Oblique Impact Simulations Research Articles

Effective friction in adhesive mixtures intended for inhalation: Simulation of oblique impact of adhesive units

Oblique impact between adhesive units was studied using the Discrete Element Method (DEM) as a means to assess the effective friction coefficient and its dependence on particle shape, surface coverage ratio (SCR; 0.5, 0.75 and 1) and impact angle ( 1 5 ∘ − 7 5 ∘ ) in a low handling velocity regime (0.6 – 1.6 m/s). Adhesive units were created in silico from a spherical carrier particle (100 μm diameter) and monodisperse fine (drug) particles (3 μm large) of a spherical, triangular bipyramidal or tetrahedral shape. The particle interaction was modeled using the Hertz-Mindlin contact model with JKR adhesion (surface energy 0.03 J/m 2 ). A total of over 300 simulations were performed and the effective friction coefficient was extracted from the normal and tangential forces experienced by the carrier particles. The adhered fines resulted in a significantly reduced friction coefficient in comparison to the bare carriers but no additional reduction was observed with increasing SCR, suggesting a saturation already at an SCR of 0.5. The effective friction coefficient was independent of the impact velocity for relative velocities over 1 m/s. The impact angle had a significant effect on the friction coefficient, with head-on type collisions (15°) resulting in the lowest and grazing-type collisions (75°) the highest values. This was especially pronounced for the spherical fines whereas the triangular bipyramidal and especially the tetrahedral fines resulted in a more modest dependence on impact angle but overall considerably higher friction coefficients. These results could be used to better understand and formulate adhesive mixtures. • Adhesive units with different fine shapes were formed in-silico. • Binary collisions with different impact angle to study effective friction. • Effective friction is signifcantly lower compared to bare carrier particles. • Tetrahedral shape with angles towards grazing impact showed highest friction.

Effect of Impact Velocity and Angle on Deformational Heating and Postimpact Temperature

AbstractThe record of impact‐induced shock heating in meteorites is an important key for understanding the collisional history of the solar system. Material strength is important for impact heating, but the effect of impact angle and impact velocity on shear heating remains poorly understood. Here, we report three‐dimensional oblique impact simulations, which confirm the enhanced heating due to material strength and explore the effects of impact angle and impact velocity. We find that oblique impacts with an impact angle that is steeper than 45‐degrees produce a similar amount of heated mass as vertical impacts. On the other hand, grazing impacts produce less heated mass and smaller heated regions compared to impacts at steeper angles. We derive an empirical formula of the heated mass, as a function of the impact angle and velocity. This formula can be used to estimate the impact conditions (velocity and angle) that occurred and caused Ar loss in the meteoritic parent bodies. Furthermore, our results indicate that grazing impacts at higher impact velocities could generate a similar amount of heated material as vertical impacts at lower velocities. As the heated material produced by grazing impacts has experienced lower pressure than the material heated by vertical impacts, our results imply that grazing impacts may produce weakly shock‐heated meteorites.

A lattice Boltzmann simulation of oblique impact of a single rain droplet on super-hydrophobic surface with randomly distributed rough structures

Abstract In this paper, oblique impact of a single rain droplet on super-hydrophobic surface with randomly distributed rough structures was investigated by lattice Boltzmann method. The effects of the impact angle of the droplet as well as the skewness and kurtosis of rough surface on the bouncing ability of the droplet were in this paper. It was found that the oblique impact can effectively reduce the contact time in the process of droplet bouncing off, because the energy consumption caused by the pinning effect is reduced. Moreover, the contact time most possibly reaches the shortest when the impact angle is 45°. Decreasing the skewness and keeping the kurtosis around 4.0 can enhance the bouncing ability during the droplet oblique impact on randomly distributed rough surfaces. The results are useful for the design of building structures.

Enhancement of Impact Heating in Pressure‐Strengthened Rocks in Oblique Impacts

AbstractShock‐induced metamorphism in meteorites informs us about the collisional environment and history of our solar system. Recently, the importance of material strength in impact heating was reported from head‐on impact simulations. Here, we perform three‐dimensional oblique impact simulations and confirm the additional heating due to material strength for oblique impacts. Despite a large difference in the peak pressure at the impact point at a given impact velocity, we find that the heated mass for an oblique impact is nearly the same as that for a head‐on impact. Thus, our results differ from the previous finding that the heated mass decreases as the impact becomes more oblique and show that the additional shear heating is more effective for oblique impacts than for head‐on impacts. This also indicates that material ejected during oblique impact tends to experience lower shock pressures but higher temperatures.

Near and far-field hazards of asteroid impacts in oceans

Hazards resulting from asteroid ocean impacts were modelled using hydrocode simulations to examine the near-field effects including the initial formation and subsequent long range propagation of tsunami waves that can transport potentially damaging energy far from the impact site.Three-dimensional simulations of oblique impacts into deep water, with trajectory angles ranging from 27° to 60° above the horizontal, were performed with the Los Alamos Rage hydrocode. The simulations include atmospheric effects such as ablation and airbursts. These oblique impact simulations are performed in order to help determine whether there are additional dangers due to the obliquity of impact not covered by previous studies. The energy transferred to both the air blast wave and the water are calculated as well as the amount of sea water lofted into the upper atmosphere. Water crater sizes and subsequent surface elevation profiles, surface pressures, and depth-averaged mass fluxes within the water are prepared for use in far-field propagation studies. Like previous three-dimensional simulations, these simulations show that except at exceedingly shallow entry angles below those simulated here the resulting waves are roughly circular and that the initial waves and central jet oscillation are highly turbulent and dissipate a lot of the energy.Two-dimensional axisymmetric simulations of long range propagation of impact tsunami were performed using the Lawrence Livermore ALE3D hydrocode on the NASA Pleiades supercomputer. These simulations showed that impacts under 1 gigaton TNT equivalent into the deep ocean basins will create deep-water waves that undergo dispersion, whereas impacts onto continental shelves will create shallow-water waves that do not suffer dispersion. The simulations also showed that on the order of 1% of the kinetic energy of the impact is converted into the tsunami wave. This is an order of magnitude less than previous semi-empirical estimates of ∼15% based on explosion test data and laboratory scale impacts.

Three-dimensional simulations of oblique asteroid impacts into water

Waves generated by impacts into oceans may represent the most significant danger from near-earth asteroids and comets. For impacts near populated shores, the crown splash and subsequent waves, accompanied by sediment lofting and high winds, are more damaging than storm surges from the strongest hurricanes. Asteroids less than 500 m in diameter, impacting deep water far from shores, produce waves that may be detectable over large distances, but are probably not significantly dangerous. We present new three-dimensional simulations of oblique impacts into deep water, with trajectory angles ranging from 27° to 60° (where 90° is vertical). These simulations are performed with the Los Alamos Rage hydrocode, and include atmospheric effects including ablation and airbursts. These oblique impact simulations are specifically performed in order to help determine whether there are additional dangers from the obliquity of impact not covered by previous two-dimensional studies. Water surface elevation profiles, surface pressures, and depth-averaged mass fluxes within the water are prepared for use in propagation studies.

A new analytical model to simulate high-speed impact onto composite materials targets

This paper presents the expansion and improvement of an analytical model previously published by the authors, enabling the simulation of oblique impact onto fibre reinforced composite thin targets. The paper also includes the experimental results of firing tests onto carbon/epoxy composite targets at different impact angles. An excellent agreement is observed between analytical and experimental results both of ballistic limit and residual velocity after perforation as well.

Pregnant driver injury investigations in oblique crashes

Kinetics and kinematics of an oblique impact are different when compared with frontal collisions. The objective of this research is to simulate various oblique crash scenarios that pregnant drivers may experience by using the computational pregnant occupant model, Expecting and investigate potential injuries that pregnant drivers may suffer. Half-sine acceleration pulses representing crash speeds, 15 to 45 kph are used in the simulations. Oblique impact simulations are conducted both from the nearside and the farside (offside) of the vehicle. The placental abruption and hence foetus mortality risks during oblique crashes are compared with the full-frontal impact cases.

Scaling of oblique impacts in frictional targets: Implications for crater size and formation mechanisms

Almost every meteorite impact occurs at an oblique angle of incidence, yet the effect of impact angle on crater size or formation mechanism is only poorly understood. This is, in large part, due to the difficulty of inferring impactor properties, such as size, velocity and trajectory, from observations of natural craters, and the expense and complexity of simulating oblique impacts using numerical models. Laboratory oblique impact experiments and previous numerical models have shown that the portion of the projectile’s kinetic energy that is involved in crater excavation decreases significantly with impact angle. However, a thorough quantification of planetary-scale oblique impact cratering does not exist and the effect of impact angle on crater size is not considered by current scaling laws. To address this gap in understanding, we developed iSALE-3D, a three-dimensional multi-rheology hydrocode, which is efficient enough to perform a large number of well-resolved oblique impact simulations within a reasonable time. Here we present the results of a comprehensive numerical study containing more than 200 three-dimensional hydrocode-simulations covering a broad range of projectile sizes, impact angles and friction coefficients. We show that existing scaling laws in principle describe oblique planetary-scale impact events at angles greater than 30° measured from horizontal. The displaced mass of a crater decreases with impact angle in a sinusoidal manner. However, our results indicate that the assumption that crater size scales with the vertical component of the impact velocity does not hold for materials with a friction coefficient significantly lower than 0.7 (sand). We found that increasing coefficients of friction result in smaller craters and a formation process more controlled by impactor momentum than by energy.

Hydrocode modeling of oblique impacts: The fate of the projectile

Abstract— All impacts are oblique to some degree. Only rarely do projectiles strike a planetary surface (near) vertically. The effects of an oblique impact event on the target are well known, producing craters that appear circular even for low impact angles (>15° with respect to the surface). However, we still have much to learn about the fate of the projectile, especially in oblique impact events. This work investigates the effect of angle of impact on the projectile.Sandia National Laboratories' three‐dimensional hydrocode CTH was used for a series of high‐resolution simulations (50 cells per projectile radius) with varying angle of impact. Simulations were carried out for impacts at 90, 60, 45, 30, and 15° from the horizontal, while keeping projectile size (5 km in radius), type (dunite), and impact velocity (20 km/s) constant.The three‐dimensional hydrocode simulations presented here show that in oblique impacts the distribution of shock pressure inside the projectile (and in the target as well) is highly complex, possessing only bilateral symmetry, even for a spherical projectile. Available experimental data suggest that only the vertical component of the impact velocity plays a role in an impact. If this were correct, simple theoretical considerations indicate that shock pressure, temperature, and energy would depend on sin2θ, where θ is the angle of impact (measured from the horizontal). However, our numerical simulations show that the mean shock pressure in the projectile is better fit by a sin θ dependence, whereas shock temperature and energy depend on sin3/2 θ. This demonstrates that in impact events the shock wave is the result of complex processes that cannot be described by simple empirical rules. The mass of shock melt or vapor in the projectile decreases drastically for low impact angles as a result of the weakening of the shock for decreasing impact angles. In particular, for asteroidal impacts the amount of projectile vaporized is always limited to a small fraction of the projectile mass. In cometary impacts, however, most of the projectile is vaporized even at low impact angles.In the oblique impact simulations a large fraction of the projectile material retains a net downrange motion. In agreement with experimental work, the simulations show that for low impact angles (30 and 15°), a downrange focusing of projectile material occurs, and a significant amount of it travels at velocities larger than the escape velocity of Earth.

Numerical simulation of oblique impact on orbital debris shielding

Hybrid particle-finite element methods have been proposed as a modeling methodology well suited to the problem of hypervelocity impact simulation. To evaluate the use of such numerical methods for orbital debris shielding design, a series of simulations have been conducted using a three dimensional hybrid particle-finite element code now under development. Two sets of oblique impact simulations, one for a single bumper Whipple shield and one for a dual bumper or stuffed Whipple shield, have been compared to published ballistic limit equations, the latter derived from experiment. The results indicate that hybrid particlefinite element methods can provide an accurate and computationally tractable approach to the simulation of orbital debris shield performance.

Oblique hypervelocity impact simulation for whipple shield-protected structures

Three dimensional simulation of hypervelocity impacts on space structures places extreme demands on even supercomputer resources. This is due in large part to the fact that conventional Eulerian and Lagrangian codes are ill-suited to model debris cloud evolution. To reduce the computer time and memory requirements of oblique impact simulations, a three-dimensional elastic-plastic particle dynamics model of debris cloud evolution has been developed. This numerical model has been linked to an Eulerian hydrocode and a Lagrangian structural code, and applied in the simulation of oblique hypervelocity impacts on Whipple shield-protected structures.