This is how precise my temporal resolution can be with my modified goPro and (at last) a good lens : 240 fps ( @848×480 )
Forcing freq is 60 Hz, so Faraday Freq is 30Hz, so for the usual walking mode we have 8 frame during the period of the vertical dynamic. Hence we can observe the dynamic without any strobe effect.
Question: What is the (m, n) mode of the first droplet shown in the movie ?
Even if the ear cannot detect any transition on this one, it might give somebody … ideas ?
( Sound is the derivative of the sum of all field values at the center )
Surfer attached to a spring moving with no viscosity
Integration of motion equation is done continuously via matlab DELAY DIFERENTIAL EQUATION (ddesd) solver
Hence, the dot “reads” continuously the value of the field
In the mean time, the dot “writes” to the field evry T_F (that is a “bounce”) : at each bounce, a local wave field represented by a Bessel JO function is created, which is then slowly damped (That is the memory Me parameter)
Interferences between the waves created by the last previous 300 bounces (THAT IS THE CUTOFF parameter) are computed at each integration step to obtain the shape of the wave and the motion of the dot.
On this video, you’ll see :
– How 2 dotwaves can synchronize on 2 orbits
– How a dotwave can change his orbit (with a little help from the experimentator)
Video shot with a 30 Hz camera, at a forcing frequency of 60 Hz, hence not much stroboscopic flickering
The bath is excited just at the Faraday llevel, or slighly upper.
On this video, the walking droplet is confined in a small cavity (Approx. 6 to 8 times the faraday wavelength)
We observe the emergence of several normal modes of vibration of a walking droplet in a circular corral.
At first, the movement seems “random”, then, the whole wave-particle system synchronizes, and starts turning alltogether.
Differrent modes are possible, with different radius for the droplet trajectory : on this video we see a mode with the droplet on a large radius trajectory, and also a mode where the droplet is on a short radius trajectory
Its seems that thoses radius coincide with with the knots ofs thefaraday standing waves of the cavity, hence we have a quantization of the radius of the different trajectories.
When two walking droplets start turning around each other, the distance between them is n times the wavelength (with n an integer) plus a constant.
Walking droplet trapped in a square box escapes after many rebounds.
( Watch a “tunnel effect” at 2’30)