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- Predicting the NACA0012-IK30 Airfoil Propulsive Capabilities with a Panel MethodPublication . 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.
- Influence of a Bubble Curtain Device on Microplastics DynamicsPublication . Santos, César Augusto Vaz; Camacho, E. A. R.; Silva, André; Fael, Cristina Maria SenaAir 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.
- Effects of a Dynamic Leading Edge on a Plunging AirfoilPublication . Camacho, Emanuel; Neves, Fernando M. S. P.; Marques, Flávio D.; Barata, Jorge M M; Silva, AndréThe dynamics of oscillating airfoils are of great interest in many research areas such as rotor dynamics and biomimetics. The results reported in this research provide an insight into the mechanics of birds’ leading edge and how the dynamic curvature of the airfoil can highly benefit the aerodynamic and propulsive performance, especially at high angles of attack. The main goal of the current work is to numerically investigate the influence of a deflecting leading edge on the propulsive coefficients and flowfield created by a plunging airfoil at a Reynolds number of 1.4 × 104 and a constant Strouhal number of 0.15 with different ( k, ℎ) combinations. Employing a RANS approach with the proposed NACA0012-IK30 airfoil, results show that dynamically deflecting the leading edge significantly improves the propulsive efficiency of the airfoil by either reducing the required power or improving the thrust production. The outcomes regarding the propulsive efficiency show a considerable increase of up to 92% when the higher nondimensional amplitude was considered.
- Plunging Airfoil: Reynolds Number and Angle of Attack EffectsPublication . Camacho, E. A. R.; Neves, Fernando M. S. P.; Silva, André; Barata, Jorge M. M.Natural flight has consistently been the wellspring of many creative minds, yet recreating the propulsive systems of natural flyers is quite hard and challenging. Regarding propulsive systems design, biomimetics offers a wide variety of solutions that can be applied at low Reynolds numbers, achieving high performance and maneuverability systems. The main goal of the current work is to computationally investigate the thrust-power intricacies while operating at different Reynolds numbers, reduced frequencies, nondimensional amplitudes, and mean angles of attack of the oscillatory motion of a NACA0012 airfoil. Simulations are performed utilizing a RANS (Reynolds Averaged Navier-Stokes) approach for a Reynolds number between 8.5×10^3 and 3.4×10^4, reduced frequencies within 1 and 5, and Strouhal numbers from 0.1 to 0.4. The influence of the mean angle-of-attack is also studied in the range of 0º to 10º. The outcomes show ideal operational conditions for the diverse Reynolds numbers, and results regarding thrust-power correlations and the influence of the mean angle-of-attack on the aerodynamic coefficients and the propulsive efficiency are widely explored.
- Real-time optimization of wing drag and lift performance using a movable leading edgePublication . Camacho, E. A. R.; Silva, Maíra Martins da; Silva, A. R. R.; Marques, Flávio D.A real-time optimization strategy can provide any system with a considerable boost in performance on the fly, which in real-world applications can be translated to lower energy consumption or higher efficiency. This study investigates the particular case of using real-time optimization to improve wing aerodynamic performance with a dynamically activated deflectable leading edge. Its activation aims to minimize drag and maximize lift and is governed by real-time and gradient-based optimization. An extension to a classic method is suggested to enhance gradient estimation accuracy. Experimental data are obtained at a Reynolds number of with the wing fixed at five positions. For each of these positions, optimal leading-edge deflections are found. The results indicate that deflecting the leading edge has a negligible impact on drag and lift before the stall onset. However, the reduction in the pitching moment cannot be ignored. When the wing is experiencing a proper stall, the movable leading edge yields remarkable enhancements, with the lift being approximately raised by 45% together with a substantial increase in the critical angle of attack. The findings highlight the potential of real-time optimization in experimental aerodynamic studies, reinvigorating its application in improving aircraft performance.
- Plunging Airfoil: Reynolds Number and Angle of Attack EffectsPublication . Camacho, Emanuel; Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, A. R. R.Natural flight has always been the source of imagination for the Human being, but reproducing the propulsive systems used by animals is indeed complex. New challenges in today’s society have made biomimetics gain a lot of momentum because of the high performance and versatility these systems possess when subjected to the low Reynolds numbers effects. The main objective of the present work is the computational study of the influence of the number of Reynolds, angle of attack, frequency and amplitude of the oscillatory movement of a NACA0012 airfoil in the aerodynamic performance for a constant angle of attack over time. The thrust and power coefficients are obtained which together are used to calculate the propulsive efficiency. The simulations were performed using ANSYS Fluent with a RANS approach for Reynolds numbers between 8500 and 34000, reduced frequencies between 1 and 5, and Strouhal numbers from 0.1 to 0.4. The influence of the (constant over time) angle of attack was also studied in the range of 0º to 10º. The results indicate optimal operational conditions for the different Reynolds numbers and unprecedented results of the influence of the angle of attack on the aerodynamic coefficients and the propulsive efficiency is widely explored.
- Parametric Study of a Plunging NACA0012 AirfoilPublication . Camacho, E. A. R.; Neves, Fernando M. S. P.; Silva, André; Barata, Jorge M MNatural flight has always been the source of imagination for the Human being, but reproducing the propulsive systems used by animals is indeed complex. New challenges in today’s society have made biomimetics gain a lot of momentum because of the high performance and versatility these systems possess when subjected to the low Reynolds numbers effects. The main objective of the present work is the computational study of the influence of the Reynolds number, frequency and amplitude of the oscillatory movement of a NACA0012 airfoil in the aerodynamic performance for a constant angle of attack over time. The thrust and power coefficients are obtained which together are used to calculate the propulsive efficiency. The simulations were performed using ANSYS Fluent with a RANS approach for Reynolds numbers between 8,500 and 34,000, reduced frequencies between 1 and 5, and Strouhal numbers from 0.1 to 0.4. The aerodynamic parameters were widely explored as well as their interaction, obtaining optimal operational condition zones for the different Reynolds numbers studied.
- Investigation of Asymmetric Plunging of a NACA0012 AirfoilPublication . 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.
- Leading-Edge Parametric Study of the NACA0012-IK30 AirfoilPublication . Camacho, Emanuel; Marques, Flávio D.; Silva, A. R. R.; Barata, Jorge M MIn many research areas, such as rotor dynamics and biomimetics, the dynamics of oscillating airfoils are of great interest. The findings of this study provide great insight into the importance of the leading edge regarding the propulsive characteristics of flapping airfoils. The main objective of the present work is to analyze the influence of the leading-edge pitching amplitude of the NACA0012-IK30 airfoil at a Reynolds number of 1.4x10^4, constant Strouhal number of 0.15 with three different (k,h) combinations and five leading-edge pitching amplitudes (A_alpha=0º,5º,10º,15º,20º). Using a RANS approach with the turbulence model k-omega SST coupled with the Intermittency Transition Model, results show that changing the leading-edge pitching amplitude has great impact on thrust enhancement, although presenting a small influence when it comes to lower nondimensional amplitudes. The required power coefficient is typically reduced while increasing the leading-edge pitching amplitude which, in some cases, provides an increase up to 211% in propulsive efficiency.
- Propulsive Enhancement and Dynamic Stall Mitigation in Flapping AirfoilsPublication . Camacho, Emanuel António Rodrigues; Silva, André Resende Rodrigues da; Marques, Flávio DonizettiThe study of oscillating airfoils is the centerpiece for the biomimetization of flight, exploring newer energy-extracting devices, and improving rotor blade design. Typically, these are affected by highly nonlinear aerodynamic effects, which in most cases, still require substantial research regarding the aerodynamics and parameters that govern these systems. The present investigation looks into some of these topics by scrutinizing two primary fronts: the propulsive enhancement and the dynamic stall mitigation of flapping airfoils. After a comprehensive review of past investigations, the current work proposes a newer airfoil, the NACA0012-IK30 airfoil, that introduces the concept of dynamic curvature. This bioinspired concept is applied to the conventional NACA0012, producing an innovative geometry by dividing the airfoil into two parts, where we can deflect the leading edge independently from the rest of the airfoil. This newer design went through parametrical and optimal analysis by employing a diverse set of experimental and numerical methodologies, divided into two domains: lower Reynolds number, where the propulsive capabilities are studied, and higher Reynolds number, where dynamic stall mitigation is explored. At the lower spectrum of the Reynolds number, results show that the activation of the leading edge offered by the IK30 mechanism demonstrated the ability to improve considerably the propulsive power and efficiency. When comparing the proposed geometry with standard flapping, it is clear that the suggested design can provide optimal thrust with near-optimal propulsive efficiency, something unachievable in traditional flapping. Results obtained at the higher range of the Reynolds number, where the IK30 mechanism functions with dynamic stall mitigation purposes, show the adequacy of the proposed geometry under different plunging and pitching conditions. When correctly deflecting the leading edge, the aerodynamic stall experienced both in static and dynamic conditions can be mitigated or even eradicated, leading to significant drag reductions and modest lift enhancements. While the present study yielded encouraging results, the IK30 mechanism and the broad concept of dynamic curvature need to be the focus of further research. Using newer technologies, for instance, continuous camber morphing, coupled with ingenious kinematics, will allow us to explore newer pathways to extend our knowledge and exploit the aerodynamics of unsteady airfoils.
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