Re: [Phys-L] BP or CE?

[John Denker <jsd@av8n.com>]

On 12/22/2014 03:50 PM, Anthony Lapinski wrote:

> What about these, which I sort of put into categories? Which effect
> dominates?

> perfume atomizer 
  Probably Bernoulli (dispensing); possibly also Coanda (atomizing)

> blow between two hanging cans
  I'd have to see the details.  Could easily be done
  in such a way that Coanda dominates, but that's not
  the only possibility.

> shape of plane wing
  Bernoulli can be applied, but is often very wrongly
  applied.  And you have to do a fair bit of work to
  figure out the velocity field, and you can't begin
  to apply Bernoulli until you've done that.

  Also note that there are easier ways (Kutta Zhukovsky)
  of figuring out the lift without bothering with Bernoulli.

> spin on baseball pitch
  Magnus effect.  In some ways simpler, in some ways more
  complicated than a wing.  See previous item.

> dimples on golf ball
  Dimples affect drag by re-energizing the boundary layer.
  Very tricky.  Bernoulli applies to part of the problem, 
  and not other parts.

> Wiffle ball
  No comment.  Never looked into it.

> blow over paper
  Usually Coanda

> boomerang
  Mostly just a wing, plus some angular momentum / precession

> vacuum cleaner and beach ball
  Usually mostly Coanda

> vertical Dyson fan and balloon
  Haven't seen that one; possibly same as above.

> air blower and toilet paper roll
  Haven't seen that one.

> toy blow ball pipe
  Haven't seen that one.