Certain non-Newtonian fluids which are elastic display a large resistance to extensional flow. Such behaviour leads to fluid flow arrangements which are simply not possible using ordinary Newtonian fluids. These so-called Fano flows manifest themselves in a variety of ways. In the so-called ''tubeless'' syphon, a fluid can be made to flow up through an unsupported liquid column above the free surface of the liquid. One way to achieve this is by slowly withdrawing and raising a syringe from a pool of the liquid below. In the so-called ''open channel'' syphon, after initially commencing the flow of an elastic fluid from say a beaker, the fluid will continue to flow up the side and over the lip of the beaker for sometime despite the level of its free surface having fallen considerably below the top of the beaker. In this way the slightest spill will cause the beaker to partly empty in what is commonly refereed to as a ''self-syphoning'' effect.

Fano flow syphon siphon self-syphon tubeless polyox open channel physics experiments demonstrations effect

When a rod mounted in a hand drill is dipped into a liquid and rotated, for certain non-Newtonian fluids the liquid will climb the rod - sometimes to quite spectacular heights. Such rob climbing behaviour is referred to as the Weissenberg Effect. Shearing in the flow of the liquid concentrically around the rotating rod causes the component of the stress normal to the circular flow direction to become greater in magnitude compared to the two other mutually perpendicular components. This causes the fluid around the rotating rod to contract and be squeezed up along the axis of the rod causing it to in turn "climb" the rod. The three different fluids shown in the video, all of which exhibit the Weissenberg effect, are: (i) a natural polymer formed from a guar gum solution crosslinked with sodium tetraborate in solution, (ii) pancake batter (flour, water and egg white), and (iii) a dyed synthetic polymer consisting of white glue which has again been crosslinked with sodium tetraborate in solution.

Weissenberg effect rod-climbing non-Newtonian fluid viscoelastic liquid physics experiments demonstrations

Honey is dribbled off the end of a chopstick into a pot below. As the falling stream stikes the pool of honey below, it turns itself into tight circular coils which rapidly begin to pile one on top of the other. A growing column of liquid coils of rope begin to emerge from above the surface of the honey in the pot in an effect referred to as the liquid rope-coil effect. Uneveness in the amount of sinking at the base of the growing column of coils causes it to collaspe before a new column of liquid coils re-emerge and begin to rise up again. The rate of coiling is increased as the height from which the honey is allowed to fall from is raised.

Liquid rope-coil effect coiling honey physics demonstrations experiments silicone oil

A simple experiment using (i) running water from a tap, and (ii) air blown through a straw, as it flows over the back of a vertically hanging plastic teaspoon are used to demonstrate the Coanda effect. Here the attachment of the back of the teaspoon to the flowing stream of fluid (air or water in this case) is what is referred to as the Coanda effect.

Coanda effect physics deomonstration experiment tap running water

On dribbling shampoo from a small height above a pool of the same shampoo below, every now and then liquid lanyards of shampoo leap forth in a behaviour referred to as the Kaye effect. Such behaviour is characteristic of a viscoelastic fluid.

Kaye effect leaping shampoo viscoelastic fluid non-Newtonian physics demonstration experiment

A dyed polyvinyl solution crossed linked with sodium tetraborate in solution is found to exhibit the following three different viscoelatic effects: 1. The Barus Effect (extrudate swell) 2. The Weissenberg Effect (rod-climbing) 3. The Kaye Effect (liquid leaping lanyards)

viscoelastic Barus Weissenberg Kaye effect physics experiments demonstrations non-Newtonain fluid

The motor consists of three parts only. A cylinderical neodymium magnet, a AA-battery, and a solid copper wire bent roughly into the shape of the letter M. On dropping the wire onto the top of the battery, since its lower ends touch the magnet, this completes the circuit and causes current to flow. As the current-carrying wire is now in the presence of an external magnetic field, a magnetic force acts on it. Since the wire is free to rotate, it begins to spin quite rapidly. With only three parts used, is this not the simplest motor you have ever seen?

homopolar motor physics demonstrations experiments neodymium

When the bottom of a ceramic cup filled with boiling water and a heap of instant coffee is tapped at regular intervals the pitch of the sound heard slowly increases over time. The effect takes its name from "allasso", the Greek root for to change, and "sonus", the Latin word for sound. In the past the effect has been referred to as the "Hot Chocolate Effect" but the phenomenon is found to occur in many instances beyond the humble cup of hot cocoa. It can even be heard when the base of a pint of beer is tapped after having sprinkled some table salt into it!

physics demonstrations experiments allassonic sound hot chocolate effect changing pitch

When two neodymium disc magnets with like poles facing one another are attached to either end of a AA-battery, on dropping a copper connecting wire in the shape of the letter U onto the rims of each disc causes current to flow and results in magnetic forces acting on either wheel. The resultant magnetic torque arising from each force causes the arrangement to roll off with considerable speed.

homopolar physics demonstrations experiments neodymium roller

It has been known since ancient times that when a small amount of oil is poured into water it is able to significantly reduce or calm wind-induced waves at the surface. This stilling of the waves is referred to as the Oil-on-Water Calming Effect and is the origin behind the well-known phrase "to pour oil on troubled waters."

Oil-on-Water calming effect pour oil troubled waters surface tension physics experiments demonstrations

A dyed solution of POLYOX (polyethylene oxide - it is the stuff used as the lubricant on the strip found in all modern razors) is extruded from a 50 ml syringe. On exit, a marked swelling in the liquid stream several times the diameter of the orifice is observed. The effect is referred to as the Barus Effect but it also goes by several other names including the Merrington Effect, Die Swell, and Extrudate Swell. Polyox is an example of a highly viscoelastic non-Newtonian fluid. The Barus effect is common in highly elastic fluids such as polymer solutions and melts. Water on the other hand, being non-elastic, does not exhibit the Barus effect. The Barus effect is an example of a so-called "elastic memony" effect. When a viscoelastic fluid is extruded, tensile stresses associated with the extrusion process cause at the microscopic level the long molecular chains of the fluid to stretch before relaxing again on exiting the orifice. The lateral expansion in the liquid results in a corresponding contraction in the liquid stream along the longitudinal direction.

Barus effect Merrington die-swell extrudate swell viscoelastic fluid liquid non-Newtonian physics experiment

The elegantly simple three-part homopolar motor in action.

physics demonstrations experiments homopolar motor neodymium

When wet sand along the water's edge at the beach is stepped on, it becomes partially dry in a small area surrounding one's foot. The dry patch is evident as the thin reflective film of water at the surface surrounding your foot is no longer there and has instead been drawn into the bulk of the sand beneath your foot. This drying of the sand underfoot is referred to as the Wet-Sand Effect. The effect results from the dilatancy of the media. Here the volume of the sand increases. Shearing caused beneath each foot step causes the sand to move ever so slightly from a highly compact state to one where the amount of spacing between adjacent grains of sand has increased. Water from the surface flows under gravity into the newly created space and leads to the momentarily drying in the sand with each step. The dilatancy effect of sand under an applied compressive force can be readily reproduced using a sealed plastic bottle filled with water soaked sand. A small water filled tube with one end buried into the bottle is used to monitor for any water displacement occurring in the sand. On squeezing the bottle hard, one intuitively expects the level of water in the tube to rise. To the surprise of many, the level of water actually drops and the harder one squeezes, the further the drop!

wet sand effect dilatancy wet-sand Reynolds physics experiments demonstrations beach

A compilation of shots I took with my vz.58 from the bench. The low light allowed for great visibility of the muzzle flashes.

vz 58 csa muzzle flash psi dot scope 7.62x39 7.62 czech rifle

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pp803c Demo Video dot matrix printer Printer demo