Numerical Prediction of Rotor Tip-Vortex Roll-Up in Axial Flights by Using a Time-Marching Free-Wake Method

2000 ◽  
Author(s):  
Duck Joo Lee
Keyword(s):  
Numerical Prediction ◽  
Tip Vortex ◽  
Time Marching ◽  
Free Wake

scholarly journals WIND TURBINE AERODYNAMICS PREDICTION USING FREE-WAKE METHOD IN AXIAL FLOW

2012 ◽  
Vol 19 ◽  
pp. 166-172 ◽  
Author(s):  
MIN-SOO JEONG ◽  
SEUNG-JAE YOO ◽  
IN LEE
Keyword(s):  
Wind Turbine ◽  
Three Dimensional ◽  
Axial Flow ◽  
Delay Model ◽  
Force Coefficient ◽  
Wind Turbine Aerodynamics ◽  
Time Marching ◽  
Unsteady Effects ◽  
Free Wake ◽  
Rotary Wing

Wind turbine aerodynamics remains a particularly challenging and crucial research for wind energy industry. The blade element momentum theory is the most widely used in predicting the performance of wind turbine, since the method is simple and fast numerical algorithm. The flow field generated by rotary wing is considerably important and complicated, however, the BEM method has some limitations to model the unsteady effects. To overcome these limitations, the aerodynamic analysis using a time-marching free-vortex wake method was performed in this paper. Moreover, the inboard region of the blade experience a delay in stall and enhanced values of the normal force coefficient because of rotational boundary layer augmentation and three-dimensional effects. For this reason, Raj-Selig stall delay model was applied in this research. The numerical results were compared with experimental data, and the present results show excellent agreement with experiment.

A Simplified Free Wake Method for Horizontal-Axis Wind Turbine Performance Prediction

1986 ◽  
Vol 108 (4) ◽  
pp. 400-406 ◽  
Author(s):  
A. A. Afjeh ◽  
T. G. Keith
Keyword(s):  
Wind Turbine ◽  
Performance Prediction ◽  
Vortex Method ◽  
Computational Effort ◽  
Horizontal Axis ◽  
Tip Vortex ◽  
Performance Parameters ◽  
Horizontal Axis Wind Turbine ◽  
Turbine Performance ◽  
Free Wake

Based on the assumption that wake geometry of a horizontal-axis wind turbine closely resembles that of a hovering helicopter, a method is presented for predicting the performance of a horizontal-axis wind turbine. A vortex method is used in which the wake is composed of an intense tip-vortex and a diffused inboard wake. Performance parameters are calculated by application of the Biot-Savart law along with the Kutta-Joukowski theorem. Predictions are shown to compare favorably with values from a more complicated full free wake analysis and with existing experimental data, but require more computational effort than an existing fast free wake method.

scholarly journals Impact of Tip-Vortex Modeling Uncertainty on Helicopter Rotor Blade–Vortex Interaction Noise Prediction

2021 ◽  
Vol 66 (1) ◽  
pp. 1-13
Author(s):  
Stavros Vouros ◽  
Ioannis Goulos ◽  
Calum Scullion ◽  
Devaiah Nalianda ◽  
Vassilios Pachidis
Keyword(s):  
Vortex Core ◽  
Numerical Procedure ◽  
Tip Vortex ◽  
Analytical Models ◽  
Aerodynamic Noise ◽  
Helicopter Rotor ◽  
Vortex Interaction ◽  
Blade Vortex Interaction ◽  
Free Wake ◽  
The Impact

Free-wake models are routinely used in aeroacoustic analysis of helicopter rotors; however, their semiempiricism is accompanied with uncertainty related to the modeling of physical wake parameters. In some cases, analysts have to resort to empirical adaption of these parameters based on previous experimental evidence. This paper investigates the impact of inherent uncertainty in wake aerodynamic modeling on the robustness of helicopter rotor aeroacoustic analysis. A free-wake aeroelastic rotor model is employed to predict high-resolution unsteady airloads, including blade–vortex interactions. A rotor aeroacoustics model, based on integral solutions of the Ffowcs Williams–Hawkings equation, is utilized to calculate aerodynamic noise in the time domain. The individual analytical models are incorporated into an uncertainty analysis numerical procedure, implemented through nonintrusive Polynomial Chaos expansion. The potential sources of uncertainty in wake tip-vortex core growth modeling are identified and their impact on noise predictions is systematically quantified. When experimental data to adjust the tip-vortex core model are not available the uncertainty in acoustic pressure and noise impact at observers dominated by blade–vortex interaction noise can reach up to 25% and 3.50 dB, respectively. A set of generalized uncertainty maps is derived, for use as modeling guidelines for aeroacoustic analysis in the absence of the robust evidence necessary for calibration of semiempirical vortex core models.

Numerical prediction of tip vortex cavitation behavior and noise considering nuclei size and distribution

2009 ◽  
Vol 70 (5) ◽  
pp. 674-680 ◽  
Author(s):  
Kwangkun Park ◽  
Hanshin Seol ◽  
Wooyoung Choi ◽  
Soogab Lee
Keyword(s):  
Numerical Prediction ◽  
Tip Vortex ◽  
Tip Vortex Cavitation ◽  
Cavitation Behavior

scholarly journals Load prediction of hingeless helicopter rotors including drivetrain dynamics

2021 ◽  
Author(s):  
Felix Weiss ◽  
Christoph Kessler
Keyword(s):  
Wind Tunnel ◽  
Structural Model ◽  
Wind Tunnel Test ◽  
Major Change ◽  
Load Prediction ◽  
Baseline Case ◽  
Time Marching ◽  
Free Wake ◽  
Blade Loads ◽  
Cruise Flight

AbstractIn contrast to analyses with constrained hub speed, the present study includes the dynamic response of coupled rotor-drivetrain modes in the aeromechanic simulation of rotor blade loads. The structural model of the flexible Bo105 rotor-drivetrain system is coupled to aerodynamics modeled by an analytical formulation of unsteady blade element loads combined with a generalized dynamic wake or a free wake, respectively. For two flight states, i. e. cruise flight and large blade loading, a time-marching autopilot trim of the rotor-drivetrain system in wind tunnel configuration is performed. The simulation results are compared to those of a baseline case with constant rotor hub speed. The comparison reveals a major change in the blade passage frequency harmonics of the lead-lag loads. Beside the full drivetrain model, reduced models are shown to accurately represent the drivetrain influence on blade loads, if the eigenfrequency of the coupled second collective lead-lag/drivetrain mode is properly predicted. In a sensitivity analysis, this eigenfrequency is varied by stiffness modification of a reduced drivetrain model. The resulting changes in blade loads are correlated to this eigenfrequency, which serves as a simple though accurate classification of the drivetrain regarding its influence on vibratory blade loads. Finally, the potential to improve lead-lag load predictions by application of a drivetrain model is demonstrated through the comparison of simulated loads with measurements from a wind tunnel test.

A study on the numerical prediction of propellers cavitating tip vortex

2014 ◽  
Vol 92 ◽  
pp. 137-161 ◽  
Author(s):  
Stefano Gaggero ◽  
Giorgio Tani ◽  
Michele Viviani ◽  
Francesco Conti
Keyword(s):  
Numerical Prediction ◽  
Tip Vortex
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