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Blade Element Theory

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Hoon Cheol Park – 1st expert on this subject based on the ideXlab platform

  • Comparison of Aerodynamic Forces and Moments Calculated by Three-dimensional Unsteady Blade Element Theory and Computational Fluid Dynamics
    Journal of Bionic Engineering, 2017
    Co-Authors: Loan Thi Kim Au, Hoang Vu Phan, Hoon Cheol Park

    Abstract:

    In previous work, we modified Blade Element Theory by implementing three-dimensional wing kinematics and modeled the unsteady aerodynamic effects by adding the added mass and rotational forces. This method is referred to as Unsteady Blade Element Theory (UBET). A comparison between UBET and Computational Fluid Dynamics (CFD) for flapping wings with high flapping frequencies (>30 Hz) could not be found in literature survey. In this paper, UBET that considers the movement of pressure center in pitching-moment estimation was validated using the CFD method. We investigated three three-dimensional (3D) wing kinematics that produce negative, zero, and positive aerodynamic pitching moments. For all cases, the instantaneous aerodynamic forces and pitching moments estimated via UBET and CFD showed similar trends. The differences in average vertical forces and pitching moments about the center of gravity were about 10% and 12%, respectively. Therefore, UBET is proven to reasonably estimate the aerodynamic forces and pitching moment for flight dynamic study of FW-MAV. However, the differences in average wing drags and pitching moments about the feather axis were more than 20%. Since study of aerodynamic power requires reasonable estimation of wing drag and pitching moment about the feather axis, UBET needs further improvement for higher accuracy.

  • optimal wing rotation angle by the unsteady Blade Element Theory for maximum translational force generation in insect mimicking flapping wing micro air vehicle
    Journal of Bionic Engineering, 2016
    Co-Authors: Loan Thi Kim Au, Hoang Vu Phan, Hoon Cheol Park

    Abstract:

    This paper provides a parametric study to obtain the optimal wing rotation angle for the generation of maximum translational force in an insect-mimicking Flapping-Wing Micro Air Vehicle (FWMAV) during hovering. The Blade Element Theory and momentum Theory were combined to obtain the equation from which the translational aerodynamic force could be estimated. This equation was converted into a non-dimensional form, so that the effect of normalized parameters on the thrust coefficient could be analyzed. The research showed that the thrust coefficient for a given wing section depends on two factors, the rotation angle of the wing section and the ratio of the chord to the travel distance of the wing section in one flapping cycle. For each ratio that we investigated, we could arrive at an optimal rotation angle corresponding to a maximum thrust coefficient. This study may be able to provide guidance for the FWMAV design.

  • validation of three dimensional unsteady Blade Element Theory
    대한기계학회 춘추학술대회, 2015
    Co-Authors: Thi Kim Loan Au, Hoon Cheol Park

    Abstract:

    The Blade Element Theory (BET) based on quasi-steady aerodynamics has been widely used for various engineering application such as design and analysis of helicopter Blade and wind/tidal turbine Blade design with slight modification. The BET was also used to prove that the aerodynamic force produced by flapping wings of insects cannot be properly estimated using the steady aerodynamics. We modified the BET implementing three-dimensional wing kinematics and modeling the unsteady aerodynamic force by the added mass and rotational force. The inertial force was also included to correctly predict the time history of the total force generated by flapping wings. The modified BET is called the unsteady Blade Element Theory (UBET) afterward. UBET was proven to reasonably estimate the averages and time histories of the produced forces. However, the UBET estimation has not been compared with the prediction by the computational fluid dynamics (CFD). In this paper, we used the computational fluid dynamics (CFD) software of ANSYS Fluent to compute the timehistories and averages of forces and pitching moments produced by flapping wings, and compared the results with those calculated by the unsteady Blade Element Theory (UBET). For calculations by the CFD and UBET, we used the measured three-dimensional wing kinematics generated by a flapping mechanism for three different flapping angle ranges. The comparison shows that UBET could nicely reproduce the time-histories of vertical and horizontal force components and pitching moment. The average of vertical force by UBET was about 10% difference. The time-history of pitching moment by UBET was also close to that by the CFD. The average pitching moment show larger discrepancies up to 20%. However, the pitching moment characteristics by the CFD and UBET were similar to each other. Therefore, the UBET can be used for flight stability analysis of flapping-wing micro air vehicles, replacing CFD.

Doyoung Byun – 2nd expert on this subject based on the ideXlab platform

  • Stable vertical takeoff of an insect-mimicking flapping-wing system without guide implementing inherent pitching stability
    Journal of Bionic Engineering, 2012
    Co-Authors: Hoang Vu Phan, Hoon Cheol Park, Quangtri Truong, Quoc Viet Nguyen, Tien Van Truong, Doyoung Byun

    Abstract:

    We briefly summarized how to design and fabricate an insect-mimicking flapping-wing system and demonstrate how to implement inherent pitching stability for stable vertical takeoff. The effect of relative locations of the Center of Gravity (CG) and the mean Aerodynamic Center (AC) on vertical flight was theoretically examined through static force balance consideration. We conducted a series of vertical takeoff tests in which the location of the mean AC was determined using an unsteady Blade Element Theory (BET) previously developed by the authors. Sequential images were captured during the takeoff tests using a high-speed camera. The results demonstrated that inherent pitching stability for vertical takeoff can be achieved by controlling the relative position between the CG and the mean AC of the flapping system.

  • a modified Blade Element Theory for estimation of forces generated by a beetle mimicking flapping wing system
    Bioinspiration & Biomimetics, 2011
    Co-Authors: Quangtri Truong, Hoon Cheol Park, Quoc Viet Nguyen, V T Truong, Doyoung Byun

    Abstract:

    We present an unsteady Blade Element Theory (BET) model to estimate the aerodynamic forces produced by a freely flying beetle and a beetle-mimicking flapping wing system. Added mass and rotational forces are included to accommodate the unsteady force. In addition to the aerodynamic forces needed to accurately estimate the time history of the forces, the inertial forces of the wings are also calculated. All of the force components are considered based on the full three-dimensional (3D) motion of the wing. The result obtained by the present BET model is validated with the data which were presented in a reference paper. The difference between the averages of the estimated forces (lift and drag) and the measured forces in the reference is about 5.7%. The BET model is also used to estimate the force produced by a freely flying beetle and a beetle-mimicking flapping wing system. The wing kinematics used in the BET calculation of a real beetle and the flapping wing system are captured using high-speed cameras. The results show that the average estimated vertical force of the beetle is reasonably close to the weight of the beetle, and the average estimated thrust of the beetle-mimicking flapping wing system is in good agreement with the measured value. Our results show that the unsteady lift and drag coefficients measured by Dickinson et al are still useful for relatively higher Reynolds number cases, and the proposed BET can be a good way to estimate the force produced by a flapping wing system.

Quangtri Truong – 3rd expert on this subject based on the ideXlab platform

  • Stable vertical takeoff of an insect-mimicking flapping-wing system without guide implementing inherent pitching stability
    Journal of Bionic Engineering, 2012
    Co-Authors: Hoang Vu Phan, Hoon Cheol Park, Quangtri Truong, Quoc Viet Nguyen, Tien Van Truong, Doyoung Byun

    Abstract:

    We briefly summarized how to design and fabricate an insect-mimicking flapping-wing system and demonstrate how to implement inherent pitching stability for stable vertical takeoff. The effect of relative locations of the Center of Gravity (CG) and the mean Aerodynamic Center (AC) on vertical flight was theoretically examined through static force balance consideration. We conducted a series of vertical takeoff tests in which the location of the mean AC was determined using an unsteady Blade Element Theory (BET) previously developed by the authors. Sequential images were captured during the takeoff tests using a high-speed camera. The results demonstrated that inherent pitching stability for vertical takeoff can be achieved by controlling the relative position between the CG and the mean AC of the flapping system.

  • a modified Blade Element Theory for estimation of forces generated by a beetle mimicking flapping wing system
    Bioinspiration & Biomimetics, 2011
    Co-Authors: Quangtri Truong, Hoon Cheol Park, Quoc Viet Nguyen, V T Truong, Doyoung Byun

    Abstract:

    We present an unsteady Blade Element Theory (BET) model to estimate the aerodynamic forces produced by a freely flying beetle and a beetle-mimicking flapping wing system. Added mass and rotational forces are included to accommodate the unsteady force. In addition to the aerodynamic forces needed to accurately estimate the time history of the forces, the inertial forces of the wings are also calculated. All of the force components are considered based on the full three-dimensional (3D) motion of the wing. The result obtained by the present BET model is validated with the data which were presented in a reference paper. The difference between the averages of the estimated forces (lift and drag) and the measured forces in the reference is about 5.7%. The BET model is also used to estimate the force produced by a freely flying beetle and a beetle-mimicking flapping wing system. The wing kinematics used in the BET calculation of a real beetle and the flapping wing system are captured using high-speed cameras. The results show that the average estimated vertical force of the beetle is reasonably close to the weight of the beetle, and the average estimated thrust of the beetle-mimicking flapping wing system is in good agreement with the measured value. Our results show that the unsteady lift and drag coefficients measured by Dickinson et al are still useful for relatively higher Reynolds number cases, and the proposed BET can be a good way to estimate the force produced by a flapping wing system.