Teapot effect

Last updated October 07, 2024

Diagram of tea running down the spout of a teapot Teekanneneffekt.svg — Diagram of tea running down the spout of a teapot

The teapot effect, also known as dribbling, is a fluid dynamics phenomenon that occurs when a liquid being poured from a container runs down the spout or the body of the vessel instead of flowing out in an arc.^[1]

Markus Reiner coined the term "teapot effect" in 1956 to describe the tendency of liquid to dribble down the side of a vessel while pouring.^[2]^[3] Reiner received his PhD at TU Wien in 1913 and made significant contributions to the development of the study of flow behavior known as rheology.^[1] Reiner believed the teapot effect could be explained by Bernoulli's principle, which states that an increase in the speed of a fluid is always accompanied by a decrease in its pressure. When tea is poured from a teapot, the liquid's speed increases as it flows through the narrowing spout. This decrease in pressure was what Reiner thought to cause the liquid to dribble down the side of the pot.^[4]^[3] However, a 2021 study found the primary cause of the phenomenon to be an interaction of inertia and capillary forces.^[3] The study found that the smaller the angle between the container wall and the liquid surface, the more the teapot effect is slowed down.^[5]

Research

Around 1950, researchers from the Technion Institute in Haifa (Israel) and from New York University tried to explain this effect scientifically.^[6] In fact, there are two phenomena that contribute to this effect: on the one hand, the Bernoulli equation is used to explain it, on the other hand, the adhesion between the liquid and the spout material is also important.

According to the Bernoulli explanation, the liquid is pressed against the inner edge of the spout when pouring out, because the pressure conditions at the end, the edge, change significantly; the surrounding air pressure pushes the liquid towards the spout. With the help of a suitable pot geometry (or a sufficiently high pouring speed) it can be avoided that the liquid reaches the spout and thus triggers the teapot effect. Laws of hydrodynamics (flow theory) describe this situation, the relevant ones are explained in the following sections.

Since adhesion also plays a role, the material of the spout or the type of liquid (water, alcohol or oil, for example) is also relevant for the occurrence of the teapot effect.

The Coandă effect is sometimes mentioned in this context,^[7]^[8]^[9]^[10] but it is rarely cited in the scientific literature^[8] and is therefore not precisely defined. Often several different phenomena seem to be mixed up in this one.

Continuity equation

In hydrodynamics, the behavior of flowing liquids is illustrated by flow lines. They run in the same direction as the flow itself. If the outflowing liquid hits an edge, the flow is compressed into a smaller cross-section. It only does not break off if the flow rate of liquid particles remains constant, regardless of where an imaginary cross section (perpendicular to the flow) is located. So the same amount of mass must flow in through one cross-sectional area as flows out of another. One can now conclude from this, but also observe in reality, that the flow accelerates at bottlenecks and the streamlines are bundled. This situation describes the continuity equation for non-turbulent flows.

Bernoulli equation

But what happens to the pressure conditions in the flow if you change the flow speed? The scientist Daniel Bernoulli dealt with this question as early as the beginning of the 18th century. Based on the considerations of continuity mentioned above, and incorporating the conservation of energy, he linked the two quantities of pressure and speed. The core statement of the Bernoulli equation is that the pressure in a liquid falls where the velocity increases (and vice versa): Flow according to Bernoulli and Venturi.

Impact

The pressure in the flow is reduced at the edge of the can spout. However, since the air pressure on the outside of the flow is the same everywhere, there is a pressure difference that pushes the liquid to the edge. Depending on the materials used, the outside of the spout is now wetted during the flow process. At this point, additional interfacial forces occur : the liquid runs as a narrow trickle along the spout and can until it detaches from the underside.

The unwanted teapot effect only occurs when pouring slowly and carefully.^[6] In fast pouring, the liquid flows out of the spout in an arc without dripping, so it is given a relatively high velocity with which the liquid moves away from the edge (see Torricelli outflow velocity). The pressure difference resulting from the Bernoulli equation is then not sufficient to influence the flow to such an extent that the liquid is pushed around the edge of the spout.

Since the flow conditions can be described mathematically, a critical outflow velocity is also defined. If it falls below when pouring, the liquid flows down the pot; it drips. Theoretically, this speed could be precisely calculated for a specific can geometry, the current air pressure and the fill level of the can, the spout material, the viscosity of the liquid and the pouring angle. Since, apart from the fill level, most of the influencing variables cannot be changed (at least not sufficiently precisely in practice), the only way to avoid the teapot effect is usually to choose a suitable geometry for the pot.

Another phenomenon is the reduction in air pressure between the spout and the jet of liquid due to the entrainment of gas molecules (one-sided water jet pumping effect), so that the air pressure on the opposite side would push the jet of liquid to the spout side. However, under the conditions usually prevailing when pouring tea, this effect will hardly appear.

Consequence

A good jug should, regardless of fashion, have a spout with a tear-off edge (i.e. no rounded edge) to make it more difficult to run around the edge. More importantly, the spout should first lead upwards (regardless of the position in which the jug is held). As a result, the liquid would be forced to flow upwards after going around the edge of the spout when pouring, but this is prevented by gravity. The flow can thus resist wetting even when pouring slowly and the liquid does not reach the downwardly inclined part of the spout and the body of the jug.

The image on the right^{[ clarification needed ]} shows three vessels with poor pouring behavior. Even in a horizontal position, that is standing on the table, the bottom edges of the spouts do not point upwards.^[6] Behind are four vessels with good flow characteristics resulting from well formed tips. Here, the liquid rises at the lower edge of the spout at an angle of less than 45°.^[6] In part, this only becomes apparent when one considers the normal maximum fill level: the glass carafe on the far right, for example, appears at first glance to be a poor pourer because of its slender neck. However, since such vessels are generally filled at most up to the edge of the round part of the flask, an advantageous rise at the neck is then obtained when pouring horizontally.Upward angle for the liquid when pouring. With the two lower jugs on the right, the high position of the spout (above the maximum filling level) means that the vessel has to be tilted quite a bit before pouring, so that the spout can also be pushed up directly after the edge (against gravity). indicates.

To avoid the teapot effect, the pot can be filled less, so that a larger tilting angle is necessary from the start. However, the effect or the ideal filling level again depends on the can geometry.

The teapot effect does not occur with bottles because the slender neck of the bottle always points upwards when pouring; the current would therefore have to "flow uphill" a long way.^[6] Bottle-like containers are therefore often used for liquid chemicals in the laboratory. Certain materials are also used there to prevent dripping, for example glass, which can be easily shaped or even ground to create the sharpest possible edges, or Teflon, for example, which reduces the adhesion effect described above.

Drip catcher

Related Research Articles

When a fluid flows around an object, the fluid exerts a force on the object. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it is defined to act perpendicular to the flow and therefore can act in any direction.

Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the pressure relative to the ambient pressure.

<span class="mw-page-title-main">Bernoulli's principle</span> Principle relating to fluid dynamics

Bernoulli's principle is a key concept in fluid dynamics that relates pressure, speed and height. Bernoulli's principle states that an increase in the speed of a parcel of fluid occurs simultaneously with a decrease in either the pressure or the height above a datum. The principle is named after the Swiss mathematician and physicist Daniel Bernoulli, who published it in his book Hydrodynamica in 1738. Although Bernoulli deduced that pressure decreases when the flow speed increases, it was Leonhard Euler in 1752 who derived Bernoulli's equation in its usual form.

In fluid dynamics, a vortex is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in the wake of a boat, and the winds surrounding a tropical cyclone, tornado or dust devil.

<span class="mw-page-title-main">Henri Coandă</span> Romanian inventor (1886–1972)

Henri Marie Coandă was a Romanian inventor, aerodynamics pioneer, and builder of an experimental aircraft, the Coandă-1910, which never flew. He invented a great number of devices, designed a "flying saucer" and discovered the Coandă effect of fluid dynamics.

<span class="mw-page-title-main">Coandă effect</span> Tendency of a fluid jet to stay attached to a convex surface

The Coandă effect is the tendency of a fluid jet to stay attached to a convex surface. Merriam-Webster describes it as "the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to entrain fluid from the surroundings so that a region of lower pressure develops."

A teapot is a vessel used for steeping tea leaves or a herbal mix in boiling or near-boiling water, and for serving the resulting infusion which is called tea. It is one of the core components of teaware.

Capillary action is the process of a liquid flowing in a narrow space in opposition to or at least without the assistance of any external forces like gravity.

A coffee filter is a filter used for various coffee brewing methods including but not limited to drip coffee filtering. Filters made of paper (disposable), cloth (reusable), or plastic, metal or porcelain (permanent) are used. Paper and cloth filters require the use of some kind of filter holder, whereas filters made out of other materials may present an integral part of the holder or not, depending on construction. The filter allows the liquid coffee to flow through, but traps the coffee grounds.

The Magnus effect is a phenomenon that occurs when a spinning object is moving through a fluid. A lift force acts on the spinning object and its path may be deflected in a manner not present when it is not spinning. The strength and direction of the Magnus effect is dependent on the speed and direction the of rotation of the object.

The shower-curtain effect in physics describes the phenomenon of a shower curtain being blown inward when a shower is running. The problem of identifying the cause of this effect has been featured in Scientific American magazine, with several theories given to explain the phenomenon but no definite conclusion.

<span class="mw-page-title-main">Water hammer</span> Pressure surge when a fluid is forced to stop or change direction suddenly

Hydraulic shock is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly: a momentum change. It is usually observed in a liquid but gases can also be affected. This phenomenon commonly occurs when a valve closes suddenly at an end of a pipeline system and a pressure wave propagates in the pipe.

<span class="mw-page-title-main">Siphon</span> Device involving the flow of liquids through tubes

A siphon is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in an inverted "U" shape, which causes a liquid to flow upward, above the surface of a reservoir, with no pump, but powered by the fall of the liquid as it flows down the tube under the pull of gravity, then discharging at a level lower than the surface of the reservoir from which it came.

A kettle, sometimes called a tea kettle or teakettle, is a device specialized for boiling water, commonly with a lid, spout, and handle. There are two main types: the stovetop kettle, which uses heat from a hob, and the electric kettle, which is a small kitchen appliance with an internal heating element.

Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum.

<span class="mw-page-title-main">Critical point (thermodynamics)</span> Temperature and pressure point where phase boundaries disappear

In thermodynamics, a critical point is the end point of a phase equilibrium curve. One example is the liquid–vapor critical point, the end point of the pressure–temperature curve that designates conditions under which a liquid and its vapor can coexist. At higher temperatures, the gas comes into a supercritical phase, and so cannot be liquefied by pressure alone. At the critical point, defined by a critical temperatureT_c and a critical pressurep_c, phase boundaries vanish. Other examples include the liquid–liquid critical points in mixtures, and the ferromagnet–paramagnet transition in the absence of an external magnetic field.

A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift is substantially larger than the drag. If the fluid is a gas, the foil is called an airfoil or aerofoil, and if the fluid is water the foil is called a hydrofoil.

<span class="mw-page-title-main">Iodine heptafluoride</span> Chemical compound

Iodine heptafluoride is an interhalogen compound with the chemical formula IF₇. It has an unusual pentagonal bipyramidal structure, with D_5h symmetry, as predicted by VSEPR theory. The molecule can undergo a pseudorotational rearrangement called the Bartell mechanism, which is like the Berry mechanism but for a heptacoordinated system.

<span class="mw-page-title-main">Markus Reiner</span> Israeli scientist and engineer

Markus Reiner was an Israeli scientist and a major figure in rheology.

The Gibbs–Thomson effect, in common physics usage, refers to variations in vapor pressure or chemical potential across a curved surface or interface. The existence of a positive interfacial energy will increase the energy required to form small particles with high curvature, and these particles will exhibit an increased vapor pressure. See Ostwald–Freundlich equation. More specifically, the Gibbs–Thomson effect refers to the observation that small crystals are in equilibrium with their liquid melt at a lower temperature than large crystals. In cases of confined geometry, such as liquids contained within porous media, this leads to a depression in the freezing point / melting point that is inversely proportional to the pore size, as given by the Gibbs–Thomson equation.

References

1 2 "Why Teapots Always Drip – Scientists Finally Explain the "Teapot Effect"". SciTechDaily . Vienna University of Technology. 2022-01-09. Archived from the original on 2023-01-28. Retrieved 2022-07-02.
↑ Reiner, Markus (September 1956). "The teapot effect...a problem". Physics Today . 9 (9). American Institute of Physics: 16. doi:10.1063/1.3060089 . Retrieved 2023-01-28. (1 page)
1 2 3 Ouellette, Jennifer (2021-11-10). "Dribble, dribble, dribble — Physicists say they've finally solved the teapot effect—for real this time - Is due to interplay of inertial viscous capillary forces—but gravity's less relevant". Ars Technica . Archived from the original on 2023-01-28. Retrieved 2022-07-02.
↑ Keller, Joseph Bishop (1957). "Teapot Effect" (PDF). Journal of Applied Physics . 28 (8): 859–864. Bibcode:1957JAP....28..859K. doi:10.1063/1.1722875. Archived (PDF) from the original on 2022-03-13. Retrieved 2023-01-28. (6 pages)
↑ Scheichl, Bernhard; Bowles, Robert I.; Pasias, Georgios (2021-11-10) [2021-09-08, 2021-07-01, 2021-05-17, 2020-11-09]. "Developed liquid film passing a smoothed and wedge-shaped trailing edge: small-scale analysis and the 'teapot effect' at large Reynolds numbers". Journal of Fluid Mechanics . 926. Cambridge University Press: A25-1–A25-40, S1–S12. arXiv: 2011.12168 . Bibcode:2021JFM...926A..25S. doi:10.1017/jfm.2021.612. ISSN 0022-1120. S2CID 235444365. Archived from the original on 2023-01-28. Retrieved 2023-01-28. (40+12 pages)
1 2 3 4 5 Dittmar-Ilgen, Hannelore (2007) [2006, 2004]. "Immer Ärger mit tröpfelnden Kannen". Wie der Kork-Krümel ans Weinglas kommt - Physik für Genießer und Entdecker (in German) (1 ed.). Stuttgart, Germany: S. Hirzel Verlag [ de ]. pp. 21–25. ISBN 978-3-7776-1440-3. ISBN 978-3-7776-1440-3. (172+4 pages)
↑ Reba, Imants (June 1966). "Applications of the Coanda Effect". Scientific American . Vol. 214, no. 6. pp. 84–92. Bibcode:1966SciAm.214f..84R. doi:10.1038/scientificamerican0666-84. JSTOR 24930967 . Retrieved 2023-01-28. (9 pages)
1 2 Reiner, Markus (May 1967). "Teapot means Coanda". Letters. Physics Today . 20 (5). American Institute of Physics: 15. Bibcode:1967PhT....20e..15R. doi:10.1063/1.3034300 . Retrieved 2023-01-28. (1 page)
↑ Reiner, Markus (1969). Deformation, Strain and Flow - An Elementary Introduction To Rheology (3 ed.). H. K. Lewis & Co. Ltd. ISBN 0-71860162-9. (347 pages)
↑ Ziegler, Alfred; Wodzinski, Ruth (2001) [2000, 1999]. "Die Physik des Fliegens als Bestandteil eines Unterrichts zur Strömungslehre: Zielsetzungen und Begründungen". Vorträge / Physikertagung, Deutsche Physikalische Gesellschaft, Fachausschuss Didaktik der Physik (Book, CD) (in German). Arbeitsgruppe Didaktik der Physik, Universität Kassel. pp. 549–552. Archived from the original on 2023-01-29. Retrieved 2023-01-29. Coanda-Effekt (bzw. "Kaffeekanneneffekt"-ein Tropfen folgt der Oberfläche) (NB. Calls the effect "coffeepot effect" rather than "teapot effect".)

"Tropfenfangrinne an der Innenseite der Ausgussschnauze von Gefaessen, insbesondere Kannen fuer Kaffee, Tee usw." (in German). 1928. German patent DE457585C. Archived from the original on 2023-01-29. Retrieved 2023-01-29.
"Non-drip spouts for coffee and like pots with a spout opening directed downwardly". 1938 [1936]. GB patent 477613. Archived from the original on 2023-01-29. Retrieved 2023-01-29., Alcock, Lindley & Bloore Ltd, https://web.archive.org/web/20230128230232/https://www.teaforum.org/viewtopic.php?t=1980, https://web.archive.org/web/20230128230443/https://cauldonceramics.com/products/re-engineered-ian-mcintyre-brown-betty-4-cup-teapot-with-infuser-in-rockingham-brown-by-cauldon-ceramics
Sakowski, Christian (2023). "Melitta Kaffeekannen No. 301 u. 304, D.R.P. für 1 1/2 und 4 Tassen". Mein Sammlerportal & sampor.de (in German). Berlin, Germany. Archived from the original on 2023-01-29. Retrieved 2023-01-29. (NB. Picture shows the anti-drip groove and pinhole underneath the spout of Melitta coffee pots (protected by D.R.P. [ de ] patents) model No. 301 for 1½ cups and model No. 304 for 4 cups, presumably manufactured in the 1920s or 1930s.)
Walker, Jearl Dalton (1984-10-01). "The troublesome teapot effect, or why a poured liquid clings to the container". Scientific American . Vol. 251, no. 10. pp. 144–152. (9 pages)
Vanden-Broeck, Jean-Marc; Keller, Joseph Bishop (1986-05-19) [1986-09-12]. "Pouring Flows". Physics of Fluids . 29 (12): 3958–3961. Bibcode:1986PhFl...29.3958V. doi:10.1063/1.865735. (4 pages)
Vanden-Broeck, Jean-Marc; Keller, Joseph Bishop (1989) [1988-06-27, 1988-09-19]. "Pouring flows with separation". Physics of Fluids A: Fluid Dynamics . 1 (1): 156–158. Bibcode:1989PhFlA...1..156V. doi:10.1063/1.857542. (3 pages)
Kistler, Stephan F.; Scriven, Laurence Edward (1994-04-26) [1990-02-05, 1991-04-03]. "The teapot effect: sheet-forming flows with deflection, wetting and hysteresis". Journal of Fluid Mechanics . 263. Cambridge University Press: 19–62. Bibcode:1994JFM...263...19K. doi: 10.1017/S0022112094004027 . S2CID 123277240. (44 pages)
Träger, Susanne (1996). "Die nichttropfende Schnaupe". In Siemen, Wilhelm [in German] (ed.). In 80 Tassen um die Welt: Gastlichkeit und Porzellan - Ein Beitrag zur Geschichte des Porzellans für die Gastronomie vom Ende des 19. Jahrhunderts bis in Gegenwart. Schriften und Kataloge des Deutschen Porzellanmuseums (DPM) (in German). Vol. 46 (1 ed.). Hohenberg an der Eger, Germany: Deutsches Porzellanmuseum / Druckhaus Münch GmbH, Selb, Germany. p. 27. ISBN 3-927793-45-0. p. 27: Eine tropfende Schnaupe ist nicht nur bei den Kannen, die in der Gastronomie eingesetzt werden, ein Ärgernis. Was an funktionalen Mängeln im Haushaltsgebrauch noch toleriert werden kann, ist in der Gastronomie ein ernsthaftes Problem. Verschmutzte Tischtücher und vertropfte Untertassen sind kein Aushängeschild für ein gut geführtes Café. Nach dem Ausgiessen sollte keine Flüssigkeit mehr an der Außenwand der Kanne entlanglaufen und kein Tropfen an der Tülle hängen bleiben. Es gab einige absonderlich wirkende Versuche, Flüssigkeit am Ablaufen zu hindern. So sollten beispielsweise ablaufende Tropfen durch Rillen in der Kannenwandung aufgehalten werden. Bereits 1929 führte die Porzellanfabrik Weiden [ de ] Gebr. Bauscher [ de ] Kannen mit einer nichttropfenden Schnaupe ein. Infolge einer Bohrung durch den Ausguß und einer dünnen Rille auf der Innenseite der Tülle strömt die Flüssigkeit nach dem Aufrichten der Kanne durch Kapillarkraft zurück. Die Herstellung eines Tropfenfangs mit einer Bohrung ist heute produktionstechnisch zu aufwendig. Viele Versuche und Testreihen waren und sind nötig, um den idealen Neigungswinkel von Ausgüssen zu finden, damit die Flüssigkeit beim Aufrichten des Gefäßes ohne zu tropfen in die Schnaupe zurückläuft. (1+2+186+2 pages) (NB. The print run of this publication is limited to 1000 pieces.)
Hesselberth, John (January–February 1997). "How to Make Drip-Free Spouts". Clay Times. Archived from the original on 2023-01-28. Retrieved 2023-01-29.
"A groovy kind of pot". Sci/Tech. BBC News . 1998-12-08. Archived from the original on 2023-01-29. Retrieved 2023-01-29.
Seißer, Peter [in German]; Zehentmeier, Sabine; Meyer, Rudolf; Siemen, Wilhelm [in German]; Symossek, Ronja (1999). "Sortimentumstellung". In Siemen, Wilhelm [in German] (ed.). "Mit der Zeit gehen" - 100 Jahre Porzellanfabrik Walküre (1899–1999) - Ein mittelständiges Industrieunternehmen im Wandel ["Going with the times" - 100th anniversary of porcelain manufacturer Walküre (1899–1999) - A medium-sized industrial company in transition]. Schriften und Kataloge des Deutschen Porzellanmuseums (DPM) (in German). Vol. 58 (1 ed.). Hohenberg an der Eger, Germany: Deutsches Porzellanmuseum. pp. 101–105 [105]. ISBN 3-927793-57-4 . Retrieved 2024-04-26. p. 105: […] Das Interesse der "Porzellanfabrik Walküre" richtete sich dabei weniger auf das schmucklose Erscheinungsbild eines Porzellangegenstandes, sondern vielmehr auf den wortwörtlich verstandenen funktionalen Nutzen. Ausdruck dieses Bestrebens ist neben der bereits zum Standard gewordenen Deckelhalterung nun auch die nichttropfende Schnaupe. Das Problem des Tropfens ist für den Gastronomiesektor aufgrund verschmutzter Tischdecken natürlich ein besonderes Ärgernis. Unzählige Testreihen bringen verschiedene Lösungen^[A] hervor, von denen die Rille in der Kannenwandung, wie sie das Geschirr der Porzellanfabrik Walküre aufweist, sich als zuverlässig erweist und dementsprechend patentiert wird. Der Stolz dieser Erfindung wird auch nach außen hin sichtbar, indem man den speziell damit versehenen Servicen ein P, wie Patent, hinzufügte. […] Werbeblatt, Gastronomiegeschirr, Kannenmodell 604P. "P" kennzeichnet die Patentierung für die nichttropfende Schnaupe. […] (1+195+1 pages) (NB. The print run of this publication is limited to 1000 pieces. The corresponding patent appears to be D.R.P. [ de ] 476417.)
"Ig Nobel Prize Winners". Improbable Research. 2023 [2012, 1999]. Archived from the original on 2023-01-28. SPECIAL ANNOUNCEMENT: We are now, in 2012, correcting an error we made in the year 1999, when we failed to include one winner's name. We now correct that, awarding a share of the 1999 physics prize to Joseph Keller. Professor Keller is also a co-winner of the 2012 Ig Nobel physics prize, making him a two-time Ig Nobel winner. […] The corrected citation is:1999 PHYSICS PRIZE: Len Fisher [UK and Australia] for calculating the optimal way to dunk a biscuit, and Jean-Marc Vanden-Broeck [UK and Belgium] and Joseph Keller [USA], for calculating how to make a teapot spout that does not drip.
Bolton, David (Fall 2007). "Functional Teapot Options & Rules of Thumb" (PDF). CLC Ceramics. Archived (PDF) from the original on 2023-01-28. Retrieved 2023-01-29. (2 pages)
Dillon, Frank (2009-05-11). "The pot of gold - Design & Invention: It is a problem that has confounded scientists for generations". Department. Irish Times. Archived from the original on 2023-01-29. Retrieved 2023-01-29.
"How to stop a teapot dribbling". Physics Today (10). American Institute of Physics. 2009-10-28. doi:10.1063/PT.5.023796. Archived from the original on 2023-01-29. Retrieved 2023-01-28– via The Daily Telegraph.
Duez, Cyril; Ybert, Christophe [at Wikidata]; Clanet, Christophe; Bocquet, Lydéric [in French] (2010-02-26) [2009-10-17]. "Wetting controls separation of inertial flows from solid surfaces". Physical Review Letters . 104 (8). American Physical Society: 084503. arXiv: 0910.3306v1 . Bibcode:2010PhRvL.104h4503D. doi:10.1103/PhysRevLett.104.084503. PMID 20366936. S2CID 118601911. 084503. Retrieved 2023-01-29.
Mugele, Frieder G. (2010). "Was tun wenn die Teekanne tropft? Benetzungseigenschaften auf mikroskopischer Skala bestimmen das makroskopische Strömungsverhalten". Brennpunkt. Physik Journal (in German). 9 (6). Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA: 18–19. Archived from the original on 2023-01-28. Retrieved 2023-01-28. (2 pages)
Lossau, Norbert (2010-06-22). "Wie man tropfende Teekannen in den Griff bekommt". Wissenschaft. Die Welt (in German). Archived from the original on 2023-01-28. Retrieved 2023-01-28.
"Ever Wonder About the Teapot Effect?". Science World . ASTC Science World Society. 2015-10-18. Archived from the original on 2023-01-28. Retrieved 2023-01-28.
Robert (2017-02-03). "Why Do Teapots Dribble?". Trivia. guernseyDonkey.com. Archived from the original on 2022-09-25. Retrieved 2023-01-28.
Ouellette, Jennifer (2019-05-17). "I'm a little teapot — Dribble no more: Physics can help combat that pesky "teapot effect" - Dutch scientists devised a model to predict flow rate when dribbling will occur". Ars Technica . Archived from the original on 2023-01-29. Retrieved 2022-07-02.
Gagné, Jonathan [at Wikidata] (2020). "6. Kettles and Agitation - 6.1. The Teapot Effect". In Zimmer, Jean (ed.). The Physics of Filter Coffee (1 ed.). Scott Rao. pp. 127–144 [127–128]. ISBN 978-0-578-24608-6. (xvi+249+3 pages)
"Flüssigkeitenmechanik - Wiener Forscher erklärt, warum Tee aus der Kanne danebengeht - Wenn ein Flüssigkeitsstrahl nicht trifft, sondern am Behälter entlangfließt, heißt das Teekanneneffekt. Nun gibt es eine detaillierte Erklärung dafür". Der Standard (in Austrian German). Vienna, Austria: STANDARD Verlagsgesellschaft m.b.H. 2021-11-08. Retrieved 2023-01-28– via Austria Presse Agentur.
Mihai, Andrei (2021-12-01). "The maths behind the annoying teapot effect — and how to prevent it". SciLogs - Heidelberg Laureate Forum. Heidelberg, Germany: Spektrum der Wissenschaft Verlagsgesellschaft mbH. Archived from the original on 2023-01-28. Retrieved 2023-01-28.
Jones, David (2022). "Pours for thought? [The teapot effect: theory and practice]". Jones the Pots. Archived from the original on 2023-01-28. Retrieved 2023-01-28.
Hinze, Betsy (2023). "Teapot Cheat Sheet". Archived from the original on 2024-01-29. Retrieved 2024-01-29.
https://feldlilie.wordpress.com/2012/01/19/physikfrage-12485521/
https://www.stevenabbott.co.uk/practical-coatings/Teapot.php
https://thiru.de/pages/teekanne-tropft
https://www.kalkspatzforum.de/viewtopic.php?t=2417
https://teehaus-bachfischer.de/tropfenfaenger-fuer-teekannen, https://sterntee.de/navi.php?a=15902 drop catcher

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[SciTech_2022-1] 1 2 "Why Teapots Always Drip – Scientists Finally Explain the "Teapot Effect"". SciTechDaily . Vienna University of Technology. 2022-01-09. Archived from the original on 2023-01-28. Retrieved 2022-07-02.

[Reiner_1956-2] Reiner, Markus (September 1956). "The teapot effect...a problem". Physics Today . 9 (9). American Institute of Physics: 16. doi:10.1063/1.3060089 . Retrieved 2023-01-28. (1 page)

[Ouellette_2021-3] 1 2 3 Ouellette, Jennifer (2021-11-10). "Dribble, dribble, dribble — Physicists say they've finally solved the teapot effect—for real this time - Is due to interplay of inertial viscous capillary forces—but gravity's less relevant". Ars Technica . Archived from the original on 2023-01-28. Retrieved 2022-07-02.

[Keller_1957-4] Keller, Joseph Bishop (1957). "Teapot Effect" (PDF). Journal of Applied Physics . 28 (8): 859–864. Bibcode:1957JAP....28..859K. doi:10.1063/1.1722875. Archived (PDF) from the original on 2022-03-13. Retrieved 2023-01-28. (6 pages)

[Scheichl-Bowles-Pasias_2021-5] Scheichl, Bernhard; Bowles, Robert I.; Pasias, Georgios (2021-11-10) [2021-09-08, 2021-07-01, 2021-05-17, 2020-11-09]. "Developed liquid film passing a smoothed and wedge-shaped trailing edge: small-scale analysis and the 'teapot effect' at large Reynolds numbers". Journal of Fluid Mechanics . 926. Cambridge University Press: A25-1–A25-40, S1–S12. arXiv: 2011.12168 . Bibcode:2021JFM...926A..25S. doi:10.1017/jfm.2021.612. ISSN 0022-1120. S2CID 235444365. Archived from the original on 2023-01-28. Retrieved 2023-01-28. (40+12 pages)

[Dittmar-Ilgen_2007-6] 1 2 3 4 5 Dittmar-Ilgen, Hannelore (2007) [2006, 2004]. "Immer Ärger mit tröpfelnden Kannen". Wie der Kork-Krümel ans Weinglas kommt - Physik für Genießer und Entdecker (in German) (1 ed.). Stuttgart, Germany: S. Hirzel Verlag [ de ]. pp. 21–25. ISBN 978-3-7776-1440-3. ISBN 978-3-7776-1440-3. (172+4 pages)

[Reba_1966-7] Reba, Imants (June 1966). "Applications of the Coanda Effect". Scientific American . Vol. 214, no. 6. pp. 84–92. Bibcode:1966SciAm.214f..84R. doi:10.1038/scientificamerican0666-84. JSTOR 24930967 . Retrieved 2023-01-28. (9 pages)

[Reiner_1967-8] 1 2 Reiner, Markus (May 1967). "Teapot means Coanda". Letters. Physics Today . 20 (5). American Institute of Physics: 15. Bibcode:1967PhT....20e..15R. doi:10.1063/1.3034300 . Retrieved 2023-01-28. (1 page)

[Reiner_1969-9] Reiner, Markus (1969). Deformation, Strain and Flow - An Elementary Introduction To Rheology (3 ed.). H. K. Lewis & Co. Ltd. ISBN 0-71860162-9. (347 pages)

[Ziegler-Wodzinski_1999-10] Ziegler, Alfred; Wodzinski, Ruth (2001) [2000, 1999]. "Die Physik des Fliegens als Bestandteil eines Unterrichts zur Strömungslehre: Zielsetzungen und Begründungen". Vorträge / Physikertagung, Deutsche Physikalische Gesellschaft, Fachausschuss Didaktik der Physik (Book, CD) (in German). Arbeitsgruppe Didaktik der Physik, Universität Kassel. pp. 549–552. Archived from the original on 2023-01-29. Retrieved 2023-01-29. Coanda-Effekt (bzw. "Kaffeekanneneffekt"-ein Tropfen folgt der Oberfläche) (NB. Calls the effect "coffeepot effect" rather than "teapot effect".)

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]