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

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.

Delayed Detached Eddy Simulation of Rotating Stall for a Full Annulus Transonic Axial Compressor Stage

Volume 2A: Turbomachinery ◽

10.1115/gt2016-57985 ◽

2016 ◽

Cited By ~ 1

Author(s):

Jiaye Gan ◽

Hong-Sik Im ◽

Ge-Cheng Zha

Keyword(s):

Stokes Equations ◽

Axial Compressor ◽

Rotating Stall ◽

Tip Clearance ◽

Navier Stokes ◽

Stall Inception ◽

Eddy Simulation ◽

Stall Cells

This paper solves the filtered Navier-Stokes equations to simulate stall inception of NASA compressor transonic Stage 35 with delayed detached eddy simulation (DDES). A low diffusion E-CUSP Riemann solver with a 3rd order MUSCL scheme for the inviscid fluxes and a 2nd order central differencing for the viscous terms are employed. A full annulus of the rotor-stator stage is simulated with an interpolation sliding boundary condition (BC) to resolve the rotor-stator interaction. The tip clearance is fully gridded to accurately resolve tip vortices and their effect on stall inception. The DDES results show that the stall inception of Stage 35 is initialized by a weak harmonic disturbance with the length scales of the full annulus and grows rapidly with two emerging spike like disturbance. The two spike disturbances propagate in counter rotational direction with about 42% of rotor speed. The spike stall cells cover about 6 blades. They lead to two stall cells grown circumferentially and inwardly.

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

Applied Sciences ◽

10.3390/app11020784 ◽

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 ◽

Side Force ◽

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.

Detached Eddy Simulation of Transonic Rotor Stall Flutter Using a Fully Coupled Fluid-Structure Interaction

Volume 6: Structures and Dynamics, Parts A and B ◽

10.1115/gt2011-45437 ◽

2011 ◽

Cited By ~ 7

Author(s):

Hongsik Im ◽

Xiangying Chen ◽

Gecheng Zha

Keyword(s):

Stokes Equations ◽

Rotating Stall ◽

Rotor Blades ◽

Tip Clearance ◽

Weno Scheme ◽

Navier Stokes ◽

Eddy Simulation ◽

Stall Flutter ◽

Fully Coupled

Detached eddy simulation of an aeroelastic self-excited instability, flutter in NASA Rotor 67 is conducted using a fully coupled fluid/structre interaction. Time accurate compressible 3D Navier-Stokes equations are solved with a system of 5 decoupled modal equations in a fully coupled manner. The 5th order WENO scheme for the inviscid flux and the 4th order central differencing for the viscous flux are used to accurately capture interactions between the flow and vibrating blades with the DES (detached eddy simulation) of turbulence. A moving mesh concept that can improve mesh quality over the rotor tip clearance was implemented. Flutter simulations were first conducted from choke to stall using 4 blade passages. Stall flutter initiated at rotating stall onset, grows dramatically with resonance. The frequency analysis shows that resonance occurs at the first mode of the rotor blade. Before stall, the predicted responses of rotor blades decayed with time, resulting in no flutter. Full annulus simulation at peak point verifies that one can use the multi-passage approach with periodic boundary for the flutter prediction.

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

A numerical study of snow accumulation on the bogies of high-speed trains based on coupling improved delayed detached eddy simulation and discrete phase model

10.1177/0954409718805817 ◽

2018 ◽

Vol 233 (7) ◽

pp. 715-730 ◽

Cited By ~ 3

Author(s):

Mingyang Liu ◽

Jiabin Wang ◽

Huifen Zhu ◽

Sinisa Krajnovic ◽

Guangjun Gao

Keyword(s):

High Speed ◽

Numerical Study ◽

Snow Accumulation ◽

Phase Model ◽

Discrete Phase Model ◽

Eddy Simulation ◽

Flow Mechanisms ◽

Discrete Phase

A numerical simulation method based on the improved delayed detached eddy simulation coupled with a discrete phase model is used to study the influence of the snow on the performance of bogies of a high-speed train running in snowy weather. The snow particle trajectories, mass of snow packing on the bogie, and thickness of snow accumulation have been analyzed to investigate the flow mechanisms of snow accumulation on different parts of the bogies. The results show that the snow accumulation on the first bogie of the head vehicle is almost the same as that of the second bogie, but the total accumulated snow on the top side of the second bogie is more than 74% higher than that of the first bogie. Among all the components of the bogies, the motors were found to be strongly influenced by the snow accumulation. The underlying flow mechanisms responsible for the snow accumulations are discussed.

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

10.1115/1.0003278v ◽

2021 ◽

Author(s):

Purvic Patel ◽

Yunchao Yang ◽

Gecheng Zha

Keyword(s):

Axial Compressor ◽

Eddy Simulation ◽

Detached-Eddy Simulation of Ground Effect on the Wake of a High-Speed Train

Journal of Fluids Engineering ◽

10.1115/1.4035804 ◽

2017 ◽

Vol 139 (5) ◽

Cited By ~ 11

Author(s):

Chao Xia ◽

Xizhuang Shan ◽

Zhigang Yang

Keyword(s):

Vortex Shedding ◽

High Speed ◽

Vortex Pair ◽

Ground Effect ◽

Longitudinal Vortex ◽

High Speed Train ◽

Side Force ◽

Eddy Simulation ◽

The influence of ground effect on the wake of a high-speed train (HST) is investigated by an improved delayed detached-eddy simulation. Aerodynamic forces, the time-averaged and instantaneous flow structure of the wake are explored for both the stationary ground and the moving ground. It shows that the lift force of the trailing car is overestimated, and the fluctuation of the lift and side force is much greater under the stationary ground, especially for the side force. The coexistence of multiscale vortex structures can be observed in the wake along with vortex stretching and pairing. Furthermore, the out-of-phase vortex shedding and oscillation of the longitudinal vortex pair in the wake are identified for both ground configurations. However, the dominant Strouhal number of the vortex shedding for the stationary and moving ground is 0.196 and 0.111, respectively, due to the different vorticity accumulation beneath the train. A conceptual model is proposed to interpret the mechanism of the interaction between the longitudinal vortex pair and the ground. Under the stationary ground, the vortex pair embedded in a turbulent boundary layer causes more rapid diffusion of the vorticity, leading to more intensive oscillation of the longitudinal vortex pair.

Simulation of Non-Synchronous Blade Vibration of an Axial Compressor Using a Fully Coupled Fluid/Structure Interaction

Volume 7: Structures and Dynamics, Parts A and B ◽

10.1115/gt2012-68150 ◽

2012 ◽

Cited By ~ 11

Author(s):

Hong-Sik Im ◽

Ge-Cheng Zha

Keyword(s):

Boundary Condition ◽

Stokes Equations ◽

Axial Compressor ◽

Tip Vortex ◽

Weno Scheme ◽

Navier Stokes ◽

Phase Lag ◽

Tip Leakage Flow ◽

Blade Vibration ◽

Fully Coupled

In this paper non-synchronous vibration (NSV) of a GE axial compressor is simulated using a fully coupled fluid/strcuture interaction (FSI). Time accurate Navier-Stokes equations are solved with a system of 5 decoupled structure modal equations in a fully coupled manner. A 3rd order WENO scheme for the inviscid flux and a 2nd order central differencing for the viscous terms are used to resolve nonlinear interaction between vibrating blades and fluid flow. 1/7th annulus is used with a time shifted phase-lag (TSPL) boundary condition to reduce computational efforts. A fully conservative rotor/stator sliding boundary condition is employed to accurately capture unsteady wake propagation between the rotor and stator blades. The predicted dominant frequencies using the blade tip response signals are not harmonic to the engine order, which is the NSV. The blade vibration is torsionally coupled with highly oscillating blade pressure and is not damped out during the NSV. No resonance to the blade natural frequencies is found. The instability of tornado vortices in the vicinity of the rotor tip due to the strong interaction of incoming flow, tip vortex and tip leakage flow is the main cause of the NSV observed in this study.

Simulation of Dynamic Stall on an Elastic Rotor in High-Speed Turn Flight

Journal of the American Helicopter Society ◽

10.4050/jahs.65.022002 ◽

2020 ◽

Vol 65 (2) ◽

pp. 1-12

Author(s):

Johannes Letzgus ◽

Manuel Keßler ◽

Ewald Krämer

Keyword(s):

High Speed ◽

Separated Flow ◽

Flight Test ◽

Dynamic Stall ◽

Minor Role ◽

Rotor Aerodynamics ◽

Eddy Simulation ◽

A Minor

A highly loaded, high-speed turn flight of Airbus Helicopters' Bluecopter demonstrator helicopter is simulated to investigate dynamic stall using a loose computational fluid dynamics/structural dynamics (CFD/CSD) coupling of the flow solver FLOWer and the rotorcraft comprehensive code CAMRAD II. The rotor aerodynamics is computed using a high-fidelity delayed detached-eddy simulation (DDES). A three-degree-of-freedom trim of an isolated rotor is performed, yielding main-rotor control angles that agree well with the flight-test measurements. The flow field in this flight condition is found to be highly unsteady and complex, featuring massively separated flow, blade–vortex interaction, multiple dynamic-stall events, and shock-induced separation. The computed pitch-link loads are compared to flight-test measurements. This shows that all CFD/CSD cases underpredict the amplitudes of the flight test and yield phase shifts. However, overall trends agree reasonably. Also, varying the computational setup reveals that the shear stress transport–DDES turbulence model performs better than Spalart–Allmaras–DDES, that the consideration of the rotor hub and fuselage improves the agreement with flight-test data, and that the elastic twist plays only a minor role in the dynamic-stall events.

Numerical Investigation of Powered Jet Effects by RANS/LES Hybrid Methods

Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University ◽

10.1051/jnwpu/20193730565 ◽

2019 ◽

Vol 37 (3) ◽

pp. 565-571

Author(s):

Zhibin Gong ◽

Jie Li ◽

Jixiang Shan ◽

Heng Zhang

Keyword(s):

Numerical Investigation ◽

Hybrid Methods ◽

Three Dimensional ◽

Jet Flow ◽

Weno Scheme ◽

Turbulent Structures ◽

Ambient Flow ◽

Eddy Simulation ◽

For the high-precision simulation of engine jet effects, an improved delayed detached eddy simulation (IDDES) method based on the two-equation shear stress transport (SST) model is developed, and the fifth-order finite-volume weighted essentially non-oscillatory (WENO) scheme is employed to enhance accuracy of spatial discretization, and then numerical investigation of powered jet effects by RANS/LES hybrid methods is carried out. The effects of the grid distributions and the accuracy of the spatial schemes are discussed during the RANS/LES validation analysis on the fully expanded jet flow and Acoustic Reference Nozzle (ARN) jet flow. The results show that, by enlarging the grid density and improving the accuracy of the spatial schemes, the velocity distributions in the jet flow can be better predicted, the non-physical steady flow after the jet nozzle can be shortened, the instantaneous flow structures are clearer and the turbulent intensities are more accurate. Then IDDES simulation of turbofan engine jet flow is carried out. The mixing characteristics of the external fan jet flow and internal core jet flow as well as the ambient flow are obtained, and the three-dimensional turbulent structures are also given.

Investigation and Improvement of Stall Characteristic of High-Lift Configuration without Slats

International Journal of Aerospace Engineering ◽

10.1155/2019/7859482 ◽

2019 ◽

Vol 2019 ◽

pp. 1-14

Author(s):

Zhao Yang ◽

Jie Li ◽

Jing Jin ◽

Heng Zhang ◽

Youxu Jiang

Keyword(s):

Evaluation Method ◽

Leading Edge ◽

Suction Side ◽

Aerodynamic Characteristics ◽

Angle Distribution ◽

High Lift ◽

Eddy Simulation ◽

Business Jet ◽

In order to simplify the manufacturing process or because of the limitation of the propulsion system, business jet, small civil airplane, and turboprop aircraft are always designed without leading-edge slats, which poses a great challenge to the flight safety during takeoff and landing. Focusing on the low-speed stall and poststall conditions, we investigated the aerodynamic characteristics and flow mechanism of high-lift configuration without slats using an improved delayed detached eddy simulation (IDDES) model which is validated by numerical simulations of the Common Research Model (CRM). Based on the analysis of the calculated results, conclusion can be made that the stall behavior of the configurations is directly related to the onset and evaluation of flow separation on the suction side. And through further research, an efficient evaluation method that is capable of qualitatively predicting the stall performance of two-element high-lift configuration by stall angle distribution of wing sections is proposed. By using the evaluation method, together with design rules summarized from the present study, high-lift configuration with mild-stall characteristic can be obtained in the preliminary stage of design.