scholarly journals Vortex dynamics and scalar transport in the wake of a bluff body driven through a steady recirculating flow

2012 ◽  
Vol 53 (3) ◽  
pp. 747-763 ◽  
Author(s):  
Stephane B. Poussou ◽  
Michael W. Plesniak
Keyword(s):  
Vortex Dynamics ◽  
Bluff Body ◽  
Scalar Transport ◽  
Recirculating Flow

Simulation of Two-Dimensional Turbulent Recirculating Flow Field Behind a V-Shaped Bluff Body

1994 ◽  
Author(s):  
Z. Gu ◽  
M. A. R. Sharif
Keyword(s):  
Flow Field ◽  
Bluff Body ◽  
Flame Stabilization ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Combustion Chambers ◽  
Recirculating Flow ◽  
Conservative Form ◽  
Curvilinear Grid ◽  
Predictor Corrector

Abstract The two-dimensional turbulent recirculating flow fields behind a V-shaped bluff body have been investigated numerically. Similar bluff bodies are used in combustion chambers for flame stabilization. The governing transport equations in conservative form are solved by a pressure based predictor-corrector method. The standard k-ϵ turbulence closure model and a boundary fitted multi-block curvilinear grid system are used in the computation. The code is validated against turbulent flow over a backward facing step problem. The predicted flow field behind the bluff body is also compared with experiment. It is found that while the qualitative features of the flow are well predicted, there is quantitative disagreement between the measurement and prediction. This disagreement can be partially attributed to the k-ϵ turbulence model which is known to be inadequate for recirculating flows. Parametric investigation of the flow field by varying the shape and size of the bluff body is also performed and the results are reported.

scholarly journals Turbulent flame-vortex dynamics of bluff-body premixed flames

2021 ◽  
Vol 223 ◽  
pp. 28-41
Author(s):  
Marissa K. Geikie ◽  
Cal J. Rising ◽  
Anthony J. Morales ◽  
Kareem A. Ahmed
Keyword(s):  
Vortex Dynamics ◽  
Bluff Body ◽  
Turbulent Flame ◽  
Premixed Flames

scholarly journals Bluff body drag manipulation using pulsed jets and Coanda effect

2016 ◽  
Vol 805 ◽  
pp. 422-459 ◽  
Author(s):  
Diogo Barros ◽  
Jacques Borée ◽  
Bernd R. Noack ◽  
Andreas Spohn ◽  
Tony Ruiz
Keyword(s):  
Bluff Body ◽  
Three Dimensional ◽  
Base Pressure ◽  
Coanda Effect ◽  
Wake Time ◽  
Recirculating Flow ◽  
Flow Deviation ◽  
Coandǎ Effect ◽  
And Control ◽  
The Impact

The impact of fluidic actuation on the wake and drag of a three-dimensional blunt body is investigated experimentally. Jets blowing tangentially to the main flow force the wake with variable frequency and amplitude. Depending on the forcing conditions, two flow regimes can be distinguished. First, in the case of broadband actuation with frequencies comprising the natural wake time scale, the convection of the jet structures enhances wake entrainment, shortens the length of the recirculating flow and increases drag. Secondly, at higher actuation frequencies, shear-layer deviation leads to fluidic boat tailing of the wake. It additionally lowers its turbulent kinetic energy thus reducing the entrainment of momentum towards the recirculating flow. The combination of both mechanisms produces a rise in the base pressure and reduces the drag of the model. Both actuation regimes are characterized by complementary velocity, pressure and drag measurements at several upstream conditions and control parameters. By adding curved surfaces to deviate the jets by the Coanda effect, periodic actuation is reinforced and drag reductions of approximately 20 % are achieved. The unsteady Coanda blowing not only intensifies the flow deviation and the base pressure recovery but also preserves the unsteady high-frequency forcing effect on the turbulent field. The present results encourage further development of fluidic control to improve the aerodynamics of road vehicles and provide a complementary insight into the relation between wake dynamics and drag.

Effect of nonharmonic forcing on bluff-body vortex dynamics

2009 ◽  
Vol 79 (4) ◽  
Author(s):  
E. Konstantinidis ◽  
D. Bouris
Keyword(s):  
Vortex Dynamics ◽  
Bluff Body

Some features of steady separated flow from low speed to hypersonic

2008 ◽  
Vol 112 (1128) ◽  
pp. 109-113
Author(s):  
S. L. Gai
Keyword(s):  
Shear Layer ◽  
Bluff Body ◽  
Separated Flow ◽  
Base Flow ◽  
The Body ◽  
Wake Flow ◽  
Recirculating Flow ◽  
Flow Features ◽  
Hypersonic Speeds ◽  
Low Speeds

Steady non-vortex shedding base flow behind a bluff body is considered. Such a flow is characterised by the flow separation at the trailing edge of the body with an emerging shear layer which reattaches on the axis with strong recompression and recirculating flow bounded by the base, the shear layer, and the axis. Steady wake flows behind a bluff body at low speeds have been studied for more than a century (for example, Kirchhoff; Riabouchinsky). Recently, research on steady bluff body wake flow at low speeds has been reviewed and reinterpreted by Roshko. Roshko has also commented on some basic aspects of steady supersonic base flow following on from Chapman and Korst analyses. In the present paper, we examine the steady base flow features both at low speeds and supersonic speeds in the light of Roshko’s model and expand on some further aspects of base flows at supersonic and hypersonic speeds, not covered by Roshko.

IMPLEMENTATION OF THE CONDITIONAL MOMENT CLOSURE MODEL TO A TURBULENT NONPREMIXED H2/CO-AIR FLAME STABILIZED ON A BLUFF BODY

1999 ◽  
Vol 23 (3-4) ◽  
pp. 425-433 ◽  
Author(s):  
S.- H. Kim ◽  
T. Liu ◽  
K.Y. Huh
Keyword(s):  
Bluff Body ◽  
Reaction Rates ◽  
Moment Closure ◽  
Scalar Dissipation ◽  
Conditional Moment ◽  
Turbulent Diffusion Flame ◽  
Recirculating Flow ◽  
Conditional Moment Closure ◽  
Mass Fractions ◽  
Turbulent Nonpremixed

A turbulent nonpremixed flame of H2/CO-air stabilized on a bluff-body is simulated by the conditional moment closure (CMC) model. Full spatial variation of the conditional quantities is taken into account for an elliptic recirculating flow field. Comparison has shown reasonable agreement for the conditional and Favre mean temperature and mass fractions of CO and H20 between calculation and experiment. Overprediction of the peak OH mass fraction is attributed to inaccurate modelling of the conditional scalar dissipation rate. The CMC model is capable of predicting major features of a turbulent diffusion flame characterized by finite chemical reaction rates.

scholarly journals On the recirculating flow of three-dimensional asymmetric bluff bodies

2020 ◽  
Vol 61 (12) ◽  
Author(s):  
Antoine Legeai ◽  
Olivier Cadot
Keyword(s):  
Bluff Body ◽  
Reference Model ◽  
Three Dimensional ◽  
Bluff Bodies ◽  
Recirculating Flow ◽  
Bistable Dynamics ◽  
Geometrical Variation ◽  
Static Instability ◽  
State Selection

Abstract The paper investigates the role of geometrical asymmetric modifications of a rectangular flat-backed body on the properties of the recirculating flow at a Reynolds number $$Re=1.8\times 10^5$$ R e = 1.8 × 10 5 . The reference model has two reflectional symmetries denoted $$s_y$$ s y and $$s_z$$ s z in both spanwise directions. The flow is subjected to the static instability that leads to two mirrored wake states breaking the symmetry $$s_y$$ s y . Two families of geometrical variation of the fore-body and after-body are studied, each breaking one of the reflectional symmetries of the reference model. Geometrical modifications that preserve $$s_y$$ s y evidence possibilities of bistable dynamics suppression although the static instability persists. Geometrical modifications that do not preserve $$s_y$$ s y produces a large unbalance of both wake states in accordance to recent observations on real cars (Bonnavion et al. in J Wind Eng Ind Aerodyn 184:77–89, 2019). Results offer perspectives for potential drag reduction induced by appropriate coupling of bluff body geometry and wake state selection. Graphic abstract

Flow field in the wake of a bluff body driven through a steady recirculating flow

2015 ◽  
Vol 56 (2) ◽  
Author(s):  
Stephane B. Poussou ◽  
Michael W. Plesniak
Keyword(s):  
Flow Field ◽  
Bluff Body ◽  
Recirculating Flow
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