arXiv subjects

Rodolfo Ostilla Monico

Publications and source records attributed to Rodolfo Ostilla Monico.

5 recordsLinked to original sources

arXiv2026

Turbulence Decay Intensifies Clustering of Bubbles and Particles

Our understanding of inertial particle dynamics in turbulence is mostly based on flows held in a statistically stationary state, a particular regime that differs from many natural flows where energy input can often be intermittent or cyclic, or may abruptly cease. Here we investigate inertial particle and bubble dynamics in freely decaying turbulence through complementary experiments and direct numerical simulations. While particle accelerations decay monotonically in time, we find evidence that the clustering can exhibit a non-monotonic evolution, intensifying sharply before subsequently weakening. We demonstrate that both the acceleration and clustering behaviors can be mapped onto their counterparts in stationary turbulence using a dynamic rescaling of the evolving length and time scales of the turbulence. Validity conditions for the dynamic rescaling, satisfied by both the experimental and numerical datasets, are derived. The proposed mappings remain applicable across a broad range of density ratios, from light to heavy particles, and particle sizes spanning two orders of magnitude in Stokes number.

physics.flu-dyn↗

arXiv2025

Fluid Dynamical Pathways of Airborne Transmission while Waiting in a Line

Waiting in a line (or a queue) is an important, often unavoidable social interaction that occurs frequently in public spaces. Despite its wide prevalence and rich parametric variability, few studies have addressed the risks of airborne transmission while waiting in a line. Here we use a combination of scaled down laboratory experiments and direct numerical simulations (DNS) to assess the flow patterns and infection risks in a simplified waiting line setting. We observed the presence of fluid dynamical countercurrents, due to the competing effects of line kinematics and thermal gradients, which can either heighten or suppress the risks of transmission. Depending on the walking speed, an intermediate ambient temperature range can potentially heighten the infection risks by allowing the breath plume to linger in the air for extended durations; however, colder and warmer ambients both suppress the spread. The current guideline of increasing physical separation has limited impact on reducing transmission in the waiting line setting. The present work highlights the need for updated transmission mitigation guidelines that go beyond the simplicity of the six feet rule in social interactions where physical separation, duration of interaction, and periodicity of movements are factors.

physics.flu-dyn↗

arXiv2024

Particle Re-Suspension in Two-Phase Dispersed Rayleigh-Bénard Convection

The process by which particles are entrained by the fluid in Rayleigh-Bénard convection is studied by means of particle-resolved numerical simulations in a periodic domain at a Rayleigh number of $10^7$. The fluid Prandtl number is 1 and the particle-to-fluid density ratio 1.1. The results show that the horizontal velocity field near the bottom of the cell accumulates particles in heaps, or `dunes', at the base of ascending plumes. The dunes deflect the incoming flow, conferring to it a vertical velocity component which entrains the particles up the dune and into the plume. An experimental observation of this mechanism was briefly reported by Solomatov et al. (Earth Planet. Sc. Lett. 120, 387, 1993) but has not been considered further in the literature. By its very nature, such a process cannot be simulated by the point particle model. The final particle load carried by the convection depends both on the available gravitational energy of the fluid and on the effectiveness of the re-suspension mechanism.

physics.flu-dyn↗

arXiv2013

Optimal Taylor-Couette flow: Radius ratio dependence

Taylor-Couette flow with independently rotating inner (i) and outer (o) cylinders is explored numerically and experimentally to determine the effects of the radius ratio η on the system response. Numerical simulations reach Reynolds numbers of up to Re_i=9.5 x 10^3 and Re_o=5x10^3, corresponding to Taylor numbers of up to Ta=10^8 for four different radius ratios η=r_i/r_o between 0.5 and 0.909. The experiments, performed in the Twente Turbulent Taylor-Couette (T^3C) setup, reach Reynolds numbers of up to Re_i=2x10^6$ and Re_o=1.5x10^6, corresponding to Ta=5x10^{12} for η=0.714-0.909. Effective scaling laws for the torque J^ω(Ta) are found, which for sufficiently large driving Ta are independent of the radius ratio η. As previously reported for η=0.714, optimum transport at a non-zero Rossby number Ro=r_i|ω_i-ω_o|/[2(r_o-r_i)ω_o] is found in both experiments and numerics. Ro_opt is found to depend on the radius ratio and the driving of the system. At a driving in the range between {Ta\sim3\cdot10^8} and {Ta\sim10^{10}}, Ro_opt saturates to an asymptotic η-dependent value. Theoretical predictions for the asymptotic value of Ro_{opt} are compared to the experimental results, and found to differ notably. Furthermore, the local angular velocity profiles from experiments and numerics are compared, and a link between a flat bulk profile and optimum transport for all radius ratios is reported.

physics.flu-dyn↗

arXiv2013

Boundary layer dynamics at the transition between the classical and the ultimate regime of Taylor-Couette flow

Direct numerical simulations of turbulent Taylor-Couette flow are performed up to inner cylinder Reynolds numbers of {Re_i=10^5} for a radius ratio of {η=r_i/r_o=0.714} between the inner and outer cylinder. With increasing {Re_i}, the flow undergoes transitions between three different regimes: (i) a flow dominated by large coherent structures, (ii) an intermediate transitional regime, and (iii) a flow with developed turbulence. In the first regime the large--scale rolls completely drive the meridional flow while in the second one the coherent structures recover only on average. The presence of a mean flow allows for the coexistence of laminar and turbulent boundary layer dynamics. In the third regime the mean flow effects fade away and the flow becomes dominated by plumes. The effect of the local driving on the azimuthal and angular velocity profiles is quantified, in particular we show when and where those profiles develop.

physics.flu-dyn↗