Numerical Investigation of Strakes and Strakelets on a Missile at High Angles of Attack

• Main Author: Kistan, Prevani
• Format: Others
• Language: en
• Published: 2007
• Subjects: Missle; Steady Asymmetric Vortices; Side Force; Steady Symmetric Flowfield
• Online Access: http://hdl.handle.net/10539/2152

Student Number : 9803192Y - MSc(Eng) Dissertation - School of Mechanical, Industrial and Aeronautical Engineering - Faculty of Engineering and the Built Environment === A computational °uid dynamics (CFD) study was carried out to improve the aero- dynamic performance of an agile high angle of attack missile. The normal force generated by the missile strakes had to be increased at the low angles of attack and the large side forces, experienced at high angles of attack due to the formation of steady asymmetric vortices had to be eliminated using strakelets on the missile nose. The ¯rst objective was achieved by increasing the missile strake span from 0:06D to 0:13D. The larger strake span increased the e®ective diameter of the missile body and prevented °ow reattachment to the body, a problem that was experienced when the strake span was 0:06D. Due to °ow separating further away from the body, strong vortices formed on the missile strakes, resulting in an increase in the normal force generated by the missile strakes at low angles of attack. The second objective was two-fold. Prior to analysing the e®ect of the strakelets on a steady asymmetric °ow¯eld, the steady asymmetric °ow¯eld had to ¯rst be created. This was achieved by placing a permanent, geometric perturbation on the missile nose. The size of the perturbation used in the study, which was determined by an iterative process, did not force °ow separation at low angles of attack and resulted in a steady asym- metric °ow¯eld that was representative of that on a blunt-ogive body. The e®ect of changing the span of the strakelets and the axial position of the strakelets were then investigated. It was found that the strakelets with a span of 0:09D, placed 1D from the nose tip eliminated the side forces by forcing vortex symmetry. Increasing or decreasing the span of the strakelet, positioned 1D from the nose tip or placing the strakelets with a span of 0:09D closer or further away from the nose tip did not eliminate the steady vortex asymmetry.