Effect of Rectangular and Airfoil Planar Member Cross-section on Cascade Fin Aerodynamics

Tripathi, Manish and Misra, A and M S, Mahesh (2018) Effect of Rectangular and Airfoil Planar Member Cross-section on Cascade Fin Aerodynamics. In: 2018 AIAA Atmospheric Flight Mechanics Conference, 8–12 January 2018, Kissimmee, Florida.

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Grid fins are unconventional control and lifting surfaces consisting of an outer frame supporting an inner grid of small chord intersecting planar surfaces. These have been credited for their enhanced lifting characteristics at high angles of attack and high Mach numbers, miniscule hinge moments with a marginal increase in drag. These have been used on missiles, reusable launch vehicles etc. Cascade fins, with removal of all the cross members are a simplified variant of grid fins. In the present study, a sequence of viscous computational fluid dynamic simulations were performed at low subsonic velocity and high angles of attack to explicitly study the impact of planar member cross-sectional shape on the flow characteristics of a cascade fin. Investigations were carried out to elucidate the effect of NACA0012 airfoil cross-section instead of rectangular flat plate cross-section for the horizontal members of a cascade fin. Additional simulations to decipher the effect of varying minimum gap between the airfoil plates was carried out and compared against results obtained for varying gap between plates for the rectangular flat plate cascade. The solver has been validated for numerical accuracy by comparing drag and lift coefficient data available in the literature. The results are indicative of the reduced drag levels leading to an enhanced aerodynamic efficiency (0 ° - 30 ° ) due to airfoil cross-section. Similar or enhanced lifting characteristics are obtained for airfoil cascade compared to rectangular cascade before stalling. Albeit, it also leads to hastened and steeper stalling compared to that of the rectangular plate cascade. Thus, rectangular cascades perform better at higher angles. Static stability remains the same below the stalling region. Moreover, inferences related to comparison between the two cross-sections for varying gaps has also been discussed. The underlying physics associated to change in aerodynamics for respective variation has been carried out using pressure distribution plots, velocity-pressure contours and velocity vector based flow visualization plots. Thus, optimized selection of airfoil as cross-section based on aerodynamic efficiency enhancement, reduced operable angle of attack region and the higher cost of manufacturing compared to rectangular cascades with a viable gap selection can be carried out using this analysis

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IITH Creators:
IITH CreatorsORCiD
Item Type: Conference or Workshop Item (Paper)
Subjects: Others > Metallurgy Metallurgical Engineering
Divisions: Department of Mechanical & Aerospace Engineering
Depositing User: Team Library
Date Deposited: 17 Jan 2018 03:57
Last Modified: 17 Jan 2018 03:57
URI: http://raiith.iith.ac.in/id/eprint/3718
Publisher URL: https://doi.org/10.2514/6.2018-1761
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