Ice Shape Scaling for Aircraft in SLD Conditions

This paper has summarized recent NASA research into scaling of SLD conditions with data from both SLD and Appendix C tests. Scaling results obtained by applying existing scaling methods for size and test-condition scaling will be reviewed. Large feather growth issues, including scaling approaches, will be discussed briefly. The material included applies only to unprotected, unswept geometries. Within the limits of the conditions tested to date, the results show that the similarity parameters needed for Appendix C scaling also can be used for SLD scaling, and no additional parameters are required. These results were based on visual comparisons of reference and scale ice shapes. Nearly all of the experimental results presented have been obtained in sea-level tunnels. The currently recommended methods to scale model size, icing limit and test conditions are described

Overview of Icing Physics Relevant to Scaling

An understanding of icing physics is required for the development of both scaling methods and ice-accretion prediction codes. This paper gives an overview of our present understanding of the important physical processes and the associated similarity parameters that determine the shape of Appendix C ice accretions. For many years it has been recognized that ice accretion processes depend on flow effects over the model, on droplet trajectories, on the rate of water collection and time of exposure, and, for glaze ice, on a heat balance. For scaling applications, equations describing these events have been based on analyses at the stagnation line of the model and have resulted in the identification of several non-dimensional similarity parameters. The parameters include the modified inertia parameter of the water drop, the accumulation parameter and the freezing fraction. Other parameters dealing with the leading edge heat balance have also been used for convenience. By equating scale expressions for these parameters to the values to be simulated a set of equations is produced which can be solved for the scale test conditions. Studies in the past few years have shown that at least one parameter in addition to those mentioned above is needed to describe surface-water effects, and some of the traditional parameters may not be as significant as once thought. Insight into the importance of each parameter, and the physical processes it represents, can be made by viewing whether ice shapes change, and the extent of the change, when each parameter is varied. Experimental evidence is presented to establish the importance of each of the traditionally used parameters and to identify the possible form of a new similarity parameter to be used for scaling

Additional Study of Water Droplet Median Volume Diameter (MVD) Effects on Ice Shapes

This paper reports the result of an experimental study in the NASA Glenn Icing Research Tunnel (IRT) to evaluate how well the MVD-independent effect identified previously might apply to SLD conditions in rime icing situations. Models were NACA 0012 wing sections with chords of 53.3 and 91.4 cm. Tests were conducted with a nominal airspeed of 77 m/s (150 kt) and a number of MVD's ranging from 15 to 100 m with LWC of 0.5 to 1 g/cu m. In the present study, ice shapes recorded from past studies and recent results at SLD and Appendix-C conditions are reviewed to show that droplet diameter is not important to rime ice shape for MVD of 30 microns or larger, but for less than 30 m drop sizes a rime ice shape transition from convex to wedge to spearhead type ice shape is observed

Further Assessment of MVD Effects in SLD Applications

The study reported here is part of an effort to develop scaling methods for super cooled large droplet (SLD) conditions. Previously reported results showed that SLD main ice shapes can be simulated quite successfully by appendix C conditions using scaling methods developed for appendix C. However, when the velocity was higher than 100 kt, the feather size and density for SLD tests at MVDs well above 100 m was not well represented by the scaled appendix C conditions. This paper reports additional results of a study of the feather region with the objective of identifying differences between SLD and appendix C feathers. Both the feather appearance and the angle at which feathers grow from the airfoil surface were recorded over a range of MVD from 20 to 190 m for airspeeds of 100 and 200 kt and stagnation freezing fractions of 0.3 to 1.0. Tests were performed in the NASA Glenn Icing Research Tunnel (IRT) using a 91-cm-chord NACA0012 airfoil model mounted at 0 degrees AOA. Photographs are presented to illustrate details of feather appearance. Appearance was noticeably affected by the stagnation freezing fraction of the test, but not by velocity or MVD. The angle of feather growth relative to the chord line decreased with increasing stagnation freezing fraction. For a velocity of 100 kt, no significant effect of MVD on feather angle was apparent, but at 200 kt, feather angle tended to increase with MVD for glaze conditions, but not rime. This finding is based on limited data, and its significance with respect to icing physics has not been determined

Evaluation and Validation of the Messinger Freezing Fraction

One of the most important non-dimensional parameters used in ice-accretion modeling and scaling studies is the freezing fraction defined by the heat-balance analysis of Messinger. For fifty years this parameter has been used to indicate how rapidly freezing takes place when super-cooled water strikes a solid body. The value ranges from 0 (no freezing) to 1 (water freezes immediately on impact), and the magnitude has been shown to play a major role in determining the physical appearance of the accreted ice. Because of its importance to ice shape, this parameter and the physics underlying the expressions used to calculate it have been questioned from time to time. Until now, there has been no strong evidence either validating or casting doubt on the current expressions. This paper presents experimental measurements of the leading-edge thickness of a number of ice shapes for a variety of test conditions with nominal freezing fractions from 0.3 to 1.0. From these thickness measurements, experimental freezing fractions were calculated and compared with values found from the Messinger analysis as applied by Ruff. Within the experimental uncertainty of measuring the leading-edge thickness, agreement of the experimental and analytical freezing fraction was very good. It is also shown that values of analytical freezing fraction were entirely consistent with observed ice shapes at and near rime conditions: At an analytical freezing fraction of unity, experimental ice shapes displayed the classic rime shape, while for conditions producing analytical freezing fractions slightly lower than unity, glaze features started to appear

Pengaruh Framing Effect Sebagai Determinan Escalation of Commitment Dalam Keputusan Investasi: Dampak Dari Working Experiences

The prior of research have shown that the framing effect is one of determinant in explaining decisions to escalate commitment to failing projects. However , have not considered whether experience moderates the framing effect on escalation of commitment. This study reports the results of an experiment in which the effect of decision frame of investment performance with negative feedback informatian on judgment to continue project of experienced subjects is compared to inexperienced subjects. Forty six Aceh experienced managers and forty seven accounting students participated in this experiment. Two conditions based on prospect theory (negative framing and positive framing) manipulated, and two conditions of business experience, crossed between subjects. The experiment reaffirms that decision frame does not have effect on judgment of experienced subject but those frame indeed have effect on judgment to continue project of inexperienced subjects. The result of this research suggest that framing effect as drawn from prospect theory is one of explanatory power of escalation of commitment, but it can not generalized to real-world business settings

Numerical Implementation of lepton-nucleus interactions and its effect on neutrino oscillation analysis

We discuss the implementation of the nuclear model based on realistic nuclear spectral functions in the GENIE neutrino interaction generator. Besides improving on the Fermi gas description of the nuclear ground state, our scheme involves a new prescription for $Q^2$ selection, meant to efficiently enforce energy momentum conservation. The results of our simulations, validated through comparison to electron scattering data, have been obtained for a variety of target nuclei, ranging from carbon to argon, and cover the kinematical region in which quasi elastic scattering is the dominant reaction mechanism. We also analyse the influence of the adopted nuclear model on the determination of neutrino oscillation parameters.Comment: 19 pages, 35 figures, version accepted by Phys. Rev.