• 作者： 黃明志
• 中文摘要： The measured heave motion in a data buoy system is influenced by the type of accelerometerused (hull-fixed or vertically stabilized), the position of the accelerometer, the pitch response of the buoy itself, electronic noise and digitized error in analysis. These various effects introduce spurious energy into the acceleration spectrum, particularly at low frequencies. In this study, numerical time domain simulation of data buoy motions in regular and irregular waves was conducted to study the various effects of non-linearity on measured heave acceleration at low frequencies. The results of detailed studies indicate that in low sea-states, nonlinear pitch spectral transfer is the main mechanism which causes fixed accelerometer measurements to contain low-frequency spurious energy. For more severe sea-states, both nonlinear pitch and heave spectral transfer can introduce low-frequency spurious energy into stabilized accelerometer measurements. Simulation results also indicate that the stabilized accelerometer is preferred over the fixed accelerometer to reduce spurious energy at low frequencies. This spurious energy induced by nonlinear buoy motions can be effectively corrected by an empirical noise correction function which varies linearly with the wave frequency. The slope of this noise correction equation and the frequency range of correction can be found from detailed numerical simulations and field measurements.
• 英文摘要： --
• 中文關鍵字： data buoy, numerical simulation, wave tank experiment
• 英文關鍵字： --