Accurate measurement and prediction of bubble size distribution is critical in numerous chemical and thermal process. Here we focus on developing imaging based non-intrusive bubble measurement technique to measure bubble size and velocity involved in different applications.
Bubbly flow measurement with shadow image velocimetry (SIV)
SIV employs direct in-line volume illumination using low power sources such as LED and an optical setup to produce a narrow depth-of-field for 2D plane imaging. It is arguably the most suitable technique for the analysis of bubbly flows. The images captured by SIV were analyzed through a in-house developed robust image analysis algorithm. This algorithm is able to capture the sizes of both in-focus and out-of-focus bubbles as well as bubble clusters in the flow.
Bubbly flow measurement with digital inline holography (DIH)
Digital inline holography (DIH) utilizes single-beam light source that illuminates the flow particles and uses a digital sensor to record the interference pattern between the scattered and undisturbed portions of the beam. The 3D information of the particles is encoded in the holograms. The capability of this technique to capture bubbles with a relatively high dynamic range of size is demonstrated through the measurement of ventilated supercavity bubbly wake. The 3D distribution and sizes of the bubbles are calculated through digital reconstruction and segmentation algorithm in-house developed.