Study On Hydrodynamic Characteristics Of Hull With Different Stem Post Angles

As the first part of the ship’s contact with the incoming water,the bow has a great influence on the flow field around the ship,and plays a very important role in improving the resistance and seakeeping performance of the ship.The change of the ship’s bow will cause the corresponding change of the wake of the ship’s flow field,which will lead to the change of the ship’s resistance characteristics.As an important part of the bow,the bow column has a direct relationship with the hydrodynamic performance of the ship.At present,the research on bow stem mainly focuses on the structure and manufacture of bow stem,and the hydrodynamic performance related to bow stem is rarely reported.In this paper,the change of bow column Angle on hull hydrodynamic performance is studied.Based on CFD technology,the straight motion of bow type with different bow column angles in still water is simulated.The hydrodynamic characteristics of different bow column angles are compared and the influence of bow column Angle on hull hydrodynamic performance is discussed.The main research contents are as follows:In this paper,the medium-sized single ship is taken as the research object.The length of the mother ship is 21.45 m,the width of the ship is 3.8m,the design draft is 1m,and the drainage volume is 27.58m~3.On the basis of the above mother ship and on the premise that other hull parameters remain unchanged and only bow Angle is changed,Maxsurf software is used to design seven bow hull model with bow angle of 35°,50°,60°,90°,115°,130°and145°.The resistance performance of hull with different stem angles in still water is numerically analyzed and calculated.First,calculating the numerical model is established based on the CFD software Fluent,computational domain boundary and water line distance is 0.4 times the captain,the boundary and water line distance is 0.6 times the captain,the entrance of ship bow 1 times the captain,the exit from the stern three times as much as the captain,the beam direction from the profile 1 times the captain,dividing the computational domain using ANSYS ICEM structured grids,SST k-ω turbulence model,exports,entrance,plane of symmetry boundary conditions were determined and discrete method to carry on the hull resistance calculation,based on the CFD software Fluent,The static water resistance of seven different hulls is calculated at 5 kn,10 kn,15 kn,20 kn and25kn speeds.The results show that the total hull resistance of the medium-low speed inward hull is small,while that of the medium-high speed outward hull is small.Maximum total hull resistance at full speed perpendicular to the bow.Maximum total drag perpendicular to the bow at full speed.The peak value of free surface wave and the peak value of hull surface pressure in the bow of a single ship are larger than that in the inward ship at medium and low speed,and the flooding and wetness in the bow are more serious than that in the inward ship.At high speed,the crest value of free liquid surface and hull surface pressure of the inclining-type ship are larger than that of the out-clining-type ship,and the wetness of the inclining-type ship is more serious than that of the out-clining-type ship.The seakeeping performance of the hull with different head column angles under regular wave and irregular wave is numerically analyzed and calculated.Based on ANSYS AQWA software,the operating condition is set as the wave amplitude of regular wave 0.05Hz～0.5Hz,and the sailing speed is 0.The motion responses of roll,pitch and heave under three wave incidence angles(180°),(135°)and(90°)are compared and analyzed.The calculated results show that the roll RAO of a single ship with different steam post angle s has little difference under regular wave when the wave of transverse wave and oblique wave is down and in the middle and low frequency stages.At the middle and high frequency stage,the rolling RAO of the inward leaning hull is less than that of the outward leaning hull.For the pitching movement under regular waves,the pitching RAO of a single ship with different steam post angles has little difference in the downward-facing wave and the slanting wave,and in the middle and low frequency stages,the pitching responses of the two kinds of waves are different.The pitching stability of an inward bow mono ship is better than that of an outward bow mono ship under the heading wave.There is little difference in the pitch RAO of a single ship with different bow Angle.For heave movement under regular waves,the heave RAO of a single ship with different steam post angles has little difference when the wave is heading and the wave is inclined,and the heave RAO of a single ship with different steam post angles has little difference when the wave is heading and the wave is inclined.In the middle and low frequency stages,the heave of an inward bow single ship is better than that of an outward bow single ship.Under irregular waves,the bow column Angle has little effect on the motion response trend of the hull.In the three kinds of wave downturns,except for the 90° and 180° wave downturns,the change of steam post angles has no obvious effect on the pitching and rolling characteristics of the hull,and the motion response peaks of the outward bow are larger than those of the inward bow.According to the above calculation results,the influence of different steam post angles on hull hydrodynamic performance is obtained,which provides a reference for the optimal design of hull bow.