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 Aerodynamic Forces on a Bridge Pylon

2011 ◽  
Vol 243-249 ◽  
pp. 1578-1582
Author(s):  
Xu Yong Ying ◽  
Fu You Xu ◽  
Zhe Zhang ◽  
Yong Gang Tan
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Navier Stokes ◽  
Aerodynamic Forces ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Les Model

In this study, aerodynamic forces on a bridge pylon are investigated by three-dimensional computational fluid dynamics using Large eddy simulation (LES) technology. The main objective is to identify the wind load parameters of the pylon and examine the accuracy of LES model applied to the bluff-body flows. The numerical results were compared with the available wind tunnel test results. Also, a comparison between using LES and Reynolds averaged Navier-Stokes equations with the RNG model have been made. It is found that the LES model competes the RNG model in accuracy for predictions of aerodynamic forces on the pylon.

Self-Adaptive Upwinding for Large Eddy Simulation of Cross-Flow Jets

2010 ◽  
Author(s):  
Vimal Kumar ◽  
Marius Paraschivoiu
Keyword(s):  
Large Eddy Simulation ◽  
Velocity Ratio ◽  
Vortex Formation ◽  
Cross Flow ◽  
Navier Stokes ◽  
Convective Flux ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cross Flow Velocity ◽  
Self Adaptive

A self-adaptive upwinding method for large eddy simulation (LES) has been describe in cross-flow in jets. The method is an extension of an existing Reynolds-averaged Navier–Stokes (RANS) code to an LES code by adjusting the contribution of the upwinding term to the convective flux. This adjustment is essentially controlled by reducing the upwind contribution in Roe MUSCL scheme. For the comparison of flow profiles obtained from the self-adaptive upwind LES code the experimental measurements of Andreopoulos and Rodi [1] are considered. The jet-to-cross-flow velocity ratio considered is 0.5 at a Reynolds number of 20,500 based on the jet bulk velocity and the jet diameter. In general, a reasonable agreement with the measurements is obtained. However, an intense backflow near the flat wall is observed. Further a vortex formation is observed behind at a distance of 0.6D from the jet axis.

scholarly journals Large Eddy Simulation of a complete Harrier aircraft in ground effect

2009 ◽  
Vol 113 (1140) ◽  
pp. 99-106 ◽  
Author(s):  
G. J. Page ◽  
J. J. McGuirk
Keyword(s):  
Large Eddy Simulation ◽  
Ground Effect ◽  
Mean Flow ◽  
Fighter Aircraft ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features ◽  
Practical Tool ◽  
Vertical Landing ◽  
Development And Validation

Abstract This paper aims to demonstrate the viability of using the large eddy simulation (LES) CFD methodology to model a representative, complete STOVL aircraft geometry at touch down. The flowfield beneath such a jet-borne vertical landing aircraft is inherently unsteady. Hence, it is argued in the present work that the LES technique is the most suitable tool to predict both the mean flow and unsteady fluctuations, and, with further development and validation testing, this approach could be a replacement, and certainly a complementary aid, to expensive rig programmes. The numerical method uses a compressible solver on a mixed element unstructured mesh. Examination of instantaneous flowfield predictions from these LES calculations indicate close similarity with many flow features identified from ground effect flow visualisations, which are well known to be difficult to model using RANS-based CFD. Whilst significant further work needs to be carried out, these calculations show that LES could be a practical tool to model, for example, Hot Gas Ingestion for the Joint Strike Fighter aircraft.

scholarly journals Large Eddy Simulation of Microvortex Generators in a Turbulent Boundary Layer

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Andrew P. Heffron ◽  
John J. Williams ◽  
Eldad J. Avital
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Separation Bubble ◽  
Vortex Formation ◽  
Leading Edge ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features ◽  
Challenging Environment

Abstract This study investigates the flow physics on microvortex generators (MVGs) in order to improve their performance in turbulent boundary layers (TBLs). TBLs can be a challenging environment for MVGs because of the streamwise length of the generated vortex and the increased parasitic drag of the MVGs. Large eddy simulation (LES) is used to properly resolve the turbulent boundary layer of a flat-plate with a zero-pressure gradient and MVG vane. Three different vane-types are investigated (e423-Mod, triangular, and rectangular vanes) and are studied in a single vane configuration. Important flow features such as a separation bubble on the leading edge of the rectangular vanes which introduced unsteadiness into the vortex formation and degraded the MVG's efficiency was observed. The e423-Mod and triangular vanes were observed to be more aerodynamically efficient. The triangular vane was found to be the most efficient when evaluated immediately downstream of the vane. However, the vortex from the triangular vane decayed very rapidly due to it being formed very close to the wall which degraded its efficiency further downstream. The e423-Mod vane avoided this problem but its drag was very high relative to the strength of the generated vortex and its vortex experienced a brief period of rapid decay immediately downstream decreasing its efficiency. Further downstream, the vortex of the rectangular vane at 16 deg became the most efficient through a combination of low vane drag and low vortex decay in the TBL, demonstrating the need to consider a range of issues when designing an MVG.

Technical Brief: Predictions of Flow Field for Circular-Disk Bluff-Body Stabilized Flame Investigated by Large Eddy Simulation and Experiments

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Peiqing Guo ◽  
Shusheng Zang ◽  
Bing Ge
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Turbulent Flame ◽  
Circular Disk ◽  
Eddy Simulation ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Flow Features ◽  
Chemical Equilibrium Model ◽  
Shed Light

The objective of the current work is to shed light on simulating the flow features of nonpremixed flame stabilized by a circular-disk bluff-body with large eddy simulation technique. Two subgrid scale (SGS) models (Smagorinsky and Germano), combined with a constrained chemical equilibrium model, are applied to simulate this turbulent flame. Validation is made through the particle image velocimetry measurements. The comparison between the numerical simulation and experimental data shows that both models perform well and reproduce most of the significant features of the bluff-body flame, while the Germano SGS model performs better in prediction of turbulent fluctuations. These investigations show that it is possible to describe such flows with relatively simple turbulence and combustion models with moderate grids.

scholarly journals Large eddy simulation of flow around semi-conical piers vertically mounted on the bed

2021 ◽  
Author(s):  
Yasin Aghaee-Shalmani ◽  
Habib Hakimzadeh
Keyword(s):  
Large Eddy Simulation ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Flow Structures ◽  
Shear Stresses ◽  
Eddy Simulation ◽  
Large Eddy

Abstract In this paper, details, and results of three-dimensional numerical modeling of flow around the semi-conical piers vertically mounted on the bed in a channel, are presented. For flow simulation, 3-D Navier-Stokes equations are solved numerically using the finite volume method and large eddy simulation (LES). In this study, the semi-conical piers with different side slope angles are tested, and the flow around them is compared with the cylindrical reference pier. Flow structures, vortex shedding behind piers, horseshoe vortices, instantaneous and time-averaged flow structures are presented and discussed. Numerical model results show that the semi-conical piers are eventuated remarkable reduction (up to 25%) in downward flow velocity in the upstream side of the piers, and much more reduction (up to 46%) in bed shear stresses in comparison with the cylindrical pier. Moreover, the model results showed some decrease in vortex shedding frequency for the semiconical piers compared to the cylindrical pier.

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