Boundary Layer Control in Plunging and Pitching Airfoils

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Publications

Dynamic Stall Mitigation Using a Deflectable Leading Edge: The IK30 Mechanism

Publication . Camacho, Emanuel A. R.; Silva, A. R. R.; Marques, Flávio D.

One major problem affecting rotor blade aerodynamics is dynamic stall, characterized by a series of events where transient vortex shedding negatively affects drag and lift, leading to abrupt changes in the wing’s pitching moment. The present work focuses on the mitigation of such effects by using a modified NACA0012 airfoil—the NACA0012-IK30 airfoil—previously used for thrust enhancement in flapping propulsion. An experimental rig is designed to study the advantages of a deflectable leading edge on a plunging and pitching wing, more specifically its influence on the aerodynamic coefficients over time. In the first stage, results indicate that the proposed IK30 mechanism does mitigate the stall effects under static conditions, with stall visualization data corroborating it. Regarding time-varying conditions, the data presents the adequacy of the proposed geometry under different plunging and pitching conditions, which, when correctly used, can mitigate or even eradicate the adverse effects of dynamic stall experienced, leading to significant drag reductions and modest lift enhancements. In the absence of a dynamic stall, the movable leading edge can also provide operational advantages, where it does not negatively affect drag or lift but can reduce the pitching moment intensity by indirectly shifting the pressure center. This study contributes to the long-standing discussion on how to mitigate the adverse effects of dynamic stall by providing an innovative yet simple solution.

2024-12-24Journal article

Embargoed access

Investigation of Asymmetric Plunging of a NACA0012 Airfoil

Publication . Silva, Joana G. S.; Camacho, Emanuel; Silva, A. R. R.

Animals and insects have been investigated because of their locomotion form that allows simultaneous thrust and lift production at low Reynolds numbers. The present study focuses on the experimental investigation of a plunging NACA0012 airfoil under asymmetric conditions. Tests are conducted with a Reynolds number of 1x10^4, considering two nondimensional velocities, kh=0.25 and 0.50. Each of these conditions is tested with different levels of asymmetry, depending on the limitations of the experimental apparatus. Flow visualization indicates that asymmetric movements produce both thrust and lift simultaneously and that increasing the asymmetry parameter and the reduced frequency have a similar impact: leading edge vortices to become stronger and are formed earlier. The present study is an earlier work that explores the existent void of experimental data regarding asymmetric conditions of unsteady airfoils.

2023-01-19Conference object

Embargoed access

Optimal leading-edge deflection for flapping airfoil propulsion

Publication . Camacho, E. A. R.; Silva, André; Marques, Flávio D.

The aerodynamics of oscillating airfoils are crucial to understanding subjects such as rotor dynamics and bio-inspired flows. Unsteady airfoils have been studied extensively, but there is an overall lack of knowledge regarding newer and more complex kinematics. The present paper builds upon our modified version of the NACA0012 by numerically comparing its way of flapping with the standard flapping that is common in the literature. The comparison is conducted parametrically at a Reynolds number of 104 for two nondimensional amplitudes. Then, using a gradient-based optimization method, we search for pitching amplitudes that maximize the propulsive power and efficiency for both flapping modes. Results indicate that the proposed flapping methodology is more promising than conventional flapping, with thrust increases up to approximately 40%. Furthermore, the proposed mechanism achieves maximum propulsive power with near-optimal efficiency, a common limitation of traditional flapping airfoils.

2023-09-26Journal article

Embargoed access

Influence of a Bubble Curtain Device on Microplastics Dynamics

Publication . Santos, César Augusto Vaz; Camacho, E. A. R.; Silva, André; Fael, Cristina Maria Sena

Air bubble curtains have been applied to a wide range of situations, from the attenuation of underwater noise, debris control, and containment of suspended sediment to the reduction in saltwater intrusion. This work conducts a preliminary numerical study on the influence of a bubble curtain device on microplastic dynamics. Simulations are conducted with a two-phase unsteady model, and the trajectories of the microplastic particles are computed with the Discrete Phase Model (DPM). Particles are injected upstream of the bubble curtain, and their transport is analyzed under different flow conditions. Results show that the ratio between the water velocity and the air injection velocity can significantly impact the efficiency of the device in directing the particles toward the surface. Furthermore, a higher degree of turbulent mixing is seen for lower water velocities. This study highlights the intricate flow behavior, and the need for a deeper understanding of other variables such as the microplastic size and concentration and the geometry of the air injection system.

2023-10-26Conference object

Open access

Predicting the NACA0012-IK30 Airfoil Propulsive Capabilities with a Panel Method

Publication . Camacho, E. A. R.; Marques, Flávio D.; Silva, A. R. R.

Unsteady airfoils play a pivotal role in comprehending diverse aerospace applications, being one of those flapping propulsions. The present paper studies this topic by bringing back an old unsteady panel method to juxtapose its results against CFD data previously obtained. The central objective is to revive the interest in these reduced order models in the topic of unsteady airfoils, which can be extended to model highly nonlinear effects while keeping computational resources fairly low. The findings reveal that while the potential flow-based UPM (Unsteady Panel Method) struggles to accurately capture the airfoil’s propulsive power, it remains adept at estimating consumed power. Moreover, an investigation into the pressure coefficient shows the potential benefits of UPM in contexts where flow separation can be disregarded. Despite inherent limitations, these simplified methodologies offer an effective preliminary estimation of flapping airfoil propulsive capabilities.

2023-11-07Conference object

Open access