Large Eddy Simulation and investigation on the flow structure of the cascading cavitation shedding regime around 3D twisted hydrofoil

2017 ◽  
Vol 129 ◽  
pp. 1-19 ◽  
Author(s):  
Ying Chen ◽  
Xin Chen ◽  
Jie Li ◽  
Zhaoxin Gong ◽  
Chuanjing Lu
Keyword(s):  
Large Eddy Simulation ◽  
Flow Structure ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Twisted Hydrofoil

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.

Numerical Investigation of Flow Structure in Pipe Elbow With Large Eddy Simulation Approach

2009 ◽  
Author(s):  
Masa-aki Tanaka ◽  
Hiroyuki Ohshima ◽  
Hideaki Monji
Keyword(s):  
Numerical Simulation ◽  
Large Eddy Simulation ◽  
Numerical Simulations ◽  
Flow Structure ◽  
Flow Condition ◽  
Simulation Approach ◽  
Simulation Code ◽  
Eddy Simulation ◽  
Pipe Elbow ◽  
Large Eddy

At the JAEA (Japan Atomic Energy Agency), the simulation code “MUGTHES (MUlti Geometry simulation code for THErmal-hydraulic and Structure heat conduction analysis in boundary fitted coordinate)” has been developed. MUGTHES employs LES (Large Eddy Simulation) approach to calculate unsteady thermal-hydraulic phenomena and the BFC (Boundary Fitted Coordinate) system to simulate complex geometry in the system. In this study, numerical simulations for pipe elbow flows in various curvature radius ratio (Rc/D) conditions at several Reynolds number conditions. By the numerical simulation in pipe elbow at a laminar flow condition of Re = 700, the numerical schemes and the evaluation method of metrics in BFC system are verified and an appropriate mesh arrangement for elbow pipe is considered. By the numerical simulations in pipe elbow with the ratio of Rc/D = 2 under turbulent flow condition of Re = 60,000, the LES approach using standard Smagorinsky model with wall function law is examined in comparison with the experimental results. Moreover, numerical simulation for the 1/3-scaled water experiment at Re = 3.7×106 which simulates the primary cooling system of the JSFR (Japan Sodium-cooled Fast Reactor) is conducted. From comparisons of axial velocity profiles, applicability of MUGTHES to the elbow pipe flow is confirmed and the characteristic of three-dimensional flow structure relating to the structural integrity of the elbow pipe is discussed.

scholarly journals Large-Eddy Simulation of the Stable Boundary Layer with Explicit Filtering and Reconstruction Turbulence Modeling

2011 ◽  
Vol 68 (9) ◽  
pp. 2142-2155 ◽  
Author(s):  
Bowen Zhou ◽  
Fotini Katopodes Chow
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Flow Structure ◽  
Stable Boundary Layer ◽  
Strong Stability ◽  
Stable Boundary ◽  
Closure Models ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Good Agreement

Abstract Large-eddy simulation (LES) of the stably stratified atmospheric boundary layer is performed using an explicit filtering and reconstruction approach with a finite difference method. Turbulent stresses are split into the resolvable subfilter-scale and subgrid-scale stresses. The former are recovered from a reconstruction approach, and the latter are represented by a dynamic eddy-viscosity model. The resulting dynamic reconstruction model (DRM) can sustain resolved turbulence with less stringent resolution requirements than conventional closure models, even under strong atmospheric stability. This is achieved by proper representation of subfilter-scale (SFS) backscatter of turbulent kinetic energy (TKE). The flow structure and turbulence statistics for the moderately stable boundary layer (SBL) are analyzed with high-resolution simulations. The DRM simulations show good agreement with established empirical formulations such as flux and gradient-based surface similarity, even at relatively coarse resolution. Similar results can be obtained with traditional closure models at the cost of higher resolution. SBL turbulence under strong stability is also explored. Simulations show an intermittent presence of elevated TKE below the low-level jet. Overall, the explicit filtering and reconstruction approach is advantageous for simulations of the SBL. At coarse resolution, it can extend the working range of LES to stronger stability, while maintaining agreement to similarity theory; at fine resolution, good agreement with theoretical formulations provides confidence in the results and allows for detailed investigation of the flow structure under moderate to strong stability conditions.

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