scholarly journals The effect of droplet size and liquid water content on ice accretion and aerodynamic coefficients of tower legs

2013 ◽  
Vol 132-133 ◽  
pp. 362-374 ◽  
Author(s):  
H. Banitalebi Dehkordi ◽  
M. Farzaneh ◽  
P. Van Dyke ◽  
L.E. Kollar
Keyword(s):  
Water Content ◽  
Droplet Size ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Ice Accretion ◽  
Aerodynamic Coefficients

scholarly journals Theoretical Analysis of the Entrainment–Mixing Process at Cloud Boundaries. Part I: Droplet Size Distributions and Humidity within the Interface Zone

2018 ◽  
Vol 75 (6) ◽  
pp. 2049-2064 ◽  
Author(s):  
Mark Pinsky ◽  
Alexander Khain
Keyword(s):  
Water Content ◽  
Droplet Size ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Mixing Process ◽  
Governing Parameter ◽  
Interface Zone ◽  
Dry Air ◽  
Air Interface ◽  
Entrainment Mixing

Abstract The problem of a complex entrainment–mixing process is analyzed by solving a diffusion–evaporation equation for an open region in the vicinity of the cloud–dry air interface. Upon normalization the problem is reduced to a one-parametric one, the governing parameter being the potential evaporation parameter R proportional to the ratio of saturation deficit in the dry air to the available liquid water content in the cloud air. As distinct from previous multiple studies analyzing mixing within closed adiabatic volumes, we consider a principally nonstationary problem that never leads to a homogeneous equilibrium state. It is shown that at R < −1 the cloud edge shifts toward the cloud; that is, the cloud dissipates due to mixing with dry air, and the cloud volume decreases. If R > −1, the cloud edge shifts outside; that is, the mixing leads to an increase in the cloud volume. The time evolution of droplet size distribution and its moments, as well as the relative humidity within the expanding cloud–dry air interface, are calculated and analyzed. It is shown that the values of the mean volume radii rapidly decrease within the interface zone in the direction away from the cloud, indicating significant changes in the cloud edge microstructure. Scattering diagrams plotted for the cloud edge agree well with high-frequency in situ measurements, corroborating the reliability of the proposed approach. It is shown that the humidity front moves toward dry air faster than the front of liquid water content. As a result, the mixing leads to formation of a humid air shell around the cloud. The widths of the interface zone and humid shell are evaluated.

Turbulent Mixing in Shallow Trade Wind Cumuli: Dependence on Cloud Life Cycle

2015 ◽  
Vol 72 (4) ◽  
pp. 1447-1465 ◽  
Author(s):  
T. Schmeissner ◽  
R. A. Shaw ◽  
J. Ditas ◽  
F. Stratmann ◽  
M. Wendisch ◽  
...  
Keyword(s):  
Water Content ◽  
Droplet Size ◽  
Liquid Water ◽  
Turbulent Mixing ◽  
Liquid Water Content ◽  
Number Concentration ◽  
Trade Wind ◽  
Observation System ◽  
Mixing Process ◽  
The Impact

Abstract Helicopter-borne observations of the impact of turbulent mixing and cloud microphysical properties in shallow trade wind cumuli are presented. The measurements were collected during the Cloud, Aerosol, Radiation and Turbulence in the Trade Wind Regime over Barbados (CARRIBA) project. Basic meteorological parameters (3D wind vector, air temperature, and relative humidity), cloud condensation nuclei concentrations, and cloud microphysical parameters (droplet number, size distribution, and liquid water content) are measured by the Airborne Cloud Turbulence Observation System (ACTOS), which is fixed by a 160-m-long rope underneath a helicopter flying with a true airspeed of approximately 20 m s−1. Clouds at different evolutionary stages were sampled. A total of 300 clouds are classified into actively growing, decelerated, and dissolving clouds. The mixing process of these cloud categories is investigated by correlating the cloud droplet number concentration and cubed droplet mean volume diameter. A significant tendency to more inhomogeneous mixing with increasing cloud lifetime is observed. Furthermore, the mixing process and its effects on droplet number concentration, droplet size, and cloud liquid water content are statistically evaluated. It is found that, in dissolving clouds, liquid water content and droplet number concentration are decreased by about 50% compared to actively growing clouds. Conversely, the droplet size remains almost constant, which can be attributed to the existence of a humid shell around the cloud that prevents cloud droplets from rapid evaporation after entrainment of premoistened air. Moreover, signs of secondary activation are found, which results in a more difficult interpretation of observed mixing diagrams.

Transient atmospheric ice accretion on wind turbine blades

2018 ◽  
Vol 42 (6) ◽  
pp. 596-606
Author(s):  
Galal M Ibrahim ◽  
Kevin Pope ◽  
Yuri S Muzychka
Keyword(s):  
Wind Turbine ◽  
Water Content ◽  
Liquid Water ◽  
Turbine Blades ◽  
Liquid Water Content ◽  
Single Shot ◽  
Ice Accretion ◽  
Wind Turbine Blades ◽  
Median Volume ◽  
Blade Section

This article aims to predict ice loads on a wind turbine blade section at 80% of blade span, using FENSAP ICE. Using low and high liquid water content conditions of stratiform and cumuliform clouds, different icing events are simulated. Ice accretion predictions with single-shot and multi-shot approaches are presented. Blade surface roughness is also investigated, as well as the relationships between ice mass, liquid water content, median volume diameter, and temperature.

scholarly journals Microphysics and Optical Attenuation in Fog: Observations from Two Coastal Sites

2021 ◽  
Author(s):  
Qing Wang ◽  
Ryan T. Yamaguchi ◽  
John A. Kalogiros ◽  
Zachary Daniels ◽  
Denny P. Alappattu ◽  
...  
Keyword(s):  
Water Content ◽  
Droplet Size ◽  
Liquid Water ◽  
Empirical Relationship ◽  
Liquid Water Content ◽  
High Energy ◽  
Number Concentration ◽  
Future Research ◽  
Optical Attenuation ◽  
Fog Prediction

AbstractA total of 15 fog events from two field campaigns are investigated: the High Energy Laser in Fog (HELFOG) project (central California) and the Toward Improving Coastal Fog Prediction (C-FOG) project (Ferryland Newfoundland). Nearly identical sensors were used in both projects to sample fog droplet-size spectra, wind, turbulence, and thermodynamic properties near the surface. Concurrent measurements of visibility were made by the present weather detector in both experiments, with the addition of a two-ended transmissometer in the HELFOG campaign. The analyses focused first on contrasting the observed fog microphysics and the associated thermodynamics from fog events in the two locations. The optical attenuation by fog was investigated using three methods: (1) derived from Mie theory using the measured droplet-size distribution, (2) parametrized as a function of fog liquid water content, and (3) parametrized in terms of total fog droplet number concentration. The consistency of these methods was investigated. The HELFOG data result in an empirical relationship between the meteorological range and liquid water content. Validation of such relationship is problematic using the C-FOG data due to the presence of rain and other factors. The parametrization with droplet number concentration only does not provide a robust visibility calculation since it cannot represent the effects of droplet size on visibility. Finally, a preliminary analysis of the mixed fog/rain case is presented to illustrate the nature of the problem to promote future research.

scholarly journals Icing on a Non-Rotating Cylinder Under Conditions of High Liquid Water Content in the Air: I. Form and Size of Ice Deposits

1986 ◽  
Vol 32 (110) ◽  
pp. 6-11 ◽  
Author(s):  
Jouko Launiainen ◽  
Markku Lyyra
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Growth Process ◽  
Water Film ◽  
Liquid Water Content ◽  
Rotating Cylinder ◽  
Time Development ◽  
Ice Accretion ◽  
External Effects ◽  
High Liquid Water Content

AbstractIce accretion on a non-rotating cylinder was studied under icing conditions involving a wet-growth (glaze) process. Experiments were performed in an outdoor wind tunnel designed for icing studies. In this paper, the experimental method is introduced and the characteristics of form, size, and time development of deposits are given. In terms of freezing conditions, these characteristics were found to be very complex, in which all the external effects: air temperature, wind conditions, liquid water content in the air, and accretion time, are of the same order of importance. In a wet-growth process there exists above the icing surface a water film, the behaviour and dynamics of which are affected by various variables. The water film seems to play an important role in the wet-growth icing.

scholarly journals Ice Accretion Under Natural and Laboratory Conditions

1985 ◽  
Vol 6 ◽  
pp. 225-228
Author(s):  
K. Itagaki ◽  
G. E. Lemieux ◽  
H. W. Bosworth
Keyword(s):  
Transition Temperature ◽  
Water Content ◽  
New Hampshire ◽  
Liquid Water ◽  
Laboratory Experiments ◽  
Liquid Water Content ◽  
Wind Tunnels ◽  
Ice Accretion ◽  
Natural Conditions ◽  
Possible Cause

To compare results of icing studies conducted in wind tunnels with natural icing conditions, a series of rotor icing studies were made on top of Mt. Washington, New Hampshire. The results indicated that considerable differences exist between the two under conditions of similar liquid water content and temperature. The wet-to-dry growth transition temperature, for instance, with comparable temperature and liquid water content, may be more than 10°C higher under natural conditions than in wind tunnel studies. The possible cause of such discrepancies was found to be the vapor saturation existing in most laboratory experiments. The transition temperature of ice accretion measured in natural fog on board an aircraft agreed better with the results of the Mt. Washington study.

EXPERIMENTAL AND NUMERICAL INVESTIGATION OF ICE ACCRETION ON AIRFOIL

2012 ◽  
Vol 19 ◽  
pp. 227-236
Author(s):  
FANXIN MENG ◽  
WEIJIAN CHEN ◽  
DALIN ZHANG ◽  
HUI MA
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Test Section ◽  
Liquid Water Content ◽  
Open Circuit ◽  
Ice Accretion ◽  
Wing Model ◽  
Aluminum Cylinder ◽  
Ice Shapes ◽  
Coated Slide

Open Circuit Icing Research Tunnel was developed to test the ice shape under simulated icing conditions. Standard icing blade technique was used to measure liquid water content (LWC) in the icing tunnel test section. The uniformity of liquid water content was assessed by accreting ices on aluminum cylinder bars. Mean volumetric diameter (MVD) of the spray cloud was determined by soot-coated slide and verified through the limits of impingement. Ice accretion tests were performed on a NACA0012 wing model in typical rime and glaze conditions. Results were compared to ice shapes numerically predicted by Messinger method in the same conditions. It is indicated that good overall agreement is achieved in both icing shape and impingement limit.

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