Browse Topic: Camber
This paper explores novel airfoils for rotorcraft applications using a gradient-free, multi-objective genetic algorithm with 2D URANS simulations. The study considers dynamic kinematics at a Reynolds number of 5×105 and a mean Mach number of 0.35. Two optimization scenarios are analyzed: 1) pre-stall kinematics (0° ≤α ≤10°) and 2) dynamic stall kinematics (0° ≤ α ≤ 20°). The paper compares two objective functions: f1, based on the cycle averaged lift, and ˜ f1, which modifies f1 by penalizing hysteresis in the lift coefficient. The effects of uniform vs. fluctuating freestream velocity and reduced frequency on optimal airfoils are also discussed. The proposed optimization approach has resulted in novel airfoil shapes that are characterized by a drooped nose, with a convex surface on the aft upper surface similar to a reflex camber in pre-stall kinematics and less unsteadiness in the air loads for the optimized airfoils under the dynamic stall kinematics.
Smooth camber morphing aircraft offer increased control authority and improved aerodynamic efficiency. Smart material actuators have become a popular driving force for shape changes, capable of adhering to weight and size constraints and allowing for simplicity in mechanical design. University of Michigan, Ann Arbor, MI Uncrewed aerial vehicles (UAVs) are growing in popularity for both civilian and military applications, which makes improving their efficiency and adaptability for various aerial environments an attractive objective. Many studies pursue this goal using morphing techniques that incorporate shape changes not typically seen in traditional aircraft. Due to weight and volume constraints consistent with smaller flight vehicles, smart materials, such as macro fiber composites (MFCs), have been used to achieve the desired shape changes. Macro fiber composites are low-profile piezoelectric actuators which have gained substantial attention within the morphing aircraft community
The paper investigates the unsteady forces and flowfield of a cycloidal rotor blade undergoing forward flight motion through water tunnel experiments. A particle image velocimetry (PIV) system is used in conjunction with an instrumented blade to measure both the two-dimensional flow velocity around the blade and the fluid dynamic forces. The flow-field studies reveal the formation and shedding of strong leading-edge vortices in both the frontal and rear halves of the circular blade trajectory, which plays a key role in generating lift as observed from the blade force measurements. Increasing forward speed diminishes the size and strength of these leading-edge vortices due to the reduction in angle of attack, which reflects in the blade forces. With pitch kinematics symmetric between frontal and rear halves of the cycle the blade produced significantly higher forces in the rear half compared to the frontal half, which was attributed to the dynamic virtual camber and the differences in
This specification covers established inch/pound manufacturing tolerances applicable to carbon steel sheet, strip, and plate ordered to inch/pound dimensions. These tolerances apply to all conditions unless otherwise noted. The term “excl” is used to apply only to the higher figure of the specified range. Tolerances for product sizes not listed herein shall be as agreed upon by purchaser and vendor.
With an intense competitive automotive environment, it becomes imperative for any OEM to launch their products into the market in a short span of time & with a ‘First Time Right’ approach. Within the current scenario in the Automotive Industry, the selection of optimum set of hard points and wheel geometry often becomes an iterative or a trial-and-error process which is both time consuming and involves higher development cost as there may be instances where 2 to 3 sets of iterations are needed before specification is finalized for production. Through this paper, an attempt has been made to develop a methodology for deciding wheel geometry parameters (covered in the later section of this paper like Caster, Camber, Mechanical trail, etc.) [1, 2, 3, 4] for a three wheeled vehicle as a First Time Right (FTR) approach to cut down on conventional, expensive & time-consuming iterative approach. In this paper, we have studied the parameters which affects the directional stability and steering
Passengers would always like to reach their destinations with minimum commute time. Generating a higher thrust is a necessity. This implies that the turbomachinery associated with the power plant has to rotate faster and with higher efficiencies. However, high rotational speeds, mainly in the transonic regime, often lead to boundary layer separation, shocks, compressor stall, and surge. The current investigation is an attempt to reduce the abovementioned phenomena. It involves the performance study of a smoothened controlled diffusion airfoil (CDA) blade that has been optimized by “Multi-Objective Genetic Algorithm” (MOGA) by altering maximum camber location and stagger angle. Inlet pressure is varied from 15 kPa to 30 kPa and the angle of attack ranging from 40.4° to 56.4°. C48-S16-BS1 is validated and considered as the baseline profile, and all other blades are collated to this. It is observed that shifting the location of the maximum camber close to the leading edge and increasing
A tire is a prominent part of any vehicle, comprising about 33% of the total aerodynamic drag of a vehicle, and is the only part in contact with the road. In this work, an attempt is made to study the aerodynamic characteristics of a non-pneumatic tire (NPT) with hexagonal spokes (HS) in rotating conditions using SimScale® computational fluid dynamics (CFD). The effect of various parameters like camber angle, steering angle, and velocity on the aerodynamic performance is evaluated through coefficients of drag and lift. The results are compared with that of the static condition at zero yaw and zero camber to understand the effect of a rotating wheel on aerodynamic performance. Results show that the increase in the camber angle or steering angle results in reduced drag and lift coefficients. At a vehicle velocity of 40 km/h, Cd value has reduced by 24.17%, 19.81%, and 31.33% for a 1.5° camber angle, 15° steering angle, and combined case with 1.5° camber and 15° steering angles
ABSTRACT
Wheel rim is one of the most critical safety parts in a vehicle. Strength in cornering loading is one of the most important durability test requirements for automotive steel wheel rim apart from other loading conditions like vertical and impact loads. Based on the category of vehicle and customer usage pattern, the accelerated cornering test is derived for testing steel wheel rims. The simulation and certification of steel wheel rim for the required dynamic durability testing requirement involves many steps ranging from acceptance criteria derivation to reliably addressing known potential failure zones in steel wheel rims. Nave radius and crown are sensitive to cornering loads, given the pitch circle diameter at the concept stage, the known effects of these key parameters are determined from DOE and used as reliable indicators to arrive at the shape and section of the steel wheel rim. Potential failure zones are typically crown and nave radius from weather side (outer) surface and vent
Rotor morphing has been investigated in the past for improvement of rotor performance, either for reduction of rotor power demand or for vibratory load alleviation. The present study investigates the application of camber morphing for improvement of rotor performance in hover and vertical flight conditions, with a particular focus on the combination of camber morphing systems and variable RPM rotors. Camber morphing utilizes a smooth flap at the trailing edge of the rotor blade to modify the camber of blade airfoil sections without excessive drag penalties. Two different camber morphing systems will be investigated in this study, namely the active and passive systems. Passive camber morphing, which combines camber morphing with the variable speed rotor concept is the unique aspect of camber morphing which will be the primary focus of this study. The active system can be actuated at frequencies higher than 1/rev of the rotor and requires external power input for functioning. The passive
A new morphing concept called linearly variable chord-extension was studied for its effectiveness in improving the efficiency of a helicopter rotor. Apart from chord-extension itself, an additional feature which is deflection of the extended part of the chord resulting in an effective camber and additional twist to the airfoil, is also studied for its effect on rotor efficiency improvement. Trim analyses were carried out for various chord-extended rotors for hover as well as various forward flight velocities using DLR's in-house comprehensive analysis code S4. Chord-extension of up to 100 percent and chord-extension-deflection of up to 15 percent were considered. Results show that the linearly variable chord-extension concept is effective in reducing power requirement in both hover and forward flight. Deflection of the extended chord also helps reduce power requirement in hover, especially at higher blade loadings. However, the root torsional moments and hence, the pitch-link loads are
A computational investigation was conducted to identify the optimal performance of a rotor with an active camber morphing mechanism using up to twice-per-revolution (2P) control input. Using rotor comprehensive
The present study proposes and explores a new autonomous morphing concept, whereby an increase in helicopter rotor blade camber of the order of 12-13° is realized over the inboard section of the blade with increase in ambient temperature. The camber change is achieved through a proper integration of Shape Memory Alloys (SMAs) on the lower surface of the blade aft of the leading-edge spar. For a reference rotor (no-SMA) generating 21,000 lbs thrust, operation in hot conditions resulted in a 2,590lb loss in lift. When the SMA camber morphing section extends from the blade root to 50% span, the rotor recovered up to 43% of the lift loss at high temperature. If the camber-morphing section is further extended to 75% span, up to 82% of the lost lift can be recovered.
Aerodynamic shape design of the helicopter tail boom is aimed for anti-torque power requirement alleviation at hover and improvements on sideward flight characteristics. Oval type basic tail boom cross section, whose camber can be modifiable with organic shaped strakes, is proposed to supersede conventional symmetrical tail boom profiles. Performance of several contour shapes is investigated with systematically varying the position and alignment of the strakes through the 2-D RANS simulations. Cross-section shapes that shows highest potential are utilized on tail boom design and to evaluate the resulting hover performance, 3-D CFD analyses are conducted with both of RANS simulations using the actuator disk approach and URANS solutions where blade motions are modeled with overset
In order to extend the boundaries of helicopter performance and increase forward-flight speed, it is necessary to reduce the drag on the rotor hub, which can account for as much as 30% of the total parasite drag on the helicopter. Currently, there is limited experimental data available to predict the drag force on new hub configurations. The purpose of this testing is to create a database of lift and drag at various angles of attack to aid in hub design and hub drag prediction. Testing was conducted in the 12 inch-diameter water tunnel at ARL Penn State on four shapes - DBLN 526, 4:1 Ellipse, 3.25:1 Rectangle, and a new Optimized Cambered Shape (OCS) designed at UT Knoxville. Load cell data for lift and drag were obtained for angles of attack from approximately -5 degrees to 5 degrees. Drag data were also calculated using PIV velocity fields. Results are plotted and tabulated for use in future hub drag prediction toolsets.
This paper presents a coupled numerical and experimental study of an unconventional wing profile such as cp-180-050-gn (Cambered plate C = 18% T = 5% R = 0.78). This wing profile deals with low speeds. It is not currently used on any aircraft model. Otherwise, it presents interesting performances that can be exploited for the design of low-speed STOL or VTOL aircraft by mean of the very high lift that it can generate and can fit with different uses such as VAWT, cyclorotors drones, which are designed explicitly for low-speed operations. After a preliminary CFD assessment of the wing a complete experimental characterisation also at high angles of attack has been performed. The excellent agreement between CFD and experiments has allowed producing a complete analysis of the behaviour of the wing profile both before and after stall conditions. This study has the objective of analysing the viability of such an unconventional wing in traditional or over-stalling conditions. A complete
This paper considers the phenomenon that the self-steer speed when riders bank a motorcycle. This paper points out that this phenomenon originates from capsize mode. Further, it is specified that the first order differential equation representing capsize mode is included in the equation of motion of the steering system. Furthermore, it is specified that this differential equation is the first order differential equation for the roll angle. Therefore, as the roll angle increases, the roll angle further increases and the steering angle also changes, which is the mechanism of capsize mode. Finally, as a result of parameter studies, it is stated that the design parameters that most affect capsize mode were front and rear camber stiffness.
A vehicle drifts due to several reasons from its intended straight path even in the case of no steering input. Vehicle pull is a condition where the driver must apply a constant correction torque to the steering wheel to maintain a straight-line course of the vehicle. This paper presents an investigation study into the characteristics of a vehicle experiencing steering drift. The aim of the work is to study vehicle stability and the causes of vehicle drift/pull during straight line to minimize vehicle pull level and hence optimize safety measures. A wobble in the steering wheel feels like the steering wheel is shaking to the left and right. This may get worse, if speed increases. This paper focuses on modelling and evaluating effects of suspension parameters, differential friction, brake drag variation, Unbalanced mass in the wheel assembly and C.G. location of the vehicle under multibody dynamic simulation environment. Asymmetry of geometry and compliance between left and right side
Through Adams/Car software, it was developed a complete template of a double wishbone suspension with a single shock absorber per axle for a formula SAE prototype. With this template it is intended to perform a series of simulations to test its kinematics and dynamics in the situations which the vehicle will be submitted at the competition, then the shock absorber’s parameters, double wishbone geometries, camber, caster, toe and kingpin inclination can be improved, validating the system viability and getting a higher performance.
Currently, large companies as well as universities have increased the studies into vehicular dynamic behavior, mainly in order to improve driver and passenger safety. Simulations with complete model vehicle have been used for these studies. The tire is one of the most important vehicular component as the only connection with the ground and responsible for transmitting all vertical, longitudinal and lateral forces, consequenetly it is the main component on the model vehicle, being crucial for the correlation between computer simulations results and field tests, This paper presents a methodology, development and construction of a device to obtain lateral forces in any combination of toe and camber angles for different conditions of normal load, the tests can be performed on any type of ground, whether dry or wet. The tire datas used as reference were obtained through an experimental test using “Flat Trac” equipment. Based on these data, the components used to measuare the tire force
In this study, we focus on “camber angle control” and “derivative steering assistance” using “steer-by-wire” as maneuverability and stability improvement techniques that are appropriate for the electric vehicle (EV) era. Movements that produce a negative camber angle generate camber thrust, and vehicle motion performance improvements extend from the fact that the tire side force is increased by the camber thrust effect. In our experimental vehicle, a proportional steering angle system was used to create negative camber angle control via an electromagnetic actuator that allowed us to confirm improvements to both the effectiveness and stability of steering control in restricted cornering areas. More specifically, we determined that it is possible to improve critical cornering performance by executing ground negative camber angle control in proportion to the steering angle. Steer-by-wire refers to an electrical steering technique that allows the steering angle of the entire vehicle to be
This paper introduces the Shape Adaptive Blades for Rotorcraft Efficiency (SABRE) Horizon 2020 research program and presents initial comprehensive analysis results on the efficacy of adapting blade shapes as a means of reducing rotorcraft power requirements and emissions. The aims of the research program are introduced, followed by discussion of the six different morphing concepts that will be explored. The morphing mechanisms are based on active camber, chord extension, twist, and active tendon morphing technologies. SABRE will explore the use of these concepts individually and in combination, for rotor quasi-steady configuration-type morphing and up to 2/rev actuation of some of the mechanisms, with the objective being to find the best balance between emissions reductions versus complexity and added weight. Initial investigations into the potential power reductions compared to the baseline full-scale BO-105 main rotor achievable with the morphing concepts were performed using Blade
In this paper, detailed development of a nonlinear aeroelastic coupled trim model of a twin-cyclocopter in forward flight is presented. Twin-cyclocopter consists of two cycloidal rotors as main thrusters and a conventional nose rotor for pitch-torque balance. It is shown that five control inputs (mean and differential rpm, mean and differential phase offset of cyclorotors, rpm of nose rotor) are needed to balance three moments and two forces on cyclocopter in forward flight while forces along lateral direction remain balanced at all stages. In this coupled trim procedure, blade aeroelastic response equations and vehicle trim equations are solved together by simultaneously updating control inputs and blade response. To obtain the blade response and forces for a given set of control inputs, an aeroelastic model of cyclorotor and an aerodynamic model of the conventional nose rotor in forward flight is developed. The nonlinear aeroelastic model of the cyclorotor is developed by coupling
This paper describes design optimization of a rotor blade for variable pitch quadrotor unmanned air vehicle (UAV) to ensure optimal performance in hover and forward flight. In order to optimize the blade profile to maximize hover power loading, a modified Blade Element Theory based analysis is developed and validated using experimental measurements for sets of symmetric-untwisted rectangular blade and cambered-twisted variable chord blade. The blade twist and chord distribution is parametrized using fifth order polynomial functions and the BEMT analysis is coupled to Matlab optmization toolbox to maximize the power loading for an operational thrust of approximately 3N. It is observed that use of rotor blade with non-linear twist and non-linear chord variation results in significant improvement in hover performance for the variable pitch quadrotor UAV. The optimized blade profile and chord distribution with GOE-744 airfoil gives approximately 4% higher power loading than the COTS
This study provides the first in-depth analysis of the formation, strength, and convection of cycloidal rotor tip vortices. The blade force and PIV-based tip-vortex measurements were conducted for different blade aspect ratios and pitch kinematics in water at a chord Reynolds number of 18,000. Two phase-locked PIV configurations were utilized to investigate the flow field induced by the cyclorotor blade: (1) a laboratory-fixed field of view to enable investigation of vortex development at increasing vortex ages, and (2) a blade-fixed field of view to investigate the early development of the wingtip vortex at fixed 2° vortex age for varying azimuthal locations. The instantaneous blade force measurements on the cycloidal rotor showed a decrease in lift coefficient with decreasing blade aspect ratio. This is due to the higher peak swirl velocity of the tip vortex produced by the low AR blade, thereby resulting in higher induced downwash along the blade span. The aspect ratio of the blade
The present research provides a performance comparison between several low Reynolds number airfoil profiles for the Mars Helicopter. The low density of the Martian atmosphere and the relatively small Mars Helicopter rotor result in very low chord-based Reynolds number flows, Re𝒸 = O(10³ - 10⁴). At low Reynolds numbers, flat and cambered plates can out-perform conventional airfoils, making them of interest for the Mars Helicopter rotor. Performance models are generated for the Mars Helicopter rotor based on a free wake analysis, and the results are compared with Mars Helicopter isolated rotor performance from previous work. A Reynolds-Averaged Navier-Stokes based approach is used to generate the airfoil deck using OVERFLOW. The model is constructed using airfoil data tables (C81 files) that are used by the comprehensive rotor analysis code CAMRADII. Performance results for the Martian atmosphere show improved performance for the cambered plate rotor over conventional airfoils, in terms
In this paper, based on our previously preliminary out-of-plane tire model, a complete out-of-plane flexible tire model is further developed by considering the variation of dimension and parameter values among different slices of the tire model. This tire model is validated via various MSC ADAMS® FTire virtual cleat tests. Especially, the cleat tests with non-zero tire camber angles and non-symmetric cleat shapes, which can better capture the out-of-plane tire properties, are included. By comparing the predicted results of the proposed tire model with FTire for various cleat tests, it shows that the complete out-of-plane flexible ring tire model is better at fully representing the actual tire properties for some complicated cleat testing scenarios.
Since the tire inflation pressure has a significant influence on safety, comfort and environmental behavior of a vehicle, the choice of the optimal inflation pressure is always a conflict of aims. The development of a highly dynamic Tire Pressure Control System (TPCS) can reduce the conflict of minimal rolling resistance and maximal traction. To study the influence of the tire inflation pressure on longitudinal tire characteristics under laboratory conditions, an experimental sensitivity analysis is performed using a multivalent usable Corner Module Test Rig (CMTR) developed by the Automotive Engineering Group at Technische Universität Ilmenau. The test rig is designed to analyze suspension system and tire characteristics on a roller of the recently installed 4 chassis roller dynamometer. Camber angle, toe angle and wheel load can be adjusted continuously. In addition, it is possible to control the temperature of the test environment between −20 °C and +45 °C. The results of the
In order to improve robustness of vehicle dynamic performance, a steering mechanism model is proposed with alignment parameters of front wheel based on preference function method. In the steering mechanism model controllable variables include the trapezoid connection length, the base angle of steering trapezoid, the kingpin inclination angle, caster, camber and uncontrollable variables include load and initial braking velocity. Optimization objective is some vehicle dynamic performance. In the preference function method the individual performance preference and preference aggregation in designing variable space and performance variable space are analyzed. The individual performance preference includes the controllable variable preference, noise factor preference and optimization objective preference. The aggregation function is developed by aggregating all the individual performance preferences. The robustness and optimization results are solved based on mean and variance of
In this paper, detailed development of a nonlinear aeroelastic coupled trim model of a twin-cyclocopter, consisting of two cycloidal rotors (also known as cyclorotors) as main rotors and a conventional horizontal tail-rotor for anti-pitch torque and control, is presented. Coupled trim analysis requires simultaneous computation of trim controls, vehicle orientation and blade structural responses so that both blade response equations and vehicle trim equations are satisfied. To obtain the blade structural response and the hub loads in the vehicle frame for the cyclorotors, a nonlinear aeroelastic model of cyclorotor is developed. For this purpose, a high-fidelity unsteady aerodynamic analysis of a cyclorotor is developed, which includes rigorous modeling of effects such as dynamic virtual camber, effects of near and shed wake, and leading edge vortices. To include effect of blade deformations on cyclorotor performance, a structural framework consisting of fully nonlinear geometrically
This paper provides a fundamental understanding of the unsteady aerodynamic phenomena on a cycloidal rotor blade operating at ultra-low Reynolds numbers (Re∼18,000) by utilizing a combination of experimental (force and flowfield measurements) and computational (CFD) studies. For the first time ever, the instantaneous blade fluid dynamic forces on a rotating cyclorotor blade were measured, which, along with PIV-based flowfield measurements revealed the key fluid dynamic mechanisms acting on the blade. A 2D CFD analysis of the cycloidal rotor was developed and systematically validated using both force and flowfield measurements. Studies were performed with both static and dynamic blade pitching. Direct comparison of the static and dynamic pitch experimental results helped isolate the unsteady phenomena (such as dynamic stall, unsteady virtual camber, etc.) from the steady effects. The dynamic blade force coefficients were almost double the static ones clearly indicating the role of
In recent years three-wheel camber vehicles, with two wheels in the front and a single rear wheel, have been growing in popularity. We call this kind of vehicle A “Leaning Multi Wheel category Vehicle” (hereinafter referred to as a “LMWV”). A LMWV has various characteristics, but one of them stands out in particular. When a LMWV is cornering, if one of the front wheels passes over a section of road surface with a low friction coefficient, there is very little disturbance to the vehicle’s behavior and can continue to be driven as normal. However, there has been no investigation into why these vehicles have this particular characteristic. Consequently, in this paper an investigation was carried out in order to determine the behavior of a LMWV in this situation. First, measurements were taken using an actual vehicle to confirm the situation described above. As a result, it was confirmed that there is only a small change in the vehicle’s posture and also that the other front tire generates
The tire mechanics characteristics are essential for analysis and control of vehicle dynamics. Basically, the effects of sideslip, longitudinal slip, camber angle and vertical load are able to be represented accurately by current existing tire models. However, the research of velocity effects for tire forces and moments are still insufficient. Some experiments have demonstrated that the tire properties actually vary with the traveling velocity especially when the force and moment are nearly saturated. This paper develops an enhanced brush tire model and the UniTire semi-physical model for tire forces and moments under different traveling velocities for raising need of advanced tire model. The primary effects of velocity on tire performances are the rubber friction distribution characteristics at the tire-road interface. Therefore, in this paper, a simplified analytical tire model considering rubber dynamic friction is established first, which can be used to analyze the effects of
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