Numerical study of flow and noise predictions for tandem cylinders using incompressible improved delayed detached eddy simulation combined with acoustic perturbation equations

2021 ◽  
Vol 224 ◽  
pp. 108740
Author(s):  
Guang Chen ◽  
Xi-Feng Liang ◽  
Dan Zhou ◽  
Xiao-Bai Li ◽  
Fu-sang Lien
Keyword(s):  
Numerical Study ◽  
Detached Eddy Simulation ◽  
Acoustic Perturbation ◽  
Eddy Simulation ◽  
Tandem Cylinders ◽  
Delayed Detached Eddy Simulation ◽  
Perturbation Equations

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.

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

2018 ◽  
Vol 233 (7) ◽  
pp. 715-730 ◽  
Author(s):  
Mingyang Liu ◽  
Jiabin Wang ◽  
Huifen Zhu ◽  
Sinisa Krajnovic ◽  
Guangjun Gao
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Snow Accumulation ◽  
Phase Model ◽  
Detached Eddy Simulation ◽  
Discrete Phase Model ◽  
Eddy Simulation ◽  
Delayed Detached 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.

LES and Hybrid RANS/LES of a Fundamental Trailing Edge Slot

2014 ◽  
Author(s):  
Elizaveta Ivanova ◽  
Gregory M. Laskowski
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Numerical Study ◽  
Mixing Layer ◽  
Detached Eddy Simulation ◽  
Trailing Edge ◽  
Adiabatic Wall ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

This paper presents the results of a numerical study on the predictive capabilities of Large Eddy Simulation (LES) and hybrid RANS/LES methods for heat transfer, mean velocity, and turbulence in a fundamental trailing edge slot. The geometry represents a landless slot (two-dimensional wall jet) with adjustable slot lip thickness. The reference experimental data taken from the publications of Kacker and Whitelaw [1] [2] [3] [4] contains the adiabatic wall effectiveness together with the velocity and the Reynolds-stress profiles for various blowing ratios and slot lip thicknesses. The simulations were conducted at three different lip thickness and several blowing ratio values. The comparison with the experimental data shows a general advantage of LES and hybrid RANS/LES methods against unsteady RANS. The predictive capability of the tested LES models (dynamic ksgs-equation [5] and WALE [6]) was comparable. The Improved Delayed Detached Eddy Simulation (IDDES) hybrid method [7] also shows satisfactory agreement with the experimental data. In addition to the described baseline investigations, the influence of the inlet turbulence boundary conditions and their implication for the initial mixing layer and heat transfer development were studied for both LES and IDDES.

Experimental and Numerical Investigations of the Heat Transfer and Flow Field in a Trailing Edge Cooling Geometry: Part 2 — LES and Hybrid RANS/LES Study

2015 ◽  
Author(s):  
Elizaveta Ivanova ◽  
Gustavo Ledezma ◽  
Guanghua Wang ◽  
Gregory M. Laskowski
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Future Research ◽  
Detached Eddy Simulation ◽  
Trailing Edge ◽  
Validation Data ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Adiabatic Cooling ◽  
Les Model

This paper presents the results of a numerical study on the predictive capabilities of Large Eddy Simulation (LES) and hybrid RANS/LES methods for heat transfer in the trailing edge (TE) geometry experimentally investigated in Part 1. The experimental validation data includes 2D wall contours and laterally-averaged values of adiabatic cooling effectiveness. The simulations were conducted at three different blowing ratio values. The comparison with the experimental data shows a general advantage of LES and hybrid RANS/LES methods against steady-state RANS. The results obtained by means of the WALE LES model and the Improved Delayed Detached Eddy Simulation (IDDES) hybrid RANS/LES method were comparable. The presented grid dependence study shows the importance of adequate grid resolution for the predictive capabilities of trailing edge cooling LES. Furthermore, the importance of considering TE slot lands simulation quality in the numerical method assessment is discussed. Potential directions of future research needed to improve simulation reliability are outlined.

Numerical Study of Flow Physics Behind the Aerodynamic Performance on an Airfoil With Leading Edge Tubercles

2016 ◽  
Author(s):  
Mingming Zhang ◽  
Ming Zhao ◽  
Jianzhong Xu
Keyword(s):  
Numerical Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Physical Models ◽  
Vortical Flow ◽  
Detached Eddy Simulation ◽  
Flow Physics ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Solid Foundation

This paper presents a numerical analysis of the flow physics behind the effects of leading-edge protuberances on airfoil performances at low Reynolds number with an aim to provide a solid foundation for the engineering applications in the near future. An improved delayed detached eddy simulation (IDDES) method based on a transition model was proposed and validated through comparisons with experimental results. Utilizing the IDDES scheme, together with vortex dynamic method, investigations were focused on the stall and post-stall regions, respectively. It was found that an interesting ‘bi-periodic’ phenomenon within stall region, i.e. converged and diverged vortical flow in adjacent trough sections of tubercles, was created with the complicated evolution of the generated streamwise counter-rotating vortex pairs, resulting in the degraded aerodynamic characteristics as well as rather gentle stall process. For the post-stall cases, the impaired flow detachment around both peak and trough sections of tubercles were responsible for the improved airfoil performance. In addition, two physical models within the two regions were also built to further clarify the flow physics in a general way.

Numerical Study of Impulse Actuation for Stall Control

2011 ◽  
Author(s):  
SolKeun Jee ◽  
Omar D. Lopez Mejia ◽  
Robert D. Moser
Keyword(s):  
Shear Layer ◽  
Numerical Study ◽  
Separation Point ◽  
Detached Eddy Simulation ◽  
Airfoil Surface ◽  
Vortical Structures ◽  
Eddy Simulation ◽  
Separated Shear Layer ◽  
Delayed Detached Eddy Simulation ◽  
Stall Control

The response of a stalled flow to a single impulse actuation is examined numerically to investigate the mechanism by which this actuation affects the flow. Delayed detached eddy simulation is used on a stalled NACA 4415 airfoil at an angle of attack of 20 degrees and Reynolds number Re = 570,000. A brief strong jet issues normal to the airfoil surface upstream of the nominal flow separation point of the airfoil, causing the boundary layer temporally reattached. This computation shows the detailed evolution of vortical structures generated by both the baseline flow and the impulse actuation. Initial vortices from the actuation convect downstream, interact with the separated shear layer, and dismantle the layer. After the collapse of the separated shear layer, the separation point moves aft and remains delayed for a much longer period than the actuation time, similar to experimental observation [1]. The jet is simply represented as a Dirichlet velocity boundary condition, which is found to be sufficient to represent the global effects of impulse actuation on the stalled flow.

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