Research Of Spray Characteristics And Real Time Nu-Merical Prediction Of The Motion Response Of High Speed Planing Craft

The planing craft is the representative form of the Surface Vehicle, and has beenwidely used in inland patrol, sea rescue, marine rapid transport and marine conditiondetection and so on. In recent years, the fast-developing Unmanned Surface Vehiclemostly uses planning craft, and it shows attractive application prospect in militaryfield. The hydrodynamic load and motion response of the planing craft have compli-cated strong-nonlinearity in the condition of high speed which concludes instantane-ous nonlinear problems for hydrodynamic/aerodynamic coupling load, flow separa-tion of the free surface deformation, longitudinal stability in sailing, broaching of fol-lowing wave, bottom slamming and side spray, which have a critical impact on thesailing stability, mobility and security of the planing craft.In this paper, based on the research methods of computational fluid dynamics soft-ware FLUENT, the mathematical model of three DOF of the planing craft, modelingpractice and self-propulsion test, the planing craft transient hydrodynamic load, mo-tion response and control which took wind load into account were carried out. Quan-tity analysis and calculation model of spray characteristics and resistance which basedon flow field numerical calculations of the high-speed planing craft were established.Computing methods of geometric parameter in spray zone were proposed. Calculationformulas of spray resistance were deduced. Numerical and theoretical prediction ofthe planing craft transient response which consider the wind load were completed, andon his basis attitude control method of the planing craft which based on dynamic hy-drofoil were proposed, also self-propulsion test was researched. The main contentsconclude:Flow field and fluid dynamic performance numerical simulation of the high-speedplaning craft under the constraint patterns were completed and the change rule ofspray area, dynamic pressure at the planing bottom, spray resistance were deeplyanalyzed. In order to calculate geometric shape in the plane of the spray zone andReynolds number, four assumptions were proposed. It subsequently inferred: the cal-culation method of the angle between the trailing edge line and the keel-line, the angleleading edge line and the keel-line, along with Reynolds number on the basis of sprayarea. Meanwhile, Calculation formulas of spray resistance were proposed and the postprocessors were compiled, which could complete the calculation of fluid dynamicperformance in spray zone and the drawing of spray zone geometric shape. By com-paring with the empirical formula of the Davidson Lab and the results of the ITTC formula, there was consistence in the results, which verify the reliability of the spraycharacteristics numerical calculation model of the planing craft in this paper.The paper uses software FLUENT dynamic mesh technique to coupled solve lon-gitudinal three DOF motion equations of the planing craft. Numerical predictionmodel and method of the planing craft transient fluid dynamic and response werebuilded. Numerical prediction and analysis of the planing craft motion response indifferent volume froude numbers and C.G. positions were carried out. The flow cha-racteristics and motion attitude in different conditions were given and the change ruleof C.G. position and trimm angle in motion response were analyzed. The researchshows that moving C.G. position back makes the heave and trimm angle increasedwith the same speed. With the same C.G. position, from hull borne to planing condi-tion, the trimm angle increases with the incremental speed. Moreover, the trimm angledecreases and the heave increase with the incremental speed in the condition of plan-ing.When the planing craft sailing at low speed, the spray appeared at the stem aswhisker and the spray area was small. As the speed increased, the spray was obviousand appeared at the stem and the side with incremental area. Also primary spray areaand whisker were exsited. If the C.G. position was too close to the stern, the planingcraft was likely appeared “Dolphin Movement” phenomenon. This was given and ve-rified by current numerical prediction results of the motion response.What’s more, nonlinear longitudinal motion mathematical model with the windload was established, which concluded propulsion system model and control systemmodel and improved the calculation method of windward area and wind pressure arm.Calculation formulas of wetted length and area were deduced. The simulation soft-ware of longitudinal three DOF motion prediction of the planing craft was developed.Motion response prediction of the planing craft which considered the wind load wascompleted. The proportion of wind drag in the process of sailing was quantitative de-scribed and the sailing attitude was contrastive analyzed in different conditions.In addition, a new sailing attitude control device of the planing craft was proposedand designed that named as controlled motion hydrofoil system. Nonlinear longitu-dinal motion mathematical model of the planing craft with controlled hydrofoil whichconsidered the wind load was established. The strategy that controlled hydrofoil con-trolled the heave and trim angle of planing craft was proposed. The visual program forlongitudinal motion prediction of the planing craft with controlled hydrofoil was compiled. Also the control prediction and analysis of the heave and the trimm angle inthe three patterns that concluded variable-pitch hydrofoil, longitudinal motion and thecoupling motion of both under the wind load from0to8were completed. The resultsshow that: with the same external load, the range of the heave and the trimm angle inthe control of variable-pitch hydrofoil and longitudinal motion was less than the fixedcondition, that is, moving hydrofoil could have a control on attitude of the planingcraft.In order to verify the feasibility of the control scheme on planing attitude thatmoving hydrofoil had, the controlled hydrofoil system and self-propulsion modelwere designed and made. The self-propulsion test was promoted in wave pool. By sixDOF MTA the response parameters were gathered. Through analysis and handledwith these data, the result that moving hydrofoil could have a control on attitude ofthe planing craft would be verified further.In this paper, the calculation analysis on the transient fluid dynamic and response ofthe planing craft was developed. The calculation model and method for the spray re-sistance and motion prediction and control of the planing craft were established.These can be used for the research on complex locomotion mechanism of thehigh-speed planing craft in the water-air dual porous media, and it could offer reliableanalysis and research method for the design of the planing craft attitude control sys-tem.