Bernuolli's principle


#1

Your show is so great. We listen every week as often as possible. Even on Sundays!

My friend(common law husband) and I have come to a stalemate. I suggested we ask you about this question… so whatever you both think I will live by.

Yesterday as many times before I attempted to vacuum our small 800sq.ft. house.

I decided to use Dave’s little dinosaur canister style vacuum cleaner. He changed the bag for me and went to do something else. I started to vacuum and he called me all kinds of names to get me to lift the canister(which has wheels, BTW)off the ground while vacuuming. He keeps insisting because of Bernoulli’s Prinicple I need to carry it around, or else he has to vacuum.

This meathead will not let me do anything. He even cooks most of the meals.

His way is the only way!

Yikes, I’ve never been called the names he calls me.

Anyway, I suppose he should have written this but we are wondering what the engineering reason is for canisters to have wheels, and are they meant to be hovered around(instead of Hoovered-my joke) by hand or is it OK to leave the canister on it’s wheels to pull behind me when I vacuum??? Is all the “dirt” going into the atmosphere and polluting our air?

I’m leaving home if we don’t hear from you!

Seriously! Please let us know one way or the other…


#2

Tom & Ray don’t visit here, only us lesser beings.

The reason the vacuum is on wheels has nothing to do with Bernoulli. It has to do with friction. It’s so you can glide the vacuum along on wheels rather than drag it along as you vacuum.

Bernolli’s laws have to do with fluid dynamics and energy conservation. They apply to the vacuum’s insides, not the wheels. Simply stated, at a constant flow rate, the sum of the potential energy and kinetic energy per unit volume of fluid and lateral wall pressure at one point in the system will equal the sum of these factors anywhere in the system.

I’m wondering…since he doesn’t like the way you vacuum, why not just let HIM do it?


#3

The dust and dirt get trapped in the bag regardless of how it’s moved around. Maybe he doesn’t like the fact that it leaves indentations on the carpet.

TSM has the answer: Dave should do 100% of the vacuuming (and anything else that he nitpicks about.)


#4

OMG, LOL. Thank you for the laugh I just had. Sometimes a girl just wants to vacuum. My Mom used to put me to sleep with the vacuum cleaner. Somehow it’s soothing. Like washing dishes…
OK, what a great answer. I will try to read it again so I can understand Bernouilli’s principle better! Another thing is it might be a while before he gets to it. (:


#5

T&R don’t visit here, but they’re no ‘Bernoulli’ experts, anyway (neither scientists nor engineers are they). I can imagine no reason to believe your S.O.'s claim. Picking up the vacuum would make no difference in how it works. The wheels are there to let it roll along with you as you clean. “Bernoulli” has nothing to do with it.


#6

BP explains how pressure changes when the flow rate of a fluid changes. This also explains why airplane wings are able to generate lift. I don’t see how it affects the efficiency of your vacuum though. I agree with others, let him do the chore from now on. Hope that helps.


#7

The OP’s common-law husband, Dave, illustrates the old maxim that, “a little learning is a dangerous thing”. Apparently he learned a little bit about the Bernoulli Principle at one time, and his understanding of it is so muddled that he believes simple friction between carpet and vacuum cleaner somehow has something to do with the suction power of the vacuum cleaner.

In addition to his highly flawed scientific knowledge, he is apparently also a control freak of the first order.
Yes, he should do all of the vacuuming if he finds the OP’s methodology so inferior, but the OP has to go beyond that situation in order to analyze the entire quality of their relationship. I refer to, “His way is the only way”, and to “I’ve never been called the names he calls me”.

The OP should realize that she has worth and that she should not allow this type of abuse to continue.
Yes, I know that she was not directly asking for relationship advice, but this abusive relationship is just too obvious for me to not comment on it.

The OP may have been kidding when she stated, “I’m leaving home if we don’t hear from you”, but many a true thing is said in jest. I think she is aware that she is being verbally and psychologically abused, and perhaps she is just using this scenario for some reality testing regarding her abusive relationship.


#8

WOW! Oh no now it’s venturi prinicple??


#9

So that’s what he’s saying? I guess the answer’s the same, being on the floor has no effect on the vacuum, it was DESIGNED to work on the floor.


#10

OK, clarification, the exhaust exiting the vacuum creates a low pressure that lifts dust into the air. We are stirring up dirt when we vacuum. Sorry. This is what he was referring to and maybe i didn’t explain it correctly. He is willing to vacuum, and he admits to possible OCD.
Thanks everybody. Spoilers for Vacuum cleaners? Hmmm.


#11

Venturi studied Bernoulli in detail…his studies concluded that there must be a way to ?re-establish? prerestriction pressure…There must be a way to ?re-establish? velocity At the point of restriction where lateral wall pressure is lower, then fluids will move from the outside to the inside, at the point of restriction, also known as the ?jet.?
1st–distal to the restriction, he ?opened? the
restriction at an angle of no greater than 15o.
2nd–as a result, prerestriction pressure was almost achieved, as was prerestriction velocity…
3rd–he inserted a tube at the point of restriction–as he surmised, fluids DID move from the outside to the inside at the point of restriction…from high to low pressure…technically, this is the ?jet? principle…

In essence, what he realized when studying Bernoullli’s finding that as fluid passed a restriction its velocity increased, central stream pressure increased, and lateral wall pressure decreased, and this meant that past the restriction the pressure against the wall would be low. He realized that if you were to put a tube into the side of the wall past the restriction with pressure at the orafice no less than the uptream pressure, as fluid flowed past the restriction the pressure in the tube would cause fluid to move into the stream. That became the basis for carburators. And I suppose it could be argued, to some vacuum designs.

You seem much more intuitively scientific than he. I’d recommend strongly that you buy a few books on these subjects, but I have a feeling that the poor guy will end up struggling to keep from full loss of self-esteem.

Methinks your poor fella has bumped up against a wee bit of knowledge without the basics to properly understand it, misconstrued it, and is trying to apply it to your vacuum. Incorrectly.

Perhaps he should read this thread. Perhaps it’ll open his eyes.


#12

OK, what happens to the accelerated air when it departs the vacuum cleaner? Does it create a low pressure flow that lifts dirt or dust into the air? This is incredible, I’m learning so much. I will get some books. By definition on wiki how a vacuum cleaner works there is a “jet” pressure created and some dirt might be airborne.


#13

You were posting at the same time I was. I was unaware of the real issue, the dust. Simply point out that you’re vacuuming forward and the floor behind you is clean.


#14

OK, we’re getting closer. abuse may have been worth this discussion. “Saltation” is the key phrase it looks like. Sorry, guess I’m not the scientist after all but I’ve enjoyed the heck out of this discussion.
“A recent study finds that the initial saltation of sand particles induces a static electric field by friction. Saltating sand acquires a negative charge relative to the ground which in turn loosens more sand particles which then begin saltating. This process has been found to double the number of particles predicted by previous theory.[2]”

Therefore, this may be what is occurring at the back of the vaccuum cleaner. Maybe we can fix that darn hole in the gulf after all!!!


#15

I think it’s important to note that practical applications of these principles are generally applied to things like airplanes. In other words, we’re talking about very high velocity fluidic flows here. By the time the air stream gets through the bag, all the dirt in the bag, and the vacuum cleaner, it’s not coming out very fast at all, and so any low pressure that it creates due to its passage is going to be so exceedingly low that only ultrafine dust particles would be effected - - and you just finished vacuuming those up.

Far more apparent would be the effect of the moving airmass striking the dust itself - - i.e. rather than low pressure causing dust to rise, the air stream would knock dust around, like you do when you blow on a pea through a straw.

And again, because of the velocity of the air exiting the vacuum, only ultrafine dust would get bounced about, and you’ve sucked all that dust up already. Any dirt remaining in the carpet after the suction of the vacuum cleaner goes over it, is either sticky enough, large enough, or positioned just right, so that it gets trapped by the carpet fibers and won’t fly up anyway. Put another way, you just went over it with a high-suction vacuum, and he thinks a slow-speed warm air flow is going to suck up what the vacuum couldn’t?

Is he aware that walking across the carpet kicks up far more dirt, mites, and other debris than a low-speed airflow? Perhaps in the interest of maintaining the clean house he so desires, you should kick him out so he stops walking on the floor :wink:


#16

OMG, I feel so much better.


#17

Saltation he says?
sal?ta?tion? ?/s?l?te???n/ Show Spelled[sal-tey-shuhn] Show IPA
?noun

  1. a dancing, hopping, or leaping movement.
  2. an abrupt movement or transition.
  3. Geology . intermittent, leaping movement of particles of sand or gravel, as from the force of wind or running water.
  4. Biology .
    a. a sudden discontinuity in a line of descent.
    b. a mutation.

So do you have dancing sand on your floors? Mutations (no disrespect to the little ones)?

Unless you have a hole in bag, there should be nothing significant happening at the back of the vacuum cleaner. Vacuum cleaners are designed to disperse the air at exit, designed to significantly reduce the fluid pressure by dissipating it such that they do not blow dust everywhere.

But your common law hubby is being OCD. There’s not way I can see to get past this other than to let him do the vacuuming.


#18

Welll, he did take me to Car Henge and California for the first time, and he built the house, so I guess he stays. Yep, he will do the vacuuming! Definitely. This changes everything.


#19

Unfortunately, it does not change the reality of his verbal and psychological abuse of you, and that is very sad. Hopefully, one day you will realize what he is doing to you and to your self esteem.


#20

I assemble computers at home and putting the large ones on wheels both allows for portability and air intake at the bottom, I also use water to cool them, while they are running (if the have wheels why don’t they roll away insted of run?).