An Analysis on the Flow Field Structures and the Aerodynamic Noise of
                        Airfoils with Serrated Trailing Edges Based on Embedded Large Eddy Flow
                        Simulations

The aerodynamic noise caused by the flow field around a generic side view mirror (SVM) was simulated using a subdomain large eddy simulation (LES) method. In this method, the LES solution could be run only in the subdomain, which can be the flow field near the SVM. The subdomain LES results show good agreement with the cited experimental data in some related works. With the principal advantage of saving CFD cell numbers, the subdomain LES method would be a perspective way to simulate the aerodynamic noise of complex geometries such as the real automobiles.

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Prediction of flow field and aerodynamic noise of jet fan using large eddy simulation

Journal of Visualization ◽

10.1007/s12650-012-0132-3 ◽

2012 ◽

Vol 15 (3) ◽

pp. 253-259 ◽

Cited By ~ 1

Author(s):

S. Tomimatsu ◽

Y. Yamade ◽

Y. Hirokawa ◽

N. Nishikawa

Keyword(s):

Flow Field ◽

Large Eddy Simulation ◽

Aerodynamic Noise ◽

Eddy Simulation ◽

Large Eddy ◽

Jet Fan

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Study on flow field and aerodynamic noise of electric vehicle rearview mirror

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/09544070211022896 ◽

2021 ◽

pp. 095440702110228

Author(s):

Xiaowei Hao ◽

Zhigang Yang ◽

Qiliang Li

Keyword(s):

Flow Field ◽

Proper Orthogonal Decomposition ◽

Electric Vehicle ◽

Sound Pressure ◽

Pressure Level ◽

Orthogonal Decomposition ◽

Aerodynamic Noise ◽

Turbulent Pressure ◽

Rearview Mirror ◽

Proper Orthogonal

With the development of new energy and intelligent vehicles, aerodynamic noise problem of pure electric vehicles at high speed has become increasingly prominent. The characteristics of the flow field and aerodynamic noise of the rearview mirror region were investigated by large eddy simulation, acoustic perturbation equations and reduction order analysis. By comparing the pressure coefficients of the coarse, medium and dense grids with wind tunnel test results, the pressure distribution, and numerical accuracy of the medium grid on the body are clarified. It is shown from the flow field proper orthogonal decomposition of the mid-section that the sum of the energy of the first three modes accounts for more than 16%. Based on spectral proper orthogonal decomposition, the peak frequencies of the first-order mode are 19 and 97 Hz. As for the turbulent pressure of side window, the first mode accounts for approximately 11.3% of the total energy, and its peak appears at 39 and 117 Hz. While the first mode of sound pressure accounts for about 41.7%, and the energy peaks occur at 410 and 546 Hz. Compared with traditional vehicle, less total turbulent pressure level and total sound pressure level are found at current electric vehicle because of the limited interaction between the rearview mirror and A-pillar.

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Numerical study on the airfoil self-noise of three owl-based wings with the trailing-edge serrations

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410020988229 ◽

2021 ◽

pp. 095441002098822

Author(s):

Dian Li ◽

Xiaomin Liu ◽

Lei Wang ◽

Fujia Hu ◽

Guang Xi

Keyword(s):

Flow Field ◽

Noise Reduction ◽

Numerical Study ◽

Barn Owl ◽

Aerodynamic Noise ◽

Frequency Noise ◽

Trailing Edge ◽

Reduction Mechanisms ◽

Trailing Edge Serrations ◽

Bionic Airfoil

Previous publications have summarized that three special morphological structures of owl wing could reduce aerodynamic noise under low Reynolds number flows effectively. However, the coupling noise-reduction mechanism of bionic airfoil with trailing-edge serrations is poorly understood. Furthermore, while the bionic airfoil extracted from natural owl wing shows remarkable noise-reduction characteristics, the shape of the owl-based airfoils reconstructed by different researchers has some differences, which leads to diversity in the potential noise-reduction mechanisms. In this article, three kinds of owl-based airfoils with trailing-edge serrations are investigated to reveal the potential noise-reduction mechanisms, and a clean airfoil based on barn owl is utilized as a reference to make a comparison. The instantaneous flow field and sound field around the three-dimensional serrated airfoils are simulated by using incompressible large eddy simulation coupled with the FW-H equation. The results of unsteady flow field show that the flow field of Owl B exhibits stronger and wider-scale turbulent velocity fluctuation than that of other airfoils, which may be the potential reason for the greater noise generation of Owl B. The scale and magnitude of alternating mean convective velocity distribution dominates the noise-reduction effect of trailing-edge serrations. The noise-reduction characteristic of Owl C outperforms that of Barn owl, which suggests that the trailing-edge serrations can suppress vortex shedding noise of flow field effectively. The trailing-edge serrations mainly suppress the low-frequency noise of the airfoil. The trailing-edge serration can suppress turbulent noise by weakening pressure fluctuation.

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Reducing Undesired Wave Reflection at Domain Boundaries in 3D Finite Volume-Based Flow Simulations via Forcing Zones

Journal of Ship Research ◽

10.5957/jsr.2020.64.1.23 ◽

2020 ◽

Vol 64 (01) ◽

pp. 23-47

Author(s):

Robinson Peric ◽

Moustafa Abdel-Maksoud

Keyword(s):

Finite Volume ◽

Wave Reflection ◽

Three Dimensional ◽

Navier Stokes ◽

Special Focus ◽

Computational Domain ◽

Wave Reflections ◽

Flow Simulations ◽

Large Eddy ◽

Domain Boundaries

This article reviews different types of forcing zones (sponge layers, damping zones, relaxation zones, etc.) as used in finite volume-based flow simulations to reduce undesired wave reflections at domain boundaries, with special focus on the case of strongly reflecting bodies subjected to long-crested incidence waves. Limitations and possible sources of errors are discussed. A novel forcing-zone arrangement is presented and validated via three-dimensional (3D) flow simulations. Furthermore, a recently published theory for predicting the forcing-zone behavior was investigated with regard to its relevance for practical 3D hydrodynamics problems. It was found that the theory can be used to optimally tune the case-dependent parameters of the forcing zones before running the simulations. 1. Introduction Wave reflections at the boundaries of the computational domain can cause significant errors in flow simulations, and must therefore be reduced. In contrast to boundary element codes, where much progress in this respect has been made decades ago (see e.g., Clement 1996; Grilli &Horillo 1997), for finite volume-based flow solvers, there are many unresolved questions, especially:How to reliably reduce reflections and disturbances from the domain boundaries?How to predict the amount of undesired wave reflection before running the simulation? This work aims to provide further insight to these questions for flow simulations based on Navier-Stokes-type equations (Reynolds-averaged Navier-Stokes, Euler equations, Large Eddy Simulations, etc.), when using forcing zones to reduce undesired reflections. The term "forcing zones" is used here to describe approaches that gradually force the solution in the vicinity of the boundary towards some reference solution, as described in Section 2; some examples are absorbing layers, sponge layers, damping zones, relaxation zones, or the Euler overlay method (Mayer et al. 1998; Park et al. 1999; Chen et al. 2006; Choi &Yoon 2009; Jacobsen et al. 2012; Kimet al. 2012; Schmitt & Elsaesser 2015; Perić & Abdel-Maksoud 2016a; Vukčević et al. 2016).

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Investigation on hydrodynamic forces leading to coarse particle entrainment using Large-Eddy Simulations

10.5194/egusphere-egu21-13221 ◽

2021 ◽

Author(s):

Gaston Latessa ◽

Angela Busse ◽

Manousos Valyrakis

Keyword(s):

Experimental Data ◽

Flow Field ◽

Large Scale ◽

Large Eddy Simulations ◽

Flow Conditions ◽

Mean Flow ◽

Protection Measures ◽

Practical Applications ◽

Particle Entrainment ◽

Large Eddy

The prediction of particle motion in a fluid flow environment presents several challenges from the quantification of the forces exerted by the fluid onto the solids -normally with fluctuating behaviour due to turbulence- and the definition of the potential particle entrainment from these actions. An accurate description of these phenomena has many practical applications in local scour definition and to the design of protection measures.In the present work, the actions of different flow conditions on sediment particles is investigated with the aim to translate these effects into particle entrainment identification through analytical solid dynamic equations.Large Eddy Simulations (LES) are an increasingly practical tool that provide an accurate representation of both the mean flow field and the large-scale turbulent fluctuations. For the present case, the forces exerted by the flow are integrated over the surface of a stationary particle in the streamwise (drag) and vertical (lift) directions, together with the torques around the particle&#8217;s centre of mass. These forces are validated against experimental data under the same bed and flow conditions.The forces are then compared against threshold values, obtained through theoretical equations of simple motions such as rolling without sliding. Thus, the frequency of entrainment is related to the different flow conditions in good agreement with results from experimental sediment entrainment research.A thorough monitoring of the velocity flow field on several locations is carried out to determine the relationships between velocity time series at several locations around the particle and the forces acting on its surface. These results a relevant to determine ideal locations for flow investigation both in numerical and physical experiments.Through numerical experiments, a large number of flow conditions were simulated obtaining a full set of actions over a fixed particle sitting on a smooth bed. These actions were translated into potential particle entrainment events and validated against experimental data. Future work will present the coupling of these LES models with Discrete Element Method (DEM) models to verify the entrainment phenomena entirely from a numerical perspective.

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Large-Eddy and Unsteady Reynolds-Averaged Navier-Stokes Simulations of an Axial Flow Pump for Cardiac Support

Volume 2B: Turbomachinery ◽

10.1115/gt2017-65250 ◽

2017 ◽

Cited By ~ 1

Author(s):

Benjamin Torner ◽

Sebastian Hallier ◽

Matthias Witte ◽

Frank-Hendrik Wurm

Keyword(s):

Flow Field ◽

Axial Flow ◽

Pressure Head ◽

Damage Parameter ◽

Ventricular Assist Devices ◽

Navier Stokes ◽

Mean Velocity ◽

Blood Damage ◽

Large Eddy ◽

Reynolds Averaged Navier Stokes

The use of implantable pumps for cardiac support (Ventricular Assist Devices) has proven to be a promising option for the treatment of advanced heart failure. Avoiding blood damage and achieving high efficiencies represent two main challenges in the optimization process. To improve VADs, it is important to understand the turbulent flow field in depth in order to minimize losses and blood damage. The application of the Large-eddy simulation (LES) is an appropriate approach to simulate the flow field because turbulent structures and flow patterns, which are connected to losses and blood damage, are directly resolved. The focus of this paper is the comparison between an LES and an Unsteady Reynolds-Averaged Navier-Stokes simulation (URANS) because the latter one is the most frequently used approach for simulating the flow in VADs. Integral quantities like pressure head and efficiency are in a good agreement between both methods. Additionally, the mean velocity fields show similar tendencies. However, LES and URANS show different results for the turbulent kinetic energy. Deviations of several tens of percent can be also observed for a blood damage parameter, which depend on velocity gradients. Possible reasons for the deviations will be investigated in future works.

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Large Eddy Simulation of Flow and Heat Transfer Mechanism in Matrix Cooling Channel

Volume 5A: Heat Transfer ◽

10.1115/gt2017-63515 ◽

2017 ◽

Author(s):

Yigang Luan ◽

Lianfeng Yang ◽

Bo Wan ◽

Tao Sun

Keyword(s):

Heat Transfer ◽

Flow Field ◽

Large Eddy Simulation ◽

Gas Turbine ◽

Transfer Mechanism ◽

Heat Transfer Mechanism ◽

Longitudinal Vortices ◽

Eddy Simulation ◽

Flow And Heat Transfer ◽

Large Eddy

Gas turbine engines have been widely used in modern industry especially in the aviation, marine and energy fields. The efficiency of gas turbines directly affects the economy and emissions. It’s acknowledged that the higher turbine inlet temperatures contribute to the overall gas turbine engine efficiency. Since the components are subject to the heat load, the internal cooling technology of turbine blades is of vital importance to ensure the safe and normal operation. This paper is focused on exploring the flow and heat transfer mechanism in matrix cooling channels. In order to analyze the internal flow field characteristics of this cooling configuration at a Reynolds number of 30000 accurately, large eddy simulation method is carried out. Methods of vortex identification and field synergy are employed to study its flow field. Cross-sectional views of velocity in three subchannels at different positions have been presented. The results show that the airflow is strongly disturbed by the bending part. It’s concluded that due to the bending structure, the airflow becomes complex and disordered. When the airflow goes from the inlet to the turning, some small-sized and discontinuous vortices are formed. Behind the bending structure, the size of the vortices becomes big and the vortices fill the subchannels. Because of the structure of latticework, the airflow is affected by each other. Airflow in one subchannel can exert a shear force on another airflow in the opposite subchannel. It’s the force whose direction is the same as the vortex that enhances the longitudinal vortices. And the longitudinal vortices contribute to the energy exchange of the internal airflow and the heat transfer between airflow and walls. Besides, a comparison of the CFD results and the experimental data is made to prove that the numerical simulation methods are reasonable and acceptable.

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