Numerical Computation of Wave Forces on Blended Winged-Body Underwater Glider using Panel Method

Abstract

The long endurance, energy efficiency and nature of locomotion have proved underwater glider (UG) to be the most suitable choice for long-term ocean environmental monitoring and detection of marine resources. Being buoyancy driven slow speed underwater vehicle, external environmental disturbance such as waves significantly affect the operational autonomy and stability of UG along the designed glide path. The assessment of these external disturbances on UG is significantly important to design better control systems and vehicle designs. Accurate wave predictions methods are needed to improve the reliability and efficiency of UG. This study develops a formulation based on panel method for numerical computation of wave force on submerged UG operating along the glide path. The proposed method is implemented using ANSYS Hydrodynamic Diffraction (HD) and Hydrodynamic Time Response (HTR) modules which require discretization of UG surface into panels, defining mass properties and generating the desired environmental sea conditions. Numerous simulations are performed considering linearized Airy head sea waves. Deep sea water conditions with infinite length and width of water column are considered so the interference effects due to bottom and vertical boundaries can be neglected. The numerical simulations are carried out in frequency as well as time domains to calculate wave loadings for different UG submergence depths and pitch angles; and different wave amplitudes and frequencies. The surge and heave wave forces; and pitch wave moment are found to be most dominant in head sea condition. Using MATLAB curve fitting tool, the analytical formulas for dominant wave forces and moment on the UG is obtained in terms of wave and UG parameters based on the numerical simulation results. The derived analytical wave force formulations coupled with motion dynamics and hydrodynamics model provide an efficient tool to analyze UG dynamics in time domain and evaluate the influence of different wave parameters on the dynamic characteristics and navigation of UG.