Shock Mitigation Research Articles

Light Shock Stress after Outdoor Sunlight Exposure in Seedlings of Picea abies (L.) Karst. and Pinus sylvestris L. Pre-Cultivated under LEDs—Possible Mitigation Treatments and Their Energy Consumption

Year-round cultivation under light emitting diodes (LEDs) has gained interest in boreal forest regions like Fenno-Scandinavia. This concept offers forest nurseries an option to increase seedling production normally restricted by the short vegetation period and the climate conditions. In contrast to some horticultural crops which can be cultivated entirely under LEDs without sunlight, forest seedlings need to be transplanted outdoors in the nursery at a very young age before being outplanted in the field. Juvenile plants are less efficient using absorbed light and dissipating excess energy making them prone to photoinhibition at conditions that usually do not harm mature plants. The outdoor transfer can cause stress in the seedlings due to high sunlight intensity and exposure to ultraviolet (UV) radiation not typically present in the spectra of LED lamps. This study tested possible treatments for mitigating light shock stress in seedlings of Picea abies (L.) Karst. and Pinus sylvestris L. transplanted from indoor cultivation under LEDs to outdoor sunlight exposure. Three sowings were carried out in 2014 (May and June) and 2015 (May) cultivating the seedlings during five weeks under LED lights only. Afterwards, higher light intensity or UV radiation treatments were applied during one week in order to adapt the seedlings to natural outdoor conditions. After transplanting a transition phase was introduced using shading cloths for one or three weeks as outdoor treatments for light shock mitigation. Chlorophyll fluorescence (ChlF) levels and CO2 assimilation rates were measured before transplanting and followed outdoors during 5 weeks. The ChlF results revealed stress symptoms in the photoreceptors during the first days after transplanting. After five weeks outdoors the ChlF levels had recovered and the light saturation points had shifted, allowing higher CO2 assimilation rates. By the end of the vegetation period the morphological attributes showed no major differences between treatments.

Dynamic response of ductile materials containing cylindrical voids

The fracture of ductile materials is often the result of the nucleation, growth and coalescence of microscopic voids. In this thesis, we mainly focus on the dynamic void evolution in porous media containing cylindrical voids. This study covers a problem that is of particular interest in many areas of research (e.g. development of shock mitigation devices for civil or military applications). Owing to the development of additive manufacturing, the processing of porous material with cylindrical voids is an option to create lightweight materials having interesting properties in terms of energy dissipation. Therefore, our work aims at describing the dynamic response of architectured materials such as honeycomb structures. In dynamic loading, microvoids sustain an extremely rapid expansion which generates strong acceleration of particles in the vicinity of cavities. These micro-inertia effects are known to play a significant role in the macroscopic response and the development of damage in porous media. In fact, the overall macroscopic stress is found to be the sum of two contributions: a static term (micro-inertia independent term) and a dynamic term (micro-inertia dependent term), the latter being related to the microstructure (e.g. size and aspect ratio of voids). In our work, a cylindrical shell is adopted as a Representative Volume Element (internal and external radii a and b, length 2l) for the porous material. The static term is derived from a yield function available in the literature. The dynamic stress is evaluated analytically using a trial velocity field for cylindrical voids combined with the multi-scale approach developed in the literature in LEM3. It is shown that the dynamic stress is scaled by the mass density, two characteristic lengths of the voids, the porosity, the macroscopic strain rate tensor and the time derivative of the strain rate tensor. An important outcome of the model is the differential lengthscale effect which exists between in-plane and out of plane components of the macroscopic stress. Namely, it is observed for axisymmetric loading that in-plane dynamic stress components are only related to the void radius a while the out of plane stress component is linked to a and the length of the RVE, l. In the thesis, we present the dynamic response of the porous medium when subjected to various loading conditions: spherical loading, axisymmetric plane strain loading, uniaxial loading and biaxial loading. While for plane strain loading under quasi static condition, the overall axial stress is spherical, in dynamic conditions, the inertia contribution hinders the overall stress tensor from being spherical. Another important result of the proposed theory is the effect of the void length, which does not exist in quasi static conditions where the overall response is solely modulated by the porosity. The case of thin cylinders under dynamic loading reveals a peculiar damage kinetics. In fact, the damage developed in such porous materials results from an increase of the void radius and a reduction of the external radius. The void collapse for uniaxial as well as for biaxial loadings are new observations. The analytical model predictions are validated based on comparisons with finite element calculations (Abaqus/Explicit).

Tunable-with-energy intense modal interactions induced by geometric nonlinearity

Modal interactions are distinct features of nonlinear systems that can be exploited in applications such as vibration and shock mitigation, targeted (irreversible) energy transfers (TET), and acoustic/stress wave tailoring. For such applications, different types of nonlinearities, e.g. hardening, softening, smooth, non-smooth, material or geometric, have been considered. In this work, we examine the geometric nonlinearity resulting from an initially inclined element consisting of a linear spring and a viscous damper connected in parallel, having an initial angle of inclination, [Formula: see text]. Because of its inclined configuration, this element possesses strong (and doubly tunable with respect to [Formula: see text] and energy) geometrically nonlinear stiffness and damping effects, despite the linear constitutive laws governing its constituent components. First, we consider a single-degree-of-freedom linearly grounded oscillator attached to the nonlinear inclined element. Omitting dissipative effects, we investigate the frequency–energy relation of this system by employing the canonical action-angle transformation and show that, depending on the initial angle of inclination and the energy-level, the resulting nonlinearity can be tuned to be softening, hardening or a combination of both. Next, we explore the efficacy of the geometric nonlinearity to induce strong modal interactions by considering a three-degree-of-freedom lightly damped primary system that is weakly coupled to a single-degree-of-freedom lightly damped attachment with the inclined nonlinear element, subjected to impulsive excitation. Varying [Formula: see text] and the input energy, we demonstrate strong modal energy-exchanges between the modes of the primary system and the nonlinear attachment over broad energy-dependent spans of [Formula: see text]. We show that the passive self-adaptiveness of the nonlinear damping and the hardening–softening geometric nonlinearity can induce narrowband or broadband frequency TET, including high-to-low frequency energy transfers. Interestingly, over a definitive range of [Formula: see text], these modal interactions may be limited only between the nonlinear mode of the attachment and the highest-frequency linear mode of the primary system, inducing strong high-frequency targeted energy transfer to the primary system.

Mitigation of shock loading on structures using aqueous methylcellulose solution

Shock mitigation performance of aqueous methylcellulose hydrogel and water for structural applications was investigated through two dynamic loading instruments: Instrumented bar and shock tube. While aqueous methylcellulose solutions have previously been found to attenuate impact-induced forces passing through them by a unique liquid-to-solid phase transition, this is the first time studied as shock mitigators to structural elements. The results obtained with aqueous methylcellulose as mitigator were compared with an equivalent experiment conducted with water as damping medium. The liquid was loaded into a specially designed hollow aluminum box, built to allow transmission of dynamic stress waves to a thin back plate. Determination of the liquid's attenuation performance was based on the 3D Digital Image Correlation technique with high-speed photography to obtain the full-field real-time deformation data of the back-face plate throughout the dynamic loading event. It was found that upon high rate loading with the instrumented bar, the aqueous methylcellulose solution decreases the maximum out of plane displacement resulting from the dynamic loading by as much as 40% compared to water, and significantly damps the structural vibrations of the back-face plate. On the other hand, upon relatively low rate loading with shock tubes, water and aqueous methylcellulose solutions provide the same magnitude of out of plane displacement, however, the damping ratio (Logarithmic Decrement) of the structure through aqueous methylcellulose solutions is 45% greater than through water. The findings are analyzed and rationalized in terms of imparted mechanical power.

DEVELOPMENT, TEST AND SELECTION OF A SHOCK MITIGATION SEAT FOR AN ALLWEATHER LIFEBOAT

Shock and vibration exposures in fast boats at sea can be more severe than in any other mode of transport. Shock mitigation seating plays a key part in reducing the possibility of injury, but seats must be suitable for the boat and for the way the boat will be used. The RNLI recently conducted an innovative sea trial programme to assess the performance of eight seats, from three manufacturers, for use in the Severn Class all-weather lifeboat. The trials were designed to maximise data capture while minimising crew exposure. Seat performance was measured with a range of occupants and operating conditions and the final seat selection was based on analysis of over 2,500 wave impacts. These “wave by wave” trials involved normal boat operation and were much more efficient to carry out than the more conventional, but often impractical, approach of attempting to carry out controlled, timed runs at specific speeds in specific sea states. Ahead of the trial, the seat manufacturer used information on RNLI crew demographics and craft operating conditions to optimise the seat. The seat configuration was determined from laboratory drop-tests at their in-house facility, with parameters chosen that were most likely to perform well in the Severn. The laboratory test procedure followed the methods defined by the UK's Ministry of Defence Protocol 1&2 and the US Navy's NSW/CCD-080-TR-2015/010 seat testing requirement. This paper describes the sea trials approach and seat design optimisation that led to the selection of the seat for use in the Severn Class.

Two-way controllable magnetorheological elastomer mount for shock and vibration mitigation

Current passive elastomeric mounts are designed to provide mitigation for a given shock and vibration exposure and are not capable of supporting variable payload systems, due to variation in the overall system dynamics. A novel magnetorheological elastomer (MRE) mount that can reduce or increase its stiffness based on payload and shock and vibration input is designed, fabricated, and tested to provide a wide controllable stiffness range for protecting sensitive systems that may require variable weight from external shock and vibration loading. A MRE is a field-controllable material in which the stiffness properties can be altered by changing the applied magnetic field. The two-way controllable MRE mount is designed by using three-dimensional electromagnetic finite element analysis. MRE mounts were developed by using relatively thick MRE layers and built-in electromagnets and permanent magnets. A two-layer MRE mount prototype is characterized by compression and shear tests. Control system hardware and software were developed to detect shock and vibration events, and activate the two-way controllable MRE mount, accordingly. The MRE mount and the control system were tested with variable representative weights. It was demonstrated that the designed control system can detect whether the incoming input is a shock event or a vibration event. The MRE mount demonstrated the ability to soften of stiffen based on the incoming input.

A Particle Coupling Finite Element Method for Shock-Mitigation Characterization of Magnetic Granular Systems

Granular chain system could realize the impulse protection mechanism. This work presents the shock mitigation characteristics of magnetic granular chains in different configurations. Based on magneto-structural coupling algorithm, a particle coupling finite element method is proposed. The coupling process is to numerically capture the process of the pre-compression and magnetic force of each grain in magnetic analysis and the field-induced dynamic responses under impulse loadings. For validation, an experimental set-up is designed, and the experimental results are tested and compared. The numerical predicted values present a good agreement with experimental results. It is shown that, when the characteristics of peak force, peak velocity, incident kinetic energy and stress wave propagation are compared, the performance in interstitial decorated chains is superior and followed by reverse-interstitial decorated chains and then monodisperse chain. The increment of magnetic field strength enhances the field-induced pre-compression, magnetic force, and shock mitigation capacity of granular chains. Such nonlinear behavior of magnetic granular chains can be exploited in order to design new tunable devise, such as shock absorbers and impulse protector.

Design of shock mitigation mechanism using momentum exchange and avoidance of impact transmission inspired by break-fall in Judo

Design of shock mitigation mechanism using momentum exchange and avoidance of impact transmission inspired by break-fall in Judo

Numerical and experimental investigation on the shock mitigation of satellite-rocket separation

The shock mitigation technique (SMT) for the satellite-rocket separation has always been one of the hot topics in the field of aerospace. Acoustic Black Hole (ABH) phenomenon which is discovered in recent years refers to the phenomenon of the energy focalization when the stress wave propagates in the plate structure with variable thickness. The ABH and its non-ideal form have received extensive attention and research since they were put forward. Combining the theory of non-ideal ABH with the SMT of satellite-rocket separation, this paper presents a new design of the satellite joint to decrease the satellite-rocket separation shock. At first, the propagation characteristics of stress wave in the thin plate structures with non-ideal ABH are deduced, and the key law affecting the energy attenuation is found. And then, an improved model for the standard satellite joint is proposed, and both the standard and improved models are simplified. What's more, the finite element (FE) models of the simplified satellite joints are established and the shock mitigation (SM) effect is numerically verified with the explicit dynamic code LS-DYNA. At last, the near-field and the whole satellite separation shock experiments are carried out to verify the effectiveness of the SM scheme. The results got in this paper indicate that the SM design based on the non-ideal ABH theory can effectively reduce the satellite-rocket separation shock.

Rotary-impact nonlinear energy sink for shock mitigation: analytical and numerical investigations

The nonlinear energy sink (NES) is a lightweight, strongly nonlinear dynamical attachment coupled to a (typically linear) large-scale primary structure for passive vibration mitigation. There are two nonlinear mechanisms governing the dynamics of the coupled system: irreversible targeted energy transfer (TET) from the primary structure to the NES, where energy is confined and locally dissipated, and NES-induced nonlinear energy scattering between the structural modes of the primary structure. In the literature, different NES designs have been investigated to optimize their nonlinear effects on the primary structures. One such design is the rotary NES consisting of a small mass inertially coupled to the primary structure through a rigid arm; another is the vibro-impact NES with non-smooth nonlinearities and inelastic collisions with the primary structure. These types have been found to achieve strong and rapid TET and are less sensitive to energy fluctuations. In this work, a hybrid NES design is proposed based on the synergetic synthesis of the rotary and impact-based NESs in a single rotary-impact NES (RINES). The RINES incorporates a fixed rigid barrier attached (typically) to the top floor of the primary structure to inflict impacts between its rotating mass and the top floor. An analytical study to evaluate its capacity to engage in resonance capture with a primary structure is presented first, followed by numerical investigations of cases when the RINES is attached to the top floors of small- and large-scale linear primary structures under impulsive excitation. The non-smooth nonlinearities induced through the consecutive impacts resulted in effective broadband shock mitigation at highly energetic response regimes, whereas the nonlinear inertial coupling enables similar beneficial mitigation capacity at lower-energetic response regimes. Hence, the combined effect of non-smooth and inertial nonlinearities enables effective passive mitigation capacity for a broad range of applied impulsive energies.

Effects of sacrificial coatings on stiffened double cylindrical shells subjected to underwater blasts

Underwater explosion shock loadings can seriously damage the vitality and fighting capacity of warships. Plastering a layer of sacrificial coating on the ship hull is one of effective strategies to isolate shock impulses and absorb shock energy. In this paper, the shock mitigation effects of sacrificial coatings plastered on a stiffened double cylindrical shell are analyzed numerically. The numerical models are validated by conducting a series of physical experiments of a stiffened double cylindrical shell under noncontact underwater explosion. Three different configurations are considered: both the pressure and thin hulls are plastered with sacrificial coatings; only the thin hull is plastered with sacrificial coatings; and only the pressure hull is plastered with sacrificial coatings. The total pressure field in water and the dynamic response of the stiffened double cylindrical shell are obtained. The results indicate that the deformation and motion of the sacrificial coatings can more easily generate rarefaction wave, which can decrease the total shock impulse acting on the structure. Among three configurations, the configuration of the coating plastered on the thin hull has a better capability of isolating the shock impulse and reducing the shock loadings transmitted to the pressure hull. The dynamic stress and velocity responses of the shell are effectively decreased. Comparisons between different configurations suggest that the coating on the thin hull plays a key role in mitigating shock loadings, while the coating on the pressure hull has limited effects. Moreover, comparison results between the bare hull and the equivalent model which increases the thickness of the thin or pressure hulls under the same mass conditions indicate that the method of using a sacrificial coating is more effective in improving the blast resistance of the structure. The research results are useful in guiding the shock resistance design of stiffened double cylindrical shells.

Smooth waves and shocks of finite amplitude in soft materials

Recently developed soft materials exhibit nonlinear wave propagation with potential applications in energy trapping, shock mitigation and wave focusing. We address finitely deformed materials subject to combined transverse and axial impacts, and study the resultant nonlinear waves. We determine the dependency of the induced motion on the impact characteristics, pre-deformation and the employed constitutive models. When using the neo-Hookean constitutive model, we find it cannot capture shear shocks and tensile-induced shocks, in contrast with experimental results on soft materials. Conversely, we find that the Gent model predicts that compressive impact may not be sufficient to induce a quasi-pressure shock—yet it may induce a quasi-shear shock, where tensile impact can trigger quasi-pressure shock—and may simultaneously trigger a quasi-shear shock. These features are in agreement with experimental data. Further, we show that the tensile impact must be greater than a calculated threshold value to induce shock, and demonstrate that this threshold is lowered by application of pre-shear.

Experimental Measurement and Analysis of Stress/Shock Wave Propagation Speed through Pre-strained Silicone Foam Pads under Lateral Confinement

Foam materials are extensively utilized in aerospace, military, and transportation applications to mitigate blast or shock impact. When foam materials are subjected to an external high-speed impact, shock, or blast loading, an elastic wave or shock wave will form and propagate through the thickness of the foam materials. In this study, silicone foam pads, which were confined laterally and pre-strained to different levels, were experimentally characterized and theoretically analyzed to understand their effects on wave propagation characteristics under impact loading. Depending on impact velocity, either an elastic strain wave or a shock wave would be generated in the silicone foam pad with different pre-strains. Above a certain impact velocity, a shock wave will be generated whereas, below this threshold impact velocity, an elastic strain wave will be generated. This threshold impact velocity depends on the pre-strain applied to the silicone foam pad. Equations are provided to estimate the wave propagation speed for either an elastic or a shock wave from the amount of pre-strain in the silicone foam pads and the impact velocity. These equations are expected to help improve silicone foam design and assembly processes for shock or blast mitigation applications.

Hybrid controller of magnetorheological semi-active seat suspension system for both shock and vibration mitigation

The impact caused by the detonation of landmines and improvised explosive devices may directly lead to spine fracture and injury of seated occupants on special vehicles. The vibration transmitted f...

Mitigation of Shock: Post‐Occupancy Anthropology

Getting people truly on board requires not just intellectual explanations, but emotional connection. So how can the need to address climate change be made real to the average urbanite? By creating an immersive experience of a city apartment as it might look in 2050, London design studio Superflux's installation Mitigation of Shock confronts us with the likely impact of global warming on the way we live, while offering insights that we could apply to take control of our destinies. Here, studio cofounders Anab Jain and Jon Ardern, and studio researcher Danielle Knight, describe the design research process that produced it, from interviews with specialists in a broad range of fields to materials investigations and prototyping.

Energy Dissipation Characteristics in Pre-strained Silicone Foam Transitioning to Silicone Rubber

Silicone foam is used as a shock mitigation material in a variety of systems to protect internal components from being damaged during external shock or impact loading. Characterizing the shock mitigation response of silicone foam under a variety of scenarios is a critical step in designing and/or evaluating new shock mitigation systems. In this study, a Kolsky bar with pre-compression capability was used with a passive radial confinement tube to subject the sample to various levels of pre-strain followed by impact loading. The effects of both pre-strain and impact velocity on impact energy dissipation behavior were investigated for silicone foam. The energy dissipation response of silicone foam is compared to a silicone rubber manufactured using the same processing methods to understand the energy dissipation characteristics of silicone foams transitioning to a silicone rubber. The final density of the foam or rubber plays a key role in both the total energy dissipation ratio in the time domain and the energy dissipation ratio as a function of frequency in the frequency domain.

Monitoring sedimentation of magnetorheological fluids using a vertical axis monitoring system with a low aspect ratio sensor coil**This research was conducted at the University of Maryland while the first author was a visiting student.

Adaptive energy absorbers (EAs) utilizing magnetorheological fluids (MRFs) are currently being investigated for severe impact or shock mitigation problems because magnetorheological energy absorbers can adjust stroking load to account for severity of impact and payload mass. Utilizing MRFs in such EAs requires a highly stable suspension that maintains a uniform concentration. Suspension stability of MRFs can be studied using a MRF column and an automated vertical axis inductance monitoring system (AVAIMS), where an inductance sensor is translated up and down the vertical MRF column to track the mud-line, defined as the boundary between the clarified fluid at the top of the column and the MRF below. The rate of descent of the mud-line is typically referred to as the sedimentation rate of the MRF. In this paper, a refined inductance sensor is developed that features a low aspect ratio coil to better localize rapid changes in concentration or sedimentation zone boundaries, as well as to improve symmetry of the applied magnetic field in the MRF sample enclosed by the sensor. This low aspect ratio solenoid (LARS) sensor was developed to measure the vertical distribution of the concentration of carbonyl iron particles in the MRF column. Compared with the high aspect ratio solenoid sensor used in our prior work, the results of FEM simulation and sedimentation experiments demonstrate that the LARS sensor was better able to localize rapid changes in concentration or density. Using the AVAIMS with the refined LARS sensor, a method was developed, based on the measured concentration gradient profile, to identify sedimentation zone boundaries in an MRF column, and these results were compared to our prior work using the measured concentration profile only. Sedimentation zone boundaries that are consistent with Kynch’s sedimentation theory were obtained using the concentration gradient profile method, such as monotonically descending mud-line, linearly ascending gel-line, and linearly ascending cake-line. Key metrics to characterize the time histories of the sedimentation zone boundaries are measured including mud-line descent rate, gel-line ascent rate, and cake-line ascent rate. Identification of sedimentation zone boundaries using the LARS sensor in conjunction with the concentration gradient profile method exhibited two main advantages including the direct measurement and improved localization of the large concentration change that occurs at a sedimentation zone boundary, and the elimination of sensor bias.

Controllability of magnetorheological shock absorber: II. Testing and analysis

To specifically verify the application feasibility of the internal bypass magnetorheological shock absorber (MRSA) for high-speed shock mitigation systems, the controllability evaluation indexes of damping force controllability and real-time controllability of the developed internal bypass MRSA prototype are experimentally investigated in Part II of this paper. Using the self-developed drop-induced shock setup and servo-hydraulic testing machine at Hefei University of Technology, the damping force characteristics of the internal bypass MRSA, including the controllable damping force range, the dynamic range, and the constant stroking load velocity range, are tested under the high-speed impact and sinusoidal displacement excitations. The response time characteristics of the internal bypass MRSA prototype are tested under triangular displacement excitation on the servo-hydraulic testing machine, including the response times when the electromagnetic coil windings of the internal bypass MRSA energized by current driver and voltage driver. The controllability of the internal bypass MRSA for semi-active shock mitigation systems is further evaluated, analyzed, and discussed.

Controllability of magnetorheological shock absorber: I. Insights, modeling and simulation**Part of work was done while Xian-Xu ‘Frank’ Bai was a joint PhD student of Chongqing University and University of Maryland, College Park.

The smart fluids—magnetorheological (MR) fluids show the potentials for high-speed shock mitigation applications because of their fast response and large controllable damping range. In order to match the high-speed applications of MR fluids, the structural design and controllability evaluation of MR actuators are of great significance. Controllability of MR actuators are defined to be evaluated by the mechanical behaviors (i.e. damping force controllability), including the controllable damping force range, dynamic range and constant stroking load velocity range, and response time performance (i.e. real-time controllability). We proposed an internal bypass MR shock absorber (MRSA) (Bai et al 2013a IEEE Trans. Mag. 49 3422–5), which presents the possibility in vibration control and shock mitigation applications. In the internal bypass MRSA, the gap formed by the coaxially assembled inner and outer cylinders is the flow channel for MR fluids. The electromagnetic coil windings evenly wound on the outer wall of the inner cylinder and the active rings contribute to the MR effect, and continuous adjustable damping is realized through applying current into the electromagnetic coil windings. In Part I of this paper, the principle and the mechanical behaviors of the internal bypass MRSA is further in-deeply investigated via theoretical modeling and simulations. Based on the fluid dynamics—parallel plate models and the finite element analysis software ANSYS/Fluent, the mathematical model and the fluidic entities of the internal bypass MRSA are established, respectively. Response time model of the internal bypass MRSA under a voltage driver is established. The static magnetic field distributions of the internal bypass MRSA under different current excitations are obtained via ANSYS/Workbench. The response times of the internal bypass MRSA under transient impulse current excitation and transient impulse voltage excitation are obtained by transient electromagnetic simulation. The damping force performance of the conventional unicoil MRSA with an electromagnetic coil winding in positon, multicoil MRSA with five electromagnetic coil windings in positon and the internal bypass MRSA are compared and analyzed. As compared with the conventional unicoil and multicoil MRSAs with coupled structures of the piston and the electromagnetic coil windings, the internal bypass MRSA with decoupled arrangement shows much better damping force controllability. Experimental test and controllability evaluation of the internal bypass MRSA will be conducted and presented in Part II of this paper.

Investigation of shock/elastic obstacles interactions by means of a coupling technique

Arrays of obstacles have proved to be an efficient way of attenuating shock waves generated by large scale explosions. The present study intends to take into account fluid–structure interactions that may occur when elastic obstacles are used. A tractable coupling tool based on a partitioned procedure is exposed, validated on the supersonic flutter of a panel and applied to a configuration composed of square section cylinders. Several numerical difficulties related to staggering are emphasized and workarounds discussed. A methodical procedure involving one and two-way coupled simulations highlights the influence of material properties as well as the acceleration of waves in the fluid when an initial motion is prescribed to the obstacles. Finally, it is shown that uncoupled simulations may be relevant to investigate shock mitigation in some given cases.