Numerical investigations on effects of bluff body in flat plate micro thermo photovoltaic combustor with sudden expansion

2016 ◽  
Vol 23 (4) ◽  
pp. 975-982 ◽  
Author(s):  
Jia-qiang E ◽  
Hai-jiao Huang ◽  
Xiao-huan Zhao
Keyword(s):  
Flat Plate ◽  
Bluff Body ◽  
Sudden Expansion ◽  
Numerical Investigations

Influence of a plasma actuator on aerodynamic forces over a flat plate interacting with a rarefied Mach 2 flow

2016 ◽  
Vol 26 (7) ◽  
pp. 2081-2100 ◽  
Author(s):  
Sandra Coumar ◽  
Romain Joussot ◽  
Jean Denis Parisse ◽  
Viviana Lago
Keyword(s):  
Shock Wave ◽  
Flat Plate ◽  
Stokes Equations ◽  
Plasma Actuator ◽  
Heating Element ◽  
Aerodynamic Forces ◽  
Heat Management ◽  
Content Type ◽  
Numerical Investigations ◽  
Wave Angle

Purpose The purpose of this paper is to describe experimental and numerical investigations focussed on the shock wave modification induced by a dc glow discharge. The model is a flat plate in a rarefied Mach 2 air flow, equipped with a plasma actuator composed of two electrodes. The natural flow without actuation exhibits a shock wave with a hyperbolic shape. When the discharge is on, the shock wave shape remains hyperbolic but the shock wave is pushed forward, leading to an increase in the shock wave angle. In order to discriminate thermal effects from purely plasma ones, the plasma actuator is then replaced by an heating element. Design/methodology/approach The experimental study is carried out with the super/hypersonic wind tunnel MARHy located at the ICARE Laboratory in Orléans. The experimental configuration with the heating element is simulated with a code using the 2D full compressible Navier-Stokes equations adapted for the rarefied conditions. Findings For heating element temperatures equal to the flat plate wall surface ones with the discharge on, experimental and numerical investigations showed that the shock wave angle was lower with the heating element, only 50 percent of the values got with the plasma actuator, meaning that purely plasma effects must also be considered to fully explain the flow modifications observed. The results obtained with the numerical simulations are then used to calculate the aerodynamic forces, i.e. the drag and the lift. These numerical results are then extrapolated to the plasma actuator case and it was found that the drag coefficient rises up to 13 percent when the plasma actuator is used, compared to only 5 percent with the heating element. Originality/value This paper matters in the topic of atmospheric entries where flow control, heat management and aerodynamic forces are of huge importance.

Efficient Airload Determination for Bluff Body Aeromechanics

2014 ◽  
Author(s):  
Sorin Pirau ◽  
Vrishank Raghav ◽  
Alex Forbes ◽  
Brandon Liberi ◽  
Narayanan Komerath
Keyword(s):  
Flat Plate ◽  
Bluff Body ◽  
Free Stream ◽  
Periodic Problem ◽  
Ensemble Averaging ◽  
Aerodynamic Loads ◽  
Load Variations ◽  
Continuous Rotation ◽  
Cylinder Model ◽  
Support Interference

A continuous-rotation testing technique is applied to capture the variation of aerodynamic loads with attitude on objects of arbitrary shape. The technique converts the problem of measuring static air loads at various attitudes into a periodic problem. Phase-resolved ensemble-averaging is used to capture load variations with arbitrarily fine azimuthal resolution. The airload variations are obtained in closed form as discrete Fourier series. Experiments on a cylinder model of equal length and diameter were used to study the ability to capture asymmetries, and resolve support interference issues. A closed cuboid is used to correlate with prior work. A flat plate with a central cylindrical load, and a porous box are also studied. Free-swing tests using rigid tethers fixed to a pitch-yaw-roll gimbal mount are used to derive dynamic behavior in a free stream. The cylinder results showed the ability to resolve the effect of minor geometric asymmetries on airloads. The flat plate at 10 degrees pitch shows strong differences in dynamics between cases with a rounded versus squared-off edge facing the freestream. The porous box shows the differences between cases with and without one side blocked.

On the steady separated flow around an inclined flat plate

1997 ◽  
Vol 333 ◽  
pp. 403-413 ◽  
Author(s):  
W. W. H. YEUNG ◽  
G. V. PARKINSON
Keyword(s):  
Flat Plate ◽  
Bluff Body ◽  
Separation Bubble ◽  
Separated Flow ◽  
Leading Edge ◽  
Source Model ◽  
Pressure Distributions ◽  
Wide Range ◽  
Trailing Edges ◽  
Edge Separation

An inviscid analytic model is proposed for the steady separated flow around an inclined flat plate. With the plate normal to the stream, the model reduces to the wake-source model of Parkinson & Jandali originally developed for flow external to a symmetrical two-dimensional bluff body and its wake. At any other inclination, the Kutta condition is satisfied at both leading and trailing edges of the plate, and, in the limit that the angle of attack approaches zero, classical airfoil theory is recovered. A boundary condition is formulated based on some experimental results of Abernathy, but no additional empirical information is required. The predicted pressure distributions on the wetted surface for a wide range of angle attack are found to be in good agreement with experimental data, especially at smaller angles of attack. An extension to include a leading-edge separation bubble is explored and results are satisfactory.

Experimental Analysis of V- to M-Shape Transition of Premixed CH4/H2/Air Swirling Flames

2013 ◽  
Author(s):  
T. F. Guiberti ◽  
L. Zimmer ◽  
D. Durox ◽  
T. Schuller
Keyword(s):  
Combustion Chamber ◽  
Bluff Body ◽  
Lewis Number ◽  
Critical Value ◽  
Operating Conditions ◽  
Chamber Wall ◽  
Sudden Expansion ◽  
Shape Transition ◽  
Flow Conditions ◽  
Swirling Flames

Lean premixed swirling flames stabilized at the sudden expansion of a combustion chamber generally take a V or a M shape, depending on the burner geometry and flow conditions. It is not rare to observe transitions between these shapes as operating conditions of the combustor are modified, but the governing mechanisms of these transitions are not well understood. An experimental study is conducted to analyze the transition from an initially V-shaped flame to a M-shaped flame for swirling flames fed by CH4/H2/air mixtures anchored on a central bluff body when flow conditions and geometrical elements of the combustor are modified. Two situations are identified depending whether strong flame wall interactions take place at the quartz tube confining the flame. When the V-flame front is impinging and quenched at the combustion chamber wall, the transition to a M-shape is triggered by a flashback mechanism along the wall followed by the propagation of the flame tip along the outer shear-layer of the swirling jet in the direction of the external rim of the burner. This mechanism is controlled by the mixture Lewis number, a Karlovitz number based on the velocity gradient at the combustor wall, the swirl imparted to the flow and the cross section area ratio between the injection unit and combustion chamber defining a confinement ratio. Experiments conducted at a given mixture Lewis number indicate that the onset of flashback is determined by decreasing the Karlovitz number under a critical value. It is shown that this critical value decreases when the Lewis number increases, but it also depends on the confinement ratio and swirl number. In the absence of direct interaction between the V-flame tip and the chamber wall, the situation differs and this flashback mechanism along the combustion chamber wall ceases. Attempts are made in this case to identify the governing parameters triggering the V- to M-shape transition for small confinement ratios.

Numerical investigations of the wake behind a confined flat plate

2022 ◽  
Vol 94 ◽  
pp. 108924
Author(s):  
D. Aljubaili ◽  
L. Chan ◽  
W. Lu ◽  
A. Ooi
Keyword(s):  
Flat Plate ◽  
Numerical Investigations
Sign in / Sign up

Export Citation Format

Share Document