Flowing Water

A ceramic teapot with a drip catcher shaped like a slice of lemon. The teapot is painted with a pattern of leaves and grapes, and the caption reads 'A Drip Catcher On A Teapot'.

Water flows out of different teapots differently. I never took the time to notice this phenomenon. It wasn’t until recently when it was brought to my attention that I started to look at the water flow from my teapots. This blog is dedicated to my favorite geophysicist.

Water Flow 

Green tea from a cast iron teapot pouring into a black handle-less teacup. The teapot and teacup are setting on top of a black countertop with a jar of sweets in the background.

I purchased a new water kettle. I thought no one would notice because I have several tea kettles and this new one was just one more in my arsenal of tea equipment. I was mistaken. The new tea kettle was noticed and commented on. The comment was my muse for this blog.

The geophysicist that used the tea kettle immediately stated “This kettle has wonderful laminar flow.” I said thank you and then promptly asked for a definition for laminar flow. I was surprised to find a geological definition for what I knew all along regarding teapots and tea kettles. Various teapots have a better flow of water out the spout than other teapots and tea kettles.

Laminar Flow 

An aesthetic photo of a glass teapot in midair pouring water onto the ground. The background is black.

Fluid flowing smoothly can be referred to as laminar flow. Laminar flow is a term relating to fluid dynamics. The effects of laminar flow can be seen, for example, in geology, aerospace, and in sailing. The pattern of water flowing over rocks can leave smooth carved out sections of rock, rippled effects on rocks, or stippled indentations on rocks depending upon the water flow. Laminar flow can also be seen making its mark in how air flows over and around airplanes in flight, creating a smooth or bumpy flight. Air behaves as a fluid when in motion. It can flow smoothly or turbulently, thus creating good or terrible laminar flow. Air flowing around the sail of a boat could have good laminar flow pulling the boat in a forward and smooth motion. If the air flow is a turbulent laminar flow, the sail boat would stall and not move forward in the water.

Ideally, fluid particles flow in a smooth manner, and an orderly manner. It is a fluid motion that is not gurgulling, sputtering, or otherwise turbulent. Positive or good laminar flow is related to the velocity (or speed) of the flow and the density or viscosity of the fluid. Good laminar flow occurs when the flow rate is below the point of the flow becoming turbulent. Think of a water faucet turned on to an average rate of water flow. Usually the average flow rate produces a smooth water flow out of the faucet. If the water faucet handle is turned to allow maximum flow rate, the water flowing out of the faucet has now become a forceful, kinetic stream of water. It has become a turbulent water flow. 

A smooth flow rate, or good laminar flow, is also dependent upon the viscosity of the fluid. If a fluid is extremely thick, and has a gelatinous consistency, it will not flow in a smooth and orderly fashion. For example, pouring syrup on pancakes would most likely have good laminar flow because the syrup is thin enough to flow smoothly out of the bottle. An example of poor laminar flow is pouring hair conditioner out of a bottle. The conditioner typically is too thick to pour out of the bottle in a smooth, even flow. The conditioner will sputter, stop flowing, or when the bottle is shaken vigorously up and down, the conditioner will forcefully spurt out in a glob due to the velocity and its viscosity. 

TeaPot Flow 

A black cast iron kettle pouring hot water into a white teapot. The teapot has a wooden handle at the top. Matching white teacups are surrounding the teapot.

The flow of water from a teapot or a tea kettle can be a peaceful, steady stream of water. Water poured out of a teapot or a tea kettle could also be a sputtering, inconsistent flow that could potentially splash on the person who is pouring the water. The flow is affected by the design of the spout as well as the velocity of the pouring and the viscosity of the fluid. 

If the spout is too wide in the open end of the spout, then typically the water spurts out forcefully. A spout that is too narrow in the opening can create a thin line of liquid that doesn’t flow in a consistent manner. Rather, it could possibly flow in a trickle, or a dribble. 

I have had teapots with short or long spouts that have had good laminar flow. The spout length itself doesn’t necessarily negate a good water flow or a poor flow. In my estimation, I think good laminar flow is derived from a ratio of length of spout, to curve of spout, and spout opening size. I am not an engineer, a physicist, or a ceramic artist. I do not design teapots or tea kettles. These are mere ruminations on what I think makes good laminar flow in a teapot.

Test Flow 

I would recommend pouring water out of the teapot as a test flow prior to incorporating the teapot at a table. If the teapot dribbles, or sputters, a drip catcher could be slipped over the end of the teapot to catch the dribbles. A spout with a chip in the end will result in a turbulent laminar flow and spurt out the tea. A drip catcher and a slower pouring of the tea may help even the flow from a chipped teapot spout. 

Whatever the flow of your water, keep your tea flowing,

Leslie

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