Ting Zhang¹, Denghao Wu^1,2,*, Shijun Qiu², Peijian Zhou¹, Yun Ren³, Jiegang Mou¹

FDMP-Fluid Dynamics & Materials Processing, Vol.18, No.5, pp. 1349-1361, 2022, DOI:10.32604/fdmp.2022.019617 - 27 May 2022

Abstract Stall phenomena increase the complexity of the internal flow in centrifugal pump impellers. In order to tackle this problem, in the present work, a large eddy simulation (LES) approach is applied to determine the characteristics of these unstable flows. Moreover, a vorticity identification method is used to characterize quantitatively the vortex position inside the impeller and its influencing area. By comparing the outcomes of the numerical simulations and experimental results provided by a Particle Image Velocimetry (PIV) technique, it is shown that an apparent “alternating stall” phenomenon exists inside the impeller when relatively small flow More >

Jingfa Li¹, Bo Yu^1,*, Qianqian Shao², Dongliang Sun¹

CMES-Computer Modeling in Engineering & Sciences, Vol.125, No.2, pp. 541-563, 2020, DOI:10.32604/cmes.2020.011835 - 12 October 2020

Abstract In this work, the drag-reducing mechanism of high-Reynoldsnumber turbulent channel flow with surfactant additives is investigated by using large eddy simulation (LES) method. An N-parallel finitely extensible nonlinear elastic model with Peterlin’s approximation (FENE-P) is used to describe the rheological behaviors of non-Newtonian fluid with surfactant. To close the filtered LES equations, a hybrid subgrid scale (SGS) model coupling the spatial filter and temporal filter is applied to compute the subgrid stress and other subfilter terms. The finite difference method and projection algorithm are adopted to solve the LES governing equations. To validate the correctness More >

Lijian Xu¹, Tianyang Yang², Lekang Yin³, Ye Kong², Yuri Vassilevski^4,5, Fuyou Liang^1,5,6,*

CMES-Computer Modeling in Engineering & Sciences, Vol.124, No.2, pp. 509-526, 2020, DOI:10.32604/cmes.2020.010719 - 20 July 2020

Abstract Computational modeling methods have been increasingly employed to quantify aortic hemodynamic parameters that are challenging to in vivo measurements but important for the diagnosis/treatment of aortic disease. Although the presence of turbulence-like behaviors of blood flow in normal or diseased aorta has long been confirmed, the majority of existing computational model studies adopted the laminar flow assumption (LFA) in the treatment of sub-grid flow variables. So far, it remains unclear whether LFA would significantly compromise the reliability of hemodynamic simulation. In the present study, we addressed the issue in the context of a specific aortopathy,… More >

Chong Liu, Yang Du, Jianjun Liang, Hong Meng, Jian Wang, Peili Zhang^*

FDMP-Fluid Dynamics & Materials Processing, Vol.16, No.3, pp. 537-547, 2020, DOI:10.32604/fdmp.2020.09119 - 25 May 2020

Abstract Gas explosion is a process involving complex hydrodynamics and chemical reactions. In order to investigate the interaction between the flame behavior and the dynamic overpressure resulting from the explosion of a premixed gasoline-air mixture in a confined space, a large eddy simulation (LES) strategy coupled with sub-grid combustion model has been implemented. The considered confined space consists of a long duct and four branches symmetrically distributed on both sides of the long duct. Comparisons between the simulated and experimental results have been considered with regard to the flame structure, flame speed and overpressure characteristics. It… More >

Yadong Zhang^{1, *}, Jiye Zhang²

FDMP-Fluid Dynamics & Materials Processing, Vol.16, No.1, pp. 105-120, 2020, DOI:10.32604/fdmp.2020.07959 - 01 February 2020

Abstract The object of research of this paper is the DSA380 high-speed pantograph. The near-field unsteady flow around the pantograph was investigated using large eddy simulation (LES) while the far-field aerodynamic noise was analysed in the frame of the Ffowcs Williams-Hawkings (FW-H) acoustic analogy. According to the results, the contact strip, base frame and knuckle are the main aerodynamic noise sources, with vortex shedding, flow separation and recombination around the pantograph being related key physical factors. The aerodynamic noise radiates outwards in the form of spherical waves when the distance of the noise receiving point is… More >

Jiali Liu¹, Mengge Yu^{2, *}, Dawei Chen¹, Zhigang Yang³

FDMP-Fluid Dynamics & Materials Processing, Vol.16, No.1, pp. 21-30, 2020, DOI:10.32604/fdmp.2020.07658 - 01 February 2020

Abstract In order to investigate how the aerodynamic drag and noise produced by the roof air conditioner of a high-speed train can be reduced, the related unsteady flow in the near-field was computed using the method of large eddy simulation. In this way, the aerodynamic source for noise generation has initially been determined. Then, the far-field aerodynamic noise has been computed in the framework of the Lighthill’s acoustics analogy theory. The propulsion height and flow-guide angle of the roof air conditioner were set as the design variables. According to the computational results, a lower propulsion height More >

Da-guo Wang^1,2, Bin Hu¹, Qing-xiang Shui¹

CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.4, pp. 297-320, 2015, DOI:10.3970/cmes.2015.107.297

Abstract A numerical large eddy simulation (LES) method combined with the characteristic-based operator-splitting finite element method is proposed. The subgrid eddy viscosity model is used to calculate sub-grid stress in LES. In each time step, the governing equations are split into diffusive and convective parts. The convective part is first discretized by using the characteristic Galerkin method and then solved explicitly. The backward-facing step flow and the flow past a single cylinder are adopted to validate the model. Results agree with existing numerical results or experimental data. The flow past two cylinders in tandem arrangement is More >

Nadjib Ghiti¹

CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.3, pp. 195-208, 2014, DOI:10.3970/cmes.2014.099.195

Abstract This paper presents a large eddy simulation of three dimensional vertically impinging jet on a horizontal plate. The air impinging jet was simulated using the perturbed method based on a high vortex number in the jet inlet for different ranges of Reynolds number Re= 6000, 8000, 10000, 12000, 14000 and for the same distance between the jet and the impinging plate. The effect of the Reynolds number of the air jet impinging on a horizontal plate was studied; the study showed that the vorticity magnitude is increased with the increasing of the Reynolds number. The More >

Shigenao Maruyama^a, Masud Behnia^b, Masasazumi Chisaki^c, Takuma Kogawa^c,*, Junnosuke Okajima^a, Atsuki Komiya^a

Frontiers in Heat and Mass Transfer, Vol.4, No.2, pp. 1-6, 2013, DOI:10.5098/hmt.v4.2.3002

Abstract The diffusion process of deep seawater drawn up by a vertical pipe deployed in the ocean is investigated. This vertical pipe is based on the principal of perpetual salt fountain. Numerical simulations of seawater upwelling from the pipe are performed based on experiments conducted in the Mariana trench region. Two turbulence modeling approaches were examined: k-ε model and Large Eddy Simulations (LES). The results in both models show that diffusion of the deep seawater diffusion after ejection from the pipe. The LES results show a 50% lower vertical penetration compared to the k-ε model as well More >

L.Q. Moreira¹, F.P. Mariano², A. Silveira-Neto¹

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.2, pp. 113-140, 2011, DOI:10.3970/cmes.2011.075.113

Abstract Turbulence in fluid flow is one of the most challenging problems in classical physics. It is a very important research problem because of its numerous implications, such as industrial applications that involve processes using mixtures of components, heat transfer and lubrication and injection of fuel into the combustion chambers and propulsion systems of airplanes. Turbulence in flow presents characteristics that are fully nonlinear and that occur at high Reynolds numbers. Because of the nonlinear nature of turbulent flow, an increase in the Reynolds number implies an increase in the Kolmogorov wave numbers, and the flow… More >