Modeling Articulated Human Body Dynamics Under a Representative Blast Loading

2011 ◽  
Author(s):  
X. G. Tan ◽  
Andrzej J. Przekwas ◽  
Gregory Rule ◽  
Kaushik Iyer ◽  
Kyle Ott ◽  
...  
Keyword(s):  
Blast Wave ◽  
Human Body ◽  
Fluid Dynamic ◽  
Free Field ◽  
Time History ◽  
Blast Loading ◽  
Blast Waves ◽  
Time Step ◽  
Time Step Size ◽  
Body Dynamics

Blast waves resulting from both industrial explosions and terrorist attacks cause devastating effects to exposed humans and structures. Blast related injuries are frequently reported in the international news and are of great interest to agencies involved in military and civilian protection. Mathematical models of explosion blast interaction with structures and humans can provide valuable input in the design of protective structures and practices, in injury diagnostics and forensics. Accurate simulation of blast wave interaction with a human body and the human body biodynamic response to the blast loading is very challenging and to the best of our knowledge has not been reported yet. A high-fidelity computational fluid dynamic (CFD) model is required to capture the reflections, diffractions, areas of stagnation, and other effects when the shock and blast waves respond to an object placed in the field. In this effort we simulated a representative free field blast event with a standing human exposed to the threat using the Second Order Hydrodynamic Automatic Mesh Refinement Code (SHAMRC). During the CFD analysis the pressure time history around the human body is calculated, along with the fragment loads. Subsequently these blast loads are applied to a fully articulated human body using the multi-physics code CoBi. In CoBi we developed a novel computational model for the articulated human body dynamics by utilizing the anatomical geometry of human body. The articulated human body dynamics are computed by an implicit multi-body solver which ensures the unconditional stability and guarantees the quadratic rate of convergence. The developed solver enforces the kinematic constraints well while imposing no limitation on the time step size. The main advantage of the model is the anatomical surface representation of a human body which can accurately account for both the surface loading and the surface interaction. The inertial properties are calculated using a finite element method. We also developed an efficient interface to apply the blast wave loading on the human body surface. The numerical results show that the developed model is capable of reasonably predicting the human body dynamics and can be used to study the primary injury mechanism. We also demonstrate that the human body response is affected by many factors such as human inertia properties, contact damping and the coefficient of friction between the human body and the environment. By comparing the computational results with the real scenario, we can calibrate these input parameters to improve the accuracy of articulated human body model.

A Comparative Study of the Human Body Finite Element Model Under Blast Loadings

2012 ◽  
Author(s):  
X. G. Tan ◽  
R. Kannan ◽  
Andrzej J. Przekwas
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Human Body ◽  
Material Properties ◽  
Complex Geometry ◽  
Blast Loading ◽  
Element Model ◽  
Stress Wave Propagation ◽  
Brain Response ◽  
Time Step

Until today the modeling of human body biomechanics poses many great challenges because of the complex geometry and the substantial heterogeneity of human body. We developed a detailed human body finite element model in which the human body is represented realistically in both the geometry and the material properties. The model includes the detailed head (face, skull, brain, and spinal cord), the skeleton, and air cavities (including the lung). Hence it can be used to accurately acquire the stress wave propagation in the human body under various loading conditions. The blast loading on the human surface was generated from the simulated C4 blast explosions, via a novel combination of 1-D and 3-D numerical formulations. We used the explicit finite element solver in the multi-physics code CoBi for the human body biomechanics. This is capable of solving the resulting large system containing millions of unknowns in an extremely scalable fashion. The meshes generated for these simulations are of good quality. This enables us to employ relatively large time step sizes, without resorting to the artificial time scaling treatment. In order to study the human body dynamic response under the blast loading, we also developed an interface to apply the blast pressure loading on the external human body surface. These newly developed models were used to conduct parametric simulations to find out the brain biomechanical response when the blasts impact the human body. Under the same blast loading we also show the differences of brain response when having different material properties for the skeleton, the existence of other body parts such as torso.

Turbulence Radiation Interactions in a Statistically Homogeneous Turbulence With Approximated Coal Type Particulate

2012 ◽  
Author(s):  
Mathew Cleveland ◽  
Sourabh Apte ◽  
Todd Palmer
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Equations ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Transfer Equations ◽  
Low Mass ◽  
Dynamic Time ◽  
Radiative Transfer Equations ◽  
Coal Type

Turbulent radiation interaction (TRI) effects are associated with the differences in the time scales of the fluid dynamic equations and the radiative transfer equations. Solving on the fluid dynamic time step size produces large changes in the radiation field over the time step. We have modified the statistically homogeneous, non-premixed flame problem of Deshmukh et al. [1] to include coal-type particulate. The addition of low mass loadings of particulate minimally impacts the TRI effects. Observed differences in the TRI effects from variations in the packing fractions and Stokes numbers are difficult to analyze because of the significant effect of variations in problem initialization. The TRI effects are very sensitive to the initialization of the turbulence in the system. The TRI parameters are somewhat sensitive to the treatment of particulate temperature and the particulate optical thickness, and this effect is amplified by increased particulate loading.

scholarly journals Clearing of Blast Waves on Finite-Sized Targets – an Overlooked Approach

2011 ◽  
Vol 82 ◽  
pp. 669-674 ◽  
Author(s):  
Andrew Tyas ◽  
Terry Bennett ◽  
James A. Warren ◽  
Stephen D. Fay ◽  
Sam E. Rigby
Keyword(s):  
Blast Wave ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Blast Loading ◽  
Blast Waves ◽  
Total Impulse ◽  
Cast Doubt ◽  
The Face ◽  
Loading Parameter ◽  
Semi Empirical

The total impulse imparted to a target by an impinging blast wave is a key loading parameter for the design of blast-resistant structures and façades. Simple, semi-empirical approaches for the prediction of blast impulse on a structure are well established and are accurate in cases where the lateral dimensions of the structure are sufficiently large. However, if the lateral dimensions of the target are relatively small in comparison to the length of the incoming blast wave, air flow around the edges of the structure will lead to the propagation of rarefaction or clearing waves across the face of the target, resulting in a premature reduction of load and hence, a reduction in the total impulse imparted to the structure. This effect is well-known; semi-empirical models for the prediction of clearing exist, but several recent numerical and experimental studies have cast doubt on their accuracy and physical basis. In fact, this issue was addressed over half a century ago in a little known technical report at the Sandia Laboratory, USA. This paper presents the basis of this overlooked method along with predictions of the clearing effect. These predictions, which are very simple to incorporate in predictions of blast loading, have been carefully validated by the current authors, by experimental testing and numerical modelling. The paper presents a discussion of the limits of the method, concluding that it is accurate for relatively long stand-off blast loading events, and giving some indication of improvements that are necessary if the method is to be applicable to shorter stand-off cases.

Blast Wall Shielding Effectiveness

2017 ◽  
Author(s):  
Jihui Geng ◽  
J. Kelly Thomas
Keyword(s):  
Blast Wave ◽  
High Explosive ◽  
Blast Loading ◽  
Blast Waves ◽  
Shielding Effectiveness ◽  
Wave Shape ◽  
Mitigation Option ◽  
Blast Damage ◽  
Wave Parameters ◽  
Vapor Cloud

Blast walls are frequently considered as a potential mitigation option to reduce the applied blast loading on a building or structure in cases where unacceptably high levels of blast damage are predicted. There are three general explosion types of interest with respect to blast loading: High Explosive (HE), Pressure Vessel Burst (PVB), and Vapor Cloud Explosion (VCE). The blast waves resulting from these explosion types can differ significantly in terms of blast wave shape and duration. The effectiveness of a blast wall depends on these blast wave parameters (shape and duration), as well as the blast wall parameters (e.g., height, width and standoff distance from the protected structure). The effectiveness of a blast wall in terms of mitigating the blast loading on a protected structure depends on the combination of the blast wave and blast wall parameters. However, little guidance is available on the effectiveness of blast walls as a mitigation option for non-HE explosion sources. The purpose of this paper is to characterize the effect of blast wave parameters on the effectiveness of a blast wall and to provide guidance on how to determine whether a blast wall is an effective and practical blast damage mitigation option for a given blast loading.

Free-Field Blast Loading for TBI and Lung Injury Correlation

2015 ◽  
Author(s):  
Mark Rapo ◽  
Christopher Ostoich ◽  
Brett Juhas ◽  
Brian Powell ◽  
Philemon Chan
Keyword(s):  
Lung Injury ◽  
Fluid Dynamic ◽  
Free Field ◽  
Blast Loading ◽  
Medical Outcomes ◽  
Cfd Simulations ◽  
Blast Overpressure ◽  
Modeling Analysis ◽  
Wide Range ◽  
Closed Head Trauma

This paper presents a study to provide guidance on the use of body-worn blast overpressure sensors to predict the risk of blast induced closed head trauma and lung injury. Data collected from blast sensor systems, when used in combination with modeling and simulation, can recreate the full loading on the warfighter [1]. Using field blast data from a 4 sensor time-synched blast system, the incident blast wave and direction was reconstructed and used as input to computational fluid dynamic (CFD) simulations of blast impacting an outfitted warfighter. Pressures around the head and underneath the helmet were found to be in agreement with experimental data. The peak resultant head velocity, which is shown to be a correlate of concussion, was also found to correlate with incident impulse over a wide range of blast conditions. Lung injury was assessed for every blast condition, revealing that some blast directions and intensities more readily engage multiple modes of injury. With the accurate reconstruction of the true blast loading to a warfighter, damage correlates obtained from biomechanical modeling analysis can be calculated for correlation with medical outcomes.

Development and validation of a biofidelic head form model to assess blast-induced traumatic brain injury

2017 ◽  
Vol 15 (3) ◽  
pp. 257-267
Author(s):  
Devon Downes ◽  
Amal Bouamoul ◽  
Simon Ouellet ◽  
Manouchehr Nejad Ensan
Keyword(s):  
Finite Element ◽  
Brain Injury ◽  
Blast Wave ◽  
Skull Fracture ◽  
Free Field ◽  
Blast Loading ◽  
Human Head ◽  
Arbitrary Lagrangian Eulerian ◽  
Element Analysis ◽  
Head Form

Traumatic Blast Injury (TBI) associated with the human head is caused by exposure to a blast loading, resulting in decreased level of consciousness, skull fracture, lesions, or death. This paper presents the simulation of blast loading of a human head form from a free-field blast with the end goal of providing insight into how TBI develops in the human head. The developed numerical model contains all the major components of the human head, the skull, and brain, including the tentorium, cerebral falx, and gray and white matter. A nonlinear finite element analysis was employed to perform the simulation using the Arbitrary Lagrangian–Eulerian finite element method. The simulation captures the propagation of the blast wave through the air, its interaction with the skull, and its transition into the brain matter. The model quantifies the pressure histories of the blast wave from the explosive source to the overpressure on the skull and the intracranial pressure. This paper discusses the technical approach used to model the head, the outcome from the analysis, and the implication of the results on brain injury.

scholarly journals Seismic response of elevated water reservoirs

1982 ◽  
Vol 15 (2) ◽  
pp. 68-76
Author(s):  
B. Hunt ◽  
M. J. N. Priestley
Keyword(s):  
Time History ◽  
Water Level Fluctuations ◽  
Wave Mechanics ◽  
Step Size ◽  
Time Step ◽  
Computer Prediction ◽  
Simplified Approach ◽  
Time Step Size ◽  
Surface Displacements ◽  
Elevated Water

Equations previously developed for a ground-supported, rigid cylindrical reservoir and based on the classical approximations
of linearized, inviscid wave mechanics are extended to cope
with the case of elevated reservoirs supported by flexible columns. Solutions for column shear forces and free surface displacements are developed in a form suitable for computer prediction of time-history response. Sensitivity of results to the time-step size and the number of slosh modes is examined, and it is concluded
that accurate estimates of water level fluctuations can only be obtained if at least 10 modes are used. A realistic example is presented to illustrate the method, and the response to two accelerograms is compared with predictions obtained from Housner's simplified approach.

Exact Solution of Time History Response for Dynamic Systems With Arbitrary Viscous Damping Using Complex Modal Analysis

2007 ◽  
Author(s):  
Lonny L. Thompson ◽  
Manoj Kumar M. Chinnakonda
Keyword(s):  
Modal Analysis ◽  
State Space ◽  
Piecewise Linear ◽  
Time History ◽  
Quadrature Rules ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Complex Eigenvalues ◽  
Time History Response

A solution method for general, non-proportional damping time history response for piecewise linear loading is generalized to exact solutions which include piecewise quadratic loading. Comparisons are made to Trapezoidal and Simpson’s quadrature rules for approximating the time integral of the weighted generalized forcing function in the exact solution to the decoupled modal equations arising from state-space modal analysis of linear dynamic systems. Closed-form expressions for the weighting parameters in the quadrature formulas in terms of time-step size and complex eigenvalues are derived. The solution is obtained step-by-step from update formulas derived from the piecewise linear and quadratic interpolatory quadrature rules starting from the initial condition. An examination of error estimates for the different force interpolation methods shows convergence rates depend explicitly on the amount of damping in the system as measured by the real-part of the complex eigenvalues of the state-space modal equations and time-step size. Numerical results for a system with general, non-proportional damping, and driven by a continuous loading shows that for systems with light damping, update formulas for standard Trapezoidal and Simpson’s rule integration have comparable accuracy to the weighted piecewise linear and quadratic force interpolation update formulas, while for heavy damping, the update formulas from the weighted force interpolation quadrature rules are more accurate. Using a simple model representing a stiff system with general damping, we show that a two-step modal analysis using real-valued modal reduction followed by state-space modal analysis is shown to be an effective approach for rejecting spurious modes in the spatial discretization of a continuous system.

A Computational Approach to Assessing Blast Damage in Urban Centers Using AUTODYN

2004 ◽  
Author(s):  
Malcolm S. Cowler ◽  
Xiangyang Quan ◽  
Greg E. Fairlie
Keyword(s):  
Shock Front ◽  
Urban Environment ◽  
Blast Wave ◽  
Structural Damage ◽  
Free Field ◽  
Impulsive Loading ◽  
Urban Environments ◽  
Blast Waves ◽  
Urban Centers ◽  
Military Organizations

Recent terrorist attacks have prompted considerable interest in predicting damage to structures that could result from explosive blasts in densely populated urban environments. This is a particular concern for government and military organizations wishing to improve the safety of facilities and insurance providers who want to quantify risks. Blast waves from explosions are characterized by a shock front propagating into the surrounding air, followed by an exponential decay in pressure. Structural damage can be caused by either the magnitude of the peak pressure or the impulsive loading over time. Thus, any assessment of damage requires accurate computation of the entire pressure history on the structure. Semi-empirical approaches, such as CONWEP, although able to predict free-field and single-reflected pressures accurately, are unable to account for the effect that the urban environment has on amplifying, dissipating or focusing the blast wave. This paper describes a numerical finite difference approach, using the non-linear dynamics program AUTODYN, which allows an accurate prediction of the pressure fields that develop as a blast wave propagates through an urban environment by recursively remapping the solution through numerical regions that expand to track the evolving shock front. Data for specific urban layouts can be imported into AUTODYN from geographic information system (GIS) services.

scholarly journals Review of Blast Loading Models, Masonry Response, and Mitigation

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Eid Badshah ◽  
Amjad Naseer ◽  
Muhammad Ashraf ◽  
Feroz Shah ◽  
Kareem Akhtar
Keyword(s):  
Boundary Conditions ◽  
Urban Environment ◽  
Blast Wave ◽  
Material Properties ◽  
Free Field ◽  
Blast Loading ◽  
Masonry Structure ◽  
Mitigation Strategies ◽  
Masonry Buildings ◽  
Wave Parameters

Different models for prediction of blast loading, response of masonry structure against blast load, and various mitigation strategies are discussed. Variation of peak positive incident pressure with scale distance in free field spherical burst and surface burst scenarios, proposed by different researchers, is presented and compared. The variation is found significant in the region of small scaled distances. Blast wave parameters in urban environment have been found different from the free field scenario. Effects of geometry, boundary conditions, and material properties on response of masonry buildings were found significant. Different mitigation strategies such as blast wall, landscaping, architecture, and retrofitting techniques are presented.

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