Flow Field Characterization and Visualization of Grid Fin Subsonic Flow

Abstract

Grid fins are unconventional control surfaces consisting of an outer frame supporting an inner grid of intersecting planar surfaces. Although afflicted with higher drag, these have been credited for their enhanced lifting characteristics at high angles of attack and high Mach numbers, alongside reduced hinge moments accounting for the recent upsurge in their usage on numerous aerospace applications. Present investigations carry out elaborate flow field visualization and characterization underlining the rudimentary physics through a sequence of subsonic numerical simulations performed at different angles of attack and different gap (between the members) to chord ratios on a simplified grid fin variant called cascade fin. The study makes use of a new nondimensionalization technique called cumulative nondimensionalization to decipher the effect of cascading on individual members of the fin. Hence, after a comprehensive examination of the aerodynamic coefficients, pressure coefficient distribution, pressure gradient, velocity gradient, boundary layer velocity profile, and flow field visualization, the study elucidates physics associated with hastened stall angle, augmented lift-drag, and bounded efficiency accretion for gap increment.

Effect of aspect ratio variation on subsonic aerodynamics of cascade type grid fin at different gap-to-chord ratios

“…The study underscores the impact of g/c variation on grid fin aerodynamics leading to delayed α max , reduced maximum lift, and subtle efficiency reduction for lower g/c. Qualitatively, these variations are similar to the ones observed earlier in references (49,52,53) . Thus, the trends associated with experimental data pertaining to g/c variation comprehended in this study conform well with the pre-existing data.…”

“…The results were further corroborated through comprehensive numerical analysis performed by the authors in Ref. (53). These investigations lead to a greater understanding of the underlying flow-physics associated with these trends.…”

“…The effect leading to these variations for the lower g/c variants had been termed as cascade effect in earlier studies carried out by the authors in Ref. (53) This effect, as discussed in Ref. 52is a result of the interference between the flow corresponding to the neighbouring members.…”

“…Moreover, owing to the increased influence of g/c parameter on grid fin stall and lifting characteristics as established earlier by the authors in Ref. (53), AR variation is analysed for different g/c variants. The study makes use of data related to force and moment coefficients for different grid fin configurations.…”

Experimental analysis of cell pattern on grid fin aerodynamics in subsonic flow

“…However, investigations involving explicit examination of the impact of these parameters were scarce. Current research elaborately comprehends the effects of individual parameters 34,35 in subsonic flow, which can assist in optimizing the design of these fins for enhanced aerodynamic efficiency. As a part of this work, current paper establishes the impact of various grid fin cell patterns on its overall subsonic flow aerodynamics and comprehensively compares them with the baseline model (BM) tested by the authors.…”