Prediction of Store Trajectory Response to Unsteady Aerodynamic Loads

ABSTRACTRecent advances in coaxial rotor design have shown benefits of this configuration. Nevertheless, issues related to rotor-head drag, aerodynamic performance, wake interference, and vibration should also be considered. Simulating the unsteady aerodynamic loads for a coaxial rotor, including the aerodynamic interactions between rotors and rotor blades, is an essential part of analysing their vibration characteristics. In this article, an unsteady aerodynamic analysis based on a vortex particle method is presented. In this method, a reversed-flow model for the retreating side of the coaxial rotor is proposed based on an unsteady panel technique. To account for reversed flow, shedding a vortex from the leading edge is used rather than from the trailing edge. Moreover, vortex-blade aerodynamic interactions are accounted for. The model considers the unsteady pressure term induced on a blade by tip vortices of other blades, and thus accounts for the aerodynamic interaction between the rotors and its contribution to the unsteady airloads. Coupling the reversed-flow model and the vortex-blade aerodynamic interaction model with the viscous vortex-particle method is used to simulate the complex wake of the coaxial rotor. The unsteady aerodynamic loads on the X2 coaxial rotor are simulated in forward flight, and compared with the results of PRASADUM (Parallelized Rotorcraft Analysis for Simulation And Design, developed at the University of Maryland) and CFD/CSD computations with the OVERFLOW and the CREATE-AV Helios tools. The results of the present method agree with the results of the CFD/CSD method, and compare to it better than the PRASADUM solutions. Furthermore, the influence of the aerodynamic interaction between the coaxial rotors on the unsteady airloads, frequency, wake structure, induced flow, and force distributions are analysed. Additionally, the results are also compared against computations for a single-rotor case, simulated at similar conditions as the coaxial rotor. It is shown that the effect of tip vortex interaction plays a significant role in unsteady airloads of coaxial rotors at low speeds, while the rotor blade passing effect is obviously strengthened at high-speed.

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Numerical Validation of Floating Offshore Wind Turbine Scaled Rotors for Surge Motion

Energies ◽

10.3390/en11102578 ◽

2018 ◽

Vol 11 (10) ◽

pp. 2578 ◽

Cited By ~ 4

Author(s):

Krishnamoorthi Sivalingam ◽

Steven Martin ◽

Abdulqadir Singapore Wala

Keyword(s):

Wind Turbine ◽

Turbine Rotor ◽

Power Converter ◽

Experimental Results ◽

Offshore Wind ◽

Speed Ratio ◽

Offshore Wind Turbine ◽

Floating Offshore Wind Turbine ◽

Aerodynamic Loads ◽

Unsteady Aerodynamic

Aerodynamic performance of a floating offshore wind turbine (FOWT) is significantly influenced by platform surging motions. Accurate prediction of the unsteady aerodynamic loads is imperative for determining the fatigue life, ultimate loads on key components such as FOWT rotor blades, gearbox and power converter. The current study examines the predictions of numerical codes by comparing with unsteady experimental results of a scaled floating wind turbine rotor. The influence of platform surge amplitude together with the tip speed ratio on the unsteady aerodynamic loading has been simulated through unsteady CFD. It is shown that the unsteady aerodynamic loads of FOWT are highly sensitive to the changes in frequency and amplitude of the platform motion. Also, the surging motion significantly influences the windmill operating state due to strong flow interaction between the rotating blades and generated blade-tip vortices. Almost in all frequencies and amplitudes, CFD, LR-BEM and LR-uBEM predictions of mean thrust shows a good correlation with experimental results.

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Numerical simulation of the unsteady aerodynamic loads on the tail fin in the vortex breakdown flow

Progress in Computational Fluid Dynamics An International Journal ◽

10.1504/pcfd.2021.10039616 ◽

2021 ◽

Vol 21 (5) ◽

pp. 274

Author(s):

Andrey Epikhin

Keyword(s):

Numerical Simulation ◽

Vortex Breakdown ◽

Aerodynamic Loads ◽

Unsteady Aerodynamic

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Linearized Euler predictions of unsteady aerodynamic loads in cascades

AIAA Journal ◽

10.2514/3.11363 ◽

1993 ◽

Vol 31 (3) ◽

pp. 540-550 ◽

Cited By ~ 78

Author(s):

Kenneth C. Hall ◽

William S. Clark

Keyword(s):

Aerodynamic Loads ◽

Unsteady Aerodynamic

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Modelling Aerodynamics Unsteady Loads on the Horizontal Tail Plane of a Civil Aircraft

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.232.543 ◽

2012 ◽

Vol 232 ◽

pp. 543-547 ◽

Cited By ~ 1

Author(s):

Raul Calderon ◽

Bertrand Aupoix ◽

Benoit Calmels ◽

Christophe David

Keyword(s):

Pressure Fluctuations ◽

Correlation Method ◽

Separated Flow ◽

Extreme Conditions ◽

Design Constraints ◽

New Approach ◽

Aerodynamic Loads ◽

Structural Fatigue ◽

Unsteady Aerodynamic ◽

Civil Aircraft

During flight, emergency descent situations are part of those extreme conditions that can lead the empennage of an aircraft to vibrate. These vibrations are mainly due to the separated flow on the upper surface of the structure which increases the pressure fluctuations on the empennage, sometimes leading to buffeting. This situation can cause structural fatigue and can induce certification and design constraints on the structure. Hence, an accurate prediction of the unsteady loads is needed to take these forces into account in the early phase of the empennage design. This paper presents a new approach to accurately model the unsteady aerodynamic loads resulting from the interaction between the horizontal tail plane and the wing wake. The method is based upon the coherence method and is compared to the method developed by Soumillon [2], based upon the correlation method. The results obtained by this new model show good agreements with the experimental data.

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Numerical Simulation of Unsteady Aerodynamic Loads over an Aircraft

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.908.264 ◽

2014 ◽

Vol 908 ◽

pp. 264-268

Author(s):

Xiao Jun Xiang ◽

Yu Qian

Keyword(s):

Mach Number ◽

Euler Equations ◽

Unsteady Aerodynamics ◽

Periodic Motions ◽

Aerodynamic Loads ◽

Unsteady Aerodynamic ◽

Sinusoidal Motion ◽

A Cell ◽

Rigid Body Motions ◽

Volume Method

The unsteady aerodynamic loads are the basic of the aeroelastic. This paper focuses on the computation of the unsteady aerodynamic loads for forced periodic motions under different Mach numbers. The flow is modeled using the Euler equations and an unsteady time-domain solver is used for the computation of aerodynamic loads for forced periodic motions. The Euler equations are discretized on curvilinear multi-block body conforming girds using a cell-centred finite volume method. The implicit dual-time method proposed by Jameson is used for time-accurate calculations. Rigid body motions were treated by moving the mesh rigidly in response to the applied sinusoidal motion. For an aircraft model, a validation of the unsteady aerodynamics loads is first considered. Furthermore, a study for understanding the influence of different Mach number was conducted. A reverse of the trend of hysteretic loops can be observed with the increasing of the Mach number.

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Comparison of the Unsteady Loads of an Airfoil in the Pitching and Plunging Motions

Volume 2: Fora ◽

10.1115/fedsm2006-98482 ◽

2006 ◽

Cited By ~ 1

Author(s):

M. Soltani ◽

M. Seddighi ◽

F. Rasi

Keyword(s):

Subsonic Flow ◽

Free Stream ◽

Incident Angle ◽

Oscillation Amplitude ◽

Stream Velocity ◽

Frequency Oscillation ◽

Aerodynamic Loads ◽

Unsteady Aerodynamic ◽

Reduced Frequency ◽

Series Of Experiments

A series of experiments were conducted on an oscillating airfoil in subsonic flow. The model was oscillated in two types of motions, pitch and plunge, at different velocities, and reduced frequencies. In addition, steady data were acquired and examined to furnish a baseline for analysis and comparison. The imposed variables of the experiment were reduced frequency, mean incident angle, amplitude of motion, and free stream velocity as well as the surface grit roughness. The unsteady aerodynamic loads were calculated using surface pressure measurements, 64 ports, along the chord for both upper and lower surfaces of the model. Particular emphases were placed on the effects of different type of motion on the unsteady aerodynamic loads of the airfoil at pre-stall, near stall, and post stall conditions. Variations of the aerodynamic coefficients with equivalent angle of attack for both pitching and plunging motions showed strong sensitivity to the reduced frequency, oscillation amplitude, Reynolds number, and mean angles of attack.

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Nonlinear, unsteady aerodynamic loads on rectangular and delta wings

10.2514/6.1977-156 ◽

1977 ◽

Author(s):

E. ATTA ◽

O. KANDIL ◽

D. MOOK ◽

A. NAYFEH

Keyword(s):

Delta Wings ◽

Aerodynamic Loads ◽

Unsteady Aerodynamic

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Vehicle dynamics of a high-speed passenger car due to aerodynamics inside tunnels

Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit ◽

10.1243/09544097jrrt125 ◽

2007 ◽

Vol 221 (4) ◽

pp. 527-545 ◽

Cited By ~ 15

Author(s):

B Diedrichs ◽

M Berg ◽

S Stichel ◽

S Krajnović

Keyword(s):

Vehicle Dynamics ◽

High Speed ◽

Ride Comfort ◽

Sensitivity Study ◽

Response Analysis ◽

Vehicle Dynamic ◽

Aerodynamic Loads ◽

Car Body ◽

Unsteady Aerodynamic ◽

Multi Body

High train speeds inside narrow double-track tunnels using light car bodies can reduce the ride comfort of trains as a consequence of the unsteadiness of the aerodynamics. This fact was substantiated in Japan with the introduction of the series 300 Shinkansen trains more than a decade ago, where the train speed is very high also in relatively narrow tunnels on the Sanyo line. The current work considers the resulting effects of vehicle dynamics and ride comfort with multi-body dynamics using a model of the end car of the German high-speed train ICE 2. The present efforts are different from traditional vehicle dynamic studies, where disturbances are introduced through the track only. Here disturbances are also applied to the car body, which conventional suspension systems are not designed to cope with. Vehicle dynamic implications of unsteady aerodynamic loads from a previous study are examined. These loads were obtained with large eddy simulations based on the geometry of the ICE 2 and Shinkansen 300 trains. A sensitivity study of some relevant vehicle parameters is carried out with frequency response analysis (FRA) and time domain simulations. A comparison of these two approaches shows that results which are obtained with the much swifter FRA technique are accurate also for sizable unsteady aerodynamic loads. FRA is, therefore, shown to be a useful tool to predict ride comfort in the current context. The car body mass is found to be a key parameter for car body vibrations, where loads are applied directly to the car body. For the current vehicle model, a mass reduction of the car body is predicted to be most momentous in the vicinity of 2 Hz.

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