Wind turbines can provide energy in developing countries. However, there are limitations to the skilled labor and manufacturing equipment required to manufacture these systems in these regions. Accordingly, the manufacturing process needs to be adapted to the potential of the developing world. In this work, a simplified wind turbine blade design is investigated. The turbine efficiency is analyzed by the blade element momentum (BEM) theory. Two different scenarios are considered to simplify the design of the wind turbine blade. The shape of the blade is simulated by a rectangular root connected to several trapezoidal segments. This results in a simple chord length distribution. The design of the twist angle is also considered. The area under the power curve is used to compare the performance of the simplified blades with that of the original design. Results show that the twist angle can be completely omitted as a tradeoff between efficiency and manufacturability. Depending on the number of simplified design segments, the area under the power curve is reduced between 13% and 25 % with respect to the original blade. The model also demonstrates how the loss in efficiency increases as the simplicity of blade design increases. Still, the design simplification enables a manufacturing process which may facilitate the use of wind energy in the developing world.

When designing a wind turbine blade, the goal is to attain the highest possible power output under specified atmospheric conditions.In this paper,the maximum likelihood estimation method was used to compute the hub height wind speed at 65m mathematical model based on the observation data of He xi Corridor wind at 10m height, taking He xi region of a certain type of 40m blade as an example, based on the Blade Element Momentum Theoty and tip loss, established the blade aerodynamic mathematic model, using the genetic algorithm on the blades. Each section of the chord, twist angle of wind energy utilization coefficient, girder cap layer thickness parameters were optimized, The aerodynamic performance and stress distribution are given out, the results showed that the optimized blade wind energy utilization coefficient is greatly improved and the quality of the blade is significantly reduced. It is suitable for wind the characteristics of the blade design condition performance supper than that of general blade.It provides a theoretical basis for the blade design.

We consider navigation for a polygonal, holonomic robot in an obstacle filled environment in SE(2). We denote the configuration space of the robot as C . In order to determine the free space, obstacles are represented as point clouds then transformed into C . The point-wise Minkowski sum of the robot and obstacle points is then calculated in C by adding the vertices and points on the convex hull of robot to obstacle points for different robot configurations. We then find a seed path using either a graph search or sample based planner. This seed path is then used in our novel method to determine overlapping convex regions for each consecutive chord of the seed path. Our proposed method represents the collision free, traversable region by defining overlapping convex corridors defined by a set of linear constraints. Within these corridors we find feasible trajectories that optimize a specified cost functional. The generated corridors along with the initial and desired poses are then used to determine an optimal path that satisfies the specified objective within the same homotopy group as the seed path. The key contributions is the proposed methods’ ability to easily generate a set of convex, overlapping polytopes that effectively represent the traversable free space. This in turn lends itself to (a) efficient computation of optimal paths, and (b) extending these basic ideas to non-Euclidean spaces such as SE(2). We provide simulated examples and implement this algorithm on the KUKA youBot omni-directional base.

The dynamic loads transmitted from the rotor to the airframe are responsible for vibrations, discomfort and alternate stress of components. A new and promising way to minimize vibration is to reduce dynamic loads at their source by performing an aeroelastic optimization of the rotor. This optimization is done thanks to couplings between the flapwise-bending motion and the torsion motion. The impact of elastic couplings (composite anisotropy) on the blade dynamic behaviour and on dynamic loads are evaluated in this paper. Firstly, analytical results, based on a purely linear modal approach, are given to understand the influence of those couplings in terms of frequency placement, aerodynamic lift load and vertical shear modification. Then, those elastic couplings are introduced on a simplified but representative blade (homogeneous beam with constant chord) and results are presented.

We study the combined effect of boundary animation (small-amplitude heaving) and incoming flow unsteadiness (incident vorticity) on the vibroacoustic signature of a thin rigid airfoil in low-Mach high-Reynolds number flow. The nonlinear dynamical problem for the vortex trajectory is studied using potential flow theory. The dynamical description then serves as an effective source term to evaluate the far-field sound using Powell-Howe’s analogy. The results identify the fluid-airfoil system as a dipole-type source, and demonstrate the significance of non-linear eddy-airfoil interaction on the acoustic radiation. At low heaving frequencies (ωa/U < 1 , where ω denotes the heaving frequency, 2 a the airfoil chord, and U the mean stream speed), the effect of heaving is minor, and the acoustic field can be approximated by neglecting airfoil motion. However, at ωa/U > 1 , heaving becomes dominant, radiating sound through an “airfoil motion” dipole (oriented along the direction of heaving) and airfoil-induced oscillations in the vortex trajectory. In contrast with the periodic “airfoil motion” signal, the non-periodic incident vortex sound has a component along the airfoil chord, which becomes significant when the vortex passes close to the airfoil. The work is suggested as a preliminary tool to examine the acoustic radiation during flapping flight at unsteady flow conditions.

A parametric one-dimensional model of suspension bridges is employed to investigate their static and dynamic aeroelastic behavior in response to a gust load and at the onset of flutter. The equilibrium equations are obtained via a direct total Lagrangian formulation where the kinematics for the deck, assumed to be linear, feature the vertical and the chord-wise displacements of the deck mean axis and the torsional rotations of the deck cross sections, while preserving their shape during rotation. The cables elasto-geometric stiffness contribution is obtained by condensing the equilibrium in the longitudinal direction assuming small horizontal displacements and neglecting the cable kinematics along the bridge chord-wise direction. The equations of motion are linearized about the prestressed static aeroelastic configuration and are obtained via an updated Lagrangian formulation. The equations of motion governing the structural dynamics of the bridge are coupled with the incompressible unsteady aero-dynamic model obtained by a set of reduced-order indicial functions developed for the cross section of a suspension bridge, here represented by a rectangular cross-section. The space dependence of the governing equations is treated using the Galerkin approach borrowing as set of trial functions, the eigenbasis of the modal space. The time integration is subsequently performed by using a numerical scheme that includes the modal reduced dynamic aeroelastic Ordinary Differential Equations (ODEs) and the added aerodynamic states also represented in ODE form, the latter being associated with the lag-state formulation pertinent to the unsteady wind-induced loads. The model is suitable to analyze the effect of a time and space non uniform gust load distributed on the bridge span. The obtained aeroelastic system is also suitable to study the onset of flutter and to investigate the sensitivity of the flutter condition on geometrical and aerodynamic parameters. The flutter instability is evaluated using appropriate frequency and time domain characteristics. The parametric continuum model is exploited to perform dynamic aeroelastic flutter analysis and gust response of the Runyang Suspension Bridge over the Yangtze river in China.

A wind energy has getting more attention due to its free-source, its nature of renewable energy, and free of carbon dioxide emission. As the wind map varies area to area, the wind energy collection strongly depends on the site. In order to maximize the amount of energy captured, an improved, low airspeed wind turbines are demanded to be designed. A wind turbine studied was created using the NACA 4412 foil shape and a decreasing chord length with increasing distance from the center of the turbine. The pitch was also varied along the span of the blade. The blade was analyzed using CFD and tested in a wind tunnel facility. The turbine was connected to a motor which was connected to a resistor and current and voltage meters. Using the voltage and current data at a prescribed rate of rotation, the model generated decent power output. The study focused mostly for a low-speed wind up to 2m/s (or 3.4 mph). For practical use the turbine would need to be scaled to a greater size and a proportional-integral-derivative controller (PID controller) that can generate higher resistance would need to be employed.

In this paper a Multi-Level System design (MLS) algorithm is presented and utilized for a wind turbine system analysis. The MLS guides the decision making process for designing a complex system where many alternatives and many mutually competing objectives and disciplines need to be considered and evaluated. Mathematical relationships between the design variables and the multiple discipline performance objectives are developed adaptively as the various design considerations are evaluated and as the design is being evolved. These relationships are employed for rewarding performance improvement during the decision making process by allocating more resources and influence to the disciplines which exhibit the improvement. Simulation tools developed by the National Renewable Energy Laboratory (NREL) are employed in the wind turbine design analysis. The Cost Of Energy (COE) comprises the overall system level objective, while performance improvements at two technical design disciplines are pursued at the same time. The optimal design of the blade geometry for maximum Annual Energy Production (AEP), and the structural design of the blade for minimum bending moment at the root of the blade comprise the two technical design disciplines. Scalar metamodels are developed for linking the design variables with the performance metrics associated with the design of the blade geometry. Main characteristics of the wind turbine, namely, the rotor diameter, the rotational speed, the maximum rated power, the hub height, the structural characteristics of the blade, and the geometric characteristics of the blade (distribution of thickness, twist angle, and chord) are employed as design variables for the overall design analysis. The optimization results and the physical insight which can be gained through a sensitivity analysis for the optimal configuration are presented and discussed.

Nonlinear limit cycle oscillations of an aeroelastic energy harvester are exploited for enhanced piezoelectric power generation from aerodynamic flows. Specifically, a flexible beam with piezoelectric laminates is excited by a uniform axial flow field in a manner analogous to a flapping flag such that the system delivers power to an electrical impedance load. Fluid-structure interaction is modeled by augmenting a system of nonlinear equations for an electroelastic beam with a discretized vortex-lattice potential flow model. Experimental results from a prototype aeroelastic energy harvester are also presented. Root mean square electrical power on the order of 2.5 mW was delivered below the flutter boundary of the test apparatus at a comparatively low wind speed of 27 m/s and a chord normalized limit cycle amplitude of 0.33. Moreover, subcritical limit cycles with chord normalized amplitudes of up to 0.46 were observed. Calculations indicate that the system tested here was able to access over 17% of the flow energy to which it was exposed. Methods for designing aeroelastic energy harvesters by exploiting nonlinear aeroelastic phenomena and potential improvements to existing relevant aerodynamic models are also discussed.

For accurate tool trajectories with respect to predetermined NURBS cutter location paths (refer to reference paths) and good tool kinematics in NC machining, many NURBS interpolation algorithms are trying to compute appropriate cutter locations on the paths during machining. Due to the high non-linearity between each interpolating chord (connecting two adjacent cutter locations) and its corresponding path segment, the existing methods can only interpolate the reference path with approximation, resulting in actual cutter trajectory with error beyond the tolerance and large feed rate fluctuations. To address problems of the current interpolation methods in this work, a new type of tool path, NURBS cutter location path with the arc length parameter, is proposed and a new approach to generating accurate paths of this type is provided through re-parameterization of the reference paths with the arc length parameter. The main features of this approach include (1) sampling points and calculating their arc lengths by decomposing an input reference path into Bezier curve segments according to criteria, and (2) fitting a NURBS tool path with the arc length parameter to the sample points until the parameterization error is less than the tolerance. This approach is applied to a benchmark for a NURBS path with the arc length parameter, and this path is then compared with the results generated using three existing interpolation methods, in order to demonstrate the advantage of this new approach.

It is well known that the solutions to the three-position motion generation problem for the synthesis of the planar four-bar linkages results in a set of center-point and circle point circles. The four-position solution set yields a cubic curve, and the five-position solution yields a set of points. There are a variety of methods including graphical and algebraic, for generating center-point and circle-point circles for the 3-position, and Burmester curves for the 4-position planar motion generation problem. Dyads are synthesized based on these solution sets. In general, it is difficult or impossible to generalize these methods to 3D mechanisms. This paper begins by briefly reviewing the geometric constructions used in classical Burmester theory. Then, it presents a method using a scalar field to find the center-point and circle-point circles by finding the points where these fields are equal. The developed method uses Euclid’s chord angle principle to generate the solutions. This principle is then generalized to 3D to form the cone angle principle. This principle is used in a manner directly analogous to the planar case to synthesize the S-S dyad. Similar gradient and superposition methods using scalar fields based on the equations for the spherical R-R dyad, and the spatial C-C dyad are used to generate the spatial equivalent to the center-point circles and Burmester curves. Although these results have been known for some time, the method for generating these solution sets is new for spatial synthesis.