Reducing the Effects of Blast to the Head Through Load Partitioning

2013 ◽  
Author(s):  
Mark A. Rapo ◽  
Tim Baumer ◽  
Philemon C. Chan ◽  
James F. MacKiewicz
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Field Tests ◽  
Navier Stokes ◽  
Head Acceleration ◽  
Cfd Simulations ◽  
Blast Overpressure ◽  
Head Protection ◽  
Size Standard

Warfighters who survive encounters with improvised explosive devices (IEDs) may incur mild traumatic brain injury (mTBI) due to blast overpressure effects. Since existing head injury criteria are mostly based on head kinematics, head acceleration is one key metric to be measured. A blast wave travels at supersonic speed with a very sharp peak overpressure rise followed by a rapid decay within a short duration. For the surface area that is covered by the helmet, the cushion/suspension subsystem is responsible for mitigating the blast effects on the head, while the exposed area of the head or face would receive a direct blast loading. Computational fluid dynamic (CFD) simulations of a blast on an upright warfighter show a significant reduction in peak force to the head when a helmet is worn. For a helmet with an attached eye-shield, the load to the head from a front blast can be reduced further. A field study was conducted to verify that the increased load partitioned away from face and to the helmet and cushioning system would result in decreased head acceleration. Blast field tests were conducted using 4 lbs. of cylindrical C4 charges at 92″ standoff. Head acceleration was measured using combinations of a free hanging mid-size standard ISO headform fitted with Team Wendy (TW) pads, an advanced combat helmet (ACH), and an eye-shield. Tests were performed with the blast hitting the front, side and back of the helmeted headform system. Headform accelerations ranging from 120–465g were recorded based on blast direction and the amount of head protection. To validate the three-dimensional Navier-Stokes’ based CFD simulations, a custom-designed blast overpressure bust (BOB) containing 22 surface pressure sensors was mounted on top of the BTD to measure the pressure distribution over the head and face when exposed to a blast. The incident overpressure of the blast was 0.25MPa, with reflected pressures reaching 1.0MPa.

Design of a rotor blade tip for the investigation of dynamic stall in the transonic wind-tunnel Göttingen

2016 ◽  
Vol 120 (1232) ◽  
pp. 1509-1533 ◽  
Author(s):  
B. Lütke ◽  
J. Nuhn ◽  
Y. Govers ◽  
M. Schmidt
Keyword(s):  
Experimental Data ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Data ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Fe Model ◽  
Stress Distributions ◽  
Cfd Simulations ◽  
Blade Tip

ABSTRACTThe aerodynamic and structural design of a pitching blade tip with a double-swept planform is presented. The authors demonstrate how high-fidelity finite element (FE) and computational fluid dynamic (CFD) simulations are successfully used in the design phase. Eigenfrequencies, deformation, and stress distributions are evaluated by means of a three-dimensional (3D) FE model. Unsteady Reynolds-averaged Navier-Stokes (RANS) simulations are compared to experimental data for a light dynamic stall case atMa= 0.5,Re= 1.2 × 106. The results show a very good agreement as long as the flow stays attached. Tendencies for the span-wise location of separation are captured. As soon as separation sets in, discrepancies between experimental and numerical data are observed. The experimental data show that for light dynamic stall cases atMa= 0.5, a factor of safety ofFoS= 2.0 is sufficient if the presented simulation methods are used.

The inlet flow structure of a conceptual open-nose supersonic drone

2021 ◽  
pp. 095441002098304
Author(s):  
Eiman B Saheby ◽  
Xing Shen ◽  
Anthony P Hays ◽  
Zhang Jun
Keyword(s):  
Flow Structure ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Computational Fluid Dynamic Simulation ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Aerodynamic Efficiency ◽  
Performance Effects

This study describes the aerodynamic efficiency of a forebody–inlet configuration and computational investigation of a drone system, capable of sustainable supersonic cruising at Mach 1.60. Because the whole drone configuration is formed around the induction system and the design is highly interrelated to the flow structure of forebody and inlet efficiency, analysis of this section and understanding its flow pattern is necessary before any progress in design phases. The compression surface is designed analytically using oblique shock patterns, which results in a low drag forebody. To study the concept, two inlet–forebody geometries are considered for Computational Fluid Dynamic simulation using ANSYS Fluent code. The supersonic and subsonic performance, effects of angle of attack, sideslip, and duct geometries on the propulsive efficiency of the concept are studied by solving the three-dimensional Navier–Stokes equations in structured cell domains. Comparing the results with the available data from other sources indicates that the aerodynamic efficiency of the concept is acceptable at supersonic and transonic regimes.

Numerical 3-D Conjugated Heat Transfer Simulation of a First Inter-Stage Internal Cooled Thermal Barrier Coated Gas Turbine Bucket

2007 ◽  
Author(s):  
Alejandro Herna´ndez Rossette ◽  
Zdzislaw Mazur C. ◽  
Jesu´s Cordero Guridi ◽  
Eric Chumacero Polanco
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Loading ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Thermal Barrier ◽  
Cfd Simulations ◽  
Temperature Changes ◽  
Heat Transfer Simulation ◽  
Conjugated Heat Transfer

As a gas turbine entry temperature (TET) increases, thermal loading on first stage blades increases too and therefore, a variety of cooling techniques and thermal barrier coatings (TBCs) are used to maintain the blade temperature within the acceptable limits. In this work a multi-block three dimensional Navier-Stokes commercial turbomachinery oriented CFD-code has been used to compute steady state conjugated heat transfer (CHT) on the blade suction and pressure coated sides of a rotating first inter-stage (nozzle and bucket) with cooling holes of a 60 MW Gas turbine. A Spallart Allmaras model was used for modeling the turbulence. Convection and radiation were modeled for a super alloy blade with and without TBC. The CFD simulations were configured with a mesh domain of nozzle and bucket inter-stage in order to predict the fluid parameters at inlet and outlet of bucket for validate with turbine inter-stage parameter data test of gas turbine manufacturer. The effects of blade surface temperature changes were simulated with both configurations coated and uncoated blades.

Real Gas Effects in Turbomachinery Flows: A Computational Fluid Dynamics Model for Fast Computations

2004 ◽  
Vol 126 (2) ◽  
pp. 268-276 ◽  
Author(s):  
Paolo Boncinelli ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Massimiliano Cecconi ◽  
Carlo Cortese
Keyword(s):  
Fluid Dynamic ◽  
Computational Cost ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Design Tool ◽  
Navier Stokes ◽  
Computational Time ◽  
Real Gas ◽  
Real Gas Effects ◽  
Low Computational Cost

A numerical model was included in a three-dimensional viscous solver to account for real gas effects in the compressible Reynolds averaged Navier-Stokes (RANS) equations. The behavior of real gases is reproduced by using gas property tables. The method consists of a local fitting of gas data to provide the thermodynamic property required by the solver in each solution step. This approach presents several characteristics which make it attractive as a design tool for industrial applications. First of all, the implementation of the method in the solver is simple and straightforward, since it does not require relevant changes in the solver structure. Moreover, it is based on a low-computational-cost algorithm, which prevents a considerable increase in the overall computational time. Finally, the approach is completely general, since it allows one to handle any type of gas, gas mixture or steam over a wide operative range. In this work a detailed description of the model is provided. In addition, some examples are presented in which the model is applied to the thermo-fluid-dynamic analysis of industrial turbomachines.

scholarly journals Numerical and Analytical Study of Fluid Dynamic Forces in Seals and Bearings

1988 ◽  
Vol 110 (3) ◽  
pp. 315-325 ◽  
Author(s):  
L. T. Tam ◽  
A. J. Przekwas ◽  
A. Muszynska ◽  
R. C. Hendricks ◽  
M. J. Braun ◽  
...  
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Circumferential Velocity ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Lumped Model ◽  
Destabilizing Factors ◽  
Recirculation Zones

A numerical model based on a transformed, conservative form of the three-dimensional Navier-Stokes equations and an analytical model based on “lumped” fluid parameters are presented and compared with studies of modeled rotor/bearing/seal systems. The rotor destabilizing factors are related to the rotative character of the flow field. It is shown that these destabilizing factors can be reduced through a descrease in the fluid average circumferential velocity. However, the rotative character of the flow field is a complex three-dimensional system with bifurcated secondary flow patterns that significantly alter the fluid circumferential velocity. By transforming the Navier-Stokes equations to those for a rotating observer and using the numerical code PHOENICS-84 with a nonorthogonal body fitted grid, several numerical experiments were carried out to demonstrate the character of this complex flow field. In general, fluid injection and/or preswirl of the flow field opposing the shaft rotation significantly intensified these secondary recirculation zones and thus reduced the average circumferential velocity, while injection or preswirl in the direction of rotation significantly weakened these zones. A decrease in average circumferential velocity was related to an increase in the strength of the recirculation zones and thereby promoted stability. The influence of the axial flow was analyzed. The lumped model of fluid dynamic force based on the average circumferential velocity ratio (as opposed to the bearing/seal coefficient model) well described the obtained results for relatively large but limited ranges of parameters. This lumped model is extremely useful in rotor/bearing/seal system dynamic analysis and should be widely recommended. Fluid dynamic forces and leakage rates were calculated and compared with seal data where the working fluid was bromotrifluoromethane (CBrF3). The radial and tangential force predictions were in reasonable agreement with selected experimental data. Nonsynchronous perturbation provided meaningful information for system lumped parameter identification from numerical experiment data.

scholarly journals RUBBLE MOUND BREAKWATER OVERTOPPING: ESTIMATION OF THE RELIABILITY OF A 3D NUMERICAL SIMULATION

2012 ◽  
Vol 1 (33) ◽  
pp. 8 ◽  
Author(s):  
Luca Cavallaro ◽  
Fabio Dentale ◽  
Giovanna Donnarumma ◽  
Enrico Foti ◽  
Rosaria E. Musumeci ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Complex Geometry ◽  
Fluid Dynamic ◽  
Complete Solution ◽  
Three Dimensional ◽  
Design Tool ◽  
Physical Models ◽  
Navier Stokes ◽  
Free Boundaries ◽  
Navier Stokes Equations

Until recently, physical models were the only way to investigate into the details of breakwaters behavior under wave attack. From the numerical point of view, the complexity of the fluid dynamic processes involved has so far hindered the direct application of Navier-Stokes equations within the armour blocks, due to the complex geometry and the presence of strongly non stationary flows, free boundaries and turbulence. In the present work the most recent CFD technology is used to provide a new and more reliable approach to the design analysis of breakwaters, especially in connection with run-up and overtopping. The solid structure is simulated within the numerical domain by overlapping individual virtual elements to form the empty spaces delimited by the blocks. Thus, by defining a fine computational grid, an adequate number of nodes is located within the interstices and a complete solution of the full hydrodynamic equations is carried out. In the work presented here the numerical simulations are carried out by integrating the three-dimensional Reynolds Average Navier-Stokes Equations coupled with the RNG turbulence model and a Volume of Fluid Method used to handle the dynamics of the free surface. The aim of the present work is to investigate the reliability of this approach as a design tool. Two different breakwaters are considered, both located in Southern Sicily: one a typical quarry stone breakwater, another a more complex design incorporating a spill basin and an armoured layer made up by Coreloc® blocks.

Fluid Dynamic Design and Optimization of Two Stage Centrifugal Fan for Industrial Burners

2011 ◽  
Author(s):  
C. Ferrari ◽  
M. Pinelli ◽  
P. R. Spina ◽  
P. Bolognin ◽  
L. Borghi
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Design Stage ◽  
Centrifugal Fan ◽  
Cfd Simulations ◽  
Two Stage ◽  
Dynamic Design ◽  
Design And Optimization ◽  
Preliminary Design Stage

In this paper, the fluid dynamic design of a two-stage centrifugal fan for industrial burner application is presented. The design is carried out by means of an integrated 1D/3D numerical procedure based on the use of CFD simulations. The CFD simulations are used either at the preliminary design stage to choose among competitive one- or two-dimensional geometries and then to test the generated three-dimensional geometries. The results show how the different design choices could impact on the performance parameters and, finally, how the analysis of the various alternatives allows the determination of the overall geometry of a complete and performing two-stage centrifugal fan.

Three-Dimensional Numerical Simulation of Non-Newtonian Blood in Two Coronary Stents

2010 ◽  
Author(s):  
F. Gori ◽  
A. Boghi
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Casson Fluid ◽  
Coronary Stents ◽  
Unsteady State ◽  
Cfd Simulations ◽  
3D Geometry ◽  
Time Variations ◽  
Rigid Walls ◽  
Newtonian Behavior

The objective of the present study is to carry out CFD simulations in a realistic 3D geometry of two coronary stents in physiological conditions and to assess the influence of the non-Newtonian behavior of blood, modeled as Casson fluid. The stents used are made of 12 rings and are similar to real coronary ones. Artery is modeled as a cylinder with rigid walls and the blood is assumed as incompressible non-Newtonian fluid in laminar flow. A commercial computational fluid dynamic code is used with a mesh composed of non uniform tetrahedrons. The simulations are performed in steady and unsteady state. Wall Shear Stress, as well as its time variations and the non-Newtonian behavior, are investigated in unsteady state. Results suggest that the Newtonian behavior is leading to an overestimation of the restenosis percent.

Computerized Fluid Dynamic Study of Parameter Effects on the Performance of Coaxial Propellers

2020 ◽  
Vol 17 (7) ◽  
pp. 3237-3242
Author(s):  
Young-Tae Kim ◽  
Chang Hwan Park ◽  
Hak Yoon Kim
Keyword(s):  
Pitch Angle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Steady State Condition ◽  
Performance Variation ◽  
Air Vehicle ◽  
Program Star ◽  
And Control

The computerized fluid dynamic (CFD) analysis was performed for 1.8 m diameter coaxial propellers to be applied to the multi-copter type Personal Air Vehicle (PAV) having conceptually 600 kg of Maximum Take-Off Weight (MTOW). Methods/Statistical analysis: Using the commercial CFD program STAR-CCM+ (13.03.11), the coaxial propellers were analyzed at the same RPM under the steady state condition. The three-dimensional Compressible Reynolds Mean Navier-Stokes equation was applied and the Moving Reference Frame (MRF) technique was used. With the optimum single pitch angle of upper propeller, the lower propeller’s pitch was changed for the varying propeller spacing to identify the performance variation and the interference effect. The lower propeller has to be different pitch setting other than the upper propeller’s optimum pitch angle because of the interfered flow effect between propellers. The propeller spacing is not so sensitive to efficiency if the spacing is more than 0.25 of propeller diameter. Study shows that the identified pitches and spacing of coaxial propellers are essential for designing the configuration and control of multi-copter type PAV which uses variable pitch propellers for safety and efficiency.

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.

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