Pressure Impulse Research Articles

A partitioned functional-decomposition scheme for modelling wave-ship-sloshing interaction

A novel partitioned function decomposition method is proposed and validated for accurately and effectively solving the interaction between waves and ships with sloshing effect. This scheme employs a hybrid functional-decomposition method that utilizes both potential and viscous flows to accurately and efficiently solve the wave-ship interaction in the external domain, while employing the original viscous method for simulating sloshing in the internal domain. To further enhance computational efficiency, a single-phase Level-set method is employed. Firstly, the issue of non-conservation in the level-set model is addressed through the application of a mass correction method. Additionally, based on the principle of mass conservation, modifications are made to the boundary conditions for free surface motion. As a result, an improved single-phase Level-set method is developed, which combines jump condition correction and mass correction. Through simulations involving linear and nonlinear free surfaces, impulsive pressures, overall forces on the tank, as well as comparisons with experimental data, it is observed that the proposed Level-set method effectively solves the sloshing in the internal domain, a problem for which the traditional single-phase Level-set method often fails to tackle with. Subsequently, by adopting a multi-block grid technique to mark tank and non-tank grid blocks and integrating the improved single-phase Level-set method with the SWENSE model, a partitioned function decomposition method is established to handle ship motions with sloshing effect in waves. It is found that simultaneously solving the internal and external flow problems using traditional implicit and explicit motion-solving methods poses certain challenges. Therefore, an implicit-inner-iteration solution method is proposed. By combining the proposed motion-solving method with the partitioned function decomposition model, satisfactory results are achieved for the wave-ship-sloshing interaction.

Effects of Global Supply Chain Pressure on Sentiment, Expectation, and Uncertainty: A VAR Approach

This paper studies the relationship of global supply chain pressure with consumer sentiment, inflation expectation, and monetary policy uncertainty in the United States. A sample from January 1998 to January 2024 is used, and this paper uses a Vector Autoregression (VAR) approach based on the method proposed by Toda and Yamamoto (1995). The Granger causality test suggests that the predictions of inflation expectation based on its own past values and the past values of the global supply chain pressure are better predictions of inflation expectation than just using the past observations of inflation expectation. In contrast, Impulse Response Functions suggest that surprise increases in global supply chain pressure lead to increased inflation expectation and monetary policy uncertainty; this shock lasts up to two years. Meanwhile, the Impulse Response Functions suggest that surprise increases in the global supply chain pressure decrease consumer sentiment (confidence), lasting up to two and a half years. Afterward, the impact converges back to zero. Additionally, the Variance Decomposition results suggest that by the final period, the impulses of the global supply chain pressure explain over 22%, 7%, and 44% of the variation of consumer sentiment, monetary policy uncertainty, and inflation expectation, respectively.

Dynamic behavior and spatio-temporal mechanical characteristics of the individual cavitation bubble on hydraulic concrete wall

This study endeavors to delve into the dynamics and consequent mechanical responses induced by an individual cavitation bubble proximal to a concrete surface. Employing the laser-induced cavitation bubbles experimental method, the dynamic behavior of a cavitation bubble near horizontal smooth and locally defective concrete surfaces is systematically investigated. Using computational fluid dynamics (CFD) simulations, the impulsive pressure induced by bubble collapse within a specific surface range is quantitatively investigated. Our results reveal that the presence of local defects on the concrete surface activates gas nuclei within the defects upon bubble shock wave emission. Gas nuclei near the surface center penetrate the bubble, prolonging the bubble’s pulsation period and reducing microjet velocities. During bubble collapse, significant concentrated stresses due to microjets near the surface center may trigger instantaneous brittle failure of the concrete surface. Moreover, shock waves form high-pressure zones within a certain range of the surface. When the dimensionless distance γ ranges from 1.1 to 1.2, a superposition phenomenon of microjets and shock waves is observed, compared to individual effects, enhancing the impulse at central point below the bubble, prolonging the duration of pressure within the specific surface horizontal range, but simultaneously accelerating the pressure’s horizontal attenuation rate along the surface. Compared to the center pressure of the wall surface, the impulse of average pressure better reflects the surface’s pressure response.

Pressure–impulse diagrams of RC beams considering fire–blast interaction

Pressure–impulse diagrams of <scp>RC</scp> beams considering fire–blast interaction

Flow-field analysis and performance assessment of rotating detonation engines under different number of discrete inlet nozzles

This study explores in depth rotating detonation engines (RDEs) fueled by premixed stoichiometric hydrogen/air mixtures through two-dimensional numerical simulations including a detailed chemical kinetic mechanism. To model the spatial reactant non-uniformities observed in practical RDE combustors, the referred simulations incorporate different numbers of discrete inlet nozzles. The primary focus here is to analyze the influence of reactant non-uniformities on detonation combustion dynamics in RDEs. By systematically varying the number of reactant injection nozzles (from 15 to 240), while maintaining a constant total injection area, the study delves into how this variation influences the behavior of rotating detonation waves (RDWs) and the associated overall flow field structure. The numerical results obtained here reveal significant effects of the number of inlets employed on both RDE stability (self-sustaining detonation wave) and performance. RDE configurations with a lower number of inlets exhibit a detonation front with chaotic behavior (pressure oscillations) due to an increased amount of unburned gas ahead of the detonation wave. This chaotic behavior can lead to the flame extinguishing or decreasing in intensity, ultimately diminishing the engine's overall performance. Conversely, RDE configurations with a higher number of inlets feature smoother detonation propagations without chaotic transients, leading to more stable and reliable performance metrics. This study uses high-fidelity numerical techniques such as adaptive mesh refinement (AMR) and the PeleC compressible reacting flow solver. This comprehensive approach enables a thorough evaluation of critical RDE characteristics including detonation velocity, fuel mass flow rate, impulse, thrust, and reverse pressure waves under varying reactant injection conditions. The insights derived from the numerical simulations carried out here enhance the understanding of the fundamental processes governing the performance of RDE concepts.

Струйный эффект при возникновении присоединенной каверны от системы импульсивных давлений

We consider the plane problem of the emergence of an attached cavity caused by the sudden action of impulsive pressures at some initial time. It is assumed that these pressures are distributed on the upper part of the boundary of a stationary circular cylinder immersed in liquid. A problem with unilateral constraints is formulated, on the basis of which the flow of liquid at the initial moment of time and the initial zone of separation of liquid particles are determined. At the next moments of time, an attached cavity is formed, the shape of which is determined based on the solution of the dynamic initial-boundary value problem of the theory of potential flows of an ideal incompressible fluid with free boundaries. The main unknowns in it are the velocity potential, the shape of the cavity, the dynamics of the separation points, and the perturbation of the external free boundary of the liquid. It is required to study the posed problem at short times, focusing on the behavior of the internal free boundary of the liquid near the separation points. When studying this problem, pressure in the cavern, which is created artificially, plays an important role. At low pressures, the internal free boundary of the liquid near the separation point is located on opposite sides of this point. In this case, the end part of the cavity resembles a stream of gas directed along the boundary of the cylinder towards the liquid.

Concerning the Parameterization of Geometric and Criticality Effects on Detonation Amplification

This study investigates the role of geometric effects and detonation criticality on the behavior of a detonation transition through an area expansion of finite length. Three reinitiation behaviors that result in an amplified pressure impulse were observed and are referred to as steady, spike, and endwall amplification. Steady amplification was characterized by an amplification event with a peak pressure impulse 2 times that of the inlet detonation, followed by a near-linear attenuation toward Chapman–Jouguet conditions. Spike amplification displayed a larger peak pressure amplification that was 3 to 5 times greater than the inlet detonation, followed by a rapid and nonlinear attenuation. Endwall behavior represents a Craven–Grieg deflagration to detonation transition scenario. These behaviors are shown to be factors of area expansion ratio and the degree to which the incoming detonation is subcrtical. A decoupling parameter, Ψd, was devised to combine these effects into a single correlation metric. The finite length of the expansion chamber also plays a role in the reinitiation behavior as observed by the endwall reinitiation behavior. A critical chamber length parameter was devised to explain this behavior and then theorized to have a relationship to Ψd with this being explored theoretically and with the limited data set available.

Influence of geometric imperfections on the seismic performance of unanchored liquid storage tanks

This paper investigates the inelastic buckling of imperfect unanchored cylindrical steel tanks subjected to seismic loads. A pushover-based seismic analysis was conducted considering the impulsive hydrodynamics pressures on the wall and base plate of the tank. Material and geometric nonlinearities were considered in the seismic analysis of the tanks. Three types of imperfections were analyzed: imperfections due to impacts, imperfections located at the bottom of the tank wall, and imperfections with the first buckling mode shape. The buckling analysis was performed for two tank geometries (one slender and one broad), and the effect of the imperfections was correspondingly evaluated. The considered imperfection amplitudes were established according to the New Zealand seismic design code for storage tanks. Additionally, amplitudes that exceed the normative limit were evaluated to further analyze the sensitivity to imperfection. The analysis revealed that geometric imperfections reduce the peak ground acceleration needed to induce buckling failure. Specifically, the critical peak ground acceleration for the slender tank decreased from 0.195 g to 0.180 g for the slender tank and from 0.600 g to 0.535 g for the broad tank. This buckling capacity reduction due to geometric imperfections were about 8 % and 11 % for the slender and the broad tanks, respectively.

Study of the interaction between a cavitation bubble and nearby biomimetic gas-entrapping microtextured surfaces and the potential damage effects on the wall using the compressible multiphases volume of fluid model

In the study, a compressible multiphase volume of fluid considering the phase change and thermal effect is presented, the interaction between a cavitation bubble and nearby biomimetic gas-entrapping microtextured surfaces is investigated using this model, and the potential damage effects on the wall are carefully analyzed. Based on this interaction, the standoff distance is classified into three types. For γ > 2.0, the cavitation bubble remains spherical during the expansion phase because it is not influenced by the entrapped gas cavities. However, during the contraction phase, it generates a jet directed away from the wall. For 1.0 < γ < 2.0, the cavitation bubble is affected by the cavities, causing it to lose its spherical shape during the expansion phase. For 0 < γ < 1.0, the cavitation bubble is close to the gas cavities, mixing with the gas cavities during the expansion phase. Two processes are identified as the main reasons for the potential damage to the wall. Furthermore, compared to a flat wall surface, the peak of the pressure impulse on the wall with entrapping gas cavities decreases by 33%, and the peak of the heat transfer quantity decreases by 59%, significantly reducing the damage to the wall.

A big bang theory of big brain trauma.

One of the biggest neurophysiological science news headlines of the 2024 summer reported a critical link between post-traumatic stress disorder (PTSD), suicide, and brain injury from blast events in members of the elite US fighting force, Navy SEALS. Researchers from the Department of Defense/Uniformed Services University Brain Tissue Repository (DOD/USU BTR) had discovered a border of neural damage between the layers of white and gray matter comprising the cortical folds of service members' brains. Described as a distinctive anatomical line of astroglial scarring along the shared junctions of gray and white cellular zones of the brain, this tissue injury was unlike that observed for concussive brain trauma. Rather, it was consistent with blast biophysics of mammalian tissues. In this new study, the damage appears to be correlated with long-term, repeated exposure to blast waves from nearby explosions or firing weapons. A cascade of progressive unexplained behaviors, cognitive decline, and severe depression in the trained fighters ensued. This analysis suggested that repetitive, impulsive pressure waves traveling through the service members' heads and brains with each blast had compromised their cognitive centers, setting a downward trajectory in their mental and physical health.

Effects of polyurethane hardness on the propagation of acoustic signals from partial discharge

AbstractPolymeric insulation is a critical component of high voltage systems. However, exposure to high electric stress can cause partial discharges (PDs) to occur and may result in the deterioration of insulation and lead to dielectric failure. These PD events are accompanied by the production of acoustic pressure impulses in the polymer. Detection of these acoustic pressure impulses can reveal the presence of PDs and locate their source. However, analysing the detected acoustic emission (AE) signal is challenging. The acoustic pressure source's nature and the propagating medium's properties, such as density, viscosity, and elasticity, significantly affect the propagating AE signal. The effects of the hardness of the polyurethane (PU) on the propagating AE signal are reported by the authors based on results obtained from laboratory experiments. It was observed that the decay rate in the magnitude of the acoustic impulse was high in PU at all hardness levels following an exponential behaviour. The analysis of the frequency spectra indicates that the higher frequency components attenuate more strongly with distance. These laboratory results can be valuable for engineers and industries as they provide valuable insight into how the physical characteristics of a material affect the propagation characteristics of AE signals during the detection and location of PD source using the AE detection technique.

Numerical derivation of pressure-impulse (P-I) diagrams of prefabricated RC columns with steel joints subjected to blast loads

In recent decades, terrorist attacks and accidental explosions have occurred frequently. The casualties are not only caused by the shock wave, but also by the structural collapse initialed from the failure of structural columns. In this paper, the dynamic response and damage mechanism of prefabricated reinforced concrete (RC) columns with steel joints (PRC) subjected to blast loads are numerically investigated. By comparing the numerical results with the experimental results, the accuracy of the finite element (FE) model is firstly verified. Then, dynamic responses and damage of PRC under blast loads induced by the TNT explosions and vapor cloud explosions (VCEs) are investigated and compared with each other. The results indicated that PRC damage under VCEs with 9.3 MPa is larger than that under TNT explosions. Conversely, the damage under VCEs with 7 MPa is smaller than that under TNT explosions, and the blast-induced damage and dynamic behavior of PRC under two types of explosions is different. Subsequently, parametric studies are further carried out to investigate the influence of key parameters of PRC, including longitudinal and transverse reinforcement ratio, column dimensions, concrete strength, steel sleeve dimensions on PRC damage. It is revealed that different parameters affect the damage for PRC column in different load regions of P-I diagrams, including the impulsive load region, dynamic load region and quasi-static load region. Increasing the sleeve length, sleeve ratio and transverse reinforcement ratio improves the shear-resistant performance of PRC, and these parameters more easily affected PRC damage in the impulsive load region. Increasing the concrete strength and column depth can increase the blast-resistant performance of PRC in three load regions. Based on parametric studies, pressure-impulse (P-I) diagrams for damage evaluation of PRC under VCEs and TNT explosions are proposed and verified. Finally, Blast-resistant design procedure of PRC based on P-I diagram is developed.

Impact of foot progression angle on spatiotemporal and plantar loading pattern in intoeing children during gait

Intoeing in children is a common parental concern, but our understanding of the impact of foot progression angle (FPA) in these children leaves remains limited. This study examines the relationship between FPA and plantar loading pattern, as well as gait symmetry in children with intoeing. The sample included 30 children with intoeing caused by internal tibial torsion, uniformly divided into three groups: unilateral intoeing, bilateral mild intoeing, and bilateral mild-moderate intoeing. The relationship between FPA and plantar loading pattern, and gait symmetry within and among groups were assessed using dynamic pedobarographic and spatiotemporal data. Results indicated a significant correlation between FPA and peak pressure, maximum force, and plantar impulse in the medial and central forefoot, and also the medial and lateral heel zones for both bilateral intoeing groups. Significant differences were observed only in subdivided stance phase, including loading response, single support, and pre-swing phases, between the unilateral intoeing and bilateral mild intoeing groups. These findings suggest that FPA significantly affects the forefoot and heel zones, potentially increasing the load on the support structures and leading to transverse arch deformation. While children with intoeing demonstrate a dynamic self-adjustment capability to maintain gait symmetry, this ability begins to falter as intoeing becomes more pronounced.

Research on damage assessment of buried pipelines with circular dent defects subjected to blast loading

In order to evaluate the damage characteristics of buried natural gas pipelines with circular dent defects subjected to blast loading, based on pressure–impulse damage theory, explosion experiment and numerical simulations were implemented to evaluate the damage of a natural gas with circular dent defects buried in soil under blast loading in this research. The ALE method was used to develop a coupled pipeline-soil simulation model using LS-DYNA software, and the validity of the established model was verified correctly compared with experimental results and empirical theory equations calculations. Furthermore, according to regulations in the Assessment and Management of Pipeline Dents (American Petroleum Institute Recommended Practice 1183), the effect with different circular dent defect diameter on the mechanical properties of natural gas was also investigated and analysed. The results showed that, under the blast loading, plastic deformation happened on the surfaces of the pipeline facing the explosive, and the high-stress zone appeared in the circumferential direction with 32.27°. The range of the high-stress zone firstly expanded along the axial direction of the pipelines and then along the circumferential direction. The larger diameter of the circular dent defects had, which resulted in a failure at the defects under the condition of the depth of the defects keeping constant. The effect of the size of defect diameter on the amount of pipeline deformation was further investigated, and the mathematical formula described the maximum plastic deformation with different defect diameter was established. Meanwhile, a finite element model of pipeline with a diameter of 457 mm was established for numerical analysis, which implied that the larger diameter of pipeline with the same defect had, the lower risk of pipeline in failure subjected to blast loading had. And through mathematical analysis and considering the feasibility of the actual situation, the curve described the maximum plastic deformation of the natural gas pipeline with three different defects varying in diameter were established respectively. In addition, a formula to express the relationship between pipeline defect diameter and maximum plastic deformation was established, which can effectively predict the critical plastic dent deformation of pipelines with different defect diameter subjected to blast loading. Besides, based on the pressure-pulse damage theory and with the damage assessment criterion of dent depth–dent length ratio of 0.072, the pressure–impulse diagrams of buried natural gas pipelines with defect diameters of 30 mm, 40 mm and 50 mm were defined, which can be used to predict the damage of pipelines with different defect diameters. Moreover, with the pressure–impulse damage evaluation curves, mathematical formula for the buried natural gas pipeline with the circular defects were established. Furthermore, the critical circular defect diameters with 30 mm was confirmed and the unique formula was also established, which could be effectively used to evaluate the safety of buried natural gas pipelines with the critical circular defects.

Prompt Disappearance of Magnetospheric Chorus Waves Caused by High‐Speed Magnetosheath Jets

AbstractMagnetosheath high‐speed jets (HSJs), localized impulses of dynamic pressure, are attracting growing attention due to their geoeffectiveness. However, how HSJs modulate chorus waves in the magnetosphere still remains unclear. Utilizing combined observations of the Time History of Events and Macroscale Interactions during Substorms satellites A and E, we report, for the first time, the prompt disappearance of the magnetospheric chorus waves caused by a HSJ. Such wave disappearance is directly due to the flux drop of energetic electrons (∼10–100 keV), leading to the cessation of wave generation, which is supported by the linear theoretical analysis. We propose that the flux drop results from the local indentation of magnetopause after the HSJ impact, where two new smaller magnetic mirrors are formed off the equator and part of electrons are then expelled by the mirror force. The HSJs should be an important factor in modulating chorus waves because of their high occurrence rate.

Dynamic Response Analysis Method of a High-Strength RC Beam Subjected to Long-Duration Blast Loading

An analysis method of normalized pressure–impulse (P-I) diagrams related to the ductility ratio of structural components is proposed, to quickly estimate the dynamic response of high-strength reinforcement concrete (RC) beams subjected to long-duration blast loading. Firstly, the overall bending deformation mode of RC beams is uncovered via explosion tests in a closed chamber, where the durations of the near-planar blast loadings are varied within 80–105 ms. Then, a single-degree-of-freedom (SDOF) model is established based on the bending deformation mode. The resistance function for the uniform pressure loading is developed using a novel approach, consisting of (1) developing and benchmarking a three-dimensional (3D) improved steel–concrete separated finite-element (FE) model; (2) using the benchmarked FE model to conduct numerical simulations for uniform pressure loading; and (3) idealizing the resistance function for uniform pressure using a bilinear relationship. Finally, the SDOF model is used to conduct parametric analyses and develop a normalized P-I diagram that can be used to analyze or design RC beams for far-field blast effects. This P-I diagram is verified using results from blast load tests that are primarily in the dynamic region. A total of 188 additional 3D nonlinear FE analyses of RC beams are conducted to expand the database in the impulse and quasi-static regions. Considering the limitations of the proposed method in predicting the shear-dominated deformation and the fracture behavior of members, the P-I diagram is applicable to the dynamic response of the bending deformation of members under far-field explosion, which can provide an important reference for the blast-resistant design and analysis of high-strength RC beams.

Assessment of a Simplified Methodology for Preliminary Blast-Resistant Design of Insulated Precast Concrete Wall Panels

Abstract A Blast loading history can be represented by the peak pressure value and the impulse. Combinations of pressure and impulse of various blast loading scenarios can be collected to draw a pressure-impulse (P-I) curve that corresponds to a level of damage of a blast-resistant structural component. The P-I curve is typically used for a preliminary design or assessment of blast resistance structural components. Generating a P I curve for a given structural component and level of protection requires repeatedly ru nning a single degree of freedom system (SDOF) model, which can be tedious for early design stages. Hence, a simplified approach (i.e., the normalization approach) was utilized to promptly generate the P- I curve for insulated precast concrete wall panels, which relies on shifting a control P I curve using normalization factors. The generated P-I curves using the normalization approach are validated with the traditional SDOF approach curves; 95% of the examined insulted panel configurations have an error between +/-7%. As a result of the reached low error percentages, a spreadsheet- design tool was developed using this approach. The tool can further enable rapid evaluation of the performance of insulated precast concrete panels under blast loading during the preliminary design phase.

Nanofillers embedded flexible piezoelectric polymer sensor pad for robotic and human finger tap analysis

Flexible pressure sensors are receiving a lot of attention due to their use in wearable electronic devices, human-machine interactive systems, and physiological signal monitoring. In this paper, we present a novel nanofiller embedded thin film based piezoelectric pressure sensor for finger tapping analysis. The active material is fabricated using poly (vinylidene fluoride) (PVDF) having zirconium oxide (ZrO2) nanofillers. It is observed that the incorporation of ZrO2 nanofillers has a substantial impact on the structural characteristics of PVDF polymer, leading to enhancements in its piezoelectric properties. Moreover, the PVDF/2 wt% ZrO2 composite film sensor showed a notable maximum piezoelectric output voltage of ∼210 millivolts at a load of 20 g (0.88 kPa applied pressure). A four-fold enhancement in response is observed in case of PVDF/2 wt% ZrO2 composite in comparison to pristine PVDF sensor. Further, a sensitivity of 0.255 ± 0.083 kPa−1 has been recorded for the composite based sensor. Additionally, maximum of 115 mV is obtained when the composite sensor is tapped manually. The recorded maximum values for impulsive pressure (38 g), high pressure (108 g), and low pressure (45 g) are 76 mV, 150 mV, and 90 mV, respectively. The sensor is efficiently able to detect robotic tapping and stress on the human fingers. An efficiency of around 90% was achieved in PVDF/ 2 wt% ZrO2 at 5 kV/cm using PE hysteresis loop data. The findings indicate that PVDF/ZrO2 composite based piezoelectric pressure sensor has promising capabilities for applications in wearable electronic devices and medical diagnostics.

Wave Impacts On Cliffs: From The Field To The Laboratory

Rock coasts occupy over 50% of the global shoreline and many sandy beaches are underlain by coastal platforms and rocky cliffs. The problem of wave-driven cliff erosion is of great societal importance, with many coastal communities located on top of cliffs that are at risk from erosion. Continuing global mean sea level rise and changes in storminess are generally expected to exacerbate the erosion of coastlines (Hurst et al., 2016), as larger waves can reach the cliff toe without breaking offshore. However, the science underpinning wave-induced cliff erosion is still at a relatively early stage. Even the relative contributions of waves to cliff erosion, which include hydraulic forces, impulse pressures and abrasion, are not well resolved. Most insights into wave impacts on cliffs come from field observations of coastal ground motion during storm events (e.g. Young et al., 2011, Huppert et al., 2020). These field investigations demonstrate the dependence of large wave impacts on both water levels and wave conditions, and in some cases the correlation of periods of large ground motion with increased erosion (Earlie et al., 2015). Unsurprisingly, although large impacts generally occur at high tide during storms characterised by large significant wave heights, the largest impacts occur when tidal levels and storm surge combine to provide water levels that are conducive to the incident waves breaking on the cliffs (Thompson et al., 2019; 2022). Larger wave heights or shallower water levels tend to lead to breaking further offshore, with a broken wave interacting with the cliff, while smaller wave heights or deeper water levels may preclude strong wave breaking on the cliffs. There have been relatively few experimental studies into wave-driven cliff erosion; these were generally undertaken under very idealised wave conditions (e.g. Sunamura, 1977) and using materials that were either too soft to approximate natural rocks (e.g. Sunamura, 1977; 1982) or too hard to be eroded (Hansom et al., 2008). Although these experiments have informed the development of rocky coast evolution models, their results have not been replicated or verified, and rigorous scaling laws to link laboratory erosion rates to field time scales are currently lacking. However, considering cliffs as steep or vertical (natural) coastal structures, a large body of experimental work has been undertaken to investigate impact pressures and their implications for the failure of engineered structures (e.g. Peregrine, 2003, Bullock et al., 2007). These investigations are complicated by the inherent variability of the wave impact pressures, even within controlled experiments undertaken with highly repeatable incident wave conditions (Raby et al., 2022). Although field and laboratory data are valuable, it is still very challenging to quantify wave contributions to cliff erosion due to the relatively short durations and variable conditions of most field records. On the other hand, most controlled laboratory investigations have typically focused on loads on non-erodible engineered structures such as seawalls. The current project seeks to advance understanding of the fundamental mechanisms and timescales of wave-driven erosion on rocky cliffs, which will be vital in improving assessments of cliff erosion hazard in high-energy wave environments as sea levels rise.

Numerical simulation of in-vessel steam explosion for China third-generation PWR

In this study, in order to evaluate the Reactor Pressure Vessel (RPV) integrity under in-vessel steam explosion loads for China third-generation Pressurized Water Reactor (PWR), 2D and 3D numerical simulation of in-vessel steam explosion is conducted using MC3D code. The sensitivity analyses for in-vessel steam explosion are performed, including break area, water temperature, water level, melt temperature, and break height. The results show that the premixing stage cannot cause RPV failure and the possibility of the steam explosion blowing the RPV upper head off is almost non-existent. When the break area increases, the maximum pressure and impulse of the RPV inner wall increase obviously first and then generally decrease slightly. With the increase of water temperature, the maximum pressure and impulse first increase and then decrease. When the water level is higher, the maximum pressure variation is small. When the water level is very low, the maximum pressure decreases. The maximum impulse generally decreases with the decrease of the water level. When the melt temperature exceeds 2850 K, the steam explosion is not sensitive to the melt temperature. With the increase of the break height, the maximum pressure and maximum impulse first increase and then decrease. Furthermore, based on the results of sensitivity analysis, two cases of conservative conditions are selected, and the RPV integrity under in-vessel steam explosion loads for China third-generation PWR is considered. The result shows that the integrity of the RPV can be maintained under the in-vessel steam explosion loads for China third-generation PWR with a large margin. These studies provide some reference to improve the severe accident management strategy in China.