Investigation of missiles with strake fins and reduction of aerodynamic cross coupling effects by optimization

Download
2015
Usta, Engin
Missiles with very low aspect ratio fins (also called strakes) are generally difficult to model by using engineering level aerodynamic methods and linear theories break due to complex nature of the flow adjacent to the mutual interference of the body and fin. Since fast prediction methods cannot accurately model vortex development along and downstream of very low aspect ratio fins, they have limited success for application to missiles with strake fins. Moreover, there is limited number of CFD studies for investigating aerodynamics of very low aspect ratio fins. In this thesis, a generic test model is selected and CFD analyses are performed to estimate the normal force and center of pressure of the strake unit with varying angle of attack at supersonic Mach numbers for two different roll orientations. The CFD results are compared with fast prediction methods (Missile DATCOM and White’s method) and wind tunnel data. By the comparative validation study, CFD analyses are proven to be reliable and robust for application to missiles with very low aspect ratio fins. In addition, a limited goal CFD based optimization study to design strake planform geometry is performed for alleviating the cross coupling effect on the pitching moment from sideslip angle while keeping static margin in a constant range. The geometrical parameters varying during the optimization problem consist of the leading edge location, chord length and span length of the strake planform. Since the configuration is monotype consisting of a body with strake and tail, automatic meshing scheme is developed and the whole processes from grid generation to CFD solutions are fully automated. For optimization problem, firstly a gradient based method is tested and then a stochastic optimization method is employed to guarantee global optimization instead of finding local minimum. Particle Swarm Optimization Method (PSO) is selected as a suitable population based stochastic optimization method for this study. The gradient based optimization method namely the steepest descent with line search is also applied for the same problem to investigate the applicability of gradient based optimization methods. It was observed that at the end of the PSO iterations, a small chord, short span strake comes out. However, it was also observed that the gradient solution ends with a short span, long chord strake geometry. Apparently, the gradient based optimization method is trapped in the local minimum. By the PSO optimization study, the cross coupling on the pitching moment from sideslip is decreased to one third of the initial value from baseline to optimum configuration while static margin is kept in a particular range.

Suggestions

Numerical investigation of characteristics of pitch and roll damping coefficients for missile models
Kayabaşı, İskander; Kurtuluş, Dilek Funda; Department of Aerospace Engineering (2012)
In this thesis the characteristics of pitch and roll damping coefficients of missile models are investigated by using Computational Fluid Dynamics (CFD) techniques. Experimental data of NACA0012 airfoil, Basic Finner (BF) and Modified Basic Finner (MBF) models are used for validation and verification studies. Numerical computations are performed from subsonic to supersonic flow regimes. Grid refinement and turbulence model selection studies are conducted before starting the dynamic motion simulations. Numer...
Validation of depth-averaged mixing length turbulence model for uniform channel flows/
Karaman, Çağrı Hasan; Aydın, İsmail; Department of Civil Engineering (2014)
A one-dimensional depth averaged turbulence model based on volumetric mixing length definition is developed for shallow flows. Numerical solution of the model is done using finite volume method for steady, uniform closed duct flows to observe lateral momentum exchange over depth discontinuities. The model is verified by comparison to two-dimensional numerical solutions and to the experimental data available in the literature. The model is then applied to uniform free surface flows in rectangular and compoun...
Design and analysis of a vertical axis water turbine for river applications using computational fluid dynamics
Demircan, Eren; Aksel, Mehmet Haluk; Pınarcıoğlu, Mehmet Melih; Department of Mechanical Engineering (2014)
The main purpose of this study is to design a Darrieus rotor type vertical axis water turbine using Computational Fluid Dynamics (CFD) in order to be used in river currents. The CFD modeling is based on two dimensional numerical solution of the rotor motion using commercial Unsteady Reynolds Averaged Navier-Stokes solvers, Ansys Fluent and CFX. To validate the two dimensional numerical solution, an experimental Darrieus rotor type water turbine from literature is studied and performance of several turbulenc...
Application of fully implicit coupled method for 2D incompressible flows on unstructured grids
Zengin, Şeyda; Tarman, Işık Hakan; Department of Engineering Sciences (2012)
In the subject of Computational Fluid Dynamics (CFD), there seems to be small number of important progress in the pressure-based methods for several decades. Recent studies on the implicit coupled algorithms for pressure-based methods have brought a new insight. This method seems to provide a huge reduction in the solution times over segregated methods. Fully implicit coupled algorithm for pressure-based methods is very new subject with only few papers in literature. One of the most important work in this a...
Static aeroelastic modeling and parametric study of stacking sequence for laminated composite missile fins
Aslan, Göktuğ Murat; Kurtuluş, Dilek Funda; Department of Aerospace Engineering (2018)
In this thesis, a surface-to-surface missile model with laminated composite fins is examined with respect to one-way static aeroelastic response under constant supersonic flight conditions. Two different modified double wedge fins or control surfaces using for control actuation system of a missile are investigated and compared in terms of aerodynamic and linear structural characteristics in order to minimize tip deflection. A serial set of steady-state supersonic Computational Fluid Dynamics (CFD) analyses ...
Citation Formats
E. Usta, “Investigation of missiles with strake fins and reduction of aerodynamic cross coupling effects by optimization,” M.S. - Master of Science, Middle East Technical University, 2015.