Viscous fingering occurs when a less viscous fluid is injected into a rock matrix saturated with a more viscous fluid. Our past research using the Rothman-Keller (RK) color gradient Lattice Boltzmann Method (LBM) for immiscible two phase flow has allowed us to study viscous fingering morphology and the complex saturation phase space as a function of the fluid’s properties (wettability of the injected fluid and viscosity ratio). In this past work, we found that the primary factor affecting the saturation at breakthrough – when the injected fluid has passed through the entire model – was the viscosity ratio, and the secondary effect was the wettability. Here, we present an extension of our LBM model to enable convection-diffusion to be simulated, thereby allowing us to vary the viscosity of the injected fluid, and mimicking the practice in Enhanced Oil Recovery (EOR) using polymer additives after breakthrough as a means of increasing the viscosity ratio and thus the eventual oil yield. The basic RK multiphase LBM models two fluid number densities moving and colliding on a discrete lattice, where a second collision term is used to model cohesion within each fluid, and contains an extra “recoloring step” to ensure fluid segregation. Here, we model an additional number density representing the concentration of a polymer additive, which affects the viscosity of the injected fluid. The Peclet number – rate of advection to diffusion of the polymer solution – is used to set the diffusion coefficient of the polymer concentration number density and hence, the relaxation time in the LBM for the polymer diffusion process. We present tests to demonstrate the method in which we increase the polymer concentration of the injected fluid after a given time and study the effect on the viscous fingering morphology and saturation evolution. This work demonstrates that the RK color gradient multiphase LBM can be used to study complex viscous fingering behavior associated with injection of water with polymer additives, which can have major scientific and practical significance.

The Lattice Boltzmann Method (LBM) is an elegant method to simulate fluid dynamics based on modelling distributions of particles moving and colliding on a lattice. We present examples of two phase flow using the Rothman and Keller (RK) colour gradient Lattice Boltzmann model to study phenomena associated with two phase immiscible fluid flow relevant to water being injected into an oil saturated sandstone. The model involves streaming and colliding two distribution functions (red and blue) representing the number densities of two fluids, where the collision step involves two terms which represents how particle distributions change in each time step due to collision while encouraging colour segregation. We conducted 2D numerical experiments to study the effect of wetting angle on the morphology of flow of a lower viscosity fluid being injected at the left of a simplified model rock matrix that was filled with a higher viscosity fluid. The cases studied involved the injected fluid being non-wetting (wetting angle = 180 degrees), neutral wetting (wetting angle = 90 degrees) and wetting (wetting angle = 0 degrees). These three cases show viscous fingering behaviour with different morphologies for the different wetting angles. For the case of the non-wetting fluid injection, a series of narrow fingers are observed. For the case of neutral wetting, broader and rounded fingers are observed. And for the case of injecting a wetting fluid, a broad but distorted front is observed approaching stable displacement. The results show the importance of the wetting angle on the morphology of viscous fingering. This study demonstrates that the multiphase Lattice Boltzmann Method can simulate phenomenology relevant to studies of enhanced oil recovery such as water injection, and hence, may lead to improved estimates of oil recovery factors.

Recent advances in modeling Rayleigh-Benard convection have demonstrated the existence of turbulent superstructures, whose life and morphology largely varies with Rayleigh (Ra) and Prandtl (Pr) numbers. These structures appear as a two scale phenomena, where small scale rolls organize in larger convection cells, and can be modelled only in 3D on a simulation box characterized by a very large (>10) width/height (W/L) ratio, and sufficiently refined to resolve the boundary layer up to Ra = 108 (>100 divisions in height) and to Ra = 1010 (>200 divisions). To achieve this goal, we use our own 3D Parallel Python implementation of the Lattice Boltzmann Method, tested to run with linear efficiency on thousands of cores. We show the dependency of horizontal fluctuations of RMS of temperature and vertical velocity in the middle of the box and illustrate how the superstructures emerge for W/L ratios of Terrestrial Planets and Super Earths, and quantify the duration of these superstructures and the likely implications for the evolution of their surface features. The effect of the P/T dependent viscosity and thermal conductivity is finally discussed.

We attempt to construct a timeline of The Hunga Tonga – Hunga Ha’apai eruption on 15 January 2022 through analyses of seismic, barometric, infrasonic, lightning, and satellite data. Satellite imagery at 04:00 UTC showed no ash in the air, but by 04:10 UTC, a plume had risen to 18 km. Over the next 20 minutes, the plume rose to 58 km. USGS determined that Mw5.8 volcanic earthquake of unknown mechanism had occurred at 04:14:45. Gravity waves were observed in satellite imagery, and barometric and infrasound stations around the world recorded ultra-low frequency pressure variations of more than 100 Pa, inducing ground-coupled airwaves around the globe, and meteo-tsunamis in the Caribbean Sea and Mediterranean Sea. Tsunami waves were recorded in coastal areas around the Pacific Ocean. From record sections, we determined speeds of 3.9 km/s and 299 m/s for the initial seismic and infrasound signals respectively, converging to an eruption onset time of ~0402 UTC ± 1 minute. The global pressure pulse has a speed of ~314 ± 3 m/s, consistent with theoretical models for Lamb waves (Bretherton, 1969), suggesting an origin time of ~0415 ± 2 minutes (consistent with the Mw5.8 volcanic earthquake, and sharp increases in lightning flash rates), and peaking around ~0429 ± 2 minutes. We suggest that Surtseyan volcanic activity commenced at ~04:02, building to a sub-Plinian eruption ~7 minutes later, before a phreato-Plinian eruption commenced at ~04:14. The peak Lamb wave amplitude at the closest station (757 km from HTHH) was 780 Pa. Assuming geometrical spreading like 1/√r (where r is the source-receiver distance), we estimate a lower bound of ~23 kPa for reduced pressure by extrapolation back to 1 km. Adding a near field term that decays like 1/r, we estimate an upper bound of 170 kPa for reduced pressure. Comparison of these values with those from other eruptions (McNutt et al. in this session) suggests the 15 January HTHH eruption was in the VEI 5-6 range.

Solar flare, as a typical large temporal-spatial turbulent magnetic reconnection (LTSTMR, the ratio of observed current sheets thickness to electron characteristic length, electron Larmor radius for low-β and electron inertial length for high-β, is on the order of 10E10–10E11; the ratio of observed evolution time to electron gyroperiod is on the order of 10E7–10E9) explosion in the solar atmosphere activities, involving sudden bursts of particle acceleration that from sudden release of magnetic energy in a few minutes to a few tens of minutes. The X rays and gamma rays are believed to result from the interactions of the high energy electrons energized and nuclear interaction of the high energy protons and other heavier ions, respectively. While many particle acceleration models consider turbulence acceleration as an effective way of generating energetic electrons, the precise turbulence roles during acceleration and heating of electrons still remain unclear. Here we show from 3D relativistic hybrid particle-in-cell and lattice Boltzmann method (RHPIC-LBM) simulation that interaction of helical magnetic structure that leads to efficient energization of electrons. By following the trajectories of the most energetic electrons, we found the strong Langmuir turbulence acceleration (LTA) through wave-wave, wave-particle interaction in the diffusion region of the flare, which can accelerate electrons effectively. and discuss the turbulence acceleration by strong Langmuir wave. The simulation of LTA is not only similar to the shock wave acceleration, but more efficient than that of the shock wave acceleration. The energy spectrum of hot electrons undergoing LTA can be studied the X ray and gamma ray production in flare. We anticipate our results to be a key point for understanding the relationship between particle acceleration mechanism and explosive energetic electrons observed in the solar flares during MHD Alfven turbulence translate into Kinetic Alfven turbulence progress.