Abstract
Meteorological particles have been shown impact both subsonic and hypersonic vehicles negatively. It is necessary to continue to develop techniques and methods that will support the analysis of particles, such as ice, that can help mitigate issues and ensure the continued safe operation of air vehicles through hard environments. The first objective of this research is to conduct computational studies that compliment recent work completed at NASA to develop realistic ice shapes for the leading edge of a 65% scale Common Research Model (CRM65) wing. The computational studies leveraged experimental data completed on an 8.9% scaled CRM65 wing to assess the ability of RANS, DES, and IDDES numerical methods to predict the aerodynamic performance parameters and to better the complex three-dimensional flow physics. Initial work utilizing RANS highlighted its capability of capturing the wake downstream and showing that the resolution of the wake was not necessary to accurately capture the integrated aerodynamic coefficients. This allowed for simplification of the numerical domain for analysis for the swept-wing with and without a leading edge ice shape. Further work highlighted that at low angles of attack, lift, drag, and pitching moment are well predicted by RANS, DES, and IDDES. However, the numerical solutions produced by DES and IDDES for both lift and pitching moment did not fare as well at higher angles of attack where the coefficient became non-linear, e.g., near the pitching moment break in the experimental data. In particular, DES and IDDES did not quantitatively capture the spanwise component of the flow over the stalled portions of the swept wing nor did they properly predict the pressure distribution along the upper surface of the wing. In contrast, a conventional RANS approach surprisingly proved superior for predicting this fluid dynamic behavior. As such, the highly complex flow over a swept iced wing at stall conditions requires further development of the DES and IDDES approaches. In particular, it is suggested that the transition between RANS and LES regions for flow separations that have high spanwise velocity components be investigated in terms of turbulent mixing in order to allow improved transition models to properly capture the three-dimensional aerodynamic behavior.
The second objective of this research is to analyze the effect on hypersonic vehicles ice particles may have with regards to impact physics and erosion. Ice particles generally represent the largest particle in the atmosphere, especially at 10 km, which represents a key portion of the flight trajectory. These particles can cause damage and erosion to various components on the vehicle including the surface material and optical radomes. A set of simulations was conducted to support understanding the physics of atmospheric ice particles impacting the forebody of a hypersonic vehicle. These simulations analyzed ice particles as a function of both shape and size. At the flight condition analyzed, results show that nearly all of the incoming particles sized from 75 to 4,000 μm will impact the forebody and experience very little change in velocity. The change in temperature of the particles prior to impact is not sufficient enough to exceed the freezing point and thus a phase change for the particles is not expected. Due to the relatively large mass percentage of clouds containing ice particles sized around 2,000 μm, this bin of particles, especially for column ice, was predicted to contribute the most to the damage and erosion of the vehicle.
