مدلسازي عددي ضرايب هبدروديناميكي يك شناور زير سطحي در حركت شتابدار

چكيده انگليسي :

70 Nnumerical Modeling of Hydrodynamic Coefficients for a Prototype Submersible in Accelerated Motion Arash shadlaghani A shadlaghani@me iut ac ir Date of Submission 1 22 2014 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Seyed Mohamad Ali Badri malbdr@cc iut ac ir Shahriar Mansourzadeh shahriar@cc iut ac irAbstractOne of the main steps in designing submersible vessels is determining the hydrodynamic forces andmoments acting on these vehicles These forces are included inertial forces added mass damping coriolis propeller and restoring forces and moments Various methods such as experimental tests semi empirical analytical method and numerical simulations are used to calculate the hydrodynamicforces With development of computer sciences applications of CFD in maritime industries are beingfeasible and important Numerical approaches have evolved to a level of accuracy which allows themto be applied to submersibles resistance computations In this research damping and added masscoefficients were calculated by numerical simulations Also Reynolds Averaged Navier stoks RANS simulations were used to solve turbulent equations In order to calculate the damping and added masscoefficients uniform straight line test with angle relative to flow direction and linear acceleratedmotion tests were simulated numerically by commercial Ansys Cfx package This code is base onfinite volume method When submarine s movement include attack and drift angles relative to flowdirection the variation of drag coefficient due to this angles are parabolic and the nonlinear dampingcoefficients may be calculated by drag and lift equations constants Also linear damping coefficientscan be calculated by damping forces and moments diagram versus attack and drift angles Firstly numerical simulation was carried out on a sphere to ensure the accuracy of approach and implementedto calculate added mass coefficients The simulations in this case were combination accelerated anduniform motions in order to investigate the influence of velocity and acceleration values Also addedmass coefficients were calculated theoretically Equivalent ellipsoids and strip theory were used inthis regards Equivalent ellipsoids method is base on potential flow theory and the submarinecomponents were replaced by optimized ellipsoids When ever mass moment of inertia for variouscomponents and replaced ellipsoids were equivalent the best ellipsoids dimensions were determined Then linear added mass of each ellipsoid was calculated by lamb s k factors Finally total added masswas calculated by summation of the ellipsoids added mass In strip theory the added mass of 2Dsections was calculated and with integrating over the length of body total added mass weredetermined The assumption of theoretical methods such as disregard viscous effects time dependentof flow nature caused the accuracy of these methods were decreased and only used to approximate ofhydrodynamic coefficients The numerical and theoretical results were compared with David TaylorInstitution reports and other numerical results It is noteworthy that non dimensional results werecompared together as well Good agreements between numerical and experimental results wereshowed the accuracy of numerical simulations in hydrodynamic problems Key words Hydrodynamic coefficients Numerical simulation Theoretical method submarine

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مدلسازي عددي ضرايب هبدروديناميكي يك شناور زير سطحي در حركت شتابدار

شبيه سازي عددي , روشهاي تحليلي , زيردريايي