Single bubble sonoluminescence: bubble dynamics and countering gravity

Abstract

When bubbles suspended in a fluid are exposed to high frequency sound pressure, they begin to glow through emission of light. This phenomenon is termed sonoluminescence. The study of a single light emitting bubble, known as Single Bubble Sonoluminescence (SBSL), can provide us with a. better and more controlled method to study sonoluminescence in an attempt to explain many of its interesting and unique characteristics. To produce SBSL, a sinusoidal ultrasound signal is applied to a water-filled flask at its resonant frequency. The pressure gradient across the bubble forces it towards the pressure antinode. The bubble undergoes nonlinear radial oscillations caused by the pressure swings of the acoustic field. During the compression phase, the bubble experiences violent collapse which results in an emission of light with spectrum that is continuous into the ultraviolet region. The maximum of the spectrum is still unknown due to the absorption of light by water in this spectral region. In our previous work, we have discovered that by introducing a sinusoidal modulation to the amplitude of the acoustic signal, it is possible to control the bubble motion. In first part of this research, we present numerical models that try to simulate the bubble dynamics. In second part we try to develop a. mechanism for balancing the gravitational acceleration in a laboratory environment. A possible solution is to use a. magnetic field gradient to counteract the buoyancy force. A difficulty with this approach is that it requires large magnetic field gradients. However, it is possible to compensate for this by adding compounds to water that will alter its molecular susceptibility.