Effect Of Yaw Research Articles

Effect of yaw on wake and load characteristics of two tandem offshore wind turbines under neutral atmospheric boundary layer conditions

In this work, we numerically investigated the effects of yaw angle on the wake and power characteristics of two National Renewable Energy Laboratory (NREL) 5 MW wind turbines based on actuator line method (ALM) and large eddy simulation (LES) under a neutral atmospheric boundary layer (ABL) with specified offshore surface roughness. The turbines are placed in tandem, with a spacing of seven rotor diameters, and the yaw angles range from 0° to 30°. The results indicate that under coordinated yaw conditions, the wakes of the two turbines significantly shift with increasing yaw angles, encroaching on the trailing edge of the turbines. The expansion of the wakes also gradually weakens, leading to a reduction in width. The superposition of the wake generated by the downstream turbine diminishes, leading to both turbines exhibiting approximately comparable physical characteristics within their respective wakes. As the wake of the upstream turbine propagates downstream, a secondary low-speed region emerges between the primary low-speed zone of the wake of downstream turbine and the surrounding atmosphere. With the increase in yaw angle, this secondary low-speed region significantly enhances the rate of wake recovery while also inducing a more pronounced deflection of the wake, thereby demonstrating a stronger entrainment effect. Regarding load characteristics, the time history of power characteristics and the power spectral density (PSD) spectra indicate a good turbine response to the inflow. The power characteristics of the upstream turbine exhibit a scaling law is closely related to the yaw angle. The quantitative relationship is established between yaw angle and the power distribution of the turbines, alongside a proposed correlation between the yaw angle and the cos 2(γ) scaled power curve. The power of upstream turbine decreases and the power of downstream turbine gradually increases with the increase in yaw angle. It is further found that the downstream turbine demonstrates optimal performance at a yaw angle of 20°due to the influence of the yawed upstream turbine. These analyses provide insights into the characteristics of wind turbine arrays under yaw conditions from the perspective of unsteady wake features, interactions, and aerodynamic performance, which can aid in wind farm unit planning and control strategies.

Effect of yaw on aerodynamic performance of co-planar multi-rotor wind turbines

The multi-rotors wind turbine (MRWT) is a promising alternative to the large-scale single-rotor wind turbine for reductions of cost. Noteworthy, yawing in MRWT is a key engineering issue for its significant effect on the output power and structural aerodynamics. In this study, the aerodynamics and near wake dynamics of a co-planar multi-rotor wind turbine with different yaw modes (self-yaw and whole yaw) are investigated through the ALM-LES method. Comparatively, the effects of the blade tip vortex interactions between adjacent rotors on both the torque and thrust of the rotor and the mixing and recovery of the wake are taken into account as well. The numerical results show that the wake vortices of the two rotors attract and approach each other under self-yaw conditions. In the whole yaw conditions, the blade tip vortex in the region between rotors appears to neutralize each other due to the opposite direction of self-rotation of the wake vortex. Moreover, the wake enhancement effect increases the inlet velocity on the blades and has almost no effect on the lift-to-drag ratio. Nevertheless, the direct influence of the blade tip vortex increases the lift-to-drag ratio and decreases the inlet velocity at the location of 0.8∼1R on the front rotor blades in the self-yaw condition; it also decreases both the lift-to-drag ratio and the inlet velocity on the rear rotor blades. Furthermore, under the whole yaw condition, such a direct influence decreases the lift-to-drag ratio on the blades of the two rotors at the location of 0.8∼1R, and increases the average inlet velocity. Conclusively, among the investigated two yaw conditions, a 15°yaw angle shows a more considerable effect on the aerodynamics MRWT than the interaction of blade tip vortex.

Investigation of a four-bladed propeller inflow at yaw

An investigation has been conducted which looks to understand the effect of yaw on the inflow of a 4-bladed propeller. Both experimental and numerical work has been conducted, with the test data used to validate and compare against the numerical methods. The numerical methods involve fully resolved CFD and the low-order Crigler method. Comparing at a yaw angle of 15°, good agreement is found between the numerical and experimental results with adjustments made to account for discrepancies between the setups. More work is still required in the experimental and numerical branches to improve the extraction of data with minimal losses and improve the fidelity of simpler methods without a great expansion of computer cost.

Vessel Target Echo Characteristics and Motion Compensation for Shipborne HFSWR under Non-Uniform Linear Motion

For shipborne high-frequency surface wave radar (HFSWR), the movement of the ship has a great impact on the radar echo, thus affecting target detection performance. In this paper, the characteristics of the target echo spectrum and the motion compensation methods for shipborne HFSWR are investigated. Firstly, simulation analysis of echo from a moving target under different ship motion conditions was conducted with a focus on the frequency shift and broadening characteristics of the target echo spectrum. The simulation results show that the non-uniform linear motion and yaw of the ship will shift and broaden the target echoes, resulting in signal-to-noise ratio (SNR) reduction. When the ship velocity and yaw angle change periodically, false target echo peaks will appear in the echo spectrum, which will reduce the accuracy of target detection. To tackle this problem, a motion compensation scheme for the target echo is proposed, including the heading compensation for the effect of yaw and the velocity compensation for non-uniform movement. The influence of the velocity and yaw angle measurement accuracy on the compensation results is also analyzed. Finally, the target echo characteristics and motion compensation method of shipborne HFSWR are verified with experimental data.

Forced Convection Teat Transfer from a Cross Circular Yawed Tube.(Dept.M)

Complementary heat transfer and flow visualization experiments were performed lo investigate the effect of yaw on tube. Wind tunnel experiments encompassing seven angles of yaw between ᶱ= o( crossflow ) and 28° yielded Nusselt numbers extending over the range of free stream Reynolds numbers from 9000 to 25000. It was found that as the cylinder was yawed with respect to the crossflow orientation, the Nusselt number at first increased, attained a maximum at a yaw angle o 5o and then decreased to a broad minimum which occurred in the range of yaw angles between 20 and 25o and then start to somewhat increase at yaw angle equal 28o. As a further supplement to the heat transfer experiments, the pattern of fluid flow adjacent to the cylinder surface was visualized by means of the oil lampblack technique. The results were compared with the available experimental data. The values of the average Nusselt numbers were fitted in a correlation. This correlation indicates that the Nusselt number is a significant function of Reynolds number and angle of yaw.

The effect of yaw on the penetration of rigid rods

We explored the effect of yaw angles on the penetration depths of rigid long rods through a series of 3D numerical simulations. In particular, we looked for normalized relations between the penetration depths and the yaw angles, in order to account for our simulation results through non-dimensional parameters. These numerically-based relations highlight the physics behind the interaction of rigid yawed rods and metallic targets, and they can be used in future attempts to account for the yawed impact by analytical modeling. We also explored the behavior of rods with real constitutive properties, impacting aluminum targets at high velocities and non-negligible yaw angles. Our simulations reproduced unique aspects of this interaction which were found experimentally two decades ago.

Control Authority of a Camber Morphing Flying Wing

Flying wings achieve their roll, pitch, and yaw controllability exclusively through spanwise variations of lift and drag due to the lack of an empennage. Instead of using conventional control surfaces, which increase the aerodynamic drag due to gaps and discontinuities, a morphing structure can be employed. This work considers a previously developed camber morphing flying wing, which uses 10 electromechanical actuators to achieve spanwise-varying trailing edge deflections, resulting in variations of the lift and drag distributions and generating moments around the roll, pitch, and yaw axes. To investigate the control authority of the aircraft across all flight maneuvers, a series of multi-objective aerostructural optimizations is carried out. The performance for the individual maneuvers, as well as the interaction of simultaneous roll, pitch, and yaw moments and the resulting control authority, is assessed. Because the same actuators are used for all maneuvers, a high degree of interaction has been found between the achieved rolling and yawing moments. By minimizing the additional drag with the morphing actuation, the undesired effect of adverse yaw is minimized. The results describe a possible control strategy for flying wing aircraft with optimal drag performance.

Analysis of wind turbine blades aeroelastic performance under yaw conditions

The aeroelastic modeling of Tjæreborg wind turbine blades was performed based on the unsteady Reynolds Averaged Navier-Stokes equations (URANS) combined with Finite Element Method (FEM) in a loosely coupled manner. This method was verified by comparing numerical and experiment results at four axial inflow wind speeds. Furthermore, the aeroelastic performance of Tjæreborg wind turbine under yaw angle of 10°, 30° and 60°were computed and analyzed. The results showed that the average power and thrust of the wind turbine decreased with increasing yaw angle, along with the increasing oscillation amplitude under large yaw angle. The aerodynamic load showed periodic change within one revolution of rotor, resulting in the blade deflection and the strain present considerably asymmetric distributions. The maximum deflection and strain occurred at azimuth angle of about90° and their minimum values occurred at azimuth angle of about 270°. Besides, both the maximum deflection and strain under yaw conditions became larger than those in axial inflow condition do. For Tjæreborg wind turbine, the coupled solver gave a higher average power and thrust than the CFD solver alone. The aerodynamic performances showed more asymmetrical characters under the combined effect of yaw and fluid structure interaction (FSI).

Comparison of computational modelling and field testing of a small wind turbine operating in unsteady flows

Small horizontal-axis wind turbines are likely to operate in a broad range of operating flow conditions, often in highly turbulent flow, due, in part, to their varied site placements. This paper compares the computational simulations of the performance of a 5 kW horizontal-axis wind turbine to detailed field measurements, with a particular focus on the impact of unsteady operating conditions on the drivetrain performance and generator output. Results indicate that the current Blade Element Momentum Theory based aerodynamic models under-predict the effect of high turbine yaw on the rotor torque, leading to a difference between predicted and measured shaft speed and power production. Furthermore, the results show discrepancies between the predicted instantaneous turbine yaw performance and measurements.

A non-Hertzian method for solving wheel–rail normal contact problem taking into account the effect of yaw

ABSTRACTA novel approach is proposed in this paper to deal with non-Hertzian normal contact in wheel–rail interface, extending the widely used Kik–Piotrowski method. The new approach is able to consider the effect of the yaw angle of the wheelset against the rail on the shape of the contact patch and on pressure distribution. Furthermore, the method considers the variation of profile curvature across the contact patch, enhancing the correspondence to CONTACT for highly non-Hertzian contact conditions. The simulation results show that the proposed method can provide more accurate estimation than the original algorithm compared to Kalker’s CONTACT, and that the influence of yaw on the contact results is significant under certain circumstances.

The Two Dimensional Microstage Used in Geometric Measurement of Rockwell Diamond Indenter

The Primary Rockwell Hardness Standard System was set up in the Center for Measurement Standards since July 1996 till June 1997. During the period, a compact laser interferometer, HP10737R 3-axis interferometer system was used to measure the effect of pitch and yaw of the Rockwell Hardness standard machine. Considering to increase the performance of hardness measurement, the geometry of the diamond tip has to be determined. In this paper, we will present the results of indenter geometry by μ-CMM (Coordinate Measuring Machine) in CMS.

Numerical Simulation of the Unsteady Aerodynamic of Wind Turbine under Yaw Condition

To be able to more accurate analysis aerodynamic characteristic variation under yaw of NREL Phase VI wind turbine. The influence of yaw on the aerodynamic characteristic by using a three-dimensional unsteady CFD methods based sliding mesh in this paper. To flow, the overall performance and Cp of the three-dimensional flow numerical simulation were compared with experimental results with the same wind speeds to confirm the reliability of the model at a given axial wind speed conditions. In the yaw conditions, the effect of yaw on the aerodynamic performance of wind turbine blades, changing law and reveal the aerodynamic performance is in the flow details and rules in different azimuth.

Design of Fuzzy Logic Controller for Lateral Dynamics Control of Aircraft by Considering the Cross-Coupling Effect of Yaw and Roll on Each Other

In this paper, we explore fuzzy logic approach for lateral control of aircrafts. Here the effect of roll on yaw and that of yaw on roll is taken into account. The dynamic modeling of lateral control system that controls the lateral dynamics of an aircraft.is presented. The aircraft being considered in this work is a standard NAVION Transport aircraft [1]. A suitable mathematical model to describe the dynamics of an aircraft is derived. A single fuzzy controller is designed which will control both yaw and roll of the aircraft simultaneously. In this paper the transfer functions for yaw and roll is derived and their effects on each other is taken into account so that the system will have greater accuracy and efficiency than the application of two separate controllers. This design is very cost effective and will significantly reduce instability and increases maneuverability. Simulation results for the response of lateral controller are presented in time domain. Finally, the performance of lateral control system is analyzed based on common criteria of step’s response

Flow past a Yawed Rectangular Cavity in Transonic and Low Supersonic Flows

The effect of yaw on the steady and unsteady pressure measurements along the floor and walls of a rectangular cavity with a length-to-depth ratio of 5 was investigated. Statistical analyses were carried out on the pressure outputs to determine modal frequencies, amplitudes, and phase relationships. Rossiter's empirical formula was found to give good estimates of the frequencies of the acoustic tones for moderate yaw angles up to 20 deg, which was the highest value tested. The dominant acoustic mode was a function ofthe yaw angle, and it switched over to a higher mode when the yaw angle exceeded a critical value. At M = 0.84 and M = 1.11, the aft wall pressure distributions and acoustic mode amplitudes showed a very different behavior with changes in yaw angle for transonic and supersonic Mach numbers.

SU‐FF‐J‐43: Significance of Patient Rotation for Dosimetry in IGRT

Purpose: Significance of Patient Rotation for Dosimetry in IGRT Method and Materials: Advances in technology has made IGRT widely available, especial Cone Beam CT (CBCT) for patient positioning. In our institution a Varian Trilogy was installed for IGRT using CBCT with On‐Board Imaging Device. The patient positioning is done by comparing and fusing the CBCT images with original CT simulation images. Once the fusion is done the system provides operator with patient shifting information in 4‐Dimension: Vertical Shift, Lateral Shift, Longitudinal Shift and Couch Rotation (Yaw), no information regarding Pitching and Roll is provided. While for majority of patient treatment on a flat (Carbon Fiber) Couch‐Top the pitching is minimum, the patient roll is not uncommon showing soft tissue fused well but clear boney mark discrepancy. Assuming patient translational shift has been corrected; we have studied the effect of patient roll and yaw for three typical sites: Prostate, Lung and Head&Neck treatment by simulating the patient rotation in computer planning system. Results: Histogram of GTV, OAR for Prostate, Lung and Head&Neck with various degrees of Roll and Yaw rotation are studied and compared with perfect matching. Up to 8 degree we found there is no effect of both roll and yaw rotation for prostate, small to negligible effect for lung. For Head and Neck IMRT treatment up to 3 degree roll, and 4 degree yaw, there is small effect in PTV 63 Gy region, but negligible effect in lower or higher dose region for treatment, and negligible effect for OAR. Conclusion: As long as patient translational shift correction is done, small degree of patient rotational shift will not effect both the dose coverage of GTV, and dose effect of OAR, at least in the 3 sites we have studied: Prostate, Lung and Head&Neck.

Effect of yaw on the starting point of curvature for reflected diffracted shock wave (subsonic and sonic cases)

Lighthill (Proc. R. Soc. A 198, 454–470, 1949) considered the diffraction of a normal shock wave passing over a small bend. The bend being small Lighthill was able to linearize the flow equations and solved the problem through several mathematical techniques. Following Lighthill (Proc. R. Soc. A 198, 454–470, 1949), Srivastava and Chopra (J. Fluid Mech. 40, 821–831, 1970) extended the work to the diffraction of oblique shock waves. Srivastava (AIAAJ 33, 2230–2231, 1995) considered the problem of starting point of curvature and extended the work to yawed wedges (Srivastava in Proceedings of the 14th International Mach reflection symposium Sun Marina Hotel, Yonezawa, Japan, 1–5 October 2000, pp. 225–249, 2002). Srivastava (Shock waves 13, 323–326, 2003) considered the problem for starting point of curvature when the relative outflow behind reflected shock before diffraction has been subsonic and sonic. The present work is an extension of the work published in Srivastava (Shock waves 13, 323–326, 2003) when the wedge has been yawed through an angle. The results have been obtained for two angles χ = 60° and χ = 40° (χ is the angle of yaw).

Yaw 를 가진 긴 관통자와 경사판재의 고속충돌 수치해석

Using the Lagrangian explicit time-integration finite element code NET3D which can treat three­dimensional high-velocity impact problems, oblique penetration processes of long rod projectile with yaw against thin plate are simulated. Through the comparison of simulation result with experimental result and other code's computational result. the adaptability and accuracy of NET3D is evaluated under the complex situation in which yaw angle and oblique angle exist simultaneously. Main research contents to be handled in this paper include the followings. First. the accuracy and efficiency estimation of NET 3D code result obtained from the oblique penetration simulations of long rod projectile with yaw against thin plate. Second, the cffect of increasing impact velocity. Third, the effect of initial yaw for the spaced-plate target. Residual velocities, residual lengths, angular velocities, and final deformed configurations obtained from the NET3D computations are compared with the experimental results and other code's computational results such as Eulerian code MESA and Lagrangian code EPIC. As a result of comparisons, it has been found that NET3D code is superior to EPIC code and MESA code in the prediction capability of residual velocity and residual length of penetrator. The key features obtained from the experiment can be successfully reproduced through NET3D simulations. Throughout the study. the applicability and accuracy of NET3D as a metallic armor system design tool is verified.

Flight investigations of the effect of yaw on the intake and fan nozzle flow of a natural laminar flow nacelle

AbstractTwo major technologies in aeronautics promise substantial improvements in the fields of economy and ecology. One is laminar flow technology and the other arises from new developments related to aircraft turbofan engines. The trend in turbofan engine development is towards engines possessing higher bypass ratios. This, however, entails larger engine dimensions, leading not only to an increase in the skin friction drag but also to negative engine-airframe interactions. As a consequence, the need for laminar flow nacelles becomes all the more important as part of the general process of engine-air-frame integration optimisation for advanced transport aircraft.This paper deals with some results obtained from flight tests with a laminar flow nacelle demonstrator and specifically addresses the topic of aerodynamics of intakes and nozzles. The results described relate to a European collaborative programme in which a natural laminar flow (NLF) nacelle was flight tested. Results of the effect of the angle of yaw on the static pressure distribution on the fan cowl including the intake of an NLF nacelle are presented for the maximum cruise flight condition. At zero yaw, a comparison of Euler calculations with flight test data is made. Measured flow variables of the fan nozzle flow directly downstream of the fan nozzle exit, exemplified by the Mach number and the flow density distributions, are also presented for the condition of maximum cruise.

Effect of Yaw on Pressure Oscillation Frequency Within Rectangular Cavity at Mach 2

We examine the effect of yaw on the frequency of oscillations in an open cavity when placed in a supersonic flow.

Effect of yaw on pressure oscillation frequency within rectangular cavity at Mach 2

Effect of yaw on pressure oscillation frequency within rectangular cavity at Mach 2