A stream of air bubbles can be most effective at cleaning produce or industrial equipment if it strikes at the correct angle.
Researchers believe that washing vegetables and food-processing equipment with flowing liquids filled with air bubbles could be effective, but little is known about how to optimize the process. Now engineers, using experiments and simulations, have shown that bubbles exert an optimal cleaning effect if they strike a surface at an angle of about 22.5° [1]. The researchers hope that this insight will help improve methods for the gentle cleaning of fruits and vegetables, potentially leading to a commercial food-cleaning device that they call a “fruit Jacuzzi.”
As bioengineer Sunghwan “Sunny” Jung of Cornell University points out, bubbles injected into fluid have long been used to clean biofilm-encrusted surfaces in settings such as wastewater treatment facilities. Experts generally believe that the technique works because bubbles flowing over a surface exert a shear force, parallel to the surface, which tends to remove attached contaminants. “It’s similar to how you move your hand along the surface of your skin when you’re cleaning your body, applying a shearing force at the surface,” says Jung. Even so, he says, little is known about the basic science behind the effect and in particular about how the motions of bubbles within the liquid might optimize the cleaning.
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