Active Flow Control of the 3D Separation on a Ahmed Body Using Steady Microjet Arrays

2010 ◽  
Author(s):  
S. Aubrun ◽  
F. Alvi ◽  
A. Leroy ◽  
A. Kourta
Keyword(s):  
Flow Control ◽  
Aerodynamic Drag ◽  
Separation Bubble ◽  
Active Flow Control ◽  
Aerodynamic Load ◽  
Flow Topology ◽  
Rear Window ◽  
Slant Angle ◽  
Control Approach ◽  
Ahmed Body

A model of a generic vehicle shape, the Ahmed body with a slant angle of 25°, is equipped with an array of blowing steady microjets 6mm downstream of the separation line between the roof and the slanted rear window. The goal of the present study is to evaluate the effectiveness of this actuation method in reducing the aerodynamic drag, by reducing or suppressing the 3D closed separation bubble located on the slanted surface. The efficiency of this control approach is quantified with the help of aerodynamic load measurements. The changes in the flow field when control is applied are examined using PIV measurements and skin friction visualizations. By activating the steady microjet array, the drag coefficient was reduced by 9 to 11%, depending on the Reynolds number. The modification of the flow topology under progressive flow control is particularly studied.

Numerical Simulation of Unsteady Flow around Ahmed Body with Active Flow Control

2013 ◽  
Vol 275-277 ◽  
pp. 402-408
Author(s):  
Bing Xin Wang ◽  
Zhu Hui ◽  
Zhi Gang Yang
Keyword(s):  
Flow Control ◽  
Recirculation Zone ◽  
Active Flow Control ◽  
The Body ◽  
Slant Angle ◽  
Control Approach ◽  
Pressure Drag ◽  
Active Flow ◽  
Velocity Pressure ◽  
Ahmed Body

The numerical investigations presented in this paper deal with active flow control approach at the rear end of the Ahmed body model with the slant angle of 25°.Results of the velocity, pressure and vorticity field demonstrate the main reasons that cause the pressure drag. The influence of the spanwise and streamwise vortices rolling up from the slant and the edges on the recirculation zone behind the body is examined. A control slot is set on the separated line at the conjunction of the roof and the slant. Two different actuation concepts by blowing and suction steady jets through the slot lead to a drug increase of 5.61% and a drug reduction of 13.20% with the efficiency of 12.53% respectively.

Wake flow analysis and control on a 47° slant angle Ahmed body

2018 ◽  
Vol 28 (5) ◽  
pp. 1061-1079 ◽  
Author(s):  
Stephie Edwige ◽  
Yoann Eulalie ◽  
Philippe Gilotte ◽  
Iraj Mortazavi
Keyword(s):  
Flow Control ◽  
Control Strategies ◽  
Flow Analysis ◽  
Wake Flow ◽  
Mean Flow ◽  
Flow Topology ◽  
Modal Decomposition ◽  
Slant Angle ◽  
Content Type ◽  
Ahmed Body

Purpose The purpose of this paper is to present numerical investigations of the flow dynamic characteristics of a 47° Ahmed Body to identify wake flow control strategy leading to drag coefficient reduction, which could be tested later on sport utility vehicles. Design/methodology/approach This study begins with a mean flow topology description owing to dynamic and spectral analysis of the aerodynamic tensor. Then, the sparse promoting dynamic modal decomposition method is discussed and compared to other modal approaches. This method is then applied on the wall and wake pressure to determine frequencies of the highest energy pressure modes and their transfers to other frequency modes. This analysis is then used to design appropriated feedback flow control strategies. Findings This dynamic modal decomposition highlights a reduced number of modes at low frequency which drive the flow dynamics. The authors especially notice that the pressure mode at a Strouhal number of 0.22, based on the width between feet, induces aerodynamic losses close to the rear end. Strategy of the proposed control loop enables to dampen the energy of this mode, but it has been transferred to lower frequency mode outside of the selected region of interest. Originality/value This analysis and methodology of feedback control shows potential drag reduction with appropriated modal energy transfer management.

LES of Active Separation Control on Bluff Bodies by Steady Blowing

2010 ◽  
Author(s):  
Sa´ndor Eichinger ◽  
Frank Thiele ◽  
Erik Wassen
Keyword(s):  
Flow Control ◽  
Aerodynamic Drag ◽  
Active Flow Control ◽  
Rear Surface ◽  
Base Flow ◽  
Back Surface ◽  
Bluff Bodies ◽  
Control Approach ◽  
Vertical Extension ◽  
Active Flow

An active flow control approach was investigated in order to reduce the aerodynamic drag of a generic square-backed vehicle. The investigations were carried out at a Reynolds number of ReL = 500,000. Large Eddy Simulations were performed which are suitable for time dependent flows around vehicles with large coherent structures. After the base flow simulations active flow control was applied in order to achieve drag reduction using steady blowing through small slits near the edges of the rear surface. The blowing velocity was equal to the inflow velocity (vblow = U0), and the blowing angle was changed from θ = 0° to θ = 60°. It is shown that these control techniques can achieve a maximum drag decrease for the θ = 45° control version of around 12%. Additionally the effect of moving floor was studied and comparison was made for the baseline and for the 45° flow control variant. It was found that the stagnation point on the rear surface moves upwards, and the vertical extension of the wake section reduces, so the evolving pressure level on the back surface increases. Finally a study of the blowing velocity was performed, changing vblow = 0.25U0 until vblow = 2.25U0 at θ = 45° blowing angle. An efficiency optimum was found around vblow = 1.25U0.

Experimental Study of Flow Control Over a Standard Road Vehicle Using Plasma Actuator

2020 ◽  
Vol 22 (4) ◽  
pp. 1047-1060
Author(s):  
S. Shadmani ◽  
S. M. Mousavi Nainiyan ◽  
R. Ghasemiasl ◽  
M. Mirzaei ◽  
S. G. Pouryoussefi
Keyword(s):  
Flow Control ◽  
Pressure Distribution ◽  
Drag Force ◽  
Separated Flow ◽  
Plasma Actuator ◽  
Road Vehicle ◽  
Slant Angle ◽  
Total Drag ◽  
Slant Surface ◽  
Ahmed Body

AbstractAhmed Body is a standard and simplified shape of a road vehicle that's rear part has an important role in flow structure and it's drag force. In this paper flow control around the Ahmed body with the rear slant angle of 25° studied by using the plasma actuator system situated in middle of the rear slant surface. Experiments conducted in a wind tunnel in two free stream velocities of U = 10m/s and U = 20m/s using steady and unsteady excitations. Pressure distribution and total drag force were measured and smoke flow visualization carried out in this study. The results showed that at U = 10m/s using plasma actuator suppress the separated flow over the rear slant slightly and be effective on pressure distribution. Also, total drag force reduces in steady and unsteady excitations for 3.65% and 2.44%, respectively. At U = 20m/s, using plasma actuator had no serious effect on the pressure distribution and total drag force.

Effect of Rear Wing on Time-Averaged Ground Vehicle Wake With Variable Slant Angle

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Md. Shehab Uddin ◽  
Fazlur Rashid
Keyword(s):  
Separation Bubble ◽  
Flow Property ◽  
Navier Stokes ◽  
Ground Vehicles ◽  
Slant Angle ◽  
Ground Vehicle ◽  
Rear Wing ◽  
Horseshoe Vortices ◽  
And Control ◽  
Ahmed Body

Abstract The slant angle plays a crucial role in the flow property of hatchback ground vehicles. An optimum slant angle is obligatory for better handling the ground vehicles when fitted with a rear wing. In this regard, the variation of time-averaged flow properties around a wing-attached hatchback ground vehicle (Ahmed body) due to a variable slant angle is accessed by this paper. The design includes a scaled Ahmed body as a reference ground vehicle and a rear wing with NACA 0018 profile. The computational studies are executed with Reynolds-averaged Navier–Stokes based k-epsilon turbulence model with nonequilibrium wall function. The vehicle's model is scaled to 75% of the actual model, and analyses are conducted with Reynolds number 2.7 × 106. After the study, it is observed that a 15 deg slant angle is the critical angle for the wing attached state in which the drag coefficient is maximum. After this angle, a sudden reduction of coefficients is observed, where 25 deg is critical for without wing condition. Besides this, the two counter-rotating horseshoe vortices in the separation bubble and side edge c-pillar vortices also behave differently due to the wing's presence. The turbulent kinetic energy variation and the variation in coefficients of surface pressure are also affected by the rear wing attachment. This paper will assist in finding the optimum slant angle for hatchback ground vehicles in the presence of a rear wing. Thus the study will help in increasing stability and control for hatchback ground vehicles.

scholarly journals Experimental Study of Flow Control Over an Ahmed Body Using Plasma Actuator

2020 ◽  
Vol 22 (1) ◽  
pp. 239-252
Author(s):  
S. Shadmani ◽  
S. M. Mousavi Nainiyan ◽  
R. Ghasemiasl ◽  
M. Mirzaei ◽  
S. G. Pouryoussefi
Keyword(s):  
Flow Control ◽  
Pressure Distribution ◽  
Drag Force ◽  
Separated Flow ◽  
Plasma Actuator ◽  
Slant Angle ◽  
Total Drag ◽  
Slant Surface ◽  
Actuator System ◽  
Ahmed Body

AbstractAhmed Body is a standard and simplified shape of a road vehicle that's rear part has an important role in flow structure and it's drag force. In this paper flow control around the Ahmed body with the rear slant angle of 25° studied by using the plasma actuator system situated in middle of the rear slant surface. Experiments conducted in a wind tunnel in two free stream velocities of U = 10 m/s and U = 20 m/s using steady and unsteady excitations. Pressure distribution and total drag force was measured and smoke flow visualization carried out in this study. The results showed that at U = 10 m/s using plasma actuator suppress the separated flow over the rear slant slightly and be effective on pressure distribution. Also total drag force reduces in steady and unsteady excitations for 3.65% and 2.44%, respectively. At U = 20 m/s, using plasma actuator had no serious effect on the pressure distribution and total drag force.

Evaporator Superheat Regulation via Emulation of Semi-Active Flow Control

2009 ◽  
Author(s):  
Matthew Elliott ◽  
Bryan P. Rasmussen
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Control Device ◽  
Operating Conditions ◽  
Limiting Factor ◽  
Efficient Operation ◽  
Control Approach ◽  
Active Feedback ◽  
Vapor Compression Cooling ◽  
Active Flow

Proper regulation of evaporator superheat is essential to ensuring safe and efficient operation of vapor compression cooling systems. Typical mechanical control devices may behave poorly under transient disturbances or as operating conditions vary, degrading system performance. Electronic expansion valves partially alleviate these problems by allowing more sophisticated control approaches, but frequent valve adjustments raise concerns about device longevity. A cascaded control approach to superheat regulation has been shown to provide significant improvements in superheat control, utilizing a hybrid of mechanical (passive) and electronic (active) feedback devices. This paper examines the emulation of a semi-active flow control device using a MEMs based actuator with high bandwidth, few moving parts, and no risk of fatigue failure. Experimental evaluation reveals this to be a comparable approach to the hybrid valve design. Moreover, further examination reveals that actuator characteristics are the limiting factor in achieving similar levels of performance using standard electronic valves.

scholarly journals Investigation of wheelhouse shapes on the aerodynamic characteristics of a generic car model

2021 ◽  
Vol 13 (12) ◽  
pp. 168781402110668
Author(s):  
Haichao Zhou ◽  
Qingyun Chen ◽  
Runzhi Qin ◽  
Lingxin Zhang ◽  
Huiyun Li
Keyword(s):  
Aerodynamic Drag ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Vehicle Speed ◽  
Cavity Volume ◽  
Detached Eddy Simulation ◽  
Slant Angle ◽  
Drag Coefficients ◽  
Ahmed Body

As vehicle speed increases, the aerodynamic drag reduction becomes increasingly significant. The aim of this paper is to find out the effects of the wheelhouse shapes on the aerodynamics of an Ahmed body with a 35 slant angle. In this paper, based on the detached-eddy simulation method, the effects of the three classic different wheelhouse on the aerodynamic performance and near wake of the Ahmed body are presented. The mesh resolution and methodology are validated against the published test results. The results show that the front wheelhouse has a significant impact on the aerodynamic performance of the Ahmed body, leading to different aerodynamic drag forces and flow fields. Enlarging the wheelhouse cavity volume could result in a gradual increase in aerodynamic drag coefficients, the ratio of the wheelhouse cavity volume increased by 2.9% and 9.8%, the drag coefficients increased by 2.5% and 4.5% respectively. The increase in aerodynamic drag was primarily caused by flow separation in the large cavity volume wheelhouse.

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