VISCOUS CFD ANALYSIS OF GENERIC MISSILE WITH GRID FINS By Swapnil. D VISCOUS CFD ANALYSIS OF GENERIC MISSILE WITH GRID FINS By Swapnil. D. Adhav. Prof: D. R. Kirk Department of Mechanical and Aerospace Engineering Florida Institute of Technology, Melbourne, FL 32901 © aerospaceweb.org

Outline Background Model Configuration Numerical Tests Results Comparison of Grid fin with Planar fin Conclusion

Background © aerospaceweb.org

Comparison With the Planar Fins

Objective Obtain Aerodynamic coefficients and Viscous Forces Establish a data for comparison with the DERA wind tunnel data and ARL studies for fluent work. © aerospaceweb.org

Model Configuration Total area of Air flow through the fin 98 mm² 19 Grid per cell Thickness of fin is 2mm

Numerical Modeling CFD Modeling a) 3D,Steay state. b) Implicit, c) coupled incompressible d) Unstructured Mesh grid e) Mach Number 0.3 Angle of Attack constant Boundary Conditions Outflow conditions at downstream, Velocity inlet in min z direction. Far field Boundary conditions for all surfaces. Re=1.2×10^6 (Turbulent Flow) Temperature=300k and Pressure=8325Pa,Pr=0.87

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Velocity contours at M=0.3

Results and Discussion Planar Fins Grid Fins C x C x viscous % Viscous DERA 0.021 0.004 20 0.072 0.011 15 ARL 0.029 0.009 0.087 0.019 21 DATA - 0.093 0.0215 22

A shock is formed in front of the grid fin A shock is formed in front of the grid fin. The simulation compares well to experiment Mach number 2.0 at Angle of attack=0˚

Mach Number 2.5

Conclusion The simulations were also successful in calculating the flow structure around the fin in the separated flow region. The Physical nature of this effect was illustrated by presenting contours of Velocity and pressure at Mach numbers 0.3. The viscous components of the axial force on the grid fin were about 2 times greater than that on the planer fins. Despite of some drawbacks, the improved maneuverability grid fins offer at high supersonic speeds and high angles of attack have resulted in several grid fin research efforts in recent years. More recent efforts have focused on using computational fluid dynamics (CFD) to better understand the characteristics of the flow passing through the fins in order to better optimize their performance.

References 1 .www.aerospaceweb.org “Computational Fluid Dynamics Analysis of Generic Missile with Grid fins by James Desprito, Harris L Edge, Paul Weinacht, Jabaraj Sahu and surya dinavahi ARL-TR-2318 September 2000. Army research Lab. “First Viscous CFD Analysis of Grid Fins gives better Prediction of Missile Trajectory” in Journal Articles by Fluent Software users. Cartesian Grid Simulations of a canard controlled Missile with Spinning tail by Scott .M. Murman Eloret and Michael J Aftosmis NASA Ames Research Center CA, AIAA-2003-3670. The research Analysis of aerodynamic numerical simulation of grid fins by WU pin, MA Yong-gang, CHEN chun Department of Computer science, china. WEBSITES 1 .www.aerospaceweb.org 2. http://www.ansys.com/industries/aerospace_isl.htm 3. http://www.aerospaceweb.org/question/weapons/q0261.shtml. 4. http://www.fluent.com/about/news/newsletters/00v9i1/a8.htm. 5. http://www.fluent.com/solutions/articles/ja136.pdf

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