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Modelling, computation and performance animation of turbomachinery systems has recently enjoyed remarkable attention in CAD research. This is also reflected its application to exhaust machine components such as turbo loaders and the exceptionally novel pressure wave machine (Comprex) in the automobile industry and gas turbines. The necessity for the thermo‐fluidic performance animation of such pressure wave machines results from the fact that the machine geometry must be adapted to the technical and thermo‐fluidic properties of the exhaust flow of the gas turbine or automobile engine. Experimental adaptation or adjustment is costly and should be validated for every application case. Thus the potential to apply accurate animation for such shock‐tube like behaviour of compressible flow is now economically promising with a view to optimizing the design of the pressure wave machine. This paper presents briefly the problem oriented algorithms used and illustrates the performance animation of the pressure wave machine operating under constant speed drive. After introducing the pressure wave machine operation, the principles and summary of the algorithms used to compute the thermodynamic behaviour within the cell, the boundary models and the accuracy of computation. A Comprex cycle operating on an engine exhaust gas with T = 920°K, p = 2bar is illustrated through 3‐dimensional representations for pressure, speed of flow and temperature. The particle path (gas and air) together with time representation of the state variables at different points of the Compex will be shown. The mass balance problem is discussed and the conditions for mass balanced flow for the gas as well as for the air side are given. The results achieved for such materially balanced pressure wave machines indicate a reduction in the costs for subsequent experimental validation and to deliver the sound base for further development towards considering the pre‐balanced transient operation cases as well.

This paper aims to conduct a combined Eulerian/Lagrangian fluid/solid transient non‐linear dynamics computational analysis of the interaction between a single planar blast wave and a human head in order to assess the extent of intra‐cranial shock wave generation and its potential for causing traumatic brain injury.

Two levels of blast peak overpressure were selected, one corresponding to the unprotected lung‐injury threshold while the other associated with a 50 percent probability for lung injury caused death. Collision of the head with a stationary/rigid barrier (at an initial collision velocity of 5 m/s) was also analyzed computationally, since blunt‐object impact conditions may lead to mild traumatic brain injury (mTBI), i.e. concussion.

A comparison between the two blast and the single blunt‐object impact cases with the corresponding head‐to‐head‐collision results showed that, while the von Mises stress‐based head‐to‐head collision mTBI thresholds are not exceeded under blast‐loading conditions investigated, the high blast‐induced peak‐pressure levels within the intra‐cranial cavity may lead to mTBI.

While concussion is not generally considered as life altering/threatening, the associated temporary loss of situational awareness or consciousness may have devastating consequences in the case of common military tactical and battle‐field scenarios. This suggests that the head‐protection gear (primarily, the helmet) which are currently designed to withstand blunt‐object and ballistic impacts, should be redesigned in order to obtain the necessary level of head protection with respect to blast impact.

The paper provides a comprehensive computational investigation of impact on a human skull/brain assembly.

The purpose of this paper is to assess the blast‐mitigation potential and the protection ability of an air‐vacated buffer placed in front of a target structure under realistic combat‐theatre conditions.

The blast‐mitigation efficacy of the air‐vacated buffer concept is investigated computationally using a combined Eulerian‐Lagrangian (CEL) fluid‐structure interaction (FSI) finite‐element analysis.

The two main findings resulting from the present work are: the air‐vacated buffer concept yields significant blast‐mitigation effects; and the buffer geometry and vacated‐air material‐state parameters (e.g. pressure, mass density, etc.) may significantly affect the extent of the blast‐mitigation effect.

The main contribution of the present work is a demonstration of the critical importance of timely deployment of the buffer relative to the arrival of the incident wave in order to fully exploit the air‐vacated buffer concept.

This paper aims to utilize purpose advanced fluid‐structure interaction, non‐linear dynamics, finite‐element analyses in order to investigate various phenomena and processes accompanying blast wave generation, propagation and interaction and to assess the blast‐wave‐mitigation potential of a piston‐cylinder assembly placed in front of the target structure.

The employed computational methods and tools are verified and validated by first demonstrating that they can quite accurately reproduce analytical solutions for a couple of well‐defined blast wave propagation and interaction problems.

The methods/tools are used to investigate the piston‐cylinder blast‐mitigation concept and the results obtained clearly reveal that significant blast‐mitigation effects can be achieved through the use of this concept. Furthermore, the results showed that the extent of the blast‐mitigation effect is a sensitive function of the piston‐cylinder geometrical parameters. Specifically, the mass of the piston and the length of the cylinder are found to be the dominant factors controlling the extent of the blast‐wave‐mitigation.

The work demonstrates that, when assessing the blast‐wave‐mitigation potential of the piston‐cylinder concept, it is critical that loading experienced by the piston be defined by explicitly modeling (fluid/structure) interactions between the blast wave(s) and the piston.

THE earlier classical treatises on aerodynamics concerned themselves with the properties of incompressible fluids. The theory developed on this basis gave an excellent theoretical background to the aeronautical engineer and made possible a scientific approach to the problems of aircraft flight. With the steady increase of aircraft speed, however, it soon became evident that the theory would have to be extended to take compressibility into account. One important result, brought out by Glauert's analysis, was the modification of the flow pattern with increasing Mach number. A more striking divergence of compressible from incompressible flow, first encountered at near sonic speeds, is the occurrence of shock waves. A shock wave, in the specialized aeronautical sense, is a pressure impulse travelling through the flow causing a sudden transition from supersonic to subsonic speeds (normal to the wave front) with an attendant increase in pressure and temperature. A brief statement of this sort, however, is of little or no value in giving an idea of the physical nature of the phenomenon. A considerable amount of attention is now focused on the repercussions of shock waves on aeroplane design. It is far easier to understand these design trends if one has a good grasp of the fundamentals underlying the problem. This article sets out to give a brief survey of these fundamentals. It is not easy also to give a complete physical picture of a shock wave but at least a discussion of their formation, propagation, etc. goes a long way towards clarifying one's ideas.

Multi-level intake structures are used to take the surface water of reservoirs. The changed boundary conditions will certainly make the water hammer phenomenon more complicated. This paper aims to find out the influence and law of the water hammer pressure after setting the stop log gates.

The authors use the computational fluid dynamics method with the adaptive grid technology to stimulate the water hammer phenomenon of the multi-level intake hydropower station. In the analysis, we set several different heights of stop log gates and two representative times in the starting up and shutdown processes to reflect the impact of multi-level intake structures.

The authors find that the setting of the stop log gates will reduce the pressure during the normal operation and will increase the period and amplitude of the water hammer wave, but will not necessarily increase the maximum water hammer pressure during the shutdown process. The relationship between the height of the stop log gates and the amplitude of the water hammer wave is affected by the shutdown time. After setting stop log gates, the depression depth and wave height of the water level in front of the dam increase when the load changes.

The authors study in this paper the water pressure of the multi-level intake hydropower station that has never been studied before and obtain some laws.

The design of the Advanced Combat Helmet (ACH) currently in use was optimized by its designers in order to attain maximum protection against ballistic impacts (fragments, shrapnel, etc.) and hard-surface/head collisions. Since traumatic brain injury experienced by a significant fraction of the soldiers returning from the recent conflicts is associated with their exposure to blast, the ACH should be redesigned in order to provide the necessary level of protection against blast loads. The paper aims to discuss this issue.

In the present work, an augmentation of the ACH for improved blast protection is considered. This augmentation includes the use of a polyurea (a nano-segregated elastomeric copolymer) based ACH external coating. To demonstrate the efficacy of this approach, blast experiments are carried out on instrumented head-mannequins (without protection, protected using a standard ACH, and protected using an ACH augmented by a polyurea explosive-resistant coating (ERC)). These experimental efforts are complemented with the appropriate combined Eulerian/Lagrangian transient non-linear dynamics computational fluid/solid interaction finite-element analysis.

The results obtained clearly demonstrated that the use of an ERC on an ACH affects (generally in a beneficial way) head-mannequin dynamic loading and kinematic response as quantified by the intracranial pressure, impulse, acceleration and jolt.

To the authors’ knowledge, the present work is the first reported combined experimental/computational study of the blast-protection efficacy and the mild traumatic brain-injury mitigation potential of polyurea when used as an external coating on a helmet.

The purpose of this paper is to study numerically the effects of heat transfer on the strength of shock waves emitted upon spherical bubble collapse.

The motion of bubble under ultrasound is predicted by solutions of the Navier‐Stokes equations for the gas inside a spherical bubble. The Gilmore model and the method of characteristics are used to model the shock wave emitted at the end of the bubble collapse.

The theory permits one to predict correctly the bubble radius‐time curve and the characteristics of shock wave in sulphuric acid solution. These simulations indicated that the heat transfer inside the bubble and the liquid layer plays a major role in the bubble behaviour and the strength of the shock waves. Also, the developed numerical scheme is checked for different gas bubble like air, Argon and Xenon. It is observed that the gas thermal conductivity plays an important role in the shock wave strength. A good agreement is observed by comparison of the results with the experimental data.

The effect of heat transfer on the emitted shock wave strength has not been studied previously. In this paper, a numerical scheme is developed to consider heat transfer on the shock. Also, this simulation is checked for different gas conductivities.

High‐power chemical lasers operating in high repetitive rate show a decrease of the output energy laser beam. In such lasers, the characteristic time which depends on the laser output is short in comparison with those related to the flow. Consequently, shock waves, acoustic waves and thermal perturbations, induced by the strong electric energy deposition and remaining in the laser cavity between two pulses, may explain the decrease of output energy of the laser beam. For a better understanding of the flowfields, a numerical approach is carried out using flux corrected transport algorithms (FCT methods) associated with a Riemann solver on the computational domain boundaries. Under two‐dimensional assumptions, the inviscid flow in the convergent‐divergent laser cavity is computed to describe the creation and propagation of the wave system and the hot gas column in both single and multidischarge operating modes. Distortions of the contact surfaces are put into evidence through the study of flowfield instabilities. Finally, the limitations of the two‐dimensional modelization become apparent. The numerical resolution is extended to a 3D case in order to take into account the optical direction. This allows to study the influence of shock waves travelling between optics and being generated by a side effect developing at the electrodes. These waves have an effect of long duration on the flowfield and lead to a high residual perturbation level.

The pressure exerted on the body by clothes is one important factor affecting the comfort of clothing, it is an effective method to evaluate pressure comfort by physiology and psychology. The purpose of this paper is to measure, electroencephalography (EEG), an index of brain activity in order to examine the effect on brain activity conditions caused by oppression exerted by clothing on the body.

EEG power spectrum analysis was conduct to verify the electrophysiological characteristic of brain caused by pressure on the body by girdle.

Experimental results showed that the intensity of α waves in the pressure condition is decreased compared to the non-pressure condition, and the somatosensory activated by pressure of girdle mainly in occipital, frontal and parietal region of brain.

It was clarified that it is impossible to evaluate the clothes pressure by physiological technique of EEG, this study has enriched methods of evaluation pressure comfort.