Why do ferrofluids spike

Sometimes physics imitates art. An engineering undergraduate at MIT, Cory Lorenz, placed a drop of a ferrofluid between two closely-spaced glass plates, applied a constant vertical magnetic field, and then added a horizontal rotating magnetic field producing the interesting spiral design shown in the first group of photos top to bottom on left. But then Lorenz reversed the order of the applied fields, and saw a pattern top to bottom on right , that looked something like Native American art, a completely unexpected result.

Out of this work could emerge possible applications of ferrofluids to tiny machines, on the scale of micrometers or nanometers. Unlike electric fields, magnetic fields cannot produce sparks, so they might provide a good way to produce more reliable micro and nano-machines.

From turning on a lamp in your home to running solar panels, batteries play a large role in our everyday lives. The black hole selected for imaging resides in the center of the Messier 87 galaxy, 55 million light years away quintillion miles away.

High energy particle physics experiments in recent past have brought into question parts of the model currently used in particle physics. The closer two magnets are brought together, the stronger the magnetic attraction--thus, if a magnet is infinitely small, the magnetic field strength can become infinitely large.

Not only is the magnetic field difficult to measure at the magnet's center, but if two singularities come close together, the forces become so large that the simulation can crash. The team also found ways to increase computational efficiency by reducing the algorithmic complexity, allowing larger simulations to be run.

When the team compared their model with wet lab experiments, it reproduced the true dynamic behavior of the ferrofluid, giving a good qualitative representation that will be useful for ferrofluid sculpture design. Increasing the model's accuracy further would provide new insights into fundamental ferrofluid behavior and lead to many new uses, from electronic sensors and switches to deformable mirrors for advanced telescopes.

DOI As the protrusion grows, the surface is stretched, increasing surface tension force until it is strong enough to balance out the magnetic normal force. The equilibrium shape is therefore a peak, which is taller and thinner when the field is stronger.

Why do these peaks form in some parts of the fluid, while others are left as valleys? The places where peaks form are essentially random, nucleated by any small bump in the fluid surface, which will then grow. That is why they are called "instabilities", since a perfectly stable surface would not have any preferential position to form a peak though there are no perfectly stable surfaces in reality.

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