Numerical Prediction of the Static Hydrodynamic Derivatives using CFD Techniques

Abstract

The master thesis was focused on the numerical prediction of the static hydrodynamic derivatives, required to solve the ship manoeuvring problem. The hydrodynamic forces and moments acting on the considered ship (KVLCC2) with the influences of the drift and rudder deflection angles were computed using CFD techniques, in correlation with the standard PMM (Planar Motion Mechanism) static tests. The corresponding hydrodynamic derivatives were calculated and the characteristics of the turning circle and Zig-Zag manoeuvres were estimated on the basis of the simulated ship trajectory. The master thesis is composed by three main parts: - The estimation of the preliminary hydrodynamics performance (ship resistance, powering and manoeuvring) using the PHP software platform, developed at the “Dunarea de Jos” University of Galati; - The computation of the hydrodynamics forces and moments acting on the 1/58 KVLCC2 ship model, during the static drift, static rudder and static drift and rudder motions, using CFD instruments (SHIPFLOW code); - The simulation of the ship trajectory and the estimation of the turning circle characteristics using the hydrodynamics derivatives obtained on the basis of CFD computation and statistical relations (Clarke, Gedling and Hine). In the first part, specific methods dedicated to the initial design stage were used: Holtrop-Mennen for ship resistance prediction and propeller series B-Wageningen in order to estimate the hydrodynamic characteristics in open water. From manoeuvrability view point, the Voitkounsky model was used to compute the hydrodynamics of the rudder (including the optimum position of the rudder stock), and the Brix model was dedicated to check the rudder cavitation. Also, Abkowitz model and statistical relations proposed by Lyster and Knights were introduced to estimate the turning circle characteristics. The second part was dedicated to estimate the hydrodynamics forces and moments acting on the ship with the propeller and rudder deflection influences, using the viscous flow theory (RANS), in deep water condition, for 0.142 Froude number, corresponding to the design speed. The potential flow theory was applied for wave resistance computation of the bare hull, and the experimental model tests performed by MOERI were used in order to validate this procedure, for a range of Froude numbers between 0.101 and 0.147. The static drift, static rudder and combined static drift and rudder numerical simulations in viscous flow assumption were done, in the following conditions: - The static drift angle, β, was varied with 2° step, in the range of -20° to 20°, the rudder being kept in the Center Line; - The static rudder deflection angle, δ, was varied with 10° step, in the range of -40° to 40°, the hull being kept on the straight ahead course; - Also, all the static drift and rudder deflection combinations were considered. The obtained hydrodynamics lateral forces Y were compared with the experimental results provided by MOERI, for static drift and static rudder. In the last part, the numerical prediction of the static hydrodynamic derivatives and the simulation of the turning circle and Zig-Zag manoeuvres were performed on the basis of two specific codes (POLINEW and PMMPROG) developed at the “Dunarea de Jos” University of Galati. The characteristics of the turning circle and Zig-Zag manoeuvres were determined, the IMO criteria being used to establish the manoeuvring performance of the ship. In conclusion, the CFD techniques may be introduced in the design process in order to increase the quality of the hydrodynamic performance prognosis, including the manoeuvrability characteristics.