scholarly journals Large Eddy Simulation and theoretical investigations of the transient cavitating vortical flow structure around a NACA66 hydrofoil

2015 ◽  
Vol 68 ◽  
pp. 121-134 ◽  
Author(s):  
B. Ji ◽  
X.W. Luo ◽  
Roger E.A. Arndt ◽  
Xiaoxing Peng ◽  
Yulin Wu
Keyword(s):  
Large Eddy Simulation ◽  
Flow Structure ◽  
Vortical Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Theoretical Investigations

Large Eddy Simulation of the Flow Around a Diffuser-Equipped Bluff Body in Ground Effect

2011 ◽  
Author(s):  
Lara Schembri Puglisevich ◽  
Gary Page
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Vortex Formation ◽  
Ground Effect ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Flow Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features

Unsteady Large Eddy Simulation (LES) is carried out for the flow around a bluff body equipped with an underbody rear diffuser in close proximity to the ground, representing an automotive diffuser. The goal is to demonstrate the ability of LES to model underbody vortical flow features at experimental Reynolds numbers (1.01 × 106 based on model height and incoming velocity). The scope of the time-dependent simulations is not to improve on Reynolds-Averaged Navier Stokes (RANS), but to give further insight into vortex formation and progression, allowing better understanding of the flow, hence allowing more control. Vortical flow structures in the diffuser region, along the sides and top surface of the bluff body are successfully modelled. Differences between instantaneous and time-averaged flow structures are presented and explained. Comparisons to pressure measurements from wind tunnel experiments on an identical bluff body model shows a good level of agreement.

Large Eddy Simulation of a Vortex Ring Impacting a Bump

2014 ◽  
Vol 6 (3) ◽  
pp. 261-280
Author(s):  
Heng Ren ◽  
Ning Zhao ◽  
Xi-Yun Lu
Keyword(s):  
Large Eddy Simulation ◽  
Vortex Ring ◽  
Three Dimensional ◽  
Vortical Flow ◽  
Flow State ◽  
Vortical Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Phenomena ◽  
Flow Evolution

AbstractA vortex ring impacting a three-dimensional bump is studied using large eddy simulation for a Reynolds number Re = 4 × 104 based on the initial diameter and translational speed of the vortex ring. The effects of bump height and vortex core thickness for thin and thick vortex rings on the vortical flow phenomena and the underlying physical mechanisms are investigated. Based on the analysis of the evolution of vortical structures, two typical kinds of vortical structures, i.e., the wrapping vortices and the hair-pin vortices, are identified and play an important role in the flow state evolution. The boundary vorticity flux is analyzed to reveal the mechanism of the vorticity generation on the bump surface. The circulation of the primary vortex ring reasonably elucidates some typical phases of flow evolution. Further, the analysis of turbulent kinetic energy reveals the transition from laminar to turbulent state. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the flow evolution and the flow transition to turbulent state.

Computation of Aerial Towed Cable Aerodynamic Performances with Large Eddy Simulation

2011 ◽  
Vol 105-107 ◽  
pp. 606-610
Author(s):  
Wei Han ◽  
Xiao Wei Kang ◽  
Yun Liang Wang ◽  
Xiao Hong Zheng
Keyword(s):  
Large Eddy Simulation ◽  
Flow Structure ◽  
Scale Model ◽  
Aerodynamic Forces ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Aerodynamic Performances ◽  
Long Time ◽  
Towed Cable ◽  
Dynamics Characteristic

The dynamics characteristic of aerial towed cable has been investigated with many models. Because of the coupling between the components of the towed cable system, the dynamics of the towed cable is complex and nonlinear. Though the aerodynamic performances of cable is studied for a long time, the results are quiet different with researchers. The ideal method to obtain the aerodynamic forces is to simulate the flow structure around the towed cable.The purposes of this paper are to simulate the flow field of the towed cable with the different inclined angles by using Large Eddy Simulation (LES) with sub-grid scale model of Smagorinsky-Lily and to study the variation of the aerodynamic forces and its influences on flow structure. The results show that the LES can predict the flow structure of the cable reasonably.

Large-Eddy Simulation of Buoyancy-Induced Flow in a Sealed Rotating Cavity

2018 ◽  
Author(s):  
Diogo B. Pitz ◽  
John W. Chew ◽  
Olaf Marxen
Keyword(s):  
Large Eddy Simulation ◽  
Boundary Layers ◽  
Flow Structure ◽  
Flow Characteristics ◽  
Global Features ◽  
Eddy Simulation ◽  
Rotating Cavity ◽  
Large Eddy ◽  
Induced Flow ◽  
Buoyancy Induced Flow

Buoyancy-induced flows occur in the rotating cavities of gas turbine internal air systems, and are particularly challenging to model due to their inherent unsteadiness. While the global features of such flows are well documented, detailed analyses of the unsteady structure and turbulent quantities have not been reported. In this work we use a high-order numerical method to perform large-eddy simulation (LES) of buoyancy-induced flow in a sealed rotating cavity with either adiabatic or heated disks. New insight is given into long-standing questions regarding the flow characteristics and nature of the boundary layers. The analyses focus on showing time-averaged quantities, including temperature and velocity fluctuations, as well as on the effect of the centrifugal Rayleigh number on the flow structure. Using velocity and temperature data collected over several revolutions of the system, the shroud and disk boundary layers are analysed in detail. The instantaneous flow structure contains pairs of large, counter-rotating convection rolls, and it is shown that unsteady laminar Ekman boundary layers near the disks are driven by the interior flow structure. The shroud thermal boundary layer scales as approximately Ra−1/3, in agreement with observations for natural convection under gravity.

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