A series of wind tunnel tests were carried out to determine the effect of shark scale-based vortex generators (SSVG) on a NACA 0015 symmetrical airfoil’s aerodynamic characteristics. Three different sets of SSVG with varying geometrical parameters, such as chord length, amplitude, and wavelength, were designed and fabricated using 3D printing. The SSVG models were blended to the baseline NACA 0015 symmetrical airfoil. The wind tunnel experiments were performed over the test airfoil mounted with different sets of SSVG at various angles of attack, ranging from 0° to 24° in increments of 3°, and operating in the range of Re = 2 × 10⁵. The results revealed that the SSVG blended test airfoil reduced the drag and increased the maximum coefficient of lift (C_Lmax), thereby enhancing the overall aerodynamic performance. The SSVG offered noteworthy aerodynamic benefits by effectively altering the flow and causing significant spanwise variation in the flow properties. Additionally, attempts were made to identify the optimum chordwise location to blend the SSVG for effective use.

We study the surface pressure data exhibiting the underlying dynamical behavior of the flow transition over the upper surface of the aerofoil by using recurrence quantification analysis (RQA). In this study, NACA 2415 aerofoil subjected to a turbulent inflow of $\text{TI}=8.46\mathrm{\%}$ at various angles of attack ranging from $\alpha =0^{°}$ to ${20}^{°}$ with an increment of $5^{°}$ corresponding to $Re=2.0\times {10}^5$ is considered. We show that the values of recurrence quantification measures effectively distinguish the underlying dynamics of time series surface pressure data at each port, which proves RQA as an effective tool in accurately predicting the flow transitions.

A series of wind tunnel tests were performed to investigate the effect of turbulent inflows on the aerodynamic characteristics of variously modified trough incident leading-edge-protuberanced (LEP) wing configurations at various turbulence intensities. A self-developed passive grid made of parallel arrays of round bars was placed at different locations of the wind tunnel to generate desired turbulence intensity. The aerodynamic forces acting over the trough incidence LEP wing configuration where obtained from surface pressure measurements made over the wing at different turbulence intensities using an MPS4264 Scanivalve simultaneous pressure scanner corresponding to a sampling frequency of 700 Hz. All the test models were tested at a wide range of angles of attack ranging between $0^{°}\le \alpha \le {90}^{°}$ at turbulence intensities varying between 5.90% ≤ TI ≤ 10.54%. Results revealed that the time-averaged mean coefficient of lift (C_L) increased with the increase in the turbulence intensity associated with smooth stall characteristics rendering the modified LEP test models advantageous. Furthermore, based on the surface pressure coefficients, the underlying dynamics behind the stall delay tendency were discussed. Additionally, attempts were made to statistically quantify the aerodynamic forces using standard deviation at both the pre-stall and the post-stall angles.

The present study explores a passive flow control technique utilizing leading-edge flags (with and without serrations) over the airfoil to improve the performance of the airfoil. These flags are attached to the leading-edge of the airfoil that oscillates naturally in response to the oncoming airflow thereby promoting favorable pressure conditions and optimizing the flow over the airfoil. NACA 63(4)-021 airfoil was modified by incorporating flags at leading-edge with different GSM (75G, 85G, 100G) and length (0.3C, 0.2C). Experimental tests were conducted in the low-speed subsonic wind tunnel at Reynolds number 1.71 × 10 ⁵ featuring leading-edge flags with and without serrations. Surface pressure data were acquired over all the test cases with the help of MPS4264 miniature pressure scanner of Scanivalve make at 700 Hz across 46 pressure taps distributed over pressure and suction surfaces. Aerodynamic forces and force coefficients for all the test cases were calculated by applying pressure integration technique to the surface pressure data acquired across angles of attack between 0° and 70° (in 5° increments). The study observed lift augmentation and a significant delay in stall resulting from the leading-edge flag’s motion. Maximum lift was increased by 8.61% and a stall delay of 5° was observed. At post-stall angles, the modified models enhance the lift by 57.7% when compared with the baseline configuration. Additionally, surface pressure distribution over the airfoil induced by leading-edge flags (with and without serrations) were also evaluated. Coefficient of pressure distributions (C _p ) confirmed that leading-edge flags with lower GSM and longer length configuration (both with and without serrations) generated wider suction regions, rendering delayed flow separation. These findings confirm the aerodynamic viability of passive leading-edge devices for flow control.