G. Ben-Dor

• Professor
• Head of Department at Ben-Gurion University of the Negev

In spite of the worldwide recognition of the importance of testing blast effects on dummy humans, there is a lack of blast simulators that are capable of generating realistic blast conditions in the laboratory. The objective of the present study was to design, construct and test a blast tube that is able to accurately reproduce loading histories of...

A simplified analysis can be employed to predict the pressure buildup behind a porous barrier fairly accurately without resorting to numerical modeling. A macroscopic approach is used in which the pressure buildup behind the porous barrier is analyzed in relation to the load inflicted on its front face thus allowing finding the effects of the diffe...

Experiments and inviscid numerical computations were performed in air at an incident shock wave Mach number of 1.3. The incident shock waves were reflected over cylindrical convex surfaces. The models differed in the radii and initial angles. Great agreement was obtained between the high-resolution computations and the high-resolution experiments....

Numerical simulations were conducted to understand the different wave configurations associated with the shock-wave reflections over double-concave cylindrical surfaces. The reflectors were generated computationally by changing different geometrical parameters, such as the radii of curvature and the initial wedge angles. The incident-shock-wave Mac...

On the basis of generalization of the Florence model to several ceramic layers, it is proved that arranging the ceramic plates in order of increasing material density implies the maximum the ballistic limit velocity of the armor in comparison with other arrangements.

This survey includes, mainly, investigations that were published during recent years and a few earlier studies that were not included in the review by the same authors published in 2012. The survey covers analytical, numerical and experimental studies in which the effect of layering, spacing and change of the order of the plates on the protective p...

This unique compendium contains a vast systematized data of 14,000 experiments on high-velocity penetration into metals, concrete, reinforced concrete, and geological media which were published in the open literature (journal papers, reports, conference proceedings) during the last 70 years. Data presented in this edition are related to the initial...

The presented experimental study investigated the geometric wall effects of a structure on the behavior of an internally detonated blast. Hitherto, most blast in tunnel studies have worked to characterize blast profiles in smooth tunnels. This simplification effectively neglects wall effects including viscosity and shock reflections off the obstacl...

The problem of finding the temperature and velocity distribution inside the boundary layer of a compressible flow over a flat plate is a well-known problem which has been discussed by many distinguished investigators in the past five decades. Excellent reviews of the work done on this classical hydrodynamic problem are available, for example, in th...

A batch of blast resistance reinforced concrete slabs were tested in the shock tube facility at the University of Missouri Kansas City (UMKC). Based on the results from the tests, a blind numerical simulation contest was announced by UMKC in collaboration with the American Concrete Institute (ACI). The authors of this paper participated in the cont...

The mission of ACI-ASCE Committee 447 is to develop and report information on the application of finite element analysis methods to concrete structures. The mission of ACI 370 is to develop and report information on the design of concrete structures subjected to blast, impact, and other short-duration dynamic loads. In this Special Publication (SP)...

Light aluminum closed-cell foams (4% relative density to solid aluminum) were experimentally studied in order to determine the added dynamic compressive strength facilitated by the trapped gas. A compression machine, an impact pendulum, and a shock tube were used to compress foam samples in strain rates varying from 10−3 s−1 to 700 s−1. Very simila...

This paper presents numerical and experimental findings regarding flow separation phenomenon in a high Mach number over expanded planar nozzle. The experimental work is done using a tapered nozzle with a variable area ratio that can produce separation Mach numbers in the range 2.6-3.5. Shadowgraph visualization reveals that depending on the nozzle...

An explosion at the entrance of an underground bunker and a suicide bomber inside an airplane are examples of scenarios in which blast waves propagate in tunnels and corridor-type structures. The need to attenuate the shock/blast wave propagating downstream a corridor and mitigate the developed loads inside the structure is essential. The interacti...

In this work, we implement an exploding wire technique to generate small-scale cylindrical blast waves in aqueous foam. The exploding wire system offers an easy to operate and effective tool for studying blast-wave/foam interaction related phenomena in real explosion scenarios. The mitigation of blast waves as a function of the thickness of the foa...

Due to the increase in global terror threats, many resources are being invested in efforts to find and utilize efficient protective means and technologies against blast waves induced by conventional and nonconventional weapons. Bombs exploding in the entrance of military underground bunkers initiate a blast wave that propagates in a corridor-type s...

The numerous benefits of small scale laboratory experiments include shorter preparation and execution times, cheaper materials, usage of measurement devices that cannot be employed in field tests, and a compactness that often allows for more controlled test conditions and provide high repeatability. The exploding wire technique has been employed su...

A simple experimental technique, based on pressure transducers, capable of measuring the stress wave that propagates along the solid phase of a granular column after being hit head-on by a plane shock wave is presented. The technique is based on installing couples of gauges at different cross-sections along the granular column in such a way that on...

IJDJ140010.3d (IJD) [PREPRINTER stage] Abstract We describe virtually all known analytical models for predicting protective properties of concrete shields against normal high-speed impact by rigid projectiles. Presented formulas can be directly used in practical calculations. Particular emphasis is given to widely used one-stage and two-stage model...

When a supersonic jet emerges from the outlet of a planar nozzle at overexpended conditions oblique shocks wave form at the nozzle lips

As one of the fundamental research topics in the fields of ground penetrating waves, sound acoustics, filtration processes, blast protection and more, the propagation of waves in porous media has been widely investigated in the past few decades

When a supersonic flow,M0 >1, encounters a straight compressive wedge a straight and attached to the leading edge of the reflecting wedge shock wave is formed provided the reflecting wedge angle is smaller than the maximum flow deflection angle appropriate to flow-Mach number, M0.

Explosions near tunnels leading to underground bunkers and inside airplanes or buses are examples of scenarios in which the induced blast waves propagate in corridor-like structures. Therefore, the need to attenuate the blast wave or reduce the blast induced loads inside the structure is essential. The interaction of a shock/blast wave with barrier...

The evolution of the three-dimensional planar Richtmyer-Meshkov (RM) instability during a two shock wave interaction (i.e., reshock) is investigated by means of comparing numerical simulations and analytical modelling with experimental results of low Mach numbers (M < 1.5) and fairly high Atwood numbers (A ∼ 0.7). The study discusses and analyses t...

The survey is dedicated to approximate empirical and analytical models which were suggested for describing high-speed penetration into geological shields. This review differs from the previously published reviews on this topic in the following respects: (i) includes a large number of models; (ii) describes models suggested during recent years; (iii...

Three different approaches to macro-mechanical modeling of blast-wave mitigation in foam namely: the single-phase effective gas flow model, the two-phase mixture model and the single bubble/shock wave interaction model are critically reviewed. The nature and extent of the approximations inherent in the formulation of the first two models were exami...

We have accumulated practically all the information available in the literature regarding empirical mod-els used for describing high-speed normal penetration of rigid strikers into concrete shields, including recently posed models. The description of the models is unified; this includes recommendations on the range of applicability of the models an...

In this review we consider mainly relatively simple engineering models which can be physically substantiated although usually their justification requires a large number of assumptions. These models are characterized by the following features in the case of normal impact: either they determine the relations between the "integral characteristics" of...

This important monograph is the first comprehensive compendium of engineering models used in high-speed penetration mechanics. The book consists of two parts. The first part is in fact a handbook giving a very detailed summary of the engineering models used for the analysis of high-speed penetration of rigid projectiles into concrete, metals and ge...

Using Florence’s model a problem of two-component ceramic-faced lightweight armors design against ballistic impact is solved. Approximate analytical formulas are derived for areal density and thicknesses of the plates of the optimal armor as functions of parameters determining the properties of the materials of the armor components, cross-section a...

Shock-wave propagation through different arrays of solid obstacles and its attenuation are analyzed by means of numerical simulations. The two-dimensional compressible Navier–Stokes equations are solved using a fifth-order weighted essentially non-oscillatory scheme, in conjunction with an immersed-boundary method to treat the embedded solids withi...

This important monograph is the first comprehensive compendium of engineering models used in high-speed penetration mechanics. The book consists of two parts. The first part (more than a quarter of the book's content) is in fact a handbook giving a very detailed summary of the engineering models used for the analysis of high-speed penetration of ri...

Diaphragm gauges were developed in order to measure blast impulses. These gauges can be used to measure blast in air, water, soil and other environments. Such instrumented gauges were used in blast tests of the Israeli Home Front Command that were conducted in January, 2008. In these tests, the diaphragms were positioned on the foundations of a str...

In spite of a large number of publications on shape optimization of penetrating projectiles there are no dedicated surveys of these studies. The goal of the present review is to close this gap. The review includes more than 50 studies published since 1980 and devoted to solving particular problems of shape optimization of high-speed penetrators. We...

Effort to enhance protective properties of shields against high speed impact triggered investigations of the ballistic performance of multilayer barriers having different structure, their comparison with each other and with the monolithic barriers. In spite of a large number of publications on these topics there are no comprehensive surveys of this...

Multiphase flows, which involve compressible or incompressible fluids with linear or nonlinear dynamics, are found in all areas of technology at all length scales and flow regimes. In this contribution, we discuss application of aqueous-foam barriers against blast wave impact. The first experiments demonstrating this behaviour were conducted in the...

A phenomenological study of the process occurring when a plane shock wave reflected off an aqueous foam column filling the test section of a vertical shock tube has been undertaken. The experiments were conducted with initial shock wave Mach numbers in the range and foam column heights in the range 100-450 mm. Miniature piezotrone circuit electroni...

IntroductionFree Field TestsShock Tube TestingTheoretical ApproachesConclusions AcknowledgementsReferences

The starting process of supersonic planar nozzles has been the subject of great number of the shock tube researches in the past. Initially this was motivated by the need to clearly separate the unsteady and quasi-steady parts of the expansion flow and thus specify the so-called ”test time” period of shock tube tunnels. Among other, the best known i...

Major resources have being invested in the last two decades in an effort to find and utilize efficient protective technologies against terror attacks. Most of the resources have been directed to civil and military structures and protection of civil population from explosion induced blast wave loads. Explosive devices exploding inside a bus or an ai...

The interaction of shock waves with rigid obstacles is of significant interest in aerodynamic science and other engineering applications. During the interaction of a shock wave with an obstacle, a very complex wave pattern which affects the shockwave induced flow is formed. The interaction process depends on a variety of physical parameters such as...

For many applications where solid and heavy protections against blast are inoperative, the mitigation of the blast wave loading in a cost-effective manner could be achieved using aqueous foam. The protective behavior of aqueous foam is mainly ascribed to high compressibility of the gas bubbles, which is generally accomplished with energy losses due...

The physical understanding and modeling of shock mitigation are important for the development of an effective barrier arrangement related to disaster management. While it is not currently feasible to simulate and analyze full configurations in detail, sufficient progress has been made to analyze the dynamics of simpler building block flows that pro...

Flow separation in convergent divergent (CD) nozzles occurs when the dynamic pressure of the fluid in the boundary layer is not high enough to overcome the rising pressure ratio along the diverging part of the nozzle. This phenomenon hasmany engineering application aspects such as jet engine performance, noise from jet engines, limitations on the c...

The Concrete Damage Model that is implemented in the LS-Dyna code is capable of simulating the behavior of plain concrete under complex static and dynamic loading conditions. However, the values for the numerous parameters, which are required as an input, are left for the user to provide. In this study the Concrete Damage Model was calibrated for a...

The Richtmyer-Meshkov (RM) instability is of critical importance in inertial confinement fusion (ICF) and astrophysics. In the present work a systematic study has been made of the growth of the turbulent mixing zone (TMZ) under re-shock conditions. In this study, shock-tube experiments were done by Leinov et al. [1] changing the re-shock arrival ti...

The measurement of shock and stress waves under the action of explosion and impact loading has long been a concern of scientists and engineers. A number of methods have been developed over the years for measuring the physical parameters that are involved in the material dynamics resulting from an explosion. This work describes the development, cali...

While a CFD simulation of the flow in overexpanded planar nozzles shows, inside an ideal nozzle, the existence of a hysteresis process in the transition from regular to Mach and from Mach to regular reflections such a process does not appear in tapered nozzles. Previous simulations have dealt only with the flow outside the nozzle and thus concluded...

We investigate the problem of optimization of multi-layered metallic shield whereby the goal is to determine the sequence of materials and the thicknesses of the layers that provide the maximum ballistic limit velocity of the shield. Optimization is performed under the following constraints: fixed areal density of the shield, the upper bound on the...

Among the materials, which are capable of dissipating or absorbing the blast energy, aqueous foams is a good solution, when the place and the time of the blast are known in advance. If the height and the density of foam barrier are sufficient, the blast energy transmitted to nearby objects and personnel could be reduced to harmless levels. Unfortun...

Blast waves mitigate in foam due to various mechanisms, whose contribution to the final result is not fully understood yet. Actually, blast waves can destroy the foam barrier that is usually prone to decay and thus subsides with time. Fortunately, different time scales allow separating between these processes. The foam shattering, for example, coul...

When a large amount of explosive that is stored inside a structure explodes, a blast wave is generated. The strength of the blast depends on both the explosive (type and weight) and the properties of the storing structure, since part of the blast energy is needed to destroy the structure. If one is to determine the dynamic load (e. g., pressure and...

Two different approaches were undertaken in order to investigate the interaction of shock waves with circular cylinder: an experimental approach in which experiments were conducted in a shock tube, equipped with a schlieren based optical system to monitor the wave propagation; and a numerical approach where an in-house computer code was used to sim...

International Journal of Aerospace Innovations V Vo ol lu um me e 2 2 · · N Nu um mb be er r 4 4 · · D De ec ce em mb be er r 2 20 01 10 0 Abstract A numerical study of the flow in overexpanded planar nozzles shows the existence of Mach reflection hysteresis inside an ideal nozzle while in tapered (constant angle) nozzles it does not appear. When i...

Many empirical and semi-empirical models that are widely used in impact dynamics employ the dependencies between the impact (initial) velocity and the depth of penetration (DOP). These dependencies are often obtained by statistical processing of experimental results and are not based on the theoretical models of penetration. In this study we develo...

The depths of penetration into a semi-infinite shield by a monolithic striker and by a sequence of several segments having the same total mass (a segmented impactor) are compared for high-speed and hypervelocity penetration regimes. On the basis of the approach that does not require specifying particular models and their parameters, we suggest crit...

a b s t r a c t On the basis of general assumptions that are pertinent to penetration modeling, we inves-tigated the effect of layering of metallic shields on their protective characteristics against sharp-nosed rigid impactors and established/explained a number of general features of the penetration phenomenon. The main results can be formulated a...

Nuclear Engineering and Design j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / n u c e n g d e s a b s t r a c t We extended the existing engineering two-stage models for high-speed penetration of projectiles into concrete shields and suggested a semi-empirical model that is applicable for truncated bodies of revo-lu...

The pressures and loads induced on the center of the end-wall of a shock tube by a shock wave that passes through different types of obstacles are investigated. Efforts have been made to understand the effect of the obstacle geometry on the load development. The experiments were conducted in a shock tube apparatus in which a modular test section wa...

We investigate the effect of steel plate lining at the rear face of the reinforced concrete panel on the ballistic properties using the semi-empirical model. We determine the structure of the two-layered shield that provides the maximum critical velocity for a given area density and depends on the mechanical properties of concrete and characteristi...

We generalize the existing engineering approaches to modeling of high-speed penetration of projectiles into semi-infinite concrete shields and suggest a modified semi-empirical two-stage model that is applicable for bodies of revolution with a flat bluntness. At the first stage of penetration (cratering), the resistance force is described as a line...

A computational fluid dynamics simulation of the flow in an overexpanded planar nozzle shows the existence of Mach-reflection hysteresis inside the nozzle. Previous simulations have dealt only with the flow outside the nozzle and thus concluded that the hysteresis phenomenon takes place outside the nozzle even when viscous effects are introduced. W...

The effects of coal fly ash dispersed in foams on the coarsening and drainage dynamics are investigated in a free drainage experiment. The growth rate of the bubbles is not significantly changed. The rates of the fluid drainage are significantly slower when powder is present, which cannot be attributed to an increase in the fluid’s viscosity associ...

We present macroscopic experiments that show how the decay phenomenon affects the sound wave mitigation in wet aqueous foams and how both effects depend on the mass concentration of added particles of coal fly ash. To measure the mitigation of a sound wave as a function of the drainage time and particle concentration both a standing-wave and a sing...

International Journal of Aerospace Innovations V Vo ol lu um me e 1 1 · · N Nu um mb be er r 2 2 · · J Ju un ne e 2 20 00 09 9 Abstract The increasing availability of computing power and the relative ease of use of commercial CFD software bring the ability to compute supersonic nozzle flow within reach of most engineers. In order to get accurate re...

We develop a general engineering approach that allows predicting the characteristic parameters of different objects using the known (e.g., from experiments) characteristic parameters of several objects. The suggested method can be applied when the complete model for determining the characteristics of these objects using commonly accepted methods is...

An experimental and numerical systematic study of the growth of the Richtmyer–Meshkov instability-induced mixing following a re-shock is made, where the initial shock moves from the light fluid to the heavy one, over an incident Mach number range of 1.15–1.45. The evolution of the mixing zone following the re-shock is found to be independent of its...

We investigate theoretically the effect of layering of concrete shields using a wide class of semi-empirical models. We have found that (i) the ballistic limit velocity (BLV) of the multilayered shield does not depend on the order of the plates in the shield, (ii) monolithic shield is superior to any layered shield with the same thickness, and (iii...

A dynamic gage, capable of continuously measuring high-rate displacements of structures, has been developed and tested by the research team of the Protective Technologies Research & Development Center (PTR&DC) of the Faculty of Engineering Sciences of the Ben-Gurion University of the Negey. The gage, which was originally developed in order to monit...

a b s t r a c t We investigate the problem of determining a shape of the impactor that provides the minimum ballistic limit velocity against fiber-reinforced plastic laminates, using a simplified model. The suggested approach accounts for the non-unique choice of the phenomenological parameter of the model and for the comparatively weak variation o...

a b s t r a c t We describe an approach for determining the dependence between the resistance force acting on a penetrator and the instantaneous depth of penetration and velocity using a phenomenological correlation between the impact velocity and the depth of penetration into a semi-infinite shield.

A new version of the Florence model taking into account the ballistic resistance of the ceramic plate in a two-component armor is suggested, verified and used for armor optimization. The direct problems (maximization of the ballistic limit velocity for a given areal density (AD) or a total thickness (TT) of the armor) and the inverse problems (mini...

a b s t r a c t We suggest an engineering method that allows using the known (e.g., from the experi-ments) data on the depth of penetration of several high-speed impactors for predicting the depth of penetration for the impactors having different shapes. The suggested method is based on the conjecture that a complete description of the impactor–shi...

The interactions between shock waves and boundary layers is a phenomenon frequently encountered in hypersonic flight. The existence of such shocks interactions produces a very high localized heat-transfer rates, oscillating pressure fields on the vehicle surface and can alter the aerodynamic characteristics of the vehicle. The flowfield perturbatio...

It is well established, nowadays, that if the particles added to aqueous foams are hydrophilic, have proper size and shape they concentrate within the Plateau borders and decrease the liquid drainage. The fact that solid additives can increase the protective performances of a particulate aqueous foam is also well known and even patented. This study...

The double-cone configuration is well suited to study fondamental aspects of high-enthalpy flows, as the shock interaction resulting from the interaction of the hypersonic flow with the double cone is sensitive to the high-temperature effects. A CFD campaign to compute the flow over a double cone is performed with considering different levels of mo...

Dynamic tests of three reinforced concrete samples and six Dynablok samples were performed in the blast simulator facility at the University of California San-Diego (UCSD), The purpose of these tests was to evaluate the performance of a novel protective wall design. These tests were numerically simulated at the Protective Technologies Research and...

The concept of passive shock deflectors investigated in this paper allows an easy entry of a shock wave into a shelter, while initiating further reflections and turbulent vortices by diffracting the transmitted shock over a single 90 degrees-chevron facing the incoming flow. Gas dynamic aspects of different chevron placements that control the varia...

A statistical model predicting the evolution of turbulent mixing zone fronts was developed recently by Alon et al. It suggests that the three physical elements that govern the Rayleigh-Taylor and Richtmyer-Meshkov mixing zone evolution are the single-bubble evolution, the single-spike evolution, and the interaction between neighboring bubbles. In t...

A systematic study has been made of the growth of the turbulent mixing zone (TMZ) after a re-shock in the framework of the Richtmyer–Meshkov instability where the initial shock is from the light fluid to the heavy one. The growth rate of the TMZ after the re-shock was found to be independent of its amplitude during the re-shock and to depend direct...