Observation Of Pattern Formation Research Articles

Pattern formation in odd viscoelastic fluids

Nonreciprocal interactions fueled by local energy consumption can be found in biological and synthetic active matter at scales where viscoelastic forces are important. Such systems can be described by “odd” viscoelasticity, which assumes fewer material symmetries than traditional theories. Here we study odd viscoelasticity analytically and using lattice Boltzmann simulations. We identify a pattern-forming instability which produces an oscillating array of fluid vortices, and we elucidate which features govern the growth rate, wavelength, and saturation of the vortices. Our observation of pattern formation through odd mechanical response can inform models of biological patterning and guide engineering of odd dynamics in soft active matter systems. Published by the American Physical Society 2024

Observation of Pattern Formation during Electromagnetic Levitation Using High-Speed Thermography

Electromagnetic levitation (EML) was employed for studying the velocity and morphology of the solidification front as a function of undercooling of metallic materials. The limitation of the EML technique with respect to low melting alloys that emit outside the visible light spectrum was overcome by employing state-of-the-art high-speed mid-wavelength infrared cameras (MWIR cameras) with a photon detector. Due to the additional thermography contrast provided by the emission contrast of the solid and liquid phases, conductor, and semi-conductor, the pattern formation of Al-based alloys was studied in detail, revealing information on the nucleation, phase selection during solidification, and the influence of convection.

Observation of Pattern Formation in Optical Parametric Oscillators

We have observed transverse pattern formation in a near-confocal, type II, triply resonant optical parametric oscillator (OPO) operating close to frequency degeneracy for the signal and idler modes. In the region of observation of these patterns, the OPO oscillation threshold increases. Complex ring patterns and latticelike structures are observed. These patterns are due to the nonlinear coupling of many transverse modes (on the order of 25). The transverse distribution of the light is different in the signal, idler, and transmitted pump modes.