miguel bustamante

We present a theoretical and numerical study of Fourier-space triad phase dynamics in the one-dimensional stochastically forced Burgers equation at Reynolds number $Re\approx 2.7\times 10^{4}$. We demonstrate that Fourier triad phases over the inertial range display a collective behaviour characterised by intermittent periods of synchronisation and alignment, reminiscent of the Kuramoto model (Chemical Oscillations, Waves, and Turbulence, Springer, 1984) and directly related to collisions of shocks in physical space. These periods of synchronisation favour efficient energy fluxes across the inertial range towards small scales, resulting in strong bursts of dissipation and enhanced coherence of the Fourier energy spectrum. The fast time scale of the onset of synchronisation relegates energy dynamics to a passive role: this is further examined using a reduced system with the Fourier amplitudes fixed in time – a phase-only model. We show that intermittent triad phase dynamics persists ...

Additive manufacturing encompasses a plethora of techniques to manufacture structures from a computational model. Among them, fused filament fabrication (FFF) relies on heating thermoplastics to their fusion point and extruding the material through a nozzle in a controlled pattern. FFF is a suitable technique for tissue engineering, given that allows the fabrication of 3D-scaffolds, which are utilized for tissue regeneration purposes. The objective of this study is to assess a low-cost/open-source 3D printer (In-House), by manufacturing both solid and porous samples with relevant microarchitecture in the physiological range (100-500 μm pore size), using an equivalent commercial counterpart for comparison. For this, compressive tests in solid and porous scaffolds manufactured in both printers were performed, comparing the results with finite element analysis (FEA) models. Additionally, a microarchitectural analysis was done in samples from both printers, comparing the measurements of both pore size and porosity to their corresponding computer-aided design (CAD) models. Moreover, a preliminary biological assessment was performed using scaffolds from our In-House printer, measuring cell adhesion efficiency. Finally, Fourier transform infrared spectroscopy - attenuated total reflectance (FTIR-ATR) was performed to evaluate chemical changes in the material (polylactic acid) after fabrication in each printer. The results show that the In-House printer achieved generally better mechanical behavior and resolution capacity than its commercial counterpart, by comparing with their FEA and CAD models, respectively. Moreover, a preliminary biological assessment indicates the feasibility of the In-House printer to be used in tissue engineering applications. The results also show the influence of pore geometry on mechanical properties of 3D-scaffolds and demonstrate that properties such as the apparent elastic modulus (Eapp) can be controlled in 3D-printed scaffolds.