Ultrasonic Measurement of the Burn Rate of Crude Oil Slick During In Situ Burning

During in situ burning (ISB), measuring the thickness and burn rate in real time can yield critical insights to enhance oil spill mitigation efficiency. At present, no technology has been developed for real-time monitoring of burn rates during ISB. To address this gap, an innovative ultrasonic approach was proposed for the direct measurement of oil slick thickness and burn rate during ISB, utilizing ultrasonic transducers submerged in water. Laboratory experiments were conducted utilizing four crude oils with varying dynamic viscosities. The time of flight (TOF) of ultrasound propagating in the oil slick was computed by employing the second cross correlation method. To determine the slick thickness, the harmonic mean (HM) of the speed of sound was derived from the temperature gradient within the oil slick, as measured by a series of thermocouples, based on the established correlation between sound speed and temperature. The slick thickness was successfully measured during ISB, and the burn rate was directly calculated from the variations in thickness. The ultrasonic measurements correlated well with weight-based assessments, and the burn rate matched other theoretical predictions and experimental data. Additionally, the burn rate showed a significant correlation with viscosity. The successful measurement of slick thickness and burn rate represents a significant advancement toward bridging the gap between existing techniques and the demand for real-time analysis of dynamics during ISB. This method has strong potential for real-time monitoring of thickness changes and burn rates utilizing an underwater robotic platform during ISB operations in open waters.