Published online by Cambridge University Press: 22 July 2019
While numerous theoretical studies exist on microstreaming around acoustically excited, trapped gas bubbles, experimental approaches have mainly been conducted for bubbles attached to a solid boundary. One of the main difficulties lies in the positional stability of the microbubble. In the present work we trigger surface modes by bubble coalescence, with the advantage of limiting translational instabilities and controlling the orientation of the axisymmetric deformation. Furthermore, streaming is visualised by fluorescent tracer particles. In this way, bubble dynamics and streaming patterns can be studied together. Different types of streaming patterns are observed and correlated to the respective mode number. Besides the mode number, the bubble size and the phase difference between modal components are identified as important parameters in the definition of the pattern type.
Bubble dynamics of a bubble oscillating with a predominant mode 2 (radius R0 = 46.9 μm at acoustic pressure pa = 20.6 kPa). This case is presented in figure 4 in the main document, the corresponding microstreaming can be found in movie 2. For reasons of document size the video is limited to 40 images and furthermore compress to jpeg format. The created avi-document is played with a frame rate of 8 frames per second. Further parameters are: driving frequency - 31.25 kHz, sampling frequency - 180.064 kHz, frame size - 128 pixel × 128 pixel (0.256 mm × 0.256 mm).
Microstreaming of a bubble oscillating with a predominant mode 2 (radius R0 = 46.9 μm at acoustic pressure pa = 20.6 kPa). This case is presented in figure 4 in the main document, the corresponding bubble dynamics can be found in movie 1. For reasons of document size the video is limited to 40 images and furthermore compress to jpeg format. The created avi-document is played with a frame rate of 8 frames per second. Further parameters are: driving frequency - 31.25 kHz, sampling frequency - 400 Hz, frame size - 1024 pixel × 768 pixelpixel (2.048 mm × 1.536 mm).
Bubble dynamics of a bubble oscillating with a predominant mode 3 (radius R0 = 70.5 μm at acoustic pressure pa = 12.8 kPa). This case is presented in figure 5 in the main document, the corresponding microstreaming can be found in movie 4. For reasons of document size the video is limited to 40 images and furthermore compressed to jpeg format. The created avi-document is played with a frame rate of 8 frames per second. Further parameters are: driving frequency - 31.25 kHz, sampling frequency - 180.064 kHz, frame size - 128 pixel × 128 pixel (0.256 mm × 0.256 mm).
Microstreaming of a bubble oscillating with a predominant mode 3 (radius R0 = 70.5 μm at acoustic pressure pa = 12.8 kPa). This case is presented in figure 5 in the main document, the corresponding bubble dynamics can be found in movie 3. For reasons of document size the video is limited to 40 images and furthermore compressed to jpeg format. The created avi-document is played with a frame rate of 8 frames per second. Further parameters are: driving frequency - 31.25 kHz, sampling frequency - 600 Hz, frame size - 1024 pixel × 768 pixelpixel (2.048 mm × 1.536 mm).
Bubble dynamics of a bubble oscillating with a predominant mode 4 (radius R0 = 55.7 μm at acoustic pressure pa = 23.6 kPa). This case is presented in figure 6 in the main document, the corresponding microstreaming can be found in movie 6. For reasons of document size the video is limited to 40 images and furthermore compressed to jpeg format. The created avi-document is played with a frame rate of 8 frames per second. Further parameters are: driving frequency - 31.25 kHz, sampling frequency - 180.064 kHz, frame size - 128 pixel × 128 pixel (0.256 mm × 0.256 mm).
Microstreaming of a bubble oscillating with a predominant mode 4 (radius R0 = 55.7 μm at acoustic pressure pa = 23.6 kPa). This case is presented in figure 6 in the main document, the corresponding bubble dynamics can be found in movie 5. For reasons of document size the video is limited to 40 images and furthermore compressed to jpeg format. The created avi-document is played with a frame rate of 8 frames per second. Further parameters are: driving frequency - 31.25 kHz, sampling frequency - 400 Hz, frame size - 1024 pixel × 768 pixelpixel (2.048 mm × 1.536 mm).