽

...

Keyword(s):

Significant Contribution ◽

Trace Gas ◽

Horizontal Gradients ◽

Tropical Tropopause ◽

Tropopause Region ◽

Gas Measurements ◽

Transport And Mixing ◽

Extratropical Tropopause ◽

Background Air

Abstract. We present airborne in-situ trace gas measurements which were performed on eight campaigns between November 2001 and July 2003 during the SPURT-project (SPURenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region). The measurements on a quasi regular basis allowed an overview on the seasonal variations of the trace gas distribution in the tropopause region over Europe from 35°–75° N to investigate the influence of transport and mixing across the extratropical tropopause on the lowermost stratosphere. From the correlation of CO and O3 irreversible mixing of tropospheric air into the lowermost stratosphere is identified. The CO distribution indicates that transport and subsequent mixing of tropospheric air across the extratropical tropopause predominantely affects a layer, which closely follows the shape of the local tropopause. In addition the seasonal cycle of CO2 illustrates the strong coupling of that layer to the extratropical troposphere. Both, horizontal gradients of CO on isentropes as well as the CO-O3-distribution in the lowermost stratosphere reveal that the influence of quasi-horizontal transport and subsequent mixing weakens with distance from the local tropopause. However, at large distances from the tropopause a significant influence of tropospheric air is still evident. The relation between N2O and CO2 indicates that a significant contribution of air originating from the tropical tropopause contributes to the background air in the extratropical lowermost stratosphere.

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