Role of irradiation in the formation of a nonequilibrium boundary layer

1974 ◽  
Vol 6 (4) ◽  
pp. 688-689
Author(s):  
S. Ya. Bronin ◽  
A. N. Lagar'kov
Keyword(s):  
Boundary Layer ◽  
Nonequilibrium Boundary Layer

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

Role of low-level jets and boundary-layer properties on the NBL budget technique

2005 ◽  
Vol 135 (1-4) ◽  
pp. 35-43 ◽  
Author(s):  
N. Mathieu ◽  
I.B. Strachan ◽  
M.Y. Leclerc ◽  
A. Karipot ◽  
E. Pattey
Keyword(s):  
Boundary Layer ◽  
Low Level ◽  
Low Level Jets

scholarly journals Numerical analysis of the chemical kinetic mechanisms of ozone depletion and halogen release in the polar troposphere

2013 ◽  
Vol 13 (9) ◽  
pp. 24171-24222 ◽  
Author(s):  
L. Cao ◽  
H. Sihler ◽  
U. Platt ◽  
E. Gutheil
Keyword(s):  
Boundary Layer ◽  
Surface Area ◽  
Ozone Depletion ◽  
Reaction Rates ◽  
The Arctic ◽  
Strong Impact ◽  
Reactive Surface ◽  
A Value ◽  
Halogen Species

Abstract. In recent years, the role of halogen species (e.g. Br, Cl) in the troposphere of polar regions is investigated after the discovery of their importance for boundary layer ozone destruction in the polar spring. Halogen species take part in an auto-catalytic chemical cycle including key self reactions. In this study, several chemical reaction schemes are investigated, and the importance of specific reactions and their rate constants is identified by a sensitivity analysis. A category of heterogeneous reactions related to HOBr activate halogen ions from sea salt aerosols, fresh sea ice or snow pack, driving the "bromine explosion". In the Arctic, a small amount of NOx may exist, which comes from nitrate contained in the snow, and this NOx may have a strong impact on ozone depletion. The heterogeneous reaction rates are parameterized by considering the aerodynamic resistance, a reactive surface ratio, β, i.e. ratio of reactive surface area to total ground surface area, and the boundary layer height, Lmix. It is found that for β = 1, the ozone depletion process starts after five days and lasts for 40 h for Lmix = 200 m. Ozone depletion duration becomes independent of the height of the boundary layer for about β≥20, and it approaches a value of two days for β=100. The role of nitrogen and chlorine containing species on the ozone depletion rate is studied. The calculation of the time integrated bromine and chlorine atom concentrations suggests a value in the order of 103 for the [Br] / [Cl] ratio, which reveals that atomic chlorine radicals have minor direct influence on the ozone depletion. The NOx concentrations are influenced by different chemical cycles over different time periods. During ozone depletion, the reaction cycle involving the BrONO2 hydrolysis is dominant. A critical value of 0.002 of the uptake coefficient of the BrONO2 hydrolysis reaction at the aerosol and saline surfaces is identified, beyond which the existence of NOx species accelerate the ozone depletion event – for lower values, deceleration occurs.

Role of Freestream Slow Acoustic Waves in a Hypersonic Three-Dimensional Boundary Layer

AIAA Journal ◽  
2018 ◽  
Vol 56 (9) ◽  
pp. 3570-3584 ◽  
Author(s):  
Guoliang Xu ◽  
Gang Liu ◽  
Jianqiang Chen ◽  
Song Fu
Keyword(s):  
Boundary Layer ◽  
Acoustic Waves ◽  
Three Dimensional ◽  
Dimensional Boundary

In-situ estimates of the role of radiative cooling for shallow convective organization

2021 ◽  
Author(s):  
Benjamin Fildier ◽  
Caroline Muller ◽  
Ludovic Touze-Peiffer ◽  
Anna Lea Albright
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Radiative Cooling ◽  
Shallow Convection ◽  
Field Campaign ◽  
Radiative Processes ◽  
Horizontal Gradients ◽  
Convective Organization

<p>This study investigates the role of radiative processes in shaping the spatial distribution of shallow clouds, using in-situ measurements retrieved during the EUREC4A field campaign. Horizontal gradients in atmospheric radiative cooling above the boundary layer had been advanced as important drivers of shallow circulation and low-level winds, through their effect on surface pressure gradients. Modeling studies first recognized their importance in idealized simulations of deep convection in radiative-convective equilibrium, then found a weaker role for idealized cases of very shallow convection; but recent work using remote-sensing data argued for their importance in strengthening the circulation close to the margin between dry and moist regions, on synoptic scales, arguing for a possible significance for these radiative effects on observed cloud structures.</p><p>Here we investigate cases of intermediate scale, observed during the EUREC<sup>4</sup>A field campaign, where shallow convection extends vertically up to 4 km, and whose spatial organization can be described on mesoscales as “fish” or “flower” patterns. We perform careful radiative transfer calculations, using state-of-the-art spectroscopic data and over two thousand of dropsondes and radiosondes launched, to capture the fine details of radiative cooling profiles usually missed by satellite measurements. The large number of sondes allows us to sample radiative cooling information for the organization pattern of interest and analyze it in conjunction with the direct wind and humidity measurements. We also use geostationary estimates of precipitable water in clear-sky in order to cross-check the sonde data, and connect them to the organization pattern and to the position of the moist margin.</p><p>Our results target the following relationships previously identified in idealized simulations: (a) between horizontal gradients in moisture and in top-of-the-boundary-layer radiative cooling, (b) between these radiative cooling gradients and surface wind anomalies across the moist margin, and (c) between the strength of surface winds as a function of the distance from the moist margin. These results will allow us to test the importance of radiative transfer processes in a real case of shallow convective organization.</p>

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