Generation Mechanism and Reduction Method of Induced Drag Produced by Interacting Wingtip Vortex System

2017 ◽  
Vol 34 (2) ◽  
pp. 231-241
Author(s):  
M. Zhang ◽  
Y. K. Wang ◽  
S. Fu
Keyword(s):  
Reduction Method ◽  
Tip Vortex ◽  
Detached Eddy Simulation ◽  
Vortex System ◽  
Eddy Simulation ◽  
Induced Drag ◽  
Delayed Detached Eddy Simulation ◽  
Resistance Reduction ◽  
Wingtip Vortex ◽  
Formation And Evolution

AbstractThe formation and evolution of wingtip vortex system generated from three wing configurations are simulated with the improved delayed detached eddy simulation (IDDES) method. Numerical results show that each layout produces an interacting wingtip vortex system. These three corresponding vortical interactions are, respectively, the interaction between wingtip vortex and its counter-rotating vortex, winglet-tip vortex, and winglet four-vortex system. The fluid entrainment of ambient fluid and vortical impulse transport resulted from inductive effect have been founded generally existing in its formation and evolution. These two dominated mechanisms account for induced drag generation. On one hand, the winglet with toed-out angle is considered capable of changing the flow field around the winglet, and decomposing the winglet-tip vortex into four small vortices. Due to quite few fluid entrainment effects, this typical four-vortex system that cannot merge and only dissipate in the near wake scarcely contributes to the induced drag. On the other hand, a potential drag reduction method is also indicated that a lower induced drag can be obtained when the merger of wingtip and winglet-tip vortex is controlled and eliminated. This investigation will offer a novel perspective to guide the design of wingtip device and method of crusing resistance reduction for aircrafts.

Improved Delayed Detached Eddy Simulation (IDDES) of a 1.5 Stage Axial Compressor Non-Synchronous Vibration

2020 ◽  
Author(s):  
Purvic Patel ◽  
Yunchao Yang ◽  
Gecheng Zha
Keyword(s):  
Rotor Blade ◽  
High Speed ◽  
Stokes Equations ◽  
Axial Compressor ◽  
Suction Side ◽  
Tip Vortex ◽  
Weno Scheme ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

Abstract This paper utilizes the Improved Delayed Detached Eddy Simulation (IDDES) to investigate the non-synchronous vibration (NSV) mechanism of a 1.5 stage high-speed axial compressor. The NSV occurs at a part speed in the rig test. A low diffusion E-CUSP approximate Riemann solver with a third order Weighted Essentially Non-Oscillating (WENO) scheme for the inviscid flux and a second order central differencing scheme for the viscous flux are employed to solve the 3D time accurate Navier-Stokes equations. The fully conservative sliding boundary condition is used to preserve the wake-propagation. The aerodynamic instability in the tip region induces two alternating low pressure regions near the leading and the trailing edge on the suction side of the rotor blade. It is observed that the circumferential tip vortex motion in the rotor passage above 75 % span and its coupling forces cause NSV at the operating speed. This instability moves in the counter-rotating direction in the rotational frame. The NSV results using URANS simulation is also presented for comparison. The predicted frequency with the IDDES and URANS using rigid blades agrees well with the measured frequency in the rig test. In addition to the NSV, the IDDES solver also captures the dominant engine order frequencies. The tip flow structures show the vortex filament with one end on the suction side of the rotor blade and other side terminating on the casing or the pressure side of the rotor blade.

Transition and Turbulence Modeling for the Prediction of Cavitating Tip Vortices

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Rens Liebrand ◽  
Maarten Klapwijk ◽  
Thomas Lloyd ◽  
Guilherme Vaz
Keyword(s):  
Boundary Layer ◽  
Turbulence Modeling ◽  
Tip Vortex ◽  
Vapor Flow ◽  
Cavity Size ◽  
Detached Eddy Simulation ◽  
Tip Vortices ◽  
Eddy Simulation ◽  
Numerical Predictions ◽  
Delayed Detached Eddy Simulation

Abstract This study evaluates the influence of transition and turbulence modeling on the prediction of wetted and cavitating tip vortices for an elliptical wing, while investigating the numerical errors. Transition modeling increases the quality of numerical predictions since the assumption of a fully turbulent boundary layer, commonly found in literature, contributes to underprediction of the tip vortex cavity size. By applying the local correlation-based transition model (LCTM) and controlling the boundary layer thickness using different turbulent inflow conditions, the pressure in the vortex was found to reduce by 20% for an Angle of Attack (AoA) of 5 deg. The consequent increase in cavity size was found to be of a similar order of magnitude. At 9 deg AoA, transition always occurs just downstream of the leading edge, making this AoA more suitable to investigate the effect of different turbulence modeling approaches. Azimuthal and axial velocity fields are validated against stereographic-particle image velocimetry (S-PIV) measurements. The time-averaged velocity profiles predicted by delayed detached-eddy simulation (DDES) and improved delayed detached-eddy simulation (IDDES) are close to the experiments; however, no velocity fluctuations and vortex dynamics are observed around the vortex. A comparison of wetted and cavitating simulations shows that the cavity leads to a change in the balance between production and destruction of turbulence kinetic energy, which reduces the turbulent diffusion in and around the cavity compared to wetted flow conditions. Consequently, the vapor flow exhibits the characteristics of a potential flow. Whether this is physically plausible remains to be investigated.

Numerical study of the flow over the modified simple frigate shape

2020 ◽  
pp. 095441002097775
Author(s):  
Tong Li ◽  
Yibin Wang ◽  
Ning Zhao
Keyword(s):  
Bluff Body ◽  
Recirculation Zone ◽  
Numerical Study ◽  
Reference Value ◽  
Flow Fields ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Simulation Results

The simple frigate shape (SFS) as defined by The Technical Co-operative Program (TTCP), is a simplified model of the frigate, which helps to investigate the basic flow fields of a frigate. In this paper, the flow fields of the different modified SFS models, consisting of a bluff body superstructure and the deck, were numerically studied. A parametric study was conducted by varying both the superstructure length L and width B to investigate the recirculation zone behind the hangar. The size and the position of the recirculation zones were compared between different models. The numerical simulation results show that the size and the location of the recirculation zone are significantly affected by the superstructure length and width. The results obtained by Reynolds-averaged Navier-Stokes method were also compared well with both the time averaged Improved Delayed Detached-Eddy Simulation results and the experimental data. In addition, by varying the model size and inflow velocity, various flow fields were numerically studied, which indicated that the changing of Reynolds number has tiny effect on the variation of the dimensionless size of the recirculation zone. The results in this study have certain reference value for the design of the frigate superstructure.

scholarly journals Numerical Investigation on the Influence of the Streamlined Structures of the High-Speed Train’s Nose on Aerodynamic Performances

2021 ◽  
Vol 11 (2) ◽  
pp. 784
Author(s):  
Zhenxu Sun ◽  
Shuanbao Yao ◽  
Lianyi Wei ◽  
Yongfang Yao ◽  
Guowei Yang
Keyword(s):  
Drag Reduction ◽  
Pressure Distribution ◽  
Flow Separation ◽  
High Speed ◽  
Leeward Side ◽  
Detached Eddy Simulation ◽  
Side Force ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Asymmetrical Design

The structural design of the streamlined shape is the basis for high-speed train aerodynamic design. With use of the delayed detached-eddy simulation (DDES) method, the influence of four different structural types of the streamlined shape on aerodynamic performance and flow mechanism was investigated. These four designs were chosen elaborately, including a double-arch ellipsoid shape, a single-arch ellipsoid shape, a spindle shape with a front cowcatcher and a double-arch wide-flat shape. Two different running scenes, trains running in the open air or in crosswind conditions, were considered. Results reveal that when dealing with drag reduction of the whole train running in the open air, it needs to take into account how air resistance is distributed on both noses and then deal with them both rather than adjust only the head or the tail. An asymmetrical design is feasible with the head being a single-arch ellipsoid and the tail being a spindle with a front cowcatcher to achieve the minimum drag reduction. The single-arch ellipsoid design on both noses could aid in moderating the transverse amplitude of the side force on the tail resulting from the asymmetrical vortex structures in the flow field behind the tail. When crosswind is considered, the pressure distribution on the train surface becomes more disturbed, resulting in the increase of the side force and lift. The current study reveals that the double-arch wide-flat streamlined design helps to alleviate the side force and lift on both noses. The magnitude of side force on the head is 10 times as large as that on the tail while the lift on the head is slightly above that on the tail. Change of positions where flow separation takes place on the streamlined part is the main cause that leads to the opposite behaviors of pressure distribution on the head and on the tail. Under the influence of the ambient wind, flow separation occurs about distinct positions on the train surface and intricate vortices are generated at the leeward side, which add to the aerodynamic loads on the train in crosswind conditions. These results could help gain insight on choosing a most suitable streamlined shape under specific running conditions and acquiring a universal optimum nose shape as well.

scholarly journals Delayed Detached-Eddy Simulation and Particle Image Velocimetry Investigation of S-Duct Flow Distortion

AIAA Journal ◽  
2017 ◽  
Vol 55 (6) ◽  
pp. 1893-1908 ◽  
Author(s):  
Daniel Gil-Prieto ◽  
David G. MacManus ◽  
Pavlos K. Zachos ◽  
Geoffrey Tanguy ◽  
François Wilson ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Duct Flow ◽  
Detached Eddy Simulation ◽  
Flow Distortion ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Image Velocimetry
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