Your first experiment (suspended ball in inverted funnel) demonstrates Bernoulli's principle well: the flow diameter increases, so the flow speed decreases, so pressure must have increased, so the ball is pulled upward toward low pressure. However, your second experiment does not demonstrate Bernoulli's principle, which describes the relationship between pressure and velocity *within a flow*. The principle says nothing about the difference in pressure between air inside and outside of a flow. Here are some ways you can see that the flow pressure is not lower than atmospheric pressure, as you claimed: 1. Note that the air flows out of the hose into the atmosphere, which can only happen if the air in the hose is at higher pressure. 2. Attach strings to the end of the hose and point the hose straight down; note that the strings are not moved horizontally into the flow. 3. Color the flow with dye and note that the flow doesn't get narrower as it would if it has lower pressure than the atmosphere. The reason for the ball being suspended in your tilted upward flow from the hose is that the upper, flow-side curved surface of the ball deflects some of the air molecules away from the flow due to that part of the flow sticking to and following the ball's surface away from the flow. By Newton's third law, this deflection of air away from the flow pulls the ball toward the flow. This is the Coanda effect.
First experiment is also Coanda effect. Whenever you have a jet of fluid flowing into a stationary fluid entrainment is gonna occur, so Bernoulli and the continuity equation cannot be applied here. As the jet moves around the ball , static air under the ball gets entrained in the jet , creating a low pressure region until that jet hugs the convex underside of the ball due to a vacuum been created. The removal of air from that region causes atmospheric pressure to hold the ball up. The purpose of the funnel is to create the pressure gradient that holds the ball up. The funnel prevents the atmospheric pressure from above from countering the atmospheric pressure from below that holds the ball up.
Thanks so much...I was searching for this exact experiment
Your first experiment (suspended ball in inverted funnel) demonstrates Bernoulli's principle well: the flow diameter increases, so the flow speed decreases, so pressure must have increased, so the ball is pulled upward toward low pressure. However, your second experiment does not demonstrate Bernoulli's principle, which describes the relationship between pressure and velocity *within a flow*. The principle says nothing about the difference in pressure between air inside and outside of a flow. Here are some ways you can see that the flow pressure is not lower than atmospheric pressure, as you claimed: 1. Note that the air flows out of the hose into the atmosphere, which can only happen if the air in the hose is at higher pressure. 2. Attach strings to the end of the hose and point the hose straight down; note that the strings are not moved horizontally into the flow. 3. Color the flow with dye and note that the flow doesn't get narrower as it would if it has lower pressure than the atmosphere.
The reason for the ball being suspended in your tilted upward flow from the hose is that the upper, flow-side curved surface of the ball deflects some of the air molecules away from the flow due to that part of the flow sticking to and following the ball's surface away from the flow. By Newton's third law, this deflection of air away from the flow pulls the ball toward the flow. This is the Coanda effect.
First experiment is also Coanda effect. Whenever you have a jet of fluid flowing into a stationary fluid entrainment is gonna occur, so Bernoulli and the continuity equation cannot be applied here.
As the jet moves around the ball , static air under the ball gets entrained in the jet , creating a low pressure region until that jet hugs the convex underside of the ball due to a vacuum been created. The removal of air from that region causes atmospheric pressure to hold the ball up.
The purpose of the funnel is to create the pressure gradient that holds the ball up. The funnel prevents the atmospheric pressure from above from countering the atmospheric pressure from below that holds the ball up.
Thanks sir
So cool, He loves it you can tell.