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(a) The schematic of the experimental apparatus. (b) At θ = 5 o , a bubble with radius a = 0.7 mm bounces backward and collides the surface below the first collision point. (c) At θ = 10 o , the bubble bounces backward, but ultimately collides at a point above the first collision point. (d) At θ = 20 o , the bubble no longer undergoes backflipping. The corresponding videos are included in Ref. [29].
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Oblique collision of solid particles with surfaces has been a topic of extensive study in Newtonian mechanics, which also explains the motion of bubbles and droplets to some extent. Here, we observe that air bubbles exhibit a backflipping behavior when they collide with a tilted surface. Our experiments reveal that bubbles with radii 0.6-0.7 mm und...
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... perform experiments in a tank filled with deionized water to visualize the bubble motion while colliding with a tilted smooth surface. We place a custom-made needle at the bottom of the tank connecting the needle to a syringe pump (New Era) through a 3D-printed mount and tubing as depicted in Fig. 1 (a). The needle is made to generate bubbles of uniform radius at low pump flow rates with a standard deviation of less than 0.02 mm. We then use a 3D-printed tower that has a manual pulley design to hold a clean glass slide at the desired inclined angle, θ, on top of the needle as shown in Fig. 1 (a). The distance between the needle and ...
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... a 3D-printed mount and tubing as depicted in Fig. 1 (a). The needle is made to generate bubbles of uniform radius at low pump flow rates with a standard deviation of less than 0.02 mm. We then use a 3D-printed tower that has a manual pulley design to hold a clean glass slide at the desired inclined angle, θ, on top of the needle as shown in Fig. 1 (a). The distance between the needle and the lowest edge of the glass slide is approximately 12 cm to ensure that the bubbles reach their terminal velocity before collision. We use a high-speed camera (Photron SA-Z), a macro lens (Nikkor 105 mm), an extension bellows (Nikon PB-6), and a 10x magnifying lens (Neewer) to record the bubble ...
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... addition to different bubble sizes, we test different θ, ranging from 0 o to 20 o . Figure 1(a) shows different trajectories of an air bubble with a = 0.7 mm from the first collision at t = t 0 to the second collision at t = t 1 . We define a dimensionless time, τ = (t − t 0 )/(t 1 − t 0 ), normalized by its period between the two bounces (i.e., t 1 − t 0 ). ...
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... two bounces (i.e., t 1 − t 0 ). At θ = 0 o , the bubble bounces normal to the surface (video 1 in Ref. [29]). As we tilt the surface at a low angle θ, the bubble initially bounces forward like an elastic collision, but then reverses and moves backward until it collides with the surface at a location behind the first collision spot, as shown in Fig. 1(b) for θ = 5 o (video 2 in Ref. [29]). We herein define the backward motion of the bubble as backflipping as shown in Fig. 1(b). As we increase θ to 10 o , the bubble still exhibits a backflipping behavior; however, the bubble collides on a point past the first collision point, as shown in Fig. 1(c) (video 3 in Ref. [29]). We refer to ...
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... surface at a low angle θ, the bubble initially bounces forward like an elastic collision, but then reverses and moves backward until it collides with the surface at a location behind the first collision spot, as shown in Fig. 1(b) for θ = 5 o (video 2 in Ref. [29]). We herein define the backward motion of the bubble as backflipping as shown in Fig. 1(b). As we increase θ to 10 o , the bubble still exhibits a backflipping behavior; however, the bubble collides on a point past the first collision point, as shown in Fig. 1(c) (video 3 in Ref. [29]). We refer to such a backflipping motion of the bubble as weak backflipping. Finally, at θ = 20 o , the bubble no longer backflips as shown ...
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... behind the first collision spot, as shown in Fig. 1(b) for θ = 5 o (video 2 in Ref. [29]). We herein define the backward motion of the bubble as backflipping as shown in Fig. 1(b). As we increase θ to 10 o , the bubble still exhibits a backflipping behavior; however, the bubble collides on a point past the first collision point, as shown in Fig. 1(c) (video 3 in Ref. [29]). We refer to such a backflipping motion of the bubble as weak backflipping. Finally, at θ = 20 o , the bubble no longer backflips as shown in Fig. 1(d) (video 4 in Ref. ...
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... Fig. 1(b). As we increase θ to 10 o , the bubble still exhibits a backflipping behavior; however, the bubble collides on a point past the first collision point, as shown in Fig. 1(c) (video 3 in Ref. [29]). We refer to such a backflipping motion of the bubble as weak backflipping. Finally, at θ = 20 o , the bubble no longer backflips as shown in Fig. 1(d) (video 4 in Ref. ...