On 2026 August 5, at approximately 06:35 UT, a spent Falcon 9 upper stage will impact the lunar surface near Einstein Crater. This event will occur on sunlit terrain near the eastern limb as seen from Earth. The impact flash and resultant ejecta plume from this event are potentially observable from ground- and space-based observational facilities. This event provides an opportunity to attempt the recording of an artificial impact in real-time; although many of the properties of the event (such as visual magnitude) are imprecisely predicted at present. Moreover, this event provides an opportunity to test a pipeline for localising impacts on the lunar surface for future seismic experiments, investigating the dust and plume dynamics from impact events on the Moon, and considering hazards from artificial space debris impacts. Both professional and amateur astronomers are encouraged to attempt observations of this event.

Polycrystalline diamond compact (PDC) cutters are used in geothermal energy drilling operations as they are exceptionally effective due to their strength and resistance to abrasion. It is important to understand the effect of downhole conditions to accurately model rock-cutter-rock interactions, as well as wear on the bit and drilling efficiency. Cutting efficiency is determined through the weight on the bit, rotational speeds, and other cutter and rock parameters in drilling, here we can comment on cutting efficiency through the cutting force. The ultimate goal of this research is to numerically model the PDC cutter–rock interaction in 3-D to find an optimal arrangement of parameters for efficient geothermal drilling. Using the combined finite discrete element method (FDEM), we model rock fracture and fragmentation for a single PDC cutter for both atmospheric and realistic well pressure conditions. We present the numerical analysis progression of PDC cutter-rock interaction in 2-D and 3-D for a range of cutting speeds, depth of cuts, and pressures using sandstone and granite as our rock materials. These parameters are varied to understand the optimal configuration to increase drilling performance as determined by cutting force, damage style, and fracture energy. Our models successfully reproduce laboratory values, which increases our understanding of rock fracture at downhole conditions.

Modeling fracture and damage processes is a challenging, yet critical capability for promoting safe and sustainable design in geotechnical, energy, and hydrological applications. Numerical methods capable of modeling fracture processes are rarely asked to make blind predictions against experimental observations. Here, we report results from a numerical study of blind fracture prediction in an additively manufactured, three-point bend specimen. We record a number of physical mechanisms associated with the fracture of the specimen and make a blind prediction against experimental results that were unknown when the numerical study was performed. We then compare results from our model to the blind data set. We find that the combined finite discrete element method performs exceptionally well in the simulation and prediction of fracture processes.

In recent decades a whole new research discipline dealing with physics of discontinua has emerged. Unlike continuum, discontinuum builds a picture of the world where a large number of independent agents interact with each other in order to produce virtual emergent phenomena that closely match real world emergent phenomena. The discontinuum assumption complements the continuum assumption and both assumptions often work together in what is termed hybrid continuum-discontinuum formulations. In this chapter some key simulation tools of Computational Physics of Discontinua are introduced, while hybrid continuum-discontinuum simulation approaches and the combined finite-discrete element method (FDEM) are described in some detail. In this context, the concept of virtual experimentation and its extensions towards AI (artificial intelligence) based scientific discovery, together with accompanying custom-made hardware architectures, are introduced and explained.

ABSTRACT: We aim to model PDC cutter-rock interactions in 3-D through numerical study to find an optimal arrangement of parameters for efficient geothermal drilling. Using the combined finite discrete element method (FDEM), we model realistic pressure conditions and rock fracture and fragmentation. FDEM can model both continuum and discontinuous mechanical behavior, which allows for modeling of fracture in targeted rock at downhole conditions. We simulate PDC cutter-rock interaction in 3-D for a range of back rake angles, cutting speeds, and depth of cuts using granite as our target rock material. These parameters are varied to investigate the impact on the cutting force and fracture dynamics in an effort to benchmark performance. We reproduce results from numerical rock cutting tests and qualitative results from laboratory experiments. We report on the progress of the numerical analysis for this complex multi-physics problem. 1 INTRODUCTION Geothermal energy is an important form of clean energy in the United States and other parts of the world. Geothermal energy drilling involves deeper, hotter, and harder rock sources than conventional/unconventional oil and gas targets (Dwivedi et al., 2008; Kumari et al., 2017). Understanding the mechanics of geothermal energy drilling is essential to reducing the overall cost, of which drilling can be over half of the total cost (Pierce and Livesay, 1994). A commonly used drill bit due to its strength and resistance to abrasive wear is the polycrystalline diamond compact (PDC) cutter bit (Dougherty et al., 2014; Yang et al., 2018). The combination of deep, hard rock means the forces in geothermal drilling are typically larger and drilling performance needs to be increased. The rate of penetration (ROP) determines the efficiency of drilling, as in how much rock material can be removed. A high ROP would remove more rock material, however, higher ROP means higher forces on the drill bit. Determining the forces on the drill bit under a geothermal drilling interaction allows us insight into drilling performance.

Characterizing fluid flow in a porous and permeable material is fundamental to energy and hydrological applications, yet direct measurements of permeability are very difficult to conduct in situ. However, attending fluid flow through a material are various mechanical responses, e.g., strain fields and acoustic emissions, and these mechanical responses may hold important clues to the fluid flow in the material, specifically the permeability. Here we report results from a numerical study of fluid flow through a channel, defined by confining side blocks, that contains a particle bed. For a range of inlet velocities, we study the strain and acoustic emission in the confining side blocks. The simulations are repeated for different configurations of the particle bed. We find a one-to-one correspondence between strain and acoustic emission and the quantities that determine the permeability. Thus, strain and acoustic emission may serve as ingredients in an unconventional scheme for remote monitoring to learn the permeability.

ABSTRACT Three-point bending test is a widely used laboratory test for the estimation of the flexural force-displacement response of the material. It is well known that the results of the three-point bending test are sensitive to the specimen and the loading. In this work, the impact of the boundary effects on a single notch three-point bending test is studied using LANL's combined finite-discrete element method (FDEM) based code, the Hybrid Optimization Software Suite (HOSS). To this goal, a series of virtual experiments with different specimens and boundary conditions are conducted. The influence of the notch location, and fixture shape are studied. Results clearly show that these boundary conditions greatly influence on the fracture initiation and propagation behaviors as well as the flexural force-displacement response. INTRODUCTION Three-point bending test is a long-used technique applied mainly in the oil and gas industry to estimate the fracture toughness of rocks in the laboratory. In this test, the vertical tension is applied to the convex side of a sheet or plate specimen placed on two supporting fixtures with a set distance apart. A variety of numerical approached have been proposed to analyze the crack initiation and growth behavior of three-point bending test in the past several decades (Fakhimi, 2005; Kokot, G., Binkowski, 2011; Ramos, 2015; Klasztorny, 2018: Sauvage, 2020). However, the effect of boundary conditions is still lacking consideration in the previous studies. Motivated by the prior works and the knowledge gaps remaining in effect of boundary conditions, a finite-discrete element method (FDEM) model is applied here to interpret three-point bending experiment results in order to characterize dependence of rock fracture behavior on boundary conditions and notch location. The present study therefore aims to capture the crack initiation and propagation behavior for laboratory experiments using material properties and traction-separation law that has been calibrated by comparing the simulation results with lab experiments provided by Jiang et al. (2021) and Jiang et al. (2022), regardless of notch location. This study aims to revisit the effect of boundary conditions on crack initiation and growth behavior under three-point bending test. For this purpose, a 2D plane-strain model is developed using HOSS, a combined finite-discrete element method (FDEM) based code. Different boundary conditions and notch locations are considered for lab-scale simulations. Indeed, simulation results indicated that the crack initiation location and crack growth behavior can vary with different boundary conditions and notch locations, which can challenge the general belief that the crack initiation and propagation behavior should not be affected by the boundary conditions greatly.

HOSS (Hybrid Optimization Software Suite) is a fracture mechanics code that properly conserves mass, energy and momentum. HOSS-FSIS was utilized to conduct exploratory calculations (2D plane strain/3D) for the G-tunnel event 2020 where a pseudo NPE 1.1kt HE equivalent source is used. The purpose of this analysis is to determine if the HOSS fluid-solid coupling solver can capture relevant down-tunnel phenomenology.

Characterizing fluid flow in a porous material with permeability is fundamental to energy and hydrological applications, yet direct measurements of permeability are very difficult to conduct in situ. However, attending fluid flow through a material are various mechanical responses, e.g., strain fields, acoustic emission. These mechanical responses may hold important clues to the fluid flow in the material, to the permeability. Here we report results from a numerical study of fluid flow in a channel, defined by confining side blocks, that contains a particle bed. For a range of inlet velocities, we study the strain and acoustic emission in the side blocks. Simulations are repeated for different configurations of the particle bed. We find that the observed mechanical response accords with an analytic model of this system, providing promising evidence for using mechanical measurements, particularly strain and acoustic emission, as surrogates for direct measurement of permeability.

Large scale computational models are important for studying impact cratering events that are prevalent both on Earth and, more broadly, in this solar system. To address these problems, models must reliably account for both large length scales (e.g., kilometers) and relatively long time scales (hundreds of seconds). This work benchmarks two such approaches, a more traditional hydrodynamics approach and a finite-discrete element method (FDEM), for impact cratering applications. Both 2D and 3D results are discussed for two different impact velocities, 5 km/s and 20 km/s, striking normal to the target and, for 3D simulations, 45° from vertical. In addition, comparisons to previously published data are presented. Finally, differences in how these methods model damage are discussed. Ultimately, both approaches show successful modeling of several different impact scenarios.

Nearly thirty years since its inception, the combined finite-discrete element method (FDEM) has made remarkable strides in becoming a mainstream analysis tool within the field of Computational Mechanics. FDEM was developed to effectively “bridge the gap” between two disparate Computational Mechanics approaches known as the finite and discrete element methods. At Los Alamos National Laboratory (LANL) researchers developed the Hybrid Optimization Software Suite (HOSS) as a hybrid multi-physics platform, based on FDEM, for the simulation of solid material behavior complemented with the latest technological enhancements for full fluid–solid interaction. In HOSS, several newly developed FDEM algorithms have been implemented that yield more accurate material deformation formulations, inter-particle interaction solvers, and fracture and fragmentation solutions. In addition, an explicit computational fluid dynamics solver and a novel fluid–solid interaction algorithms have been fully integrated (as opposed to coupled) into the HOSS’ solid mechanical solver, allowing for the study of an even wider range of problems. Advancements such as this are leading HOSS to become a tool of choice for multi-physics problems. HOSS has been successfully applied by a myriad of researchers for analysis in rock mechanics, oil and gas industries, engineering application (structural, mechanical and biomedical engineering), mining, blast loading, high velocity impact, as well as seismic and acoustic analysis. This paper intends to summarize the latest development and application efforts for HOSS.

Most of the surface of Mars is covered with unconsolidated rocky material, known as regolith. High‐fidelity models of the dynamics of impacts in such material are needed to help with the interpretation of seismic signals that are now recorded by SEIS, the seismometer of InSight. We developed a numerical model for impacts on regolith, using the novel Hybrid Optimization Software Suite (HOSS), which is a Lagrangian code mixing finite and discrete element formulations. We use data from hypervelocity impact experiments performed on pumice sand at the NASA Ames Vertical Gun Range to identify and calibrate key model parameters. The model provides insight into the plastic‐elastic transition observed in the data and it also demonstrates that gravity plays a key role in the material response. Waveforms for receivers situated vertically below the impact point are correctly modeled, while more research is needed to explain the shallow receivers' signals.