Talk:Venturi effect

I removed the reference to flutes, as the simple venturi effect isn't (to my knowledge) the main effect in a flute. If that offends anyone, please feel free to add it back in with more explanation. zowie 03:15, 22 September 2005 (UTC)

Merge Venturi and Venturi effect

I think these two articles should be merged because they are both relatively short and both try to discuss how the principal and the device work. It should be easy to cover both in sub-sections of a single article if there is need to differentiate. -- Bovineone 02:19, 8 May 2006 (UTC)

I think they should be kept separate, they are similar but different topics. I think they are fine the way they are.

Is there a reason why the article says "Trevor Quillin is a sleepy man. " under the practical uses section?

I believe these are the same effect - I vote Merge. Nimur 14:40, 3 June 2006 (UTC)

In in?

"The Venturi effect is visible in:" I don't know how to edit these things, but it says "visible in" and then the list items start with "in" again. So, e.g., it says "visible in in large cities..." when you read it through. Otherwise, it seems to be a very nice article, merged or not.

Aortic Regurge

What did you mean by "... visible in the capillaries of the human circulatory system, where it indicates aortic regurgitation"? Why does AR cause a Venturi effect in capillaries? Is flow not so slow in capillaries that any such effect would be tiny? j.k.baillie 23rd July 2006

An everyday example of the venturi effect mixing air and liquid.

In the Experimental apparatus, Venturi Tubes it says

A venturi can also be used to mix a fluid with air. If a pump forces the fluid through a tube connected to a system consisting of a venturi to increase the water speed (the diameter decreases), a short piece of tube with a small hole in it, and last a venturi that decreases speed (so the pipe gets wider again), air will be sucked in through the small hole because of changes in pressure. At the end of the system, a mixture of fluid and air will appear.

and the general description of the effect it says

The Venturi effect is a special case of Bernoulli's principle, in the case of fluid or air flow through a tube or pipe with a constriction in it.

It seems to indicate the converse could happen too...?

So if Air under pressure is forced through a venturi tube it will be able to suck a liquid in through a small hole producing aerated liquid.

eg The Venturi effect is used when a coffee machine uses steam under pressure to draw up and froth milk.

202.138.204.101 01:44, 1 December 2006 (UTC)

That is also how carburetors work. The Lightning Stalker 07:55, 11 December 2006 (UTC)

"A simple way to demonstrate the Venturi effect is to squeeze and release a flexible hose that is carrying water. If the flow is strong enough, the constriction will remain even if the hose would normally spring back to its normal shape: the partial vacuum produced in the constriction is sufficient to keep the hose collapsed."

Has anybody ever tried this -- it sounds pretty strange to me. 68.11.47.74 02:40, 30 March 2007 (UTC)

How is this Venturi effect demonstrated in "the effective burning of human waste waste"?

What?

This page only explains what the Venturi effect is through a number of terms that are impossible to understand for a layman. These terms are linked to, but requiring people to read about those as well makes it harder to understand what this is all about.

Could someone please add a simple explanation of what this is about, too? Something like

"In Physics, the Venturi Effect refers to a situation where materials in gaseous or fluid form take on a lower pressure than those in the surrounding area. This happens because (...technical explanation...)"

I'm not sure whether this is accurate (which is why I didn't add it myself), but it would be tremendously helpful.

Another good example of this is demonstrated when you blow across the top of a straw and the drop in pressure pulls some of the liquid up the straw.

Static ports on aircraft like a Cessna 182 are simply holes in the sides of the fuselage. Air flows across these holes at the same speed as the aircraft's air speed, yet the pressure at the static port is the same as ambient, regardless of the aircraft speed (within the range of a Cessna 182). I don't see how the straw situation is any different, unless you're not blowing directly perpendicular to the opening in the straw. Jeffareid (talk) 06:54, 17 March 2008 (UTC)

That's because it's not. The static port measures the static pressure of the air, which is all the same unless some other mechanism converts some of the theoretical dynamic pressure (ie, "air flowing past") into a real static pressure, eg angling the opening forward. The explanation of venturis here seems to be so oversimplified as to be wrong. --Adx (talk) 06:22, 20 June 2010 (UTC)

No, I got this wrong, based on my errant ramblings on the Bernoulli principle talk page. Actually it sounds correct apart from the last sentence, but that's just luck. Now I understand: Flowing air itself doesn't "have" a lower pressure. A venturi does, because it forces the flow to constrict and expand within a solid pipe - the pressure gradients at each end mean the fast flowing section happens to have a lower pressure, just like an axial flow jet engine happens to have a higher pressure inside it. A static port measures the real (static) pressure with little error irrespective of the speed of gas flowing by. If the port is tilted, it begins to measure some of the imaginary (dynamic) pressure which is nothing more than a way to express the kinetic energy in the flow. --Adx (talk) 00:12, 21 June 2010 (UTC)

 —Preceding unsigned comment added by 192.122.250.250 (talk) 13:44, 4 October 2007 (UTC) 

The straw example is the coanda effect. The jet of air out of your mouth entrains the surrounding air. I think it's unrelated to the venturi effect. In my opinion, the Cessna example is fundamentally different because the airflow isn't a jet. Tinos (talk) 23:30, 1 May 2010 (UTC)

Um, air is a fluid.

"A venturi can also be used to mix a fluid with air." - Do you mean "mix a liquid with a gas"?

Air is a fluid. You can read about this on a website called "Wikipedia". —Preceding unsigned comment added by 99.231.124.188 (talk) 23:37, 23 February 2008 (UTC)

An item that should be added to practical uses

This is a tap water driven syphon for aquariums. Click on the link, then images, then go to page 3 to see diagram.

aquarium_syphon

It's not significantly different than the one patented in 1933. Click on image, and note figure 4.

washer_syphon

Is there a better name than syphon or siphon for these type of devices? I use the 1984 patented version for my aquarium, but recall an almost identical device I used to drain a basement back in the mid 1960's.

I've tried to find a diagram for one of these outside of patents, but I've had no luck in finding one. Jeffareid (talk) 01:40, 16 March 2008 (UTC)

Another practical use for venturis (usually multiple): as a flow measurement device, specifically a Gas Meter Prover as shown HERE: [1] —Preceding unsigned comment added by 204.73.77.18 (talk) 14:48, 27 May 2009 (UTC)

Passive solar design applications of the Venturi effect

Besides high winds experienced among tall buildings,it should be noted that the effect Venturi defined has been applied quite deliberately for thousands of years in vernacular architectures, and is a core principle in contemporary passive energy design in architecture. For an architectural vision of the applied Venturi effect that may have cross disciplinary value, see Hassan Fathy's work online at the unu website, or google anything along the lines of passive solar, passive energy, solar chimney,or cooling towers. From a passive strategies perspective, the Venturi effect appears as how Nature seeks equilibrium when a constant flow crosses a channel with a nonconstant shape,(a funnel or a constriction): there will be compensations in changes in velocity and therefore pressure. I also see applied in (Fathys descriptions)the strategy of simply connecting extremes (hot to cold, or high pressure to low pressure, or high velocity to low velocity) to force accelerated airflow to then capture in evaporative mechanisms. Someone verify please, but I really think, to aid in definition, just this alone does not involve the Venturi Effect when there isnt an actual constriction in the channel: that is just a more general harnessing of the principle of equistasis. In traditional passive designs, there usually is a constriction added (one side has larger openings than the other,or a flume or chimney is built) and when that dissimilarity in opening sizes occur, it is said that the Venturi effect is amplifying the system. In that, then, it appears the Venturi Effect is the effect of a physical funnel.Sparrow7 (talk) 09:21, 14 June 2008 (UTC)Sparrow7

Venturi effect to tackle back pressure in rotary discharge valve. I have a problem which I think I can use the venturi effect to overcome it. The pneumatic conveying pipe that sweeps away the discharge the rotary valve discharge of light materials (husks and dust) above it does however create a back pressure that prevents the light material from dropping down to the pneumatic valve below it. In the worst situation, it actually creates an upward draft that force back the light materials. I think I can constrict the airflow of the pneumatic pipe at the front of the point of rotary valve diccharge discharge so that the vacuum or reduce pressure created will be able to suck back the light material, or at least reduce the back pressure. Can anyone confirm this? —Preceding unsigned comment added by Xiaotingchum (talk • contribs) 09:57, 3 September 2008 (UTC)

Choked flow

Some extracts:

Before 26th January 2009:

The limiting case of the Venturi effect is choked flow, in which a constriction in a pipe or channel limits the mass flow rate through the channel, because the local pressure in the constriction cannot drop below the vapour pressure in a liquid. Limiting ventury effect is also associated with choked flow of compressible fluid through a convergent-divergent nozzle. Here the choked flow is a limiting venturi condition which occurs when the mass flow rate will not increase with a further decrease in the downstream pressure environment.

From 26th January 2009 (Version by Cousin Merle):

The limiting case of the Venturi effect is when a fluid reaches the state of choked flow, where the fluid velocity approaches the local speed of sound. In choked flow the mass flow rate will not increase with a further decrease in the downstream pressure environment.

However, mass flow rate for a compressible fluid can increase with increased upstream pressure, which will increase the density of the fluid through the constriction (though the velocity will remain constant). This is the principle of operation of a convergent-divergent nozzle.

It looks to me as though the later version is better in some ways but leaves out something that looks likely to be correct and important.

Man with two legs (talk) 13:44, 26 January 2009 (UTC)

Hi Man. Your version is a significant improvement. The original comment about cannot drop below the vapour pressure in a liquid is nonsense. Choking occurs with gases as well as liquids. I suggest you delete the word environment from the expression downstream pressure environment. It is the pressure that is relevant. Dolphin51 (talk) 22:29, 26 January 2009 (UTC)

Actually, they are not my edits. But I am not at all clear that cannot drop below the vapour pressure in a liquid is nonsense. In a gas, the corresponding limit would presumably be vacuum. It seems plausible to me that the speed of sound is not the only thing limiting flow. Man with two legs (talk) 13:18, 27 January 2009 (UTC)

Venturi formula? (closed outlet)

Hi I've been struggling to find a formula to compute the air mass flow through the throat of a closed outlet venturi tube. What I have is a reciprocating single cylinder air compressor that has a venturi tube at it's outlet with the outlet of the venturi tube flowing into a closed tube with a constant volume. Overall I'd like to achieve a plot of the mass air flow through the throat area of the venturi with respect to crank angle of one cycle of the compressor. The beginning pressure throughout everything would be atmospheric.

Thanks for your time & any replies or suggestions is appreciated,

-nick —Preceding unsigned comment added by Nar456 (talk • contribs) 04:08, 3 February 2009 (UTC)

the pulsus birefringens is not due to the venturi effect as said in the main article. the second pulse felt is due to the reflected primary pressure wave from the peripheries which returns to the palpating fingers - consistent with the observation that this pulse is better felt in the peripheries rather than the carotids. the pressure in the aorta is not any lower at any time because there is greater flow in it. the 'fall' is only in relation to the higher pressure that the heart is generating to put accross a higher volume of blood.Hgoel (talk) 16:44, 11 February 2009 (UTC)hgoel

A Question on Double Venturi

Consider a venturi (X1) followed by another pressure reducing system (X2) (Not necessarily another venturi)

Given that if you apply 2bar pressure at the inlet of this 2nd pressure reducing system (X2) we get 1.24Bar pressure at the end of it.

Then what should be the pressure applied at the start of system (X1) to get the 2bar pressure at the start of (X2) if these two systems are connected in series in the sequence X1---X2.

Reply on pashu4you@yahoo.co.in

Why is it called the 'Venturi' effect

the article doesn't mention why it is called the Venturi effect. —Preceding unsigned comment added by Fintim (talk • contribs) 13:57, 9 October 2009 (UTC)

Examples - Air flows over the top of an aircraft wing.

Air flows over the top of an aircraft wing. The stable air around the plane and the foil above the cord line of the wing create a venturi around the wind going directly over the wing. Hence creating a low preasure on top of the wing lifting it upward.

This is not a good example of venturi effect. From this Nasa article: a wing section isn't really half a Venturi nozzle. nasa_airplane_bernnew.html Jeffareid (talk) 01:28, 28 March 2010 (UTC)

I agree with Jeff. In fact, a lot of the so-called examples of venturi effect listed in this article are not really examples at all, or at least not good examples. I recommend a thorough review of all the current examples to remove those that don't belong here. Is there any opposition to such a review? Dolphin51 (talk) 07:03, 28 March 2010 (UTC)

I agree with Dolphin51's proposal to review the article to weed out unwanted "examples" of venturi effect. Salih (talk) 07:22, 28 March 2010 (UTC)

The wing reference is now removed. I leave it to the experts here to remove the other invalid examples. Jeffareid (talk) 10:13, 29 March 2010 (UTC)

The article still contains this statement implying that Ventri/Bernoulli is related to wing behaviour: ″The Bernoulli Principle and its corollary, the Venturi effect, are essential to aerodynamic as well as hydrodynamic design concepts. Airfoil and hydrofoil designs to lift and steer air and water vessels (airplanes, ships and submarines) are derived from applications of the Bernoulli Principle and the Venturi effect″ - Per the above discussion, I think this should be removed. Infact, I think the entire block of text at the bottom of examples should go - it doesn't belong in examples, and the rest of the article has all the explanation necessary already. Please let me know if there are any concerns or objections.SteveSmith98 (talk) 13:13, 3 March 2018 (UTC)

Pressure after constriction

I would like to propose clarifying the article but want to double check my thinking before going ahead.

It seems to me that the pressure and velocity in the widened pipe downstream of the constriction will be the same as before the constriction (neglecting friction losses and vertical drop). This would be the reason why, even if the pipe ultimately discharges at atmospheric pressure, a venturi tube is able to produce a partial vacuum. The pressure in the constriction is not only lower than the pressure immediately upstream as emphasized in the article, but also immediately downstream.

I think it's important to clarify this, as it's easy to make the mistake of assuming that once the pressure is "lost" in the constriction, it is never regained. Under that misapprehension, it's not clear how the pressure in the constriction can ever be lower than atmospheric.

If someone could confirm the above, I'll go ahead and change it (and possibly the diagram). Frustratingly, text books and other sites I have consulted also neglect this point.--Russell E (talk) 02:19, 5 May 2010 (UTC)

I agree that as the fluid passes the constriction and enters the region of increasing pipe diameter its speed decreases and, in accordance with Bernoulli's principle, its pressure increases. If the diameter of the pipe downstream of the constriction is the same as the diameter upstream then, neglecting viscous forces and changes in elevation, the speeds and pressures upstream and downstream will be the same.

In reality there will be viscous forces so downstream of the constriction the pressure will progressively reduce to atmospheric pressure at the outlet of the pipe. But if the pipe is very long this effect will be insignificant immediately downstream of the constriction. Dolphin (t) 03:36, 5 May 2010 (UTC)

Thumb over hose is not a correct example and is misleading - I think

The inclusion of 'or a thumb on a garden hose' in the opening sentence is not correct. In the case of a hosepipe the water is exiting to atmosphere. Putting a thumb over the end of a hose simply restricts the flow rate and a slowed flow rate causes reduced pressure losses by means of friction along the hose. A thumb over a hose is increasing the pressure of the water arriving at the end of the hose and thus the exit velocity goes up thanks to the pressure. The water does not speed up due to it having to pass the restriction of the thumb and then fill the hose beyond as it would with a squashed portion of hose part way along. --Narrowneck (talk) 20:11, 21 November 2011 (UTC)

I agree so I removed the offending words. See my diff. Dolphin (t) 02:14, 22 November 2011 (UTC)

what happens if you blow backwards through a venturi meter,

What happens if you blow backwards through this apparatus? Will the higher flow side still have less pressure? — Preceding unsigned comment added by 64.146.180.237 (talk) 04:22, 5 February 2013 (UTC)

Applicability of Bernoulli's equation in the measuring tube

I wonder about the applicability of Bernoulli's equation to this problem: The argumentation is that the static pressure in the region with the fast flow is reduced and therefore the water in a measuring tube rises to a lower value. However, in the measuring tube v=0. So if Bernoulli's equation was valid, the full static pressure should be recovered. So why is only the static pressure transmitted into the tube (and Bernoulli's equation not valid)? --46.128.146.13 (talk) 20:05, 8 March 2015 (UTC)

The flow is not through the measuring tube, so there is no reason to apply Bernoulli's principle there. The measuring tube at the constriction is measuring the pressure in the fluid flowing through the constriction. That flow is faster, so the pressure at that point is less, which is demonstrated by the lower fluid level in the measuring tube. Apuldram (talk) 16:42, 12 August 2017 (UTC)

Clarinet?

I tried to find out where the Clarinet claim comes from ("The barrel of the modern-day clarinet, which uses a reverse taper to speed the air down the tube, enabling better tone, response and intonation"), and found this. Seems like the list of applications on Wikipedia was copied word-for-word from that book, or the other way around. However, I couldn't find any other source talking about it. All I could find was this article which claimed that the effect is used for the clarinet tone holes, not for the tube itself. Esn (talk) 08:35, 2 January 2017 (UTC)

Squeezing a Hose?

The examples section contains this statement:

A simple way to demonstrate the Venturi effect is to squeeze and release a flexible hose in which fluid is flowing: the partial vacuum produced in the constriction is sufficient to keep the hose collapsed.

It's uncited, and also somewhat laughable. I've never witnessed this myself, I've ask many others now none of whom have ever seen this, I've searched for online demonstrations and cannot find any. When I go squeeze a hose and let go, the hose quickly re-expands, which is of course obvious. This statement appears to be a copy/paste from a book called "Archimedes to Hawking: Laws of Science and the Great Minds Behind Them" by Cliff Pickover, who is not an expert in this field. The full quote goes:

I have frequently seen the Venturi effect in action when squeezing a flexible hose through which water flows. If the flow is sufficiently strong, the constriction I put in the hose remains in the hose, even when I remove my hand, because the partial vacuum produced in the constriction is sufficient to keep the hose collapsed.

...The very next paragraph in his book then restates the venturi-wing-myth:

The fact that pressure falls with increasing velocity is exploited by an airplane wing, which is designed to create an area of fast flowing air on its upper surface. The pressure near this area is lower; thus, the wing tends to be pulled upward.

My point here is: This source has no credibility. Without a better source, the hose-squeeze-myth should be removed.

Does anyone have any concerns? SteveSmith98 (talk) 12:39, 15 March 2018 (UTC)

I agree that the anecdote about a flexible hose retaining its shape when squeezed should be either attributed to a source, or erased. (I have never observed this phenomenon with hoses.)

The paragraph you describe as "the next paragraph ... restates the venturi-wing myth." I don't see any great problem with this statement. There are things that have been written, overstating the nexus between the venturi and the wing, but I don't see that this is one of them - it doesn't even contain the word "venturi". What aspect of the statement do you regard as myth? Dolphin (t) 13:01, 15 March 2018 (UTC)

Ok, I'll remove the bulging hose.

The paragraph above, that I disagree with, isn't (as far as I noticed) in the wikipedia article so discussing it further is academic.The paragraph doesn't contain the word "venturi" but is in a section about the "venturi effect" and makes a general statement that "pressure falls with increasing velocity" which is an overgeneralization and ignores all the applicability restrictions of Bernoulli, especially same-streamline-comparison aspect of it.SteveSmith98 (talk) 11:59, 19 March 2018 (UTC)

References

Explanation/definition of equation

In the equation stating the pressure differential between V1 and V2 are both those units squared within the equation? That is how it would appear from the way it's written ... or am I simply missing something. Thank you.

Tapalmer99 (talk) 12:51, 13 May 2018 (UTC)

Tapalmer99 (talk) 12:51, 13 May 2018 (UTC)

Add Mass flow and subscripts v and m

Following the flow equations under [orifice plate] add "v" subscript to show Qv as volume flow. Then recommend adding an equation for mass flow Qm with subscript m. https://en.wikipedia.org/wiki/Orifice_plate#Expansibility_factor DLH (talk) 20:35, 6 November 2019 (UTC)

Capitalisation?

Should Venturi be capitalised? How far should we take this? COMMONNAME never capitalises it, in describing the device. Should "Venturi Effect" be capitalised? As a proper name, or as a phrase (i.e. one or two words capitalised?) Andy Dingley (talk) 17:01, 3 December 2019 (UTC)