Showing papers on "Glaze ice published in 1994"

Prediction of ice shapes and their effect on airfoil drag

Abstract: Calculation of ice shapes and the resulting drag increases are presented for a NACA 0012 airfoil. The calculations were made using a combination of modified LEWICE and interactive boundary-layer codes for a wide range of values of parameters such as airspeed and temperature, the droplet size and liquid water content of the cloud, and the angle of attack of the airfoil. Based on experimental data, an improved correlation of equivalent sand-grain roughness was developed. Calculated ice shapes are in good agreement with experimental data for rime ice, but some differences are shown between predictions and experimental data for glaze ice. Calculated drag coefficients generally follow trends shown by the experimental data.

Prediction of ice shapes and their effect on airfoil drag

Abstract: Calculation of ice shapes and the resulting drag increases are presented for a NACA 0012 airfoil. The calculations were made using a combination of modified LEWICE and interactive boundary-layer codes for a wide range of values of parameters such as airspeed and temperature, the droplet size and liquid water content of the cloud, and the angle of attack of the airfoil. Based on experimental data, an improved correlation of equivalent sand-grain roughness was developed. Calculated ice shapes are in good agreement with experimental data for rime ice, but some differences are shown between predictions and experimental data for glaze ice. Calculated drag coefficients generally follow trends shown by the experimental data.

Rime-, mixed- and glaze-ice evaluations of three scaling laws

Abstract: This report presents the results of tests at NASA Lewis to evaluate three icing scaling relationships or 'laws' for an unheated model. The laws were LWC x time = constant, one proposed by a Swedish-Russian group and one used at ONERA in France. Icing tests were performed in the NASA Lewis Icing Research Tunnel (IRT) with cylinders ranging from 2.5- to 15.2-cm diameter. Reference conditions were chosen to provide rime, mixed and glaze ice. Scaled conditions were tested for several scenarios of size and velocity scaling, and the resulting ice shapes compared. For rime-ice conditions, all three of the scaling laws provided scaled ice shapes which closely matched reference ice shapes. For mixed ice and for glaze ice none of the scaling laws produced consistently good simulation of the reference ice shapes. Explanations for the observed results are proposed, and scaling issues requiring further study are identified.

An Experimental Study of the Flowfield on a Semispan Rectangular Wing with a Simulated Glaze Ice Accretion. Ph.D. Thesis, 1993 Final Report

Abstract: Wind tunnel experiments were conducted in order to study the effect of a simulated glaze ice accretion on the flowfield of a semispan, reflection-plane, rectangular wing at Re = 1.5 million and M = 0.12. A laser Doppler velocimeter was used to map the flowfield on the upper surface of the model in both the clean and iced configurations at alpha = 0, 4, and 8 degrees angle of attack. At low angles of attack, the massive separation bubble aft of the leading edge ice horn was found to behave in a manner similar to laminar separation bubbles. At alpha = 0 and 4 degrees, the locations of transition and reattachment, as deduced from momentum thickness distributions, were found to be in good agreement with transition and reattachment locations in laminar separation bubbles. These values at y/b = 0.470, the centerline measurement location, matched well with data obtained on a similar but two dimensional model. The measured velocity profiles on the iced wing compared reasonably with the predicted profiles from Navier-Stokes computations. The iced-induced separation bubble was also found to have features similar to the recirculating region aft of rearward-facing steps. At alpha = 0 degrees and 4 degrees, reverse flow magnitudes and turbulence intensity levels were typical of those found in the recirculating region aft of rearward-facing steps. The calculated separation streamline aft of the ice horn at alpha = 4 degrees, y/b = 0.470 coincided with the locus of the maximum Reynolds normal stress. The maximum Reynolds normal stress peaked at two locations along the separation streamline. The location of the first peak-value coincided with the transition location, as deduced from the momentum thickness distributions. The location of the second peak was just upstream of reattachment, in good agreement with measurements of flows over similar obstacles. The intermittency factor in the vicinity of reattachment at alpha = 4 degrees, y/b = 0.470, revealed the time-dependent nature of the reattachment process. The size and extent of the separation bubble were found to be a function of angle of attack and the spanwise location. Three dimensional effects were found to be strongest at alpha = 8 degrees. The calculated separation and stagnation streamlines were found to vary little with spanwise location at alpha = 0 degrees. The calculated separation streamlines at alpha = 4 degrees revealed that the bubble was largest near the centerline measurement plane, whereas the tip-induced vortex flow and the model root-tunnel wall boundary-layer interaction reduced the size of the bubble. These effects were found to be most dramatic at alpha = 8 degrees.

An Experimental Study of the Aerodynamics of a Swept and Unswept Semispan Wing with a Simulated Glaze Ice Accretion

Abstract: Two semispan wings, one with a rectangular planform and one with 30 degrees of leading edge sweep were tested. Both had a NACA 0012 airfoil section, and both were tested clean and with simulated glaze ice shapes on their leading edges. Several surface roughness were tested. Each model geometry is documented and each surface roughness is explained. Aerodynamic performance of the wing in the form of sectional lift and integrated three-dimensional lift is documented through pressure measurements obtained from rows of surface pressure taps placed at five span locations on the wing. For the rectangular wing, sectional drag near the midspan is obtained from wake total pressure profiles. The data is presented in tabular and graphical form and is also available on computer disk.