scholarly journals Experimental Studies of Ice Crystal Accretion on an Axisymmetric Body at Engine-Realistic Conditions

2018 ◽  
Author(s):  
Alexander J. Bucknell ◽  
Matthew McGilvray ◽  
David Gillespie ◽  
Geoff Jones ◽  
Alasdair Reed ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Axisymmetric Body ◽  
Ice Crystal

Empirical Formulation for number of ice crystal fragments by sublimational breakup

2020 ◽  
Author(s):  
Akash Deshmukh ◽  
Vaughan Phillips
Keyword(s):  
Relative Humidity ◽  
Cloud Model ◽  
Experimental Studies ◽  
Ice Crystal ◽  
Initial Size ◽  
Sublimation Process ◽  
Numerical Formulation ◽  
High Concentrations ◽  
Ice Multiplication ◽  
Ice Production

<p>There is much uncertainty about high concentrations of ice observed in clouds and their origins. In the literature, there have been previous experimental studies reported about the sublimation process of an ice crystal causes emission of fragments by breakup.   Such sublimational breakup is a type of secondary ice production, which in natural clouds can cause ice multiplication. </p><p>To represent this process of sublimation breakup in any cloud model, the present study proposes a numerical formulation of the number of ice fragments generated by sublimation of pristine ice crystal. This is done by amalgamating laboratory observations from previous published studies. The number of ice fragments determined by relative humidity (RH) and initial size of the ice particle were measured in the published experiments, and by simulating them we are able to infer parameters of a sublimation breakup scheme.   At small initial sizes, the dependency on size prevails, whereas at larger sizes both dependencies are comparable. This formulation is compared with observations to see the behaviour of it.</p>

scholarly journals A Molecular Perspective on Water Vapour Accommodation into Ice and Its Dependence on Temperature

2020 ◽  
Author(s):  
Daniel Schlesinger ◽  
Samuel J. Lowe ◽  
Tinja Olenius ◽  
Xiangrui Kong ◽  
Jan B. C. Pettersson ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Order Parameter ◽  
Potential Temperature ◽  
Experimental Studies ◽  
Accommodation Coefficient ◽  
Recent Experimental Data ◽  
Ice Crystal ◽  
Cloud Particle ◽  
Data Set ◽  
Accommodation Process

<div> <div> <div> <p>Accommodation of vapour phase water molecules into ice crystal surfaces is a fundamental process controlling atmospheric ice crystal growth. Experimental studies investigating the accommodation process with various different techniques report widely spread values of the water accommodation coefficient on ice, αice, and the results on its potential temperature- dependence are inconclusive. We run molecular dynamics simulations of molecules condensing onto the basal plane of ice Ih using the TIP4P/Ice empirical force field and characterize the accommodated state from this molecular perspective, utilizing the interaction energy, the tetrahedrality order parameter and the distance below the instantaneous interface as criteria. Changes of the order parameter turn out to be a suitable measure to distinguish between surface and bulk states of a molecule condensing onto the disordered interface. In light of the findings from the molecular dynamics, we discuss and re- analyse a recent experimental data set on αice obtained with an environmental molecular beam (EMB) setup [Kong et al, Journal of Physical Chemistry A, 2014] using kinetic molecular flux modelling, aiming at a more comprehensive picture of the accommodation process from a molecular perspective. These results indicate that the experimental observations indeed cannot be explained by evaporation alone. At the same time our results raise the issue of rapidly growing relaxation times upon decreasing temperature, challenging future experimental efforts to cover relevant time scales. Finally, we discuss the relevance of the water accommodation coefficient on ice in the context of atmospheric cloud particle growth processes. </p> </div> </div> </div>

Experimental Studies of Ice Crystal Accretion on Axisymmetric Bodies at Aeroengine Conditions

2020 ◽  
Vol 36 (6) ◽  
pp. 836-850
Author(s):  
Alexander Bucknell ◽  
Matthew McGilvray ◽  
David R. H. Gillespie ◽  
Geoff Jones ◽  
Alasdair Reed ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Ice Crystal ◽  
Axisymmetric Bodies

Studies on Unsteady Pressure Fields in the Region of Separating and Reattaching Flows

1990 ◽  
Vol 112 (4) ◽  
pp. 402-408 ◽  
Author(s):  
H. S. Govinda Ram ◽  
V. H. Arakeri
Keyword(s):  
Pressure Fluctuation ◽  
Experimental Studies ◽  
Axisymmetric Body ◽  
Two Dimensional ◽  
Pressure Surface ◽  
Pressure Fields ◽  
Maximum Value ◽  
Mean Pressure ◽  
Surface Fluctuation ◽  
Body Shapes

Experimental studies on the measurement of pressure fields in the region of separating and reattaching flows behind several two-dimensional fore-bodies and one axisymmetric body are reported. In particular, extensive measurements of mean pressure, surface pressure fluctuation, and pressure fluctuation within the flow were made for a series of two-dimensional fore-body shapes consisting of triangular nose with varying included angle. The measurements from different bodies are compared and one of the important findings is that the maximum values of rms pressure fluctuation levels in the shear layer approaching reattachment are almost equal to the maximum value of the surface fluctuation levels.

scholarly journals Impulsive Motion Inside a Cylindrical Cavity

Mathematics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 192
Author(s):  
Yuriy Savchenko ◽  
Georgiy Savchenko ◽  
Yuriy A. Semenov
Keyword(s):  
Cylindrical Cavity ◽  
Experimental Studies ◽  
Added Mass ◽  
Axisymmetric Body ◽  
The Body ◽  
Successive Approximations ◽  
Method Of Successive Approximations ◽  
Main Concern ◽  
Free Boundaries ◽  
Hodograph Method

Experimental studies of supercavitating models moving at speeds in the range from 400 m/s to 1000 m/s revealed a regime of bouncing motion, in which the rear part of an axisymmetric body periodically bounces against the free boundaries of the supercavity. The impulsive force generated by the impacts is the main concern in this paper. The analysis is performed in the approximation of two-dimensional potential flow of an ideal and incompressible liquid with negligible surface tension effects. The primary interest of the study is to determine the added mass taking into account the shape of the cavity. The theoretical study is based on the integral hodograph method, which makes it possible to obtain analytic expressions for the flow potential and for the complex velocity in an auxiliary parameter plane and obtain a parametric solution to the problem. The problem is reduced to a system of two integro-differential equations in two unknowns: the velocity magnitude on the cavity boundary and the slope of the velocity angle to the body. The equations are solved numerically using the method of successive approximations. The obtained results show that the added mass of an arc impacting a cylindrical cavity depends heavily on the arc angle. As the angle tends to zero or the radius of the cavity tends to infinity, the obtained solution predicts the added mass corresponding to a plate impacting a flat free surface.

scholarly journals Contact freezing: a review of experimental studies

2013 ◽  
Vol 13 (19) ◽  
pp. 9745-9769 ◽  
Author(s):  
L. A. Ladino Moreno ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Qualitative Difference ◽  
Experimental Studies ◽  
Experimental Information ◽  
Cloud Formation ◽  
Ice Crystal ◽  
Ice Cloud ◽  
Quantitative Calculation ◽  
Ice Nuclei ◽  
Immersion Freezing ◽  
Reported Data

Abstract. This manuscript compiles both theoretical and experimental information on contact freezing with the aim to better understand this potentially important but still not well quantified heterogeneous freezing mode. There is no complete theory that describes contact freezing and how the energy barrier has to be overcome to nucleate an ice crystal by contact freezing. Experiments on contact freezing conducted using the cold plate technique indicate that it can initiate ice formation at warmer temperatures than immersion freezing. Additionally, a qualitative difference in the freezing temperatures between contact and immersion freezing has been found using different instrumentation and different ice nuclei. There is a lack of data on collision rates in most of the reported data, which inhibits a quantitative calculation of the freezing efficiencies. Thus, new or modified instrumentation to study contact nucleation in the laboratory and in the field are needed to identify the conditions at which contact nucleation could occur in the atmosphere. Important questions concerning contact freezing and its potential role for ice cloud formation and climate are also summarized.

Experimental studies of spontaneous and forced transition on an axisymmetric body

AIAA Journal ◽  
1986 ◽  
Vol 24 (3) ◽  
pp. 397-403 ◽  
Author(s):  
J. T. Kegelman ◽  
T. J. Mueller
Keyword(s):  
Experimental Studies ◽  
Axisymmetric Body

scholarly journals A Molecular Perspective on Water Vapour Accommodation into Ice and Its Dependence on Temperature

2020 ◽  
Author(s):  
Daniel Schlesinger ◽  
Samuel J. Lowe ◽  
Tinja Olenius ◽  
Xiangrui Kong ◽  
Jan B. C. Pettersson ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Order Parameter ◽  
Potential Temperature ◽  
Experimental Studies ◽  
Accommodation Coefficient ◽  
Recent Experimental Data ◽  
Ice Crystal ◽  
Cloud Particle ◽  
Data Set ◽  
Accommodation Process

<div> <div> <div> <p>Accommodation of vapour phase water molecules into ice crystal surfaces is a fundamental process controlling atmospheric ice crystal growth. Experimental studies investigating the accommodation process with various different techniques report widely spread values of the water accommodation coefficient on ice, αice, and the results on its potential temperature- dependence are inconclusive. We run molecular dynamics simulations of molecules condensing onto the basal plane of ice Ih using the TIP4P/Ice empirical force field and characterize the accommodated state from this molecular perspective, utilizing the interaction energy, the tetrahedrality order parameter and the distance below the instantaneous interface as criteria. Changes of the order parameter turn out to be a suitable measure to distinguish between surface and bulk states of a molecule condensing onto the disordered interface. In light of the findings from the molecular dynamics, we discuss and re- analyse a recent experimental data set on αice obtained with an environmental molecular beam (EMB) setup [Kong et al, Journal of Physical Chemistry A, 2014] using kinetic molecular flux modelling, aiming at a more comprehensive picture of the accommodation process from a molecular perspective. These results indicate that the experimental observations indeed cannot be explained by evaporation alone. At the same time our results raise the issue of rapidly growing relaxation times upon decreasing temperature, challenging future experimental efforts to cover relevant time scales. Finally, we discuss the relevance of the water accommodation coefficient on ice in the context of atmospheric cloud particle growth processes. </p> </div> </div> </div>

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