Acoustic levitation in a cylindrical cavity; a modal superposition approach
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Sound and vibration (MPSOV), MSc
Publicerad
2023
Författare
Johansson, Simon
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
A method has been developed for calculating the acoustic radiation force acting on
a small spherical bead in a sound field within a rigid boundary cylindrical cavity,
using a modal approach. Modes are selected by a method comparing their relative
strengths, within a specified dB range below the strongest mode. The total sound
field is calculated as the superposition of fields from different excitation points, each
composed of a summation of mode shapes within the specified range. The total
sound field is then used to calculate the force, by use of a previously established
model.
Three different simulated acoustic traps with a sound field excited by a plane transducer
array at the bottom of the cylinder are presented. The traps are constructed
by numerical optimization of the transducer phases and amplitudes such that the
total sound field gives rise to converging forces at a designated position. One of
the three simulated traps was also tested experimentally, where an acoustic trap at
the designated position was not found. However, three other traps, one about 1 cm
above the designated position, one in the center of the cylinder, and one about 5
mm offset from the center radially and in height, were found. Two of these alternate
traps are also predicted by the developed model, which points towards the existence
of a trap at the designated position as well, although hard to find by manual bead
placement. The third found trap is not predicted by the model. Further research is
needed to understand why that is, and how the model can be improved
Beskrivning
Ämne/nyckelord
Acoustic levitation, Cylindrical cavity, Modal superposition, Ultrasound, Phased array