Theoretical Aspccts of Cloud Drop Distributions

1949 ◽  
Vol 2 (3) ◽  
pp. 376 ◽  
Author(s):  
EB Kraus ◽  
B Smith
Keyword(s):  
Cooling Rate ◽  
Drop Size ◽  
Initial Temperature ◽  
Theoretical Study ◽  
Air Pressure ◽  
Size Spectrum ◽  
Condensation Nuclei ◽  
Cloud Drop ◽  
Rate Of Cooling

A theoretical study indicates that the number and size of the drops formed in a cloud vary with the rate of cooling, the initial temperature, and the air pressure. The faster the cooling rate, the lower the initial temperature, and the lower the altitude, the greater is the number of drops and the smaller their size. The drop size spectrum also depends, to a large extent, on the number of available condensation nuclei. Furthermore, it tends to be widened by sedimentation and turbulence.

Acidity variations across the cloud drop size spectrum and their influence on rates of atmospheric sulfate production

1994 ◽  
Vol 21 (22) ◽  
pp. 2393-2396 ◽  
Author(s):  
Jeffrey L. Collett ◽  
Aaron Bator ◽  
Xin Rao ◽  
Belay B. Demoz
Keyword(s):  
Drop Size ◽  
Size Spectrum ◽  
Cloud Drop ◽  
Sulfate Production

Directional freezing of spermatozoa and embryos

2014 ◽  
Vol 26 (1) ◽  
pp. 83 ◽  
Author(s):  
Amir Arav ◽  
Joseph Saragusty
Keyword(s):  
Cooling Rate ◽  
Drop Size ◽  
Mechanical Damage ◽  
Rapid Freezing ◽  
Wild Animals ◽  
Microscope Slide ◽  
Freezing Method ◽  
Wide Range ◽  
Sexed Semen ◽  
Directional Freezing

Directional freezing is based on a simple thermodynamic principle whereby the sample is moved through a predetermined temperature gradient at a velocity that determines the cooling rate. Directional freezing permits a precise and uniform cooling rate in small- and large-volume samples. It avoids supercooling and reduces mechanical damage caused by crystallisation. Directional solidification was used to date for slow and rapid freezing, as well as for vitrification of oocytes and embryos by means of the minimum drop size technique: small drops are placed on a microscope slide that is moved at high velocity from the hot base to the cold base. Sperm samples from a wide range of domestic and wild animals were successfully cryopreserved using the directional freezing method. The bovine sexed semen industry may benefit from the increased survival of spermatozoa after directional freezing.

Liquid Jets in Subsonic Air Crossflow at Elevated Pressure

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Jinkwan Song ◽  
Charles Cary Cain ◽  
Jong Guen Lee
Keyword(s):  
Weber Number ◽  
Momentum Flux ◽  
Drop Size ◽  
Density Ratio ◽  
Flux Ratio ◽  
Mie Scattering ◽  
Air Pressure ◽  
Scattering Intensity ◽  
Nozzle Orifice ◽  
Momentum Flux Ratio

The breakup, penetration, droplet size, and size distribution of a Jet A-1 fuel in air crossflow has been investigated with focus given to the impact of surrounding air pressure. Data have been collected by particle Doppler phased analyzer (PDPA), Mie-scattering with high speed photography augmented by laser sheet, and Mie-scattering with intensified charge-coupled device (ICCD) camera augmented by nanopulse lamp. Nozzle orifice diameter, do, was 0.508 mm and nozzle orifice length to diameter ratio, lo/do, was 5.5. Air crossflow velocities ranged from 29.57 to 137.15 m/s, air pressures from 2.07 to 9.65 bar, and temperature held constant at 294.26 K. Fuel flow provides a range of fuel/air momentum flux ratio (q) from 5 to 25 and Weber number from 250 to 1000. From the results, adjusted correlation of the mean drop size has been proposed using drop size data measured by PDPA as follows: (D0/D32)=0.267Wea0.44q0.08(ρl/ρa)0.30(μl/μa)-0.16. This correlation agrees well and shows roles of aerodynamic Weber number, Wea, momentum flux ratio, q, and density ratio, ρl/ρa. Change of the breakup regime map with respect to surrounding air pressure has been observed and revealed that the boundary between each breakup modes can be predicted by a transformed correlation obtained from above correlation. In addition, the spray trajectory for the maximum Mie-scattering intensity at each axial location downstream of injector is extracted from averaged Mie-scattering images. From these results, correlations with the relevant parameters including q, x/do, density ratio, viscosity ratio, and Weber number are made over a range of conditions. According to spray trajectory at the maximum Mie-scattering intensity, the effect of surrounding air pressure becomes more important in the farfield. On the other hand, effect of aerodynamic Weber number is more important in the nearfield.

Evaluations of cooling rate and initial temperature on thermal shock behavior of ZrB2-SiC ceramic

2018 ◽  
Vol 741 ◽  
pp. 509-513 ◽  
Author(s):  
Anzhe Wang ◽  
Ping Hu ◽  
Cheng Fang ◽  
Dongyang Zhang ◽  
Xinghong Zhang
Keyword(s):  
Thermal Shock ◽  
Cooling Rate ◽  
Initial Temperature ◽  
Sic Ceramic ◽  
Thermal Shock Behavior

Influence of Ambient Air Pressure on Pressure-Swirl Atomization

1987 ◽  
Author(s):  
X. F. Wang ◽  
A. H. Lefebvre
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Ambient Air ◽  
Air Pressure ◽  
Spray Angle ◽  
Flow Number ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Continuous Increase ◽  
Pressure Swirl

The spray characteristics of six simplex atomizers are examined in a pressure vessel using a standard light diffraction technique. Attention is focused on the effects of liquid properties, nozzle flow number, spray cone angle, and ambient air pressure on mean drop size and drop-size distribution. For all nozzles and all liquids it is found that continuous increase in air pressure above the normal atmospheric value causes the SMD to first increase up to a maximum value and then decline. An explanation for this characteristic is provided in terms of the measurement technique employed and the various competing influences on the overall atomization process. The basic effect of an increase in air pressure is to improve atomization, but this trend is opposed by contraction of the spray angle which reduces the relative velocity between the drops and the surrounding air, and also increases the possibility of droplet coalescence.

EFFECTS OF COMPOSITION AND TEMPERATURE ON REBCO SINGLE CRYSTALS GROWN BY FLUX METHOD

2000 ◽  
Vol 14 (25n27) ◽  
pp. 2682-2687 ◽  
Author(s):  
A. UBALDINI ◽  
G. A. COSTA ◽  
M. M. CARNASCIALI ◽  
M. FERRETTI
Keyword(s):  
Rare Earth ◽  
Cooling Rate ◽  
Single Crystals ◽  
Initial Temperature ◽  
Equilibrium Composition ◽  
Initial Ratio ◽  
Flux Method ◽  
High Quality ◽  
Temperature Changes ◽  
Large Side

The flux method is the most popular technique to obtain high quality and large side single crystals of YBa 2 Cu 3 O x (YBCO) and REBa 2 Cu 3 O x (REBCO). It is known that, for the YBCO, the interval of temperature for growing single crystals is between about 1010°C and 930°C, whereas, for the REBCO phases, the maximal temperature changes as function of rare earth. In this work, we studied the effect of different thermal programs on the side the YBCO crystals. The initial temperature and the cooling rate were changed. We studied the influence of a different initial ratio between Nd and Ba and between Sm and Ba on the equilibrium composition in NdBCO and SmBCO crystals.

scholarly journals Thermal delay of drop coalescence

2017 ◽  
Vol 833 ◽  
Author(s):  
Michela Geri ◽  
Bavand Keshavarz ◽  
Gareth H. McKinley ◽  
John W. M. Bush
Keyword(s):  
Critical Temperature ◽  
Residence Time ◽  
Temperature Difference ◽  
Initial Temperature ◽  
Theoretical Study ◽  
Fluid Viscosity ◽  
Drop Coalescence ◽  
Thermocapillary Flows ◽  
Silicone Oils ◽  
Thermal Delay

We present the results of a combined experimental and theoretical study of drop coalescence in the presence of an initial temperature difference $\unicode[STIX]{x0394}T_{0}$ between a drop and a bath of the same liquid. We characterize experimentally the dependence of the residence time before coalescence on $\unicode[STIX]{x0394}T_{0}$ for silicone oils with different viscosities. Delayed coalescence arises above a critical temperature difference $\unicode[STIX]{x0394}T_{c}$ that depends on the fluid viscosity: for $\unicode[STIX]{x0394}T_{0}>\unicode[STIX]{x0394}T_{c}$, the delay time increases as $\unicode[STIX]{x0394}T_{0}^{2/3}$ for all liquids examined. This observed dependence is rationalized theoretically through consideration of the thermocapillary flows generated within the drop, the bath and the intervening air layer.

scholarly journals Evaluating Light Rain Drop Size Estimates from Multiwavelength Micropulse Lidar Network Profiling

2013 ◽  
Vol 30 (12) ◽  
pp. 2798-2807 ◽  
Author(s):  
Simone Lolli ◽  
Ellsworth J. Welton ◽  
James R. Campbell
Keyword(s):  
Drop Size ◽  
Total Error ◽  
Size Spectrum ◽  
Drop Diameter ◽  
Transmission Losses ◽  
Light Rain ◽  
Color Ratio ◽  
Aerosol Scattering ◽  
Rain Drop ◽  
The Impact

Abstract This paper investigates multiwavelength retrievals of median equivolumetric drop diameter D0 suitable for drizzle and light rain, through collocated 355-/527-nm Micropulse Lidar Network (MPLNET) observations collected during precipitation occurring 9 May 2012 at the Goddard Space Flight Center (GSFC) project site. By applying a previously developed retrieval technique for infrared bands, the method exploits the differential backscatter by liquid water at 355 and 527 nm for water drops larger than ≈50 μm. In the absence of molecular and aerosol scattering and neglecting any transmission losses, the ratio of the backscattering profiles at the two wavelengths (355 and 527 nm), measured from light rain below the cloud melting layer, can be described as a color ratio, which is directly related to D0. The uncertainty associated with this method is related to the unknown shape of the drop size spectrum and to the measurement error. Molecular and aerosol scattering contributions and relative transmission losses due to the various atmospheric constituents should be evaluated to derive D0 from the observed color ratio profiles. This process is responsible for increasing the uncertainty in the retrieval. Multiple scattering, especially for UV lidar, is another source of error, but it exhibits lower overall uncertainty with respect to other identified error sources. It is found that the total error upper limit on D0 approaches 50%. The impact of this retrieval for long-term MPLNET monitoring and its global data archive is discussed.

scholarly journals Estimating drizzle drop size and precipitation rate using two-colour lidar measurements

2010 ◽  
Vol 3 (3) ◽  
pp. 671-681 ◽  
Author(s):  
C. D. Westbrook ◽  
R. J. Hogan ◽  
E. J. O'Connor ◽  
A. J. Illingworth
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Drop Size ◽  
Liquid Water Content ◽  
Precipitation Rate ◽  
Infrared Light ◽  
Cloud Base ◽  
Size Spectrum ◽  
Drop Diameter ◽  
Lidar Measurements

Abstract. A method to estimate the size and liquid water content of drizzle drops using lidar measurements at two wavelengths is described. The method exploits the differential absorption of infrared light by liquid water at 905 nm and 1.5 μm, which leads to a different backscatter cross section for water drops larger than ≈50 μm. The ratio of backscatter measured from drizzle samples below cloud base at these two wavelengths (the colour ratio) provides a measure of the median volume drop diameter D0. This is a strong effect: for D0=200 μm, a colour ratio of ≈6 dB is predicted. Once D0 is known, the measured backscatter at 905 nm can be used to calculate the liquid water content (LWC) and other moments of the drizzle drop distribution. The method is applied to observations of drizzle falling from stratocumulus and stratus clouds. High resolution (32 s, 36 m) profiles of D0, LWC and precipitation rate R are derived. The main sources of error in the technique are the need to assume a value for the dispersion parameter μ in the drop size spectrum (leading to at most a 35% error in R) and the influence of aerosol returns on the retrieval (≈10% error in R for the cases considered here). Radar reflectivities are also computed from the lidar data, and compared to independent measurements from a colocated cloud radar, offering independent validation of the derived drop size distributions.

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