טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAdar Motti
SubjectNumerical Study of Flare Separation
DepartmentDepartment of Aerospace Engineering
Supervisors Dr. Yuval Levy
Professor Emeritus Alon Gany


Abstract

Protecting aircraft from IR seeking AA missiles involves dispersing flares which are actually rods that are made of a certain pyrotechnic material that burn in the air. An essential part of the process of certifying a flare to be carried on and released from an aircraft involves assuring its safe separation from the parent aircraft. The purpose of the current work is to numerically study the influence of the combustion process on the flare’s motion in the vicinity of an aircraft. The effects of heat and mass addition to the flow, and shrinkage of the flare have been investigated using CFD tools. An Euler/Navier-stokes flow solver has been modified to include physical models of mass and heat addition. Shrinkage of the flare was introduced through a shrinkage model of the flare’s grid. Six degrees of freedom motion calculation of the flare movement has also been introduced into the code. A large number of runs was conducted starting from two starting conditions where each run was conducted in order to investigate the effect of a certain physical model. The results show that there is a negligible effect of the shrinkage and mass addition on the flare motion. However, heat addition has a sizeable effect on the flare motion. The effect of the heat transfer mainly reduces the angular motion of the flare. The cause for the reduced angular motion when heat addition is present is the increase of the flow velocity about the flare, leading to a larger and more uniform separation of the flow, which results in a uniform pressure distribution on the aft part of the flare, leading to reduced aerodynamic moments.