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Aerodynamic and Aeroelastic Analysis of a Cycloidal Rotor
Abstract
This work presents aerodynamic and aeroelastic models used to investigate the behavior of a cycloidal rotor scaled for personal transportation applications. Three different models are considered. The impact of solidity on performance is evaluated using a two-dimensional RANS viscous flow model with the boundary layer fully resolved. An aeroelastic multibody model is used to further evaluate the effects of aeroelasticity on the performance of the rotor.
... They have the additional advantage of vectoring the thrust. Previous work [7,8] shown that this latest configuration is by far the most promising configuration. A concept illustration is shown on Fig. 4. To allow the study of the rotor, various aerodynamic and aeroelastic models were developed. ...
... These models were presented in previous articles. [7,8] The results presented here are obtained from a further development of the algebraic model which is explained in detail in the following section. ...
... The smaller correctors κ required for the IAT21 and McNabb experimental data may be due to the fact that their experimental model had full cylinders which are known to reduce the tree-dimensionality of the flow. To verify this hypothesis, a previously developed three dimensional fluid dynamics model [8] is used to confirm the influence of the use of endplates on the rotor. A short description of the model along with the found effect of the endplates is presented in the following paragraph. ...
A mathematical model is presented for the solution of the aerodynamic performances of a cycloidal rotor. It is solved algebraically for the cases where the forces and incoming wind velocity share the same direction. The model is validated against experimental data coming from three different sources. It is then used to evaluate the viability of using a cycloidal rotor as a replacement for the traditional tail rotor of a helicopter. By doing so, power is saved by the helicopter having non-null advance ratios. The savings reach 50% at an advance ratio of 0.33. It was found that imposing a constant cycloidal rotor angular velocity does not reduce the efficiency and that high pitch angles are the most efficient. The experimental data indicates that three dimensional effects have an influence on the cycloidal rotor performance. A three dimensional Euler fluid dynamic analysis confirms the experimental findings. Copyright © (2014) by the Royal Aeronautical Society. All rights reserved.
... Recent computational studies were focused on modeling only the aerodynamics of cyclorotors [28,29]. However, systematic studies to understand the role of blade flexibility and the resulting deflections on cyclorotor performance have been very limited [30][31][32]. The present study focuses on investigating the aeromechanics of a cyclorotor while using moderately and highly flexible blades. ...
... In the preceding equations [Eqs. (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)], e g is the chordwise location of blade c.g. ahead of the elastic axis. The variation of strain energy is computed using the following formula [Eq. ...
In this paper, the aeromechanics of a cycloidal rotor (or cyclorotor) is investigated to understand the effect of blade flexibility on the performance of the rotor in hover. Toward this, experiments are conducted on cyclorotors using moderately and highly flexible blades. These studies show that, with increasing blade flexibility, the rotor thrust decreases; whereas the power consumption increases, leading to a significant drop in power loading (thrust/power). To investigate these phenomena, a coupled aeroelastic model of cyclorotor is developed by coupling an unsteady aerodynamics model with a beam-based structural model and is systematically validated with experimental results. The aerodynamic model contains rigorous modeling of various physics behind the operation of the cyclorotor, such as the nonlinear dynamic virtual camber, the effect of near and shed wakes, and the leading-edge vortex. In comparison with a second-order nonlinear structural model, inclusion of a geometrically exact structural model proves to be essential in accurate prediction of rotor deflections and performance. Based on a systematic analysis performed using the validated model, it is observed that the large torsional deflections of the blades are a key reason for the drop in thrust. The torsional deflections are mainly produced by centrifugal force and nonlinear moments due to bending curvatures.
... They assessed the potential of cycloidal rotors to be used in large-size unmanned or small-size manned vehicle propellers. Previous work by the current authors led to the development of various models for the study of the cycloidal rotor under different configurations (Gagnon et al., 2014a(Gagnon et al., , 2014b(Gagnon et al., , 2014c. ...
... The smaller correctors required for the IAT21 and McNabb experimental data may be because of the fact that their experimental model had full cylinders which are known to reduce the three-dimensionality of the flow. To verify this hypothesis, a previously developed three-dimensional fluid dynamics model (Gagnon et al., 2014c) is used to confirm the influence of the use of endplates on the rotor. A short description of the model along with the computed effect of the endplates is presented in the following paragraph. ...
Purpose-Few modeling approaches exist for cycloidal rotors because they are a prototypal technology. Thus, the purpose of this study was to develop new models for their analysis and validation. These models were used to analyze cycloidal rotors and a helicopter that uses them instead of a tail rotor. Design/methodology/approach-Three different models were developed to study the aerodynamic response of cycloidal rotors. They are a simplified analytical model resolved algebraically; a multibody model resolved numerically; and an unsteady computational fluid dynamics (CFD) model. The models were validated using data coming from three different experimental sources, each with rotor spans and radii of roughly 1 m. The CFD model was used to investigate the influence of rotor arms. The efficiency and the stability of the rotor in different configurations were studied. An aeroelastic multibody simulation was used to verify the influence of flexibility on the rotor response. Findings-The analyses suggested that cycloidal rotors can increase the efficiency of a helicopter at high velocities while flexibility reduces it and may lead to instabilities. Research limitations/implications-These models do not consider the effect of boundary layer friction on the trailing vortices generated by the rotor blades. Practical implications-These models allow a four-step aerodynamic optimization procedure. First, a range of optimized configurations is obtained by the analytical model. Second, the multibody model refines that range. Third, the CFD model detects eventual problematic blade interactions. Originality/value-The models presented should serve researchers and industrials looking for a means to measure the performance of cycloidal rotors concepts. The results presented also guide an initial cycloidal rotor design.
... The rotor model is initiated by enhancing a simulation from a previous project [11,12] which had been validated against experimental data [30] for a larger rotor without endplates. That prior CFD simulation had been shown to yield more accurate quantitative results than its analogous 2D version. ...
This chapter provides a detailed method for building an unsteady 3D CFD model with multiple embedded and adjacent rotating geometries. This is done relying solely on open-source software from the OpenFOAM\(^{\textregistered }\) package. An emphasis is placed on interface meshing and domain decomposition for parallel solutions. The purpose of the model is the aerodynamic analysis of a quadrotor cyclogyro. The challenging features of this aircraft consist of a series of pairwise counterrotating rotors, each consisting of blades that oscillate by roughly 90\(^\circ \) about their own pivot point. The task is complicated by the presence of solid features in the vicinity of the rotating parts. Adequate mesh tuning is required to properly decompose the domain, which has two levels of sliding interfaces. The favored decomposition methods are either to simply divide the domain along the vertical and longitudinal axes or to manually create sets of cell faces that are designated to be held in a single processor domain. The model is validated with wind tunnel data from a past and finished project for a series of flight velocities. It agrees with the experiment in regard to the magnitude of vertical forces, but only in regard to the trend for longitudinal forces. Comparison of past wind tunnel video footage and CFD field snapshots validates the features of the flow. The model uses the laminar Euler equations and gives a nearly linear speedup on up to four processors, requiring 1 day to attain periodic stability.
... Each cycloidal rotor blade oscillates and rotates simultaneously around a fixed point and around the center of the rotor, respectively, Fig. 2. The combined motion around these two points causes each blade to change its slope angle. Thus, at each rotation, the blades cyclically vary the respective angle of attack [2][3][4]. Since the movement is cyclic, it is characterized by its frequency, amplitude and the phase angle. The variation in the phase angle and amplitude of movement allows, respectively, changes in the thrust direction and thrust magnitude [5][6][7][8]. ...
Cycloidal rotors have the inherent ability to provide vectorized thrust with fast reaction times. However, their present efficiency levels restricts their routinely use as propulsion elements for air-vehicles. Efforts have been made to improve the performance of cycloidal rotors through the optimal combination of its geometric parameters. In the present work the performance improvement of cycloidal rotors is demonstrated using a different approach, namely by imposing an unsteady change on the dynamics and structure of the vortices developed around the blades. This required change on the flow field, around the blades, was applied by adding an harmonic vibration to the traditional cycloidal movement of the blades, thus causing the blades to vibrate as they describe their oscillating pitch movement. This research on the effect of harmonic vibration, on lift and drag coefficients, was done first for a single blade profile, and later for a full cycloidal rotor, and is based on the Takens reconstruction theorem and Poincaré map. Therefore, diverse test cases and conditions were considered: a single static airfoil, an oscillating blade profile, and a complete cycloidal rotor. We concluded that the optimal combination of harmonic vibration parameters, specifically; amplitude, phase angle and vibration frequency, under adequately tuned design conditions, can have a beneficial effect on cycloidal rotor performance.
... To this end, data for a cyclogyro of similar dimensions as the wind turbine, operating in propulsion mode (V wind = 0), is used. This configuration, here denominated IAT21-L3 rotor, was analysed as a part of a major European ongoing project, which aims to develop the cyclogyro technology as a mean of propulsion for small and medium size aircraft [12,[15][16][17][18][19]. It is obvious that the results obtained for the IAT21-L3 rotor does not faithfully represent the features of a VAWT, since in propulsion mode energy is being provided and not extracted from the flow. ...
In the paper, four key design parameters with a strong influence on the performance of a small-scale high solidity variable pitch VAWT (Vertical Axis Wind Turbine), operating at low tip-speed-ratio (TSR) are addressed. To this aim a numerical approach, based on a finite-volume discretization of two-dimensional Unsteady RANS equations on a multiple sliding mesh, is proposed and validated against experimental data. The self-pitch VAWT design is based on a straight blade Darrieus wind turbine with blades that are allowed to pitch around a feathering axis, which is also parallel to the axis of rotation. The pitch angle amplitude and periodic variation are dynamically controlled by a four-bar-linkage system. We only consider the efficiency at low and intermediate TSR, therefore the pitch amplitude is chosen to be a sinusoidal function with a considerable amplitude. The results of this parametric analysis will contribute to define the guidelines for building a full size prototype of a small scale turbine of increased efficiency.
Copyright © 2015 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
... The existing aerodynamic analytical models [13][14][15] of cycloidal propellers generally fall into categories of either 2D quasi-steady or unsteady methods. These models present simple solution methodologies and almost use moment theory to model the inflow. ...
A new unsteady three-dimensional aerodynamic performance prediction approach is established to achieve fast and accurate prediction of the unsteady aerodynamics of cycloidal propellers. This model is developed by the coupling of momentum theory, lifting-line method, free wake model, and the Leishman–Beddoes semi-empirical dynamic stall model. The overall calculation process includes two parts. Firstly, to reduce the computational time and improve the computational convergence, the momentum theory is coupled with the Leishman–Beddoes semi-empirical dynamic stall model to predict a uniform inflow velocity through the cycloidal propeller disc, which is set as the initial induced velocity for iterations in the subsequent process. Then, the blade aerodynamic model, which couples the unsteady lifting-line method with the Leishman–Beddoes dynamic stall model, is used to calculate the unsteady aerodynamic response of blades. The wake of cycloidal propeller is represented by a serious of finite-length shed and trailing vortex elements, and the free wake model is utilized to model the dynamics of cycloidal propeller wake. Predictions from the present model are shown to be agreed reasonably well with the overall experimental data and the computational fluid dynamics results, both in terms of the aerodynamic performance prediction of cycloidal propeller and instantaneous blade force variations.
... The smaller correctors κ required for the IAT21 and McNabb experimental data may be due to the fact that their experimental model had full cylinders which are known to reduce the three-dimensionality of the flow. To verify this hypothesis, a previously developed three-dimensional fluid dynamics model (Gagnon et al., 2014c) is used to confirm the influence of the use of endplates on the rotor. A short description of the model along with the computed effect of the endplates is presented in the following paragraph. ...
... To this end, data for a cyclogyro of similar dimensions as the wind turbine, operating in propulsion mode (V wind ¼ 0), are used. This configuration, here denominated IAT21-L3 rotor, was analyzed as a part of an European research project, which aimed to develop the cyclogyro technology as a mean of propulsion for small and medium size aircraft [13,18,[20][21][22][23]. It is obvious that the results obtained for the IAT21-L3 rotor do not faithfully represent the features of a VAWT, since in propulsion mode energy is being provided and not extracted from the flow. ...
In this paper, four key design parameters with a strong influence on the performance of
a high-solidity variable pitch vertical axis wind turbine (VAWT) operating at low
tip-speed-ratio (TSR) are addressed. To this aim, a numerical approach, based on a
finite-volume discretization of two-dimensional (2D) unsteady Reynolds-averaged
Navier–Stokes (URANS) equations, on a multiple sliding mesh, is proposed and validated
against experimental data. The self-pitch VAWT design is based on a straight-blade Darrieus
wind turbine with blades that are allowed to pitch around a feathering axis, which
is also parallel to the axis of rotation. The pitch angle amplitude and periodic variation
are dynamically controlled by a four-bar linkage system. We only consider the efficiency
at low and intermediate TSR; therefore, the pitch amplitude is chosen to be a sinusoidal
function with a considerable amplitude. The results of this parametric analysis will
contribute to define the guidelines for building a full-size prototype of a small-scale wind
turbine of increased efficiency. [DOI: 10.1115/1.4032794]
... The EU-FP7 funded CROP (Cycloidal Rotor Optimized for Propulsion) project strives to design a cycloidal propulsion system that is suitable for manned and unmanned aerial vehicles. In order to asses the applicability of cyclorotors in large scale, several studies have been taken using pure analytical 16,17 and CFD 18,19 approximations. It was concluded that CROP could introduce into the aeronautical market several advantages in comparison with traditional VTOL, fixed wing air vehicles and hybrid aircrafts. ...
In the following paper we introduce PECyT system for enhancing the aerodynamic efficiency of cycloidal rotors. For that purpose the incorporation of Dielectric Barrier Discharge plasma actuators for active flow control on a pitching airfoil, under deep-stall conditions, will be assessed using a numerical tool. Two different arrangements of DBD actuators will be analysed, namely single-and multi-DBDs configurations. For the single-DBD plasma actuator the effect of different modes of actuation on the lift coefficient will also be studied. We will show that the multi-DBD actuator, in a steady-actuation mode, could delay stall and allows for a faster reattachment of the flow. However during the downstroke phase of the pitching cycle the unsteady operation of a single-DBD gives us the best results in terms of lift coefficient.
This work presents a study on the operational characteristics of a cyclorotor-thruster able to be applied in an aircraft, particularly in take-off and landing phases. Firstly, the behavior of cyclorotor principles in ascending and descending phases while in close distance to the ground was numerically studied. In addition, a second study phase was also conducted by Artificial Neural Network (ANN) to train the obtained database of results obtained numerically to further interpret the operating conditions in ground effect. CFD results predict that the optimum operational status of cyclorotor in close-ground altitudes is 30º pitching oscillation and 200 rpm for rotating speed. The results are indicating that the vertical distance of the aircraft highly influences their efficiency and functionality in producing thrust. A wide range of parameters is assessed using ANN analysis in several flying altitudes from the ground take-off level up to a reasonable height in which still the ground effects are noticeable. These results strongly indicate that an active control of both pitching oscillation and rotation speed is essential in operating at the optimum desired state.
Purpose
– Cycloidal rotors, also known as cyclogyros, are horizontal axis rotary-wing machines with potential for Vertical Take-Off and Landing aircraft applications. The paper aims to devise and validate a new semi-empirical analytical model that is capable of assisting in the structural and aerodynamic design of cyclogyros.
Design/methodology/approach
– The analytical model comprises a purely analytical kinematic sub-component that is used for analyzing the structural feasibility of the rotor. Several geometrical parameters are assessed, e.g. the oscillation schedule of the blades as a function of the properties of the pitching mechanical system. The dynamic sub-component of the model is used for estimating the rotor thrust production and power consumption. This sub-component is semi-empirical and uses a calibration function that was devised using the available experimental data.
Findings
– For a set of initial conditions and geometrical parameters, the model is capable of providing a real animation of the cyclogyro operation. It is shown that the motion of the blades does not comply with the requirements of a perfect cycloidal curve. The study concerning the simulation of the virtual camber effect on the drum blades, with and without the pitch effect, shows that the virtual camber strongly depends on the chord-to-radius ratio and on the aircraft advance velocity.
Originality/value
– A new analytical model capable of assisting in the geometrical and aerodynamic design of cyclogyros is here proposed. The model is capable of providing approximate estimations of the cyclogyro thrust production and power consumption under operating design conditions.
The highly efficient locomotion of birds, insects and fish is based on unsteady fluid dynamics. In recent years, research has focused on tapping into the potential that rests within these unsteady aerodynamic processes. However, most of the dynamic pitch and heave patterns encountered in nature are difficult to produce in an air vehicle that is propelled using rotating shaft power from an engine. To address this problem, this research assessed the feasibility and performance of a cycloidal propeller designed to utilize unsteady aerodynamic lift. A cycloidal propeller consists of one or more propeller blades mounted perpendicular to a rotating disk (see Figure 1). Contrary to current technical implementations of this type of propeller, dynamic pitch changes of a single blade mounted eccentrically to the propeller shaft in order to produce free leading edge stall vortices in the fluid are investigated. To generate thrust, a flow pattern that is the inverse of the von Karman vortex street is created in the fluid. The resulting time averaged flow field distant from the propeller is that of a jet. This type of propeller is particularly suited for low flow speeds, where state of the art propellers become inefficient due to flow separation on the blades. Potential applications include micro air vehicles that may use this device for propulsion as well as vertical take off and landing, and high altitude long endurance (HALE) aircraft that need to produce lift and thrust at low Reynolds numbers efficiently. The ability of a cycloidal propeller to produce similar efficiencies as dynamic pitch and heave motions reported in literature is demonstrated in this work.
In the following paper we perform an unsteady CFD analysis of the effect of several two dimensional blade geometrical parameters in the performance of CROP. The values will be analysed in terms of power loading (Thrust/Power) vs Disk Load (Thrust/Disk Area). The geometric parameters that we investigate include: blade thick-ness; rotor solidity (number of blades); and pitching amplitude.
A C-0 beam discretization based on the finite volume concept is described. In the linear case this approach leads to a collocated evaluation of the stiffness matrix of the beam; it proves to be intrinsically free from shear locking. In the nonlinear formulation only a collocated evaluation of the elastic forces is required, which dramatically simplifies the computation of the elastic contribution to the equilibrium equations. The formulation is here developed for the general geometrically nonlinear case and implemented in multibody formulation. The proposed approach proved to be consistent; its major drawback lies in the loss of symmetry of both the linear and the linearized beam matrices. For this reason the method is particularly suitable for dynamic problems like a nonlinear implicit multibody numerical approximation, in which the symmetry of the matrices is not so important, as it is already lost, whereas the ease in the generation of the contributions to the equations can lead to faster and cheaper analyses. Some applications are outlined, and the most relevant results are discussed.
After a few decades in which airships have been depromoted to the level of being only considered as a mere curiosity they seem now to reappear. The main reasons for this are related to the recent progress in technology of materials, aerodynamics, energy and propulsion. Airships are also presenting themselves as green friendly air vehicles, in particular if solar powered airships are considered. Their ability to remain aloft for long time periods have also expanded the range of mission profiles for which they are suited. Herein we have concentrated on a critical overview of propulsion mechanisms for airships. These include a detailed overview of past, present, and future enabling technologies for airship propulsion. Diverse concepts are revisited and the link between the airship geometry and flight mechanics is made for diverse propulsion system mechanisms.
This work discusses the possibility to use the cycloidal rotor technology to provide anti-torque to otherwise conventional helicopter designs. A simple analytical model of cycloidal rotor aeromechanics is provided to support its sizing. The analytical model is validated using other approaches of increasing complexity and experimental results. Three anti-torque configurations are considered: a single vertical axis rotor at the tail, a single longitudinal axis rotor at the tail, and two sideways axis rotors at both sides of the airframe. The first and the last configurations are analyzed in more detail. The required power for anti-torque capabilities is compared to that of a conventional rotor and possible advantages are discussed in terms of added lift and thrust and better control capabilities. Copyright© 2014 by the American Helicopter Society International, Inc. All rights reserved.
This paper describes the aeroelastic model to predict the blade loads and the average thrust of a micro-air-vehicle-scale cycloidal rotor. The analysis was performed using two approaches: one using a second-order nonlinear beam finite element method analysis for moderately flexible blades and a second using a multibody-based large-deformation analysis (especially applicable for extremely flexible blades) incorporating a geometrically exact beam model. An unsteady aerodynamic model is included in the analysis with two different inflow models: single streamtube and double-multiple streamtube inflow models. For the cycloidal rotors using moderately flexible blades, the aeroelastic analysis was able to predict the average thrust with sufficient accuracy over a wide range of rotational speeds, pitching amplitudes, and number of blades. However, for the extremely flexible blades, the thrust was underpredicted at higher rotational speeds, and this may be because of the overprediction of blade deformations. The analysis clearly showed that the reason for the reduction in the thrust-producing capability of the cycloidal rotor with blade flexibility may be attributed to the large nosedown elastic twisting of the blades in the upper half cylindrical section, which is not compensated by a noseup pitching in the lower half-section. The inclusion of the actual blade pitch kinematics, unsteady aerodynamics, and flow curvature effects was found crucial in the accurate lateral force prediction.
Studies of a MAV-scale cycloidal rotor (cyclocopter) were performed using performance and flow field measurements. Detailed parametric studies were conducted to determine the effects of rotational speed, the amplitude of the blade pitch angle, and the number of blades on cycloidal rotor performance. It was found that a 5-bladed cyclocopter system operating with 40° pitch produced the best power loading (thrust per unit power), with a figure of merit (based on the definition given in the paper) of 0.4. Thrust measurements suggested the presence of a sidewise force along with the vertical lift, similar to those found on rotating circular cylinders. This was confirmed using particle image velocimetry (PIV) measurements, which showed evidence of a wake skewness. The magnitudes of the measured vertical and sidewise forces were confirmed from the flow field measurements using a momentum balance technique. The thrust produced by the cyclocopter was found to increase until a geometric pitch of 40° was reached without showing any signs of blade stall. This behavior was explained using the PIV measurements, which showed the presence of high induced velocities in the rotor wake, which reduced angles of attack and delayed the occurrence of stall. Blade lift and drag were estimated from the flow field measurements, and were found to correlate well with the balance measurements. The PIV measurements clearly showed the rotational nature of the flow inside the cycloidal rotor, which is a significant source of energy loss, as well as the fact that the lower half of the rotor operates in the wake of the upper half. The induced power loss manifested as a large induced power factor in the modified momentum theory when compared to measurements.
This paper describes the aeroelastic model to predict the blade loads and the average thrust of a micro air vehicle (MAV) scale cycloidal rotor. The analysis was performed using two approaches, one using a non-linear FEM analysis for moderately flexible blades and second using a multibody based large-deformation analysis (especially applicable for extremely flexible blades). An unsteady aerodynamic model is included in the analysis with two different inflow models, uniform inflow and a double-multiple streamtube inflow model. For the cycloidal rotors using moderately flexible blades, the aeroelastic analysis was able to predict the average thrust with sufficient accuracy over a wide range of rotational speeds, pitching amplitudes and number of blades. However, for the extremely flexible blades, the thrust was underpredicted at higher rotational speeds and this may be because of the overprediction of blade deformations. The analysis clearly showed that the reason for the reduction in the thrust producing capability of the cycloidal rotor with blade flexibility may be attributed to the large nose-down elastic twisting of the blades in the upper half cylindrical section which is not compensated by a nose-up pitching in the lower half section. The inclusion of the actual blade pitch kinematics and unsteady aerodynamics was found crucial in the accurate lateral force prediction. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc.
The cycloidal propeller, which can be described as a horizontal rotary wing, offers powerful thrust levels, and a unique ability to change the direction of the thrust almost instantly. In this work, cycloidal propulsion system was designed and implemented with sinusoidal low pitch system to investigate the fundamental characteristics of hovering states. Before experimental study, computational analysis was made in commercial CFD tool, CD Adopco/Star- CD. This work gives schematic view of flow field around rotor. And it predicts the load variation on a blade with respect to revolution and the total thrust from cycloidal rotor, at specific condition. CFD analysis also makes it possible to check the camber effect. The propulsion system was built up with sinusoidal low pitch control mechanism. Thrust, power and efficiency were measured for various conditions of parameter setting. It was accomplished by designing the equipment which can change the rotational radius, number of blade, phase angle of eccentricity and amplitude of eccentricity.
A cyclocopter propelled by a cycloidal blade system is a concept of vertical takeoff and landing (VTOL) vehicle that has excellent hovering characteristics. The cycloidal blade system, which can be described as a horizontal rotary-wing, offers good thrust levels and a unique ability to change the direction of the thrust almost instantly. In this study, an unmanned, scaled cyclocopter was designed and developed by an optimization process. Flight esperiments and numerical analyses were performed to show that the cycloidal blade system can be used as a viable propulsion system. The esperimental results of the cyclocopter show good agreement with analytical predictions showing its potential as a VTOL vehicle.
The viability of a cyclorotor for powering a hover-capable micro air vehicle (MAV) was examined by making performance and flow field measurements. Parametric studies were conducted to determine the dependence of performance on rotational speed, the amplitude of the blade pitch, the blade airfoil shape, and blade flexibility. All of the experiments were conducted using a three-bladed cyclorotor system, which was built light enough to be used on an actual flight-capable MAV. While higher blade pitch angles were found to improve performance and increase the power loading of the cyclorotor, significant bending and torsional flexibility of the blades had a deleterious effect on performance. Blade section camber also proved to be detrimental to overall performance. Force measurements showed the presence of a significant sideward force on the cyclorotor (along with the vertical thrust force), analogous to that found on a spinning circular cylinder. Particle image velocimetry (PIV) measurements made in the wake of the cyclorotor provided evidence of a significant wake skewness, which was produced by the sideward force. The thrust produced by the cyclorotor was found to increase until a blade pitch angle of 45° was reached without showing any signs of blade stall. This behavior was also explained using the PIV measurements, which indicated evidence of a stall delay as well as possible increases in lift on the blades from the presence of a leading edge vortex.
The problem of interpolating between discrete fields arises frequently in computational physics. The obvious approach, consistent interpolation, has several drawbacks such as suboptimality, non-conservation, and unsuitability for use with discontinuous discretisations. An alternative, Galerkin projection, remedies these deficiencies; however, its implementation has proven very challenging. This paper presents an algorithm for the local implementation of Galerkin projection of discrete fields between meshes. This algorithm extends naturally to three dimensions and is very efficient.
Design and performance tests of cycloidal propulsion systems
- S J Kim
- C Y Yun
- D Kim
- Y Yoon
- I Park
Kim, S. J., Yun, C. Y., Kim, D., Yoon, Y., and Park, I., "Design and performance tests of cycloidal propulsion
systems," 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference,
Norfolk, Virginia, April 7-10 2003, AIAA-2003-1786.