Research On Hydrodynamic Problems Of SWATH

In order to meet the needs of high-speed shipping and military modernization, a series of high-performance ships came into being, which include the SWATH of excellent performance.SWATH has fine seakeeping qualities, wide deck area, great vitality and many other advantages, so that it has been developed rapidly.The special ship type of SWATH leads to many special hydrodynamic problems different from other ships. For example, the couple of pitching and rolling may appear when the transverse demihull spacing is large. Therefore, the effect on the motion performance of this type of ship in waves caused by transverse demihull spacing is such an important hydrodynamic problem. Furthermore, the "MUNK" toque makes SWATH easy to lose the stability, how to improve the ship's stability by technique of ship appendages is a hot issue at present. The design speed of this ship is usually low, the relationship between movement of ship and force at low or zero speed is significant for studying this ship's motion performance and it is the necessary technical support for ship design. The research of the special hydrodynamic performance of SWATH has important theoretical and practical significance for understanding the seakeeping performance of SWATH and supporting the outstanding ship's research and design work.Based on potential flow theory, this paper analyzes hydrodynamic interference and coupling between the two hulls. Lateral flow theory is used to study the viscous correction of the current method by potential flow theory, then forecasts the ship motion response and analyzes the hydrodynamic property deeply. Also the impact on ship motion by changing the transverse demihull spacing is analyzed, and the "false resonance" problem in calculation results is solved too. By means of numerical calculation method research and damping research, the problem of the unreal forecast result by using potential flow theory is overcome,a theoretical method for correctly predicting the hydrodynamic interference and coupling between the two hulls is obtained. This paper also studies the influence on ship's motion caused by fore-rear fins and compares the ship's motion response with the bare ship's to prove the effectiveness of fins, discusses the impact on the performance of ship motion of the fin's longitudinal position and size. The paper also forecasts the second order drift forces in waves by using the theory of potential flow and studied the effects on the motion performance of SWATH.Research shows that it is useful to amend the results of potential flow theory by using the method of lateral flow theory. Interference between two bodies of SWATH has a great impact on the transverse movement. Influence on the movement of the ship's first order motion and second order drift forces by changing transverse demihull spacing also shows certain regularities. Fins can improve the movement of the ship, and the effect on the condition without speed is more obvious than condition with speed.