Numerical simulation study on the characteristics and mechanism of ultrasonic cavitation cleaning of crude oil sediments

Ultrasonics is an efficient and environmentally friendly method for cleaning sediments in crude oil tanks by utilizing high-speed, high-pressure cavitation microjets. However, current research ignores the coupled interaction between ultrasonic, flow, and structural force fields during ultrasonic cleaning and removal of sediment. As a result, the regularity and dynamic mechanisms of sediment removal via ultrasonic cavitation microjets remain unclear. In this work, we developed a multi-physics field-coupled model to quantitatively characterize the effect of ultrasonic operating parameters and crude oil physical properties on cleaning efficiency. This model further reveals the dynamic mechanisms behind ultrasonic cavitation microjet sediment removal. A novel feature of the model is that it couples the multi-physics field by taking the cavitation bubble growth radius and the microjet velocity as key coupling variables. The model accurately describes the dynamic process of ultrasonic cavitation microjet cleaning. Results indicate that decreasing the ultrasonic frequency and increasing ultrasonic pressure enhances the bubble growth radius and the microjet intensity, thereby improving sediment removal. Higher crude oil viscosity, on the other hand, inhibits the cavitation microjet strength and weakens the cleaning effect. Specifically, the sediment removal increased from 0.005 to 0.036 when the ultrasonic frequency was held at 20 kHz and the ultrasonic pressure increased from 120 kPa to 1000 kPa. Conversely, sediment removal reduced from 0.011 to 0.006 as the ultrasonic frequency increased from 20 to 100 kHz. This research offers practical guidance for applying ultrasonic cavitation technology in crude oil tank sediment cleaning and highlights the potential for broader applications of this technology.