抄録
Wing-in-Surface Effect Ships (WISES) are expected to be candidates for super high speed marine vehicles in the future. They runs at high speed in close proximity to the sea surface to utilize the high lift to drag ratio of the wings due to the surface effects. Fundamental studies on the safety assessment of WISES are being carried out in the Ship Research Institute. In order to express the nonlinearity in the aerodynamic characteristics due to the surface effects and to realize an accurate and simple computer simulation model for a wide range of operation, a new attempt to model the WISES dynamics and equations of motion is made. In the equations of motions derived for WISES, height becomes an important variable, and aerodynamic derivatives with respect to height are introduced. All the derivatives are initially defined as nonlinear functions of height. Provided the height can be considered as a parameter to define the derivatives, linear equations can be obtained to approximated the nonlinear WISES motion. Nonlinear aerodynamic characteristics are approximated by a series of rectilinear lines, then the aerodynamic derivatives are linear for the corresponding piecewise zones of the height. This is called as a piecewise linear model of WISES motion. Computer algorithms for selecting the derivatives and the center of perturbation corresponding to the reference frame are introduced in the solver of the differential equations. A model of the so-called Lippisch-type WISES, which has inverse-delta wings of small aspect ratio and typical nonlinear aerodynamic characteristics, is used for investigation of motion. Results of a model test for impulsive response to elevator movement in a wind tunnel are compared with the simulation results. The test is performed in the surge-constrained condition by a supporting vertical rod and the motions are recorded. Qualitative agreements in the natural frequency and damping factor are observed between the measured and computed results, and the validity of the model is examined. By means of the stability analysis and computer simulation with the newly introduced model, behavior of WISES are investigated. It is seen that the stability and characteristics of WISES motion vary according to the height. The new model seems quite promising as a tool for the safety assessment of WISES.
