scholarly journals Assessment of the Effectiveness of Combat Eyewear Protection Against Blast Overpressure

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
A. Sundaramurthy ◽  
M. Skotak ◽  
E. Alay ◽  
G. Unnikrishnan ◽  
H. Mao ◽  
...  
Keyword(s):  
Peak Pressure ◽  
Three Dimensional ◽  
Head Orientation ◽  
Computational Results ◽  
Pressure Loading ◽  
3D Finite Element ◽  
Blast Overpressure ◽  
Explosive Devices ◽  
Peak Pressures ◽  
Good Agreement

It is unclear whether combat eyewear used by U. S. Service members is protective against blast overpressures (BOPs) caused by explosive devices. Here, we investigated the mechanisms by which BOP bypasses eyewear and increases eye surface pressure. We performed experiments and developed three-dimensional (3D) finite element (FE) models of a head form (HF) equipped with an advanced combat helmet (ACH) and with no eyewear, spectacles, or goggles in a shock tube at three BOPs and five head orientations relative to the blast wave. Overall, we observed good agreement between experimental and computational results, with average discrepancies in impulse and peak-pressure values of less than 15% over 90 comparisons. In the absence of eyewear and depending on the head orientation, we identified three mechanisms that contributed to pressure loading on the eyes. Eyewear was most effective at 0 deg orientation, with pressure attenuation ranging from 50 (spectacles) to 80% (goggles) of the peak pressures observed in the no-eyewear configuration. Spectacles and goggles were considerably less effective when we rotated the HF in the counter-clockwise direction around the superior-inferior axis of the head. Surprisingly, at certain orientations, spectacles yielded higher maximum pressures (80%) and goggles yielded larger impulses (150%) than those observed without eyewear. The findings from this study will aid in the design of eyewear that provides better protection against BOP.

ACOUSTIC THREE-DIMENSIONAL EFFECTS AROUND THE TAIWAN STRAIT: COMPUTATIONAL RESULTS

1999 ◽  
Vol 07 (01) ◽  
pp. 15-26 ◽  
Author(s):  
CHI-FANG CHEN ◽  
JANG-JIA LIN ◽  
DING LEE
Keyword(s):  
Field Data ◽  
Bottom Topography ◽  
Three Dimensional ◽  
Propagation Model ◽  
Computational Results ◽  
Submarine Canyons ◽  
Offshore Area ◽  
Ocean Environment ◽  
The Taiwan Strait ◽  
Good Agreement

A set of experiments were performed in the offshore area off the coasts of Taiwan and three-dimensional (3-D) measurements recorded. The 3-D effect on underwater propagation due to azimuthal variation of bottom topography is studied for the offshore regions southwest of Taiwan, where submarine canyons exist. A 3-D acoustic propagation model, FOR3D, is used to detect the 3-D effect. Computational results show that the 3-D effect is more prominent along the axis of the canyon than across it. Calculations show a very good agreement with field data, which indicate that the 3-D effect exists in this realistic ocean environment.

The Experimental Study and Numerical Simulation of Turbulent Flow in Pumping Forebay

2009 ◽  
Author(s):  
Chao Liu ◽  
Jiren Zhou ◽  
Li Cheng
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Computational Results ◽  
Experiment Study ◽  
Study Results ◽  
Measurement Results ◽  
Good Agreement ◽  
Made In

The experiment study was made to optimize the design of a pumping forebay. The Combined-sills were made in the forebay to eliminate the circulation and vortices of the diffusing flow successfully. The Numerical simulation of three-dimensional turbulent flow is applied on the complicate fore-and-aft flow of sills. The computational results are compared with the measurement results of physical model. The calculated results are in good agreement with the experimental data. The flow pattern is obviously improved. The study results have been applied in the project which gives a uniform approach flow to the pumping sump.

Blast Overpressure Measured on a Bare vs. Helmeted Rigid Headform

2013 ◽  
Author(s):  
Timothy Baumer ◽  
Mark A. Rapo ◽  
Jessica M. Wong ◽  
Brian J. Powell ◽  
Brett D. Juhas ◽  
...  
Keyword(s):  
Peak Pressure ◽  
Pressure Sensors ◽  
Field Tests ◽  
Sensor Location ◽  
Data Set ◽  
Blast Overpressure ◽  
Time Motion ◽  
Pressure Trace ◽  
Impact Angles ◽  
Peak Pressures

There is significant concern that blast overpressure can cause mild traumatic brain injury (mTBI). An accurate understanding of the blast flow and overpressure event as well as it’s interaction with the head and helmet system is a necessary first step in establishing loading conditions to the head. It also provides a means for model validation and other predictive capabilities. A custom-designed Blast Overpressure Bust (BOB) containing 22 surface pressure sensors was rigidly mounted in a live-fire blast event. The blast field tests were conducted in an open field using 4 lbs. of cylindrical C4 charges suspended 48″ above the pad. The BOB was mounted to a torso surrogate and positioned 92″ from the hanging charge. The BOB was oriented at blast impact angles of 0 (front-facing), 45, 90, and 180 degrees. The BOB was tested in both bare and helmeted configurations. Data recorded across a bare headform at each angle established a baseline for the pressure trace at each sensor location. Two helmeted cases were investigated: Advanced Combat Helmet (ACH) with the sling suspension system and ACH with Team Wendy pads. Results showed peak pressures on exposed surfaces normal to the blast were ∼1200kPa with side-on pressures of ∼400kPa. The addition of a helmet did not alter the peak normal pressures, but showed slight to moderate increases in pressure beneath the helmet based on the amount of cushioning present. The sling suspension, which leaves an open gap between the head and helmet, resulted in several recorded amplification points beneath the helmet with the peaks reaching ∼800kPa. The Team Wendy pads trials, which effectively fill the gap between the head and helmet, showed amplifications with peaks of ∼500kPa. An additional set of tests was conducted using an ingress barrier positioned between the head and helmet at the brim. Results showed pressures under the helmet that were lower than the bare headform trials. While it was shown that adding a helmet did in fact increase pressures relative to the bare headform case, these amplifications were still far less than the peak pressure exerted on the exposed surfaces of the headform. The data presented herein is the most robust data set to date for pressures exerted on a helmeted headform and is considered applicable to the first 3–5ms of an unconstrained system, during which time motion is minimal.

Application of a Navier-Stokes Solver to the Study of Open Rotor Aerodynamics

2009 ◽  
Author(s):  
Alexios Zachariadis ◽  
Cesare A. Hall
Keyword(s):  
Control Volume ◽  
Three Dimensional ◽  
Computational Approach ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Computational Results ◽  
Field Boundary ◽  
Rotor Aerodynamics ◽  
Open Rotor ◽  
Good Agreement

This paper establishes a proven computational approach for open rotor configurations that can be used as a basis for further studies involving open rotor aerodynamics and design. Many of the difficulties encountered in the application of computational fluid dynamics to an open rotor engine arise due to the removal of the casing that is present in conventional aeroengine turbomachinery. In this work, an advanced three-dimensional Navier-Stokes solver is applied to the open rotor. The approach needed to accurately capture the aerodynamics is investigated with particular attention to the mesh configuration and the specification of boundary conditions. A new three-step meshing strategy for generating the mesh and the most suitable type of far-field boundary condition are discussed. A control volume analysis approach is proposed for post-processing the numerical results for rotor performance. The capabilities of the solver and the applied methodology are demonstrated at both cruise and take-off operating conditions. The comparison of computational results with experimental measurements shows good agreement for both data trend and magnitudes.

3D Numerical Analysis of Centrifuge Tests on Embankments on Soft and Stiff Ground

2013 ◽  
Vol 831 ◽  
pp. 314-320
Author(s):  
Ali Sobhanmanesh ◽  
Ramli Bin Nazir ◽  
Nurly Gofar
Keyword(s):  
Numerical Analysis ◽  
Deformation Behavior ◽  
Three Dimensional ◽  
Two Dimensional ◽  
3D Finite Element ◽  
Reinforcement Condition ◽  
Centrifuge Tests ◽  
Comparison Of The Results ◽  
Plaxis 3D ◽  
Good Agreement

The behavior of reinforced and unreinforced embankment on soft and stiff grounds has been investigated using the centrifuge tests and verified using numerical simulations. Four different cases have been investigated in this study based on various types of foundation materials and reinforcement condition. Two-dimensional (2D) and three-dimensional (3D) finite element programs, Plaxis 2D and Plaxis 3D Foundation respectively used to simulate and analyze the prototypes behavior provided by centrifuge tests. Deformation behavior, settlements and effect of reinforcement have been studied in this study. Comparison of the results of the numerical analysis with the measurements obtained from the centrifuge tests shows good agreement in terms of settlement and the reduction of settlement due to geosynthetics reinforcement.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

A Free Energy Perturbation Approach to Estimate the Intrinsic Solubilities of Drug-like Small Molecules

2019 ◽  
Author(s):  
Sayan Mondal ◽  
Gary Tresadern ◽  
Jeremy Greenwood ◽  
Byungchan Kim ◽  
Joe Kaus ◽  
...  
Keyword(s):  
Solid State ◽  
Small Molecules ◽  
Three Dimensional ◽  
Aqueous Solubility ◽  
Computational Approach ◽  
Free Energy Perturbation ◽  
Perturbation Approach ◽  
Energy Perturbation ◽  
State Form ◽  
Good Agreement

<p>Optimizing the solubility of small molecules is important in a wide variety of contexts, including in drug discovery where the optimization of aqueous solubility is often crucial to achieve oral bioavailability. In such a context, solubility optimization cannot be successfully pursued by indiscriminate increases in polarity, which would likely reduce permeability and potency. Moreover, increasing polarity may not even improve solubility itself in many cases, if it stabilizes the solid-state form. Here we present a novel physics-based approach to predict the solubility of small molecules, that takes into account three-dimensional solid-state characteristics in addition to polarity. The calculated solubilities are in good agreement with experimental solubilities taken both from the literature as well as from several active pharmaceutical discovery projects. This computational approach enables strategies to optimize solubility by disrupting the three-dimensional solid-state packing of novel chemical matter, illustrated here for an active medicinal chemistry campaign.</p>

Study of dynamic pressure on the packer for deep-water perforation

Open Physics ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 215-223
Author(s):  
Hao Huang ◽  
Qiao Deng ◽  
Hui Zhang
Keyword(s):  
Deep Water ◽  
Peak Pressure ◽  
Orthogonal Design ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Calculation Model ◽  
Well Testing ◽  
Technical Problems ◽  
Wellbore Pressure ◽  
Three Dimensional Finite Element

Abstract The packer is one of the most important tools in deep-water perforation combined well testing, and its safety directly determines the success of perforation test operations. The study of dynamic perforating pressure on the packer is one of the key technical problems in the production of deep-water wells. However, there are few studies on the safety of packers with shock loads. In this article, the three-dimensional finite element models of downhole perforation have been established, and a series of numerical simulations are carried out by using orthogonal design. The relationship between the perforating peak pressure on the packer with the factors such as perforating charge quantity, wellbore pressure, perforating explosion volume, formation pressure, and elastic modulus is established. Meanwhile, the database is established based on the results of numerical simulation, and the calculation model of peak pressure on the packer during perforating is obtained by considering the reflection and transmission of shock waves on the packer. The results of this study have been applied in the field case of deep-water well, and the safety optimization program for deep-water downhole perforation safety has been put forward. This study provides important theoretical guidance for the safety of the packer during deep-water perforating.

scholarly journals Simulation of Thermal and Electric Field Distribution in Packaged Sausages Heated in a Stationary Versus a Rotating Microwave Oven

Foods ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1622
Author(s):  
Wipawee Tepnatim ◽  
Witchuda Daud ◽  
Pitiya Kamonpatana
Keyword(s):  
Temperature Distribution ◽  
Electric Field ◽  
Three Dimensional ◽  
Development Stage ◽  
Microwave Oven ◽  
Computational Time ◽  
Plastic Package ◽  
Heating Uniformity ◽  
The Cost ◽  
Good Agreement

The microwave oven has become a standard appliance to reheat or cook meals in households and convenience stores. However, the main problem of microwave heating is the non-uniform temperature distribution, which may affect food quality and health safety. A three-dimensional mathematical model was developed to simulate the temperature distribution of four ready-to-eat sausages in a plastic package in a stationary versus a rotating microwave oven, and the model was validated experimentally. COMSOL software was applied to predict sausage temperatures at different orientations for the stationary microwave model, whereas COMSOL and COMSOL in combination with MATLAB software were used for a rotating microwave model. A sausage orientation at 135° with the waveguide was similar to that using the rotating microwave model regarding uniform thermal and electric field distributions. Both rotating models provided good agreement between the predicted and actual values and had greater precision than the stationary model. In addition, the computational time using COMSOL in combination with MATLAB was reduced by 60% compared to COMSOL alone. Consequently, the models could assist food producers and associations in designing packaging materials to prevent leakage of the packaging compound, developing new products and applications to improve product heating uniformity, and reducing the cost and time of the research and development stage.

scholarly journals 3D-Volume Rendering of the Pelvis with Emphasis on Paraurethral Structures Based on MRI Scans and Comparisons between 3D Slicer and OsiriX®

2021 ◽  
Vol 45 (3) ◽  
Author(s):  
C. M. Durnea ◽  
S. Siddiqi ◽  
D. Nazarian ◽  
G. Munneke ◽  
P. M. Sedgwick ◽  
...  
Keyword(s):  
Image Processing ◽  
Secondary Analysis ◽  
Three Dimensional ◽  
3D Models ◽  
Clinical Role ◽  
Cross Sectional ◽  
3D Slicer ◽  
Mri Scans ◽  
3D Volume ◽  
Good Agreement

AbstractThe feasibility of rendering three dimensional (3D) pelvic models of vaginal, urethral and paraurethral lesions from 2D MRI has been demonstrated previously. To quantitatively compare 3D models using two different image processing applications: 3D Slicer and OsiriX. Secondary analysis and processing of five MRI scan based image sets from female patients aged 29–43 years old with vaginal or paraurethral lesions. Cross sectional image sets were used to create 3D models of the pelvic structures with 3D Slicer and OsiriX image processing applications. The linear dimensions of the models created using the two different methods were compared using Bland-Altman plots. The comparisons demonstrated good agreement between measurements from the two applications. The two data sets obtained from different image processing methods demonstrated good agreement. Both 3D Slicer and OsiriX can be used interchangeably and produce almost similar results. The clinical role of this investigation modality remains to be further evaluated.

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