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Effect of thickness-to-chord ratio on aerodynamics of non-slender delta wing

Sharifi Ghazijahani, Mohammad
Flow characterization over delta wings have gained attention in recent decades due to their prevailing usage in designs of unmanned air vehicles (UAVs). In literature,only a few studies have reported wing thickness effect on both the aerodynamic performance and detailed flow structure over delta wings. In the present investigation, the effect of thickness-to-chord (t/C) ratio on aerodynamics of a non-slender delta wing with 45 degree sweep angle is characterized in a low-speed wind tunnel using laser illuminated smoke visualization, surface pressure measurements, particle image velocimetry, and force measurements. The delta wings with t/C ratios varying from 2 % to 15 % are tested at broad range s of angle of attack and Reynolds number. The results indicate that the effect of t/C ratio on flow structure is quite substantial. Considering the low angles of attack where the wings experience leading edge vortex structure, the strength of the vortex structure increases as the t/C ratio increases. However, low t/C ratio wings have pronounced surface separations at higher angle of attack compared to the high t/C ratio wings. These results are well supported by the force measurements such that high t/C ratio wings induce higher lift coefficients, CL, at low angles of attack, whereas maximum CL values are higher and appear at higher angle of attack for low t/C ratio wings. This indicates that low t/C ratio wings are more resistive to the stall condition. Considering the lift-to-drag ratio, CL/CD, increase in t/C ratio induces remarkable drop in CL/CD values.