A bio-inspired device for drag reduction on a three-dimensional model vehicle

In this paper, we introduce a bio-mimetic device for the reduction of the drag force on a three-dimensional model vehicle, the Ahmed body (Ahmed et al 1984 SAE Technical Paper 840300). The device, called automatic moving deflector (AMD), is designed inspired by the movement of secondary feathers on bird's wing suction surface: i.e., secondary feathers pop up when massive separation occurs on bird's wing suction surface at high angles of attack, which increases the lift force at landing. The AMD is applied to the rear slanted surface of the Ahmed body to control the flow separation there. The angle of the slanted surface considered is 25° at which the drag coefficient on the Ahmed body is highest. The wind tunnel experiment is conducted at Re H  = 1.0 × 10(5)-3.8 × 10(5), based on the height of the Ahmed body (H) and the free-stream velocity (U ∞). Several AMDs of different sizes and materials are tested by measuring the drag force on the Ahmed body, and showed drag reductions up to 19%. The velocity and surface-pressure measurements show that AMD starts to pop up when the pressure in the thin gap between the slanted surface and AMD is much larger than that on the upper surface of AMD. We also derive an empirical formula that predicts the critical free-stream velocity at which AMD starts to operate. Finally, it is shown that the drag reduction by AMD is mainly attributed to a pressure recovery on the slanted surface by delaying the flow separation and suppressing the strength of the longitudinal vortices emanating from the lateral edges of the slanted surface.

[1]  Azeddine Kourta,et al.  Drag reduction by flow separation control on a car after body , 2009 .

[2]  Haecheon Choi,et al.  Mechanism of drag reduction by dimples on a sphere , 2006 .

[3]  W. H. Hucho,et al.  The Wind Tunnel's Ground Plane Boundary Layer - Its Interference with the Flow Underneath Cars , 1975 .

[4]  Jean-François Beaudoin,et al.  Drag and lift reduction of a 3D bluff-body using active vortex generators , 2010 .

[5]  Jean-François Beaudoin,et al.  Drag reduction of a bluff body using adaptive control methods , 2006 .

[6]  Philippe Planquart,et al.  Experimental aerodynamic study of a car-type bluff body , 2011 .

[7]  W. Hage,et al.  Biological surfaces and their technological application - laboratory and flight experiments on drag reduction and separation control. Invited Lecture , 1997 .

[8]  C. H. John Wang,et al.  Stall control with feathers: Self-activated flaps on finite wings at low Reynolds numbers , 2012 .

[9]  Hyungmin Park,et al.  Aerodynamics of Heavy Vehicles , 2014 .

[10]  Frank Thiele,et al.  Separation Control by Self-Activated Movable Flaps , 2004 .

[11]  Rajat Mittal,et al.  Initial Characterization of Self-Activated Movable Flaps, "Pop-Up Feathers" , 2008 .

[12]  Haecheon Choi,et al.  CONTROL OF FLOW OVER A BLUFF BODY , 2008, Proceeding of Fifth International Symposium on Turbulence and Shear Flow Phenomena.

[13]  Jean-Luc Aider,et al.  Drag reduction on the 25° slant angle Ahmed reference body using pulsed jets , 2012 .

[14]  Frank Thiele,et al.  Separation Control by Self-Activated Movable Flaps , 2007 .

[15]  E. Serre,et al.  High-order large-eddy simulation of flow over the “Ahmed body” car model , 2008 .

[16]  Azeddine Kourta,et al.  Aerodynamic drag reduction by vertical splitter plates , 2010 .

[17]  Drew Landman,et al.  Experimental and Computational Investigation of Ahmed Body for Ground Vehicle Aerodynamics , 2001 .

[18]  Azeddine Kourta,et al.  Aerodynamic drag control by pulsed jets on simplified car geometry , 2013 .

[19]  Jorg Schluter,et al.  Lift Enhancement at Low Reynolds Numbers Using Self-Activated Movable Flaps , 2010 .

[20]  David M. Driver,et al.  Progress in Reducing Aerodynamic Drag for Higher Efficiency of Heavy Duty Trucks (Class 7-8) , 1999 .

[21]  Azeddine Kourta,et al.  Biomimetic bluff body drag reduction by self-adaptive porous flaps , 2011, 1107.4975.

[22]  Gunther Ramm,et al.  Some salient features of the time - averaged ground vehicle wake , 1984 .

[23]  Patrick Gilliéron,et al.  Bluff-body drag reduction using a deflector , 2011 .

[24]  W. Hucho,et al.  Aerodynamics of Road Vehicles , 1987 .

[25]  Haecheon Choi,et al.  Biomimetic flow control based on morphological features of living creaturesa) , 2012 .

[26]  Jean-François Beaudoin,et al.  Drag and lift reduction of a 3D bluff body using flaps , 2008 .

[27]  Sebastien Depardon,et al.  Drag reduction of a 3D bluff body using coherent streamwise streaks , 2010 .