Numerical modelling of acoustic pressure fields to optimize the ultrasonic cleaning technique for cylinders

Abstract

Fouling build up is a well-known problem in the offshore industry. Accumulation of fouling occurs in different structures, e.g. offshore pipes, ship hulls, floating production platforms. The type of fouling that accumulates is dependent on environmental conditions surrounding the structure itself. Current methods deployed for fouling removal span across hydraulic, chemical and manual, all sharing the common disadvantage of necessitating halting production for the cleaning process to commence. Conventionally, ultrasound is used in ultrasonic baths to clean a submerged component by the generation and implosion of cavitation bubbles on the fouled surface; this method is particularly used in Reverse Osmosis applications. However, this requires the submersion of the fouled structure and thus may require a halt to production. Large fouled structures such as pipelines may not be accommodated. The application of high power ultrasonics is proposed in this work as a means to remove fouling on a structure whilst in operation. The work presented in this paper consists of the development of a finite element analysis model based on successful cleaning results from a pipe fouled with calcite on the inner pipe wall. A Polytec 3D Laser Doppler Vibrometer was used in this investigation to study the fouling removal process. Results show the potential of high power ultrasonics for fouling removal in pipe structures from the wave propagation across the structure under excitation, and are used to validate a COMSOL model to determine cleaning patterns based on pressure and displacement distributions for future transducer array design and optimization.

A Novel Ultrasonic Cleaning Tank Developed by Harmonic Response Analysis and Computational Fluid Dynamics

“…When we compared the sizes of the cleaning area, model D had the largest cleaning area of 100.83 cm 2 , which increased up to 39.65% compared to model A which cleaning area was 72.20 cm 2 , and larger than model B as well. From Figures 7 and 8, the acoustic pressure distribution indicated that the design of the UCT and transducer position did affect acoustic pressure distribution and cleaning area, consistent to the report in [14][15][16][17][18][19]. Actually, if we relocated some transducers to the side as in the study [17][18][19], we would get a larger cleaning area and higher acoustic pressure than in this study.…”

“…In the case which cleaning fluids flow in the UCT, when the flow rate increases, the bubble collapsing rate drops along with the cavitation [13]. The transducers' position also affects cleaning performance; if the transducers are placed in a suitable position, the cleaning performance will be high [14][15][16][17][18][19]. In order to design a UCT with high cleaning performance, computer simulation was applied to find the cause of why the UCT in this industrial factory was not cleaning properly.…”

Ultrasonic Transducer Array Performance for Improved Cleaning of Pipelines in Marine and Freshwater Applications

“…Previous work has shown capabilities to remove inner wall pipe fouling noninvasively using ultrasounds [13][14][15][16]. This is carried out by the attachment of a High-Power Ultrasonic Transducer (HPUT) onto the outer wall of a water-filled pipe.…”

UQ eSpace

“…Due to the cyclic behaviour of the wave propagation, the formed bubble would increase and decrease in radius before imploding. [12] From Figure 3, the bubble increases in radius when the pressure is heading to maximum negative pressure from maximum positive pressure (rarefaction) and decreases in radius when the pressure is heading to maximum positive pressure from maximum negative pressure (compression). Compression of the bubble can cause it to burst (adiabatically) which produces pressure of up to 50MPa and temperature up to 5000K [9].…”

“…Therefore, the effect of cavitation bubbles should be captured in the simulation instead by considering ultrasound attenuation coefficient and sound speed reduction. Other limitation includes inability to obtain response concerning instantaneous pressure increase from bubble implosions [12].…”