Showing papers on "Aerodynamic force published in 2021"
TL;DR: This paper studies the trajectory tracking problem of flapping-wing micro aerial vehicles in the longitudinal plane and shows that the tracking errors are bounded and ultimately converge to a small neighborhood around the origin.
Abstract: This paper studies the trajectory tracking problem of flapping-wing micro aerial vehicles ( FWMAVs ) in the longitudinal plane. First of all, the kinematics and dynamics of the FWMAV are established, wherein the aerodynamic force and torque generated by flapping wings and the tail wing are explicitly formulated with respect to the flapping frequency of the wings and the degree of tail wing inclination. To achieve autonomous tracking, an adaptive control scheme is proposed under the hierarchical framework. Specifically, a bounded position controller with hyperbolic tangent functions is designed to produce the desired aerodynamic force, and a pitch command is extracted from the designed position controller. Next, an adaptive attitude controller is designed to track the extracted pitch command, where a radial basis function neural network is introduced to approximate the unknown aerodynamic perturbation torque. Finally, the flapping frequency of the wings and the degree of tail wing inclination are calculated from the designed position and attitude controllers, respectively. In terms of Lyapunovʼ s direct method, it is shown that the tracking errors are bounded and ultimately converge to a small neighborhood around the origin. Simulations are carried out to verify the effectiveness of the proposed control scheme.
230 citations
23 Feb 2021
TL;DR: In this paper, the authors present an approach to model aerodynamic effects using Gaussian Processes, which they incorporate into a Model Predictive Controller to achieve efficient and precise real-time feedback control, leading to up to 70% reduction in trajectory tracking error at high speeds.
Abstract: Aerodynamic forces render accurate high-speed trajectory tracking with quadrotors extremely challenging. These complex aerodynamic effects become a significant disturbance at high speeds, introducing large positional tracking errors, and are extremely difficult to model. To fly at high speeds, feedback control must be able to account for these aerodynamic effects in real-time. This necessitates a modeling procedure that is both accurate and efficient to evaluate. Therefore, we present an approach to model aerodynamic effects using Gaussian Processes, which we incorporate into a Model Predictive Controller to achieve efficient and precise real-time feedback control, leading to up to 70% reduction in trajectory tracking error at high speeds. We verify our method by extensive comparison to a state-of-the-art linear drag model in synthetic and real-world experiments at speeds of up to 14 m/s and accelerations beyond 4 g.
129 citations
TL;DR: In this paper, the authors explored the use of metasurface in designing an aerodynamic system for potential vortex-induced vibration suppression or energy harvesting, and found that the presence of meta-surface patterns has a significant influence on the aerodynamic characteristics of the bluff body.
91 citations
TL;DR: In this article, a comb-like beam (CombBeam) based piezoelectric energy harvester (PEH) was proposed for harvesting wind energy by exploiting the galloping mechanism.
64 citations
TL;DR: In this paper, a hybrid aeroelastic-pressure balance (HAPB) technique was proposed for the measurement of unsteady aerodynamic force on a galloping prism, which can accurately predict the galloping response of the test model whereas the classical quasi-steady theory fails for the prediction.
35 citations
TL;DR: In this paper, the authors proposed a surrogate-based optimization (SBO) technique to alleviate the computational burden of aerodynamic shape optimization (ASO) to delay and mitigate the deep dynamic stall characteristics of airfoils.
33 citations
TL;DR: In this paper, the effects of the Reynolds number on the piezoelectric energy harvesting from vortex-induced vibrations (VIV) of a circular cylinder are investigated. And the results also show that the performance of a VIV-based piezolectric EH harvester is more sensitive to the Reynolds numbers for a case with low mechanical damping ratio.
31 citations
TL;DR: In this article, a DDES based on the SST κ-ω turbulence model was used to simulate the aerodynamic characteristics of a braking plate, and aerodynamic forces on the plate, the flow structure around the plate an...
Abstract: A DDES based on the SST κ–ω turbulence model was used to simulate the aerodynamic characteristics of a braking plate, and the aerodynamic forces on the plate, the flow structure around the plate an...
29 citations
TL;DR: In this article, the effect of cross passage on aerodynamic characteristics of evacuated tube transportation is simulated by overset mesh technology, and the results show that there is a linear relationship between the length of the disturbed region of normal shock wave and running time.
27 citations
TL;DR: In this paper, the effects of side ratio on the piezoelectric energy harvesting from the transverse galloping of a rectangular cylinder based on a representative electro-aero-mechanical model, in which the aerodynamic force is calculated by the quasi-steady theory.
27 citations
TL;DR: In this article, three different metasurfaces with convex cylinder, tri-prim, and wedge ornaments are designed for galloping energy harvesting, and three-dimensional CFD simulations are combined to predict the dynamic responses of the metAsurface-wrapped GPEHs.
TL;DR: Inspired by wake induced vibration (WIV) of tandem arranged cylinders, a piezoelectric wind energy harvester with up and down stream interferences is proposed for highway wind resource exploitation as discussed by the authors.
TL;DR: In this article, a piezoelectric dual synthetic jet actuator (DSJA) was installed at the leading edge of the free end for generating the DSJ, which can be adjusted through the driving voltage and driving frequency.
TL;DR: In this paper, the aerodynamic characteristics of a typical central-slotted box girder during vortex-induced vibrations (VIVs) were investigated using a sectional model wind tunnel test involving the synchronous measurement of pressure distributions and VIV responses.
TL;DR: In this paper, the aerodynamic characteristics of a circular cylinder with and without ice accretion (without icicles) were studied via wind tunnel tests (including simultaneous multi-pressure and force measurements) for Reynolds numbers (Re) of 1.29 − − − 105 − 1.27 − − 106.
TL;DR: In this paper, the aerodynamic forces on a stationary train and moving train as well as the flow fields at the bottom of the trains were compared and analyzed using a numerical algorithm.
Abstract: In this study, the aerodynamic forces on a stationary train and moving train as well as the flow fields at the bottom of the trains were compared and analysed. In addition, the numerical algorithm ...
TL;DR: In this article, the effect of collective pitch control and cyclic pitch control on power and loads of FOWT is discussed under the uniform wind velocity of 10m/s with wind tunnel and numerical investigation.
TL;DR: A vehicle-structure interaction model is used to carry out non-linear dynamic analyses to assess the train-track coupling behaviour in the presence of winds, and the influence of the most relevant geometric, mechanical and aerodynamic vehicle properties in the risk of derailment caused by crosswinds is evaluated.
TL;DR: In this paper, an aerodynamic force model associated with a Galerkin model for the unforced fluidic pinball, the two-dimensional flow around three equal cylinders with one radius distance to each other, was proposed.
Abstract: We propose an aerodynamic force model associated with a Galerkin model for the unforced fluidic pinball, the two-dimensional flow around three equal cylinders with one radius distance to each other. The starting point is a Galerkin model of a bluff-body flow. The force on this body is derived as a constant-linear-quadratic function of the mode amplitudes from first principles following the pioneering work of Noca (On the evaluation of time-dependent fluid-dynamic forces on bluff bodies. PhD thesis, California Institute of Technology, 1997), Noca et al. (J. Fluids Struct., vol. 13, issue 5, 1999, pp. 551–578) and Liang & Dong (Virtual force measurement of POD modes for a flat plate in low Reynolds number flows. AIAA Paper 2014-0054). The force model is simplified for the mean-field model of the unforced fluidic pinball (Deng et al., J. Fluid Mech., vol. 884, 2020, p. A37) using symmetry properties and sparse calibration. The model is successfully applied to transient and post-transient dynamics in different Reynolds number regimes: the periodic vortex shedding after the Hopf bifurcation and the asymmetric vortex shedding after the pitchfork bifurcation comprising six different Navier–Stokes solutions. We foresee many applications of the Galerkin force model for other bluff bodies and flow control.
TL;DR: In this article, an improved delayed detached-eddy simulation (IDDES) method was employed to predict the aerodynamic characteristics of a generic train under a crosswind with different angles of attack.
TL;DR: A comparison with a full-order computational fluid dynamics (CFD) solution shows that the essential characteristics of the nonlinear buffet phenomenon are captured by the ROM method.
TL;DR: In this paper, the effect of varied sweep duration and timing of rotation on the unsteady aerodynamic characteristics of hovering flexible and rigid wings at Re of 104 was investigated, which indicated that natural fliers adopt specific wing kinematics in addition to their wing deformation for the upward titling of their net force vector, which will significantly enhance their aerodynamic performance.
TL;DR: It appears that the distributed flow and force sensor arrays found in flying animals are instrumented arrays that exploit highly nonlinear dynamics to achieve efficient and robust flight control.
Abstract: Flying animals exploit highly nonlinear dynamics to achieve efficient and robust flight control. It appears that the distributed flow and force sensor arrays found in flying animals are instrumenta...
TL;DR: In this paper, the root mean square lift coefficient increases significantly with amplitude of oscillation at low wind speeds, while at high wind speeds the influence of structural oscillation is significantly reduced and the aerodynamic force is in a quasi-static state.
TL;DR: In this paper, the effects of turbulence intensity on the aerodynamic forces and near wake of a 3D square cylinder with a height-to-width ratio (H/d) of 5 were experimentally studied in a low-speed wind tunnel at a Reynolds number of 34-×-104.
TL;DR: In this article, a moving model (1/20 scale) was used to study the effect of high temperature at the entrance of a tunnel on the aerodynamic performance of a high-speed train passing through it.
TL;DR: The improved delayed detached eddy simulation (IDDES) was used to study the influence of the platoon configuration of trains on its aerodynamic performance and the changing law of the aerodynamic force and the lateral stability of the trains are summarized.
TL;DR: In this article, the effects of windward face-mounted ribs on aerodynamic forces acting on a square cylinder of width D under smooth flow were examined to clarify the underlying mechanism of the mitigation of wind load caused by vertical ribs.
TL;DR: Architectural facades including balconies, mullions, shading boards, and ribs are widely used outside of tall buildings for the purpose of aesthetics and function as mentioned in this paper. And these facades will af...
Abstract: Architectural facades including balconies, mullions, shading boards, and ribs are widely used outside of tall buildings for the purpose of aesthetics and function. And these facades will af...