Drag reduction using Aerospike
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This document discusses the aerodynamic drag reduction in missiles through the use of aero spikes, which replace strong bow shocks with weaker shocks, creating recirculation flow to reduce drag and heating. A CFD analysis was conducted to study these effects at supersonic speeds, showing significant reductions in drag with the implementation of aero spikes. Results indicated that drag can be reduced by up to 50%, highlighting the advantages of various aerospike configurations.
Drag reduction using Aerospike
- 2. PRESENTATION OUTLINE AIM INTRODUCTION LITERATURE SURVEY CFD ANALYSIS OF AEROSPIKE RESULTS CONCLUSIONS www.mechieprojects.com
- 3. AIM The main aim of this very brief study is to understand the phenomena of aerodynamic drag reduction in aerospace vehicles (missiles) using fixed body aero spikes. CFD study has been carried out using Fluent to study the flow phenomena ahead of a missile nose-cone for supersonic flow(M=6 & 0.75). Aero spike are protrusions ahead of a missile nose-cone which replaces the strong bow shock with a system of weaker shocks along with creating a zone of recirculation flow ahead of the fore body thus reducing both drag and aerodynamic heating. www.mechieprojects.com
- 4. BALLISTIC MISSILE TRAJECTORY LOSSES: 1.GRAVITATIONAL PULL – nothing can be done 2.AERODYNAMIC DRAG – can be minimized
- 5. DRAG TYPES CAUSES SKIN FRICTION DRAG VISCOSITY OF AIR PERSSURE DRAG and WAVE DRAG SHAPE OF FOREBODY BASE DRAG EXHAUST AND WAKE Minuteman Main contributors to drag in missile: Topol-M Trident www.mechieprojects.com
- 6. NEED FOR THE USE OF BLUNT NOSE IN SUPERSONIC MISSILES Considering only aerodynamics, sharp and pointed nose are most beneficial in supersonic flight. But the available space in a cone or a wedge shaped nose is limited. Therefore it is not practicable for the integration of avionic or a seeker. The functionality of the device for seeking a target might be increased which is often of advantage in particular for highly agile flying objects. www.mechieprojects.com
- 7. METHOD TO REDUCE WAVE DRAG Aero-spike Air-spike Flame spike Pulse jet Laser beam Microwaves Chromium coating Cavitations www.mechieprojects.com
- 8. AEROSPIKE A well known concept of reducing the wave drag while keeping a blunt nose in supersonic flight is the aero spike concept The thin antenna-like structure mounted on the nose cone is the aero- spike. Slight variations of the initial design include cones, spheres or disks that are additionally mounted on the tip of the rod. www.mechieprojects.com
- 10. HOW AEROSPIKE REDUCES DRAG? A detached bow shock stands out in front of the aerospike and remains away from the dome. As the flow behind the bow shock expands around the aerospike, a weak compression is formed at its base. The wake flow caused by the aero spike and the nearly stagnant flow near the dome creates the conically-shaped recirculation region. Recirculating region is separated from the inviscid flow within the bow shock by a flow separation shock. Within the recirculating region the pressure and temperature is reduced. Drag reduction of 50% is achieved.
- 11. Meshing in Gambit 2-D Analysis Mapped Structured Mesh The zone specified are Pressure far-field Wall Pressure outlet Axis www.mechieprojects.com
- 12. Problem definition in FLUENT Define the problem as, Solver -Pressure based Formulation -Implicit Space -2D Time -Steady Viscous -Two-equation SST-k-omega model Enable the Energy equation The fluid type used is Air defined as ideal gas Operating pressure= 0 Pa
- 13. Inputs to Pressure Far-Field Zone The reference values are taken from internal database based on average trajectory profile for long range aerospace vehicles. The input values are Static Gauge Pressure – 11111 Pa Mach no-0.75M Temperature - 216 k The fluid is air. The motion type is stationary. Wall boundary condition – no slip condition. www.mechieprojects.com
- 14. EFFECT OF AEROSPIKE for M=6.0 Hemisphere Aerospike l/d=0.5 Aerospike l/d=1.0
- 15. Actual Mach No. contour at M=6 www.mechieprojects.com
- 18. Velocity (Mach No. )Contours M=0.75
- 19. Results & Conclusion The coefficient of drag has been found for each case. From the results, it is proved that the use of aerospike reduces the drag significantly. The increase in length to diameter ratio the drag reduces Configuration Total Force (Pressure+ Viscous) Hemisphere 1295.8 N Aerospike (l/d=1) 1230.7 N Aerospike (l/d=1.5) 1206.4 N Configuration Total Force (Pressure+ Viscous) Cd Blunt Body 10192 N 0.84 Hemisphere 3526 N 0.32 Aerospike (l/d=1) 3109 N 0.2796 M=6 M=0.75 www.mechieprojects.com
- 20. Reason for Reduction in drag and Temperature Flow recirculation occurs which reduces the pressure and temperature along the length of the spike and the nosecone. In addition to the aerodynamic drag reduction, heat transfer was also reduced as the length of the spike increases. Spike lengths larger than some critical length were not effective due to the detachment of the shock structure from the point of the spike and its reformation as a strong normal shock just upstream of the body.
- 21. References 1. MEHTA, R.C. Numerical heat transfer study over spiked-blunt body at Mach 6.80, AIAA paper 2000-0344, January 2000. 2. BODONOFF, S.N. and VAS, I.E. Preliminary investigations of spiked bodies at hypersonic speeds, J Aerospace Sciences, 1959, 26, (2), pp 3. CRAWFORD D.H. Investigation of the flow over a spiked-nose hemisphere 65-74. 4. FUJITA, M. and KUBOTA, H. Numerical simulation of flow field over a spiked-nose, Computational Fluid Dynamics J, 1992, 1, (2), pp 187195. 5. GUENTHER, R.A. and REDING, J.P. Fluctuating pressure environment of a drag reduction spike, J Spacecraft and Rockets, 1977, 44, (12), pp 705-710. cylinder at a Mach number of 6.8, NASA TN D-118, December Fluid Mechanics, 1960, 8, (4), pp 584-592. 6. HUTT, G.R. and HOWE, A.J. Forward facing spike effects on bodies of different cross section in supersonic flow, Aeronaut J, 1989, 93, (6), pp 229-234. 7. KALIMUTHU, R., MEHTA, R.C. and RATHAKRISHANN, E. Blunt body drag reduction using aerospike and aerodisk at Mach 6, in the proceedings of International Conference on High Speed Trans-atmospheric Air & Space Transportation, Hyderabad, India, June 2007.