An optical fibre probe was tested in liquids with biotechnologically relevant compounds, to determine if any limits arise in bubble property determination due to these compounds. The data from this fibre probe was compared to the data from a camera for which an image processing algorithm was developed. This algorithm was able to successfully filter objects using configurable parameters. Objects had to be in focus, within a certain size range and elliptical in shape. The filtering was able to work with partially out of focus bubbles, and bubbles at the edges of the image within tolerances specified by the parameters. To provide insight into the relation between the fibre probe data and camera data a control measurement was performed in pure water, after which measurements were performed in a mixture containing 100g/L ethanol and a mixture containing 0.4M NaCl. The data sets from both measurement methods were compared for bubble velocity and bubble size. The velocity would be directly comparable,
the size was however the local height at the point where the fibre probe pierced the bubbles. As such the height directly below the fibre probe of the bubbles was determined from the images to serve as comparable data. The comparison between the probe data and camera data was inconclusive due to a dissimilarity between the distributions. Mainly the overestimation of the comparable size from the camera data was a problem. Which was likely due to the camera showing only a 2D projection of the bubble and as such the entire height would be used for this comparison. For the velocity the camera data had a narrower distribution as compared to the fibre probe data. This could be caused by the camera averaging the speed of bubbles between two or even three frames if a bubble was not detected in the middle frame, the probe might be more sensitive to these variations and as such yield a wider distribution. The image processing algorithm showed a correct processing of the images to yield usable data, the exact comparable data however still needs to be improved for this specific application.

Understanding the dynamics of bubbles in broth is crucial for various biotechnological processes conducted in bubble columns, such as the manufacturing of cultured meat. In this study, the drag coefficient of individual bubbles ascending in sodium chloride, sodium sulphate, albumin, and egg-white protein solutions was determined. This was accomplished by extracting bubble characteristics, such as the equivalent diameter and terminal velocity, from images captured by a camera system, utilizing bubble detection by a software suite. The obtained terminal velocities and computed drag coefficients were then compared to existing predictive models developed by Clift, Fan and Tsuchiya, Ishii and Zuber, and Peebles and Garber. This comparative analysis was conducted to assess the accuracy of these models in predicting bubble behavior in contaminated water. The results indicated that the drag coefficient of single bubbles rising in salt and protein solutions is higher compared to when ascending in demineralized water. The drag coefficient of single bubbles rising in protein solutions predicted by the drag model of Ishii and Zuber aligned well with the experimentally derived drag coefficients. However, both drag models tended to underpredict the drag coefficient of bubbles ascending in protein solutions. In the case of salt solutions, the drag coefficient predictions by Peebles and Garber approached the experimentally derived drag coefficients more closely although both models tended to overpredict the drag coefficient of bubbles ascending in salt solutions. Additional data acquisition of bubbles within the same size distribution rising in the examined salt and protein solutions is needed to validate and further refine these observations.