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M.J. Buszek
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We present an on-site aerodynamic investigation of runners through the Ring of Fire (RoF) methodology. The Lagrangian Particle Tracking (LPT) technique is used with helium filled soap bubbles as tracer particles and LED illumination; the acquired time-resolved data are processed through the Shake-the-Box (STB) algorithm. The RoF measurements are performed with six athletes running at an average speed of 8 m/s, resulting in a Reynolds number of 2 × 105, based on the shoulder width. While existing studies largely focus on numerical simulations and experimental measurements performed on static human models, the present analysis investigates the wake flow topology of moving runners, thus addressing a significant gap in the literature. Specifically, the ensemble-averaged streamwise velocity and vorticity fields, along with the pressure coefficient distribution in the wake, are investigated. The results reveal that, close to the athlete, the wake shape closely resembles the runner’s body outline, with the torso area exerting the greatest influence. Moreover, in the near wake, a downwash effect from the head and an upwash effect from the hips are identified. This flow behaviour is further supported by the streamwise vorticity distribution analysis, which confirms the consistent formation of vortical structures across different athlete passages. Additionally, the aerodynamic drag is evaluated by applying the momentum conservation within a control volume containing the athlete. The results, presented in terms of the drag area, reveal that the overall drag area is largely independent of the control volume length, while the individual drag area contributions vary along the wake, with the greatest variations detected close to the athlete. The computed drag areas are 30–40% lower than most of the values reported in previous experimental and numerical studies, a difference attributed to the higher realism of the experimental measurements performed in this study, which capture the fully unsteady nature of the running motion. Moreover, a linear increase in the drag area with the athlete’s height squared is found.
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We present an on-site aerodynamic investigation of runners through the Ring of Fire (RoF) methodology. The Lagrangian Particle Tracking (LPT) technique is used with helium filled soap bubbles as tracer particles and LED illumination; the acquired time-resolved data are processed through the Shake-the-Box (STB) algorithm. The RoF measurements are performed with six athletes running at an average speed of 8 m/s, resulting in a Reynolds number of 2 × 105, based on the shoulder width. While existing studies largely focus on numerical simulations and experimental measurements performed on static human models, the present analysis investigates the wake flow topology of moving runners, thus addressing a significant gap in the literature. Specifically, the ensemble-averaged streamwise velocity and vorticity fields, along with the pressure coefficient distribution in the wake, are investigated. The results reveal that, close to the athlete, the wake shape closely resembles the runner’s body outline, with the torso area exerting the greatest influence. Moreover, in the near wake, a downwash effect from the head and an upwash effect from the hips are identified. This flow behaviour is further supported by the streamwise vorticity distribution analysis, which confirms the consistent formation of vortical structures across different athlete passages. Additionally, the aerodynamic drag is evaluated by applying the momentum conservation within a control volume containing the athlete. The results, presented in terms of the drag area, reveal that the overall drag area is largely independent of the control volume length, while the individual drag area contributions vary along the wake, with the greatest variations detected close to the athlete. The computed drag areas are 30–40% lower than most of the values reported in previous experimental and numerical studies, a difference attributed to the higher realism of the experimental measurements performed in this study, which capture the fully unsteady nature of the running motion. Moreover, a linear increase in the drag area with the athlete’s height squared is found.
In aircraft structural design it is of utmost importance to minimise the structural mass while maintaining a durable structure that is able to sustain the design loads for a predetermined number of flight cycles. The present manuscript investigates a methodology for the preliminary design and analysis of a tandem-wing long-range electric vertical takeoff and landing (eVTOL) aircraft. First, a class I weight estimation for initial loads calculation is presented. Next, the flight envelope, main load cases and failure modes considered in this preliminary design are explained. Load approximations for the wing structures in cruise and take-off conditions are presented and discussed. Next, Cessna's class II semi-empirical weight estimation method is applied to calculate the mass of 11 eVTOL aircraft subsystems. A design concept for the wing tilting mechanism is proposed. Thereafter, an initial fuselage layout design is presented, followed by a discussion on design for crashworthiness. The aeroelastic behaviour of the wing and the whirl flutter considering the propeller engine structures is investigated. Lastly, refinements in the design parameterization are implemented concerning the thickness distributions in the structural elements of the wingbox, and finally a sizing of the wing rotating shaft is performed.
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In aircraft structural design it is of utmost importance to minimise the structural mass while maintaining a durable structure that is able to sustain the design loads for a predetermined number of flight cycles. The present manuscript investigates a methodology for the preliminary design and analysis of a tandem-wing long-range electric vertical takeoff and landing (eVTOL) aircraft. First, a class I weight estimation for initial loads calculation is presented. Next, the flight envelope, main load cases and failure modes considered in this preliminary design are explained. Load approximations for the wing structures in cruise and take-off conditions are presented and discussed. Next, Cessna's class II semi-empirical weight estimation method is applied to calculate the mass of 11 eVTOL aircraft subsystems. A design concept for the wing tilting mechanism is proposed. Thereafter, an initial fuselage layout design is presented, followed by a discussion on design for crashworthiness. The aeroelastic behaviour of the wing and the whirl flutter considering the propeller engine structures is investigated. Lastly, refinements in the design parameterization are implemented concerning the thickness distributions in the structural elements of the wingbox, and finally a sizing of the wing rotating shaft is performed.