Reduction of BVI Noise Using a Leading Edge Air Mass Injection Concept: A Numerical Study Using Large-Eddy Simulation

2009 ◽  
Author(s):  
Marcel Ilie
Keyword(s):  
Large Eddy Simulation ◽  
Numerical Study ◽  
Leading Edge ◽  
Air Mass ◽  
Eddy Simulation ◽  
Mass Injection ◽  
Large Eddy

Large Eddy Simulation of Heat Transfer Over In-Line Flat-Tube Array in Laminar and Turbulent Flows

2017 ◽  
Author(s):  
Salar Taghizadeh ◽  
Sumanta Acharya ◽  
Kong Ling ◽  
Yousef Kanani ◽  
Xuan Ge
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Numerical Models ◽  
Leading Edge ◽  
Flat Tube ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy

This study presents a transient three-dimensional numerical study on fluid flow and heat transfer of flat-tube array using large eddy simulation (LES) covering both laminar and turbulent flow regimes. The simulations were performed in a rectangular region containing only one tube with periodic conditions specified on all boundaries. A staggered flat-plate array was first studied, and an existing solution was used for validation purpose. The numerical models were then applied to an in-line array composed of flat tubes with an aspect ratio of 0.25 and fixed tube spacings. By varying the in-flow velocity, the tube array was studied over a wide range of Reynolds number (600–12000). Temperature, velocity, and turbulent kinetic energy distributions as well as the interactions between them are presented and analyzed. Furthermore, the local heat transfer rate was analyzed along the various parts of the tube (leading edge, flat-top and wake or trailing-edge regions). Heat transfer correlation for each region of the tube and the entire tube array is proposed.

Large Eddy Simulation of Cross Flow in Pipe Junction

2018 ◽  
Author(s):  
Jiajun Chen ◽  
Yue Sun ◽  
Hang Zhang ◽  
Dakui Feng ◽  
Zhiguo Zhang
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Exciting Force ◽  
Navier Stokes ◽  
Pipe Network ◽  
Eddy Simulation ◽  
Large Eddy

Mixing in pipe junctions can play an important role in exciting force and distribution of flow in pipe network. This paper investigated the cross pipe junction and proposed an improved plan, Y-shaped pipe junction. The numerical study of a three-dimensional pipe junction was performed for calculation and improved understanding of flow feature in pipe. The filtered Navier–Stokes equations were used to perform the large-eddy simulation of the unsteady incompressible flow in pipe. From the analysis of these results, it clearly appears that the vortex strength and velocity non-uniformity of centerline, can be reduced by Y-shaped junction. The Y-shaped junction not only has better flow characteristic, but also reduces head loss and exciting force. The results of the three-dimensional improvement analysis of junction can be used in the design of pipe network for industry.

Large Eddy Simulation of Wake-Shear Layer Interactions Over a Multi-Element Aerofoil

2020 ◽  
Author(s):  
Souvik Naskar ◽  
S. Sarkar
Keyword(s):  
Large Eddy Simulation ◽  
Shear Layer ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Suction Surface ◽  
Free Stream Turbulence ◽  
Eddy Simulation ◽  
Large Eddy

Abstract Modern commercial airliners use multi-element aerofoils to enhance take-off and landing performance. Further, multielement aerofoil configurations have been shown to improve the aerodynamic characteristics of wind turbines. In the present study, high resolution Large Eddy Simulation (LES) is used to explore the low Reynolds Number (Re = 0.832 × 104) aerodynamics of a 30P30N multi-element aerofoil at an angle of attack, α = 4°. In the present simulation, wake shed from a leading edge element or slat is found to interact with the separated shear layer developing over the suction surface of the main wing. High receptivity of shear layer via amplification of free-stream turbulence leads to rollup and breakdown, forming a large separation bubble. A transient growth of fluctuations is observed in the first half of the separation bubble, where levels of turbulence becomes maximum near the reattachment and then decay depicting saturation of turbulence. Results of the present LES are found to be in close agreement with the experiment depicting high vortical activity in the outer layer. Some features of the flow field here are similar to those occur due to interactions of passing wake and the separated boundary layer on the suction surface of high lift low pressure turbine blades.

Very Large Eddy Simulation of Passive Drag Control for a D-Shaped Cylinder

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Xingsi Han ◽  
Siniša Krajnović
Keyword(s):  
Large Eddy Simulation ◽  
Flow Control ◽  
Control Problem ◽  
Bluff Body ◽  
Numerical Study ◽  
Numerical Results ◽  
Complex Flow ◽  
Local Disturbance ◽  
Eddy Simulation ◽  
Large Eddy

The numerical study reported here deals with the passive flow control around a two-dimensional D-shaped bluff body at a Reynolds number of Re=3.6×104. A small circular control cylinder located in the near wake behind the main bluff body is employed as a local disturbance of the shear layer and the wake. 3D simulations are carried out using a newly developed very large eddy simulation (VLES) method, based on the standard k − ε turbulence model. The aim of this study is to validate the performance of this method for the complex flow control problem. Numerical results are compared with available experimental data, including global flow parameters and velocity profiles. Good agreements are observed. Numerical results suggest that the bubble recirculation length is increased by about 36% by the local disturbance of the small cylinder, which compares well to the experimental observations in which the length is increased by about 38%. A drag reduction of about 18% is observed in the VLES simulation, which is quite close to the experimental value of 17.5%. It is found that the VLES method is able to predict the flow control problem quite well.

Large Eddy Simulation on the Interactions of Wake and Film-Cooling Near a Leading Edge

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
S. Sarkar ◽  
Harish Babu
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Vortex Pair ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Constant Thickness ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Past A Cylinder ◽  
Downward Spiral

The unsteady flow physics due to interactions between a separated shear layer and film cooling jet apart from excitation of periodic passing wake are studied using large eddy simulation (LES). An aerofoil of constant thickness with rounded leading edge induced flow separation, while film cooling jets were injected normal to the crossflow a short distance downstream of the blend point. Wake data extracted from precursor LES of flow past a cylinder are used to replicate a moving bar that generates wakes in front of a cascade (in this case, an infinite row of the model aerofoils). This setup is a simplified representation of rotor-stator interaction in a film cooled gas turbine. The results of numerical simulation are presented to elucidate the formation, convection and breakdown of flow structures associated with the highly anisotropic flow involved in film cooling perturbed by convective wakes. The various vortical structures namely, horseshoe vortex, roller vortex, upright wake vortex, counter rotating vortex pair (CRVP), and downward spiral separation node (DSSN) vortex associated with film cooling are resolved. The effects of wake on the evolution of these structures are then discussed.

scholarly journals Numerical modelling of microburst with Large-Eddy Simulation

2010 ◽  
Vol 10 (10) ◽  
pp. 24345-24370
Author(s):  
V. Anabor ◽  
U. Rizza ◽  
G. A. Degrazia ◽  
E. de Lima Nascimento
Keyword(s):  
Large Eddy Simulation ◽  
Time Scale ◽  
Doppler Radar ◽  
Leading Edge ◽  
Ring Vortex ◽  
Short Time Scale ◽  
Eddy Simulation ◽  
Cloud Models ◽  
Large Eddy ◽  
The Impact

Abstract. An isolated and stationary microburst is simulated using a 3-D time-dependent, high resolution Large-Eddy Simulation (LES) model. The microburst downdraft is initiated by specifying a simplified cooling source at the top of the domain near 2 km. The modelled time scale for this damaging wind (30 m/s) is of order of few min with a spatial scale enclosing a region with 500 m radius around the impact point. These features are comparable with results obtained from full-cloud models. The simulated flow shows the principal features observed by Doppler radar and others observational full-scale downburst events. In particular are observed the expansion of the primary and secondary cores, the presence of the ring vortex at the leading edge of the cool outflow, and finally an accelerating outburst of surface winds. This result evidences the capability of LES to reproduce complexes phenomena like a Microburst and indicates the potential of LES for utilization in atmospheric phenomena situated below the storm scale and above the microscale, which generally involves high velocities in a short time scale.

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