On the estimation of in‐cloud vertical air motion using radar Doppler spectra

Abstract Using NOAA’s S-band High Power Snow-Level Radar, HPSLR, a technique for estimating the rain drop size distribution (DSD) above the radar is presented. This technique assumes the DSD can be described by a four parameter, generalized Gamma distribution (GGD). Using the radar’s measured average Doppler velocity spectrum and a value (assumed, measured, or estimated) of the vertical air motion, w, an estimate of the GGD is obtained. Four different methods can be used to obtain w. One method that estimates a mean mass-weighted raindrop diameter, Dm, from the measured reflectivity, Z, produces realistic DSDs compared to prior literature examples. These estimated DSDs provide evidence that the radar can retrieve the smaller drop sizes constituting the “drizzle” mode part of the DSD. This estimation technique was applied to 19 h of observations from Hankins, NC. Results support the concept that DSDs can be modeled using GGDs with a limited range of parameters. Further work is needed to validate the described technique for estimating DSDs in more varied precipitation types and to verify the vertical air motion estimates.

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Measurements of the Spatial Distribution and Engine Speed Dependence of Turbulent Air Motion in an I.C. Engine

10.4271/770220 ◽

1977 ◽

Cited By ~ 37

Author(s):

Peter O. Witze

Keyword(s):

Spatial Distribution ◽

Engine Speed ◽

Speed Dependence ◽

Air Motion

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Reflectivity and Liquid Water Content Vertical Decomposition Diagrams to Diagnose Vertical Evolution of Raindrop Size Distributions

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-15-0208.1 ◽

2016 ◽

Vol 33 (3) ◽

pp. 579-595 ◽

Cited By ~ 21

Author(s):

Christopher R. Williams

Keyword(s):

Water Content ◽

Liquid Water ◽

Liquid Water Content ◽

Doppler Velocity ◽

Size Distributions ◽

Vertical Column ◽

Vertical Decomposition ◽

Air Motion ◽

Raindrop Size ◽

Microphysical Processes

AbstractThis study consists of two parts. The first part describes the way in which vertical air motions and raindrop size distributions (DSDs) were retrieved from 449-MHz and 2.835-GHz (UHF and S band) vertically pointing radars (VPRs) deployed side by side during the Midlatitude Continental Convective Clouds Experiment (MC3E) held in northern Oklahoma. The 449-MHz VPR can measure both vertical air motion and raindrop motion. The S-band VPR can measure only raindrop motion. These differences in VPR sensitivities facilitates the identification of two peaks in 449-MHz VPR reflectivity-weighted Doppler velocity spectra and the retrieval of vertical air motion and DSD parameters from near the surface to just below the melting layer.The second part of this study used the retrieved DSD parameters to decompose reflectivity and liquid water content (LWC) into two terms, one representing number concentration and the other representing DSD shape. Reflectivity and LWC vertical decomposition diagrams (Z-VDDs and LWC-VDDs, respectively) are introduced to highlight interactions between raindrop number and DSD shape in the vertical column. Analysis of Z-VDDs provides indirect measure of microphysical processes through radar reflectivity. Analysis of LWC-VDDs provides direct investigation of microphysical processes in the vertical column, including net raindrop evaporation or accretion and net raindrop breakup or coalescence. During a stratiform rain event (20 May 2011), LWC-VDDs exhibited signatures of net evaporation and net raindrop coalescence as the raindrops fell a distance of 2 km under a well-defined radar bright band. The LWC-VDD is a tool to characterize rain microphysics with quantities related to number-controlled and size-controlled processes.

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The Influence of Air Motion on Bacteria Removal in Negative Pressure Isolation Rooms

HVAC&R Research ◽

10.1080/10789669.2005.10391155 ◽

2005 ◽

Vol 11 (4) ◽

pp. 563-585 ◽

Cited By ~ 14

Author(s):

Jeng-Min Huang ◽

Shih-Ming Tsao

Keyword(s):

Negative Pressure ◽

Air Motion ◽

Bacteria Removal

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Effects of the Injection Parameters on the Emissions of a Heavy Duty Diesel Engine

Volume 3: Combustion Science and Engineering ◽

10.1115/imece2009-13222 ◽

2009 ◽

Author(s):

M. Yılmaz ◽

M. Zafer Gul ◽

Y. Yukselenturk ◽

B. Akay ◽

H. Koten

Keyword(s):

Diesel Engine ◽

Direct Injection ◽

Combustion Process ◽

Design Parameters ◽

Combustion Model ◽

Particulate Emissions ◽

Multiphase Model ◽

Heavy Duty ◽

Flow Development ◽

Air Motion

It is estimated by the experts in the automotive industry that diesel engines on the transport market should increase within the years to come due to their high thermal efficiency coupled with low carbon dioxide (CO2) emissions, provided their nitrogen oxides (NOx) and particulate emissions are reduced. At present, adequate after-treatments, NOx and particulates matter (PM) traps are developed and industrialized with still concerns about fuel economy, robustness, sensitivity to fuel sulfur and cost because of their complex and sophisticated control strategy. New combustion processes focused on clean diesel combustion are investigated for their potential to achieve near zero particulate and NOx emissions. Their main drawbacks are increased level of unburned hydrocarbons (HC) and carbon monoxide (CO) emissions, combustion control at high load and limited operating range and power output. In this work, cold flow simulations for a single cylinder of a nine-liter (6 cylinder × 1.5 lt.) diesel engine have been performed to find out flow development and turbulence generation in the piston-cylinder assembly. In this study, the goal is to understand the flow field and the combustion process in order to be able to suggest some improvements on the in-cylinder design of an engine. Therefore combustion simulations of the engine have been performed to find out flow development and emission generation in the cylinder. Moreover, the interaction of air motion with high-pressure fuel spray injected directly into the cylinder has also been carried out. A Lagrangian multiphase model has been applied to the in-cylinder spray-air motion interaction in a heavy-duty CI engine under direct injection conditions. A comprehensive model for atomization of liquid sprays under high injection pressures has been employed. The combustion is modeled via a new combustion model ECFM-3Z (Extended Coherent Flame Model) developed at IFP. Finally, a calculation on an engine configuration with compression, spray injection and combustion in a direct injection Diesel engine is presented. Further investigation has also been performed in-cylinder design parameters in a DI diesel engine that result in low emissions by effect of high turbulence level. The results are widely in agreement qualitatively with the previous experimental and computational studies in the literature.

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