Density on Measurement of Beam Attenuation in Ship Wakes
气泡数密度对尾流光束衰减测量的影响

To measure the beam attenuation in ship wakes accurately and improve the reliability of detecting ship wakes by forward light attenuation,the influence of bubbles′ number density on the measurement of beam attenuation in wakes was investigated.The scattered power and un-scattered power on the detector cross-section were derived based on radiative transfer equation in small angle approximation.According to the measurement condition,transmission function,which is the ratio of the received power by detector in wakes to the received power by detector in non-wakes marine environment,was introduced.Correction coefficient,denoting the extent of multiple scattering,was further introduced.Given a typical bubble distribution in wakes,the numerical results relating the transmission function and correction coefficient to bubbles′ number density under different measuring conditions were presented.The numerical results show that,the correction coefficient increases monotonously but the transmission function decreases monotonously as the bubbles′ number density increases|the influence of bubbles′ number density on beam attenuation is different as the measurement conditions change.The results show that,given a measurement condition and transmission function,the bubbles′ number density can be quantified by means of radiative transfer equation in small angle approximation.