scholarly journals Turbulent wake past a three-dimensional blunt body. Part 2. Experimental sensitivity analysis

2014 ◽  
Vol 752 ◽  
pp. 439-461 ◽  
Author(s):  
M. Grandemange ◽  
M. Gohlke ◽  
O. Cadot
Keyword(s):  
Three Dimensional ◽  
Cross Flow ◽  
Body Part ◽  
General Concept ◽  
Bluff Bodies ◽  
Vertical Control ◽  
Induced Drag ◽  
Natural Flow ◽  
Set Up ◽  
The Impact

AbstractThe sensitivity of the flow around three-dimensional blunt geometry is investigated experimentally at Reynolds number $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}9.2\times 10^4$. Vertical and horizontal control cylinders are used to disturb the natural flow which is the superposition of two reflectional symmetry breaking states (see Part 1 of this study, Grandemange, Gohlke & Cadot, J. Fluid Mech., vol. 722, 2013b, pp. 51–84). When the perturbation breaks the symmetry of the set-up, it can select one of the two asymmetric topologies so that a mean side force is found. When the reflectional symmetry is preserved, some positions of horizontal and vertical control cylinders alter the natural bi-stability of the flow which may result in drag reduction. In addition, it is found that the horizontal perturbation affects the lift force especially when the top and bottom mixing layers are disturbed. The ability of the disturbances to suppress the bi-stable behaviour is discussed and, introducing a formalism of induced drag, a quantification of the impact on the drag of the cross-flow forces observed for the natural bi-stable wake is suggested. Finally, a general concept for a control strategy of separated flows past three-dimensional bluff bodies can be drawn up from these analyses.

scholarly journals The development of a quick-running prediction tool for the assessment of human injury owing to terrorist attack within crowded metropolitan environments

2011 ◽  
Vol 366 (1562) ◽  
pp. 127-143 ◽  
Author(s):  
Daniel J. Pope
Keyword(s):  
Terrorist Attack ◽  
Three Dimensional ◽  
Medical Personnel ◽  
Body Part ◽  
Mathematical Representation ◽  
List Type ◽  
Prediction Tool ◽  
Body Parts ◽  
Set Up ◽  
Human Injury

In the aftermath of the London ‘7/7’ attacks in 2005, UK government agencies required the development of a quick-running tool to predict the weapon and injury effects caused by the initiation of a person borne improvised explosive device (PBIED) within crowded metropolitan environments. This prediction tool, termed the HIP (human injury predictor) code, was intended to: — assist the security services to encourage favourable crowd distributions and densities within scenarios of ‘sensitivity’; — provide guidance to security engineers concerning the most effective location for protection systems; — inform rescue services as to where, in the case of such an event, individuals with particular injuries will be located; — assist in training medical personnel concerning the scope and types of injuries that would be sustained as a consequence of a particular attack; — assist response planners in determining the types of medical specialists (burns, traumatic amputations, lungs, etc.) required and thus identify the appropriate hospitals to receive the various casualty types. This document describes the algorithms used in the development of this tool, together with the pertinent underpinning physical processes. From its rudimentary beginnings as a simple spreadsheet, the HIP code now has a graphical user interface (GUI) that allows three-dimensional visualization of results and intuitive scenario set-up. The code is underpinned by algorithms that predict the pressure and momentum outputs produced by PBIEDs within open and confined environments, as well as the trajectories of shrapnel deliberately placed within the device to increase injurious effects. Further logic has been implemented to transpose these weapon effects into forms of human injury depending on where individuals are located relative to the PBIED. Each crowd member is subdivided into representative body parts, each of which is assigned an abbreviated injury score after a particular calculation cycle. The injury levels of each affected body part are then summated and a triage state assigned for each individual crowd member based on the criteria specified within the ‘injury scoring system’. To attain a comprehensive picture of a particular event, it is important that a number of simulations, using what is substantively the same scenario, are undertaken with natural variation being applied to the crowd distributions and the PBIED output. Accurate mathematical representation of such complex phenomena is challenging, particularly as the code must be quick-running to be of use to the stakeholder community. In addition to discussing the background and motivation for the algorithm and GUI development, this document also discusses the steps taken to validate the tool and the plans for further functionality implementation.

Numerical Investigation of the Impact of Part-Span Connectors on Aero-Thermodynamics in a Low Pressure Industrial Steam Turbine

2014 ◽  
Author(s):  
M. Häfele ◽  
J. Starzmann ◽  
M. Grübel ◽  
M. Schatz ◽  
D. M. Vogt ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Numerical Study ◽  
Three Dimensional ◽  
Measurement Data ◽  
Cross Flow ◽  
Low Pressure ◽  
Wet Steam ◽  
Flow Vortex ◽  
The Impact ◽  
Non Equilibrium

A numerical study on the flow in a three stage low pressure industrial steam turbine with conical friction bolts in the last stage and lacing wires in the penultimate stage is presented and analyzed. Structured high-resolution hexahedral meshes are used for all three stages and the meshing methodology is shown for the rotor with friction bolts and blade reinforcements. Modern three-dimensional CFD with a non-equilibrium wet steam model is used to examine the aero-thermodynamic effects of the part-span connectors. A performance assessment of the coupled blades at part load, design and overload condition is presented and compared with measurement data from an industrial steam turbine test rig. Detailed flow field analyses and a comparison of blade loading between configurations with and without part-span connectors are presented in this paper. The results show significant interaction of the cross flow vortex along the part-span connector with the blade passage flow causing aerodynamic losses. This is the first time that part-span connectors are being analyzed using a non-equilibrium wet steam model. It is shown that additional wetness losses are induced by these elements.

System Identification of Hydrokinetic Energy Harvester Using Flow Induced Oscillations

2018 ◽  
Author(s):  
Ralph Saxton ◽  
Soumyadip Patra ◽  
Nikolaos I. Xiros ◽  
Michael M. Bernitsas ◽  
Hai Sun
Keyword(s):  
Control System ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Rigid Bodies ◽  
Data Series ◽  
Bluff Bodies ◽  
Hydrokinetic Energy ◽  
Dynamics And Control ◽  
Using Data ◽  
Set Up

Using data series obtained by experiments at the Marine Renewable Energy Laboratory of the University of Michigan, a Data-Driven Model is constructed for further investigation of the Process Dynamics and Control System Design and Configuration. This will enable advances in hydrokinetic energy harvesting using Vortex Induced Vibrations (VIV) and galloping, or more generally, Flow Induced Oscillations (FIO). Typically in such energy converters, one or more multiple bluff bodies, such as cylinders are suspended on springs in a water flow (currents, tides, rivers). In commonly encountered flows, oscillations are induced to the bluff rigid bodies due to vortex shedding in their wake, or due to lift instabilities in galloping, or both. These phenomena are dependent on stiffness, damping, mass ratio and the resulting vortex shedding frequency. The experiments in the cases investigated generated position signal recordings for one or two cylinders used as bluff bodies in FIO in a cross-flow. The position signals are used to set up a dynamic model. The model equation helps in gaining insight into the dynamics and underlying physics of the modeled FIO and can be used for Control System Tuning and Verification.

scholarly journals Three-Dimensional Salt Dynamics in Well-Mixed Estuaries: Influence of Estuarine Convergence, Coriolis, and Bathymetry

2017 ◽  
Vol 47 (7) ◽  
pp. 1843-1871 ◽  
Author(s):  
Xiaoyan Wei ◽  
Mohit Kumar ◽  
Henk M. Schuttelaars
Keyword(s):  
Coriolis Force ◽  
Three Dimensional ◽  
Temporal Correlation ◽  
Salt Transport ◽  
Residual Circulation ◽  
Three Dimensional Model ◽  
Coriolis Effects ◽  
Set Up ◽  
The Right ◽  
The Impact

AbstractA semianalytical three-dimensional model is set up to dynamically calculate the coupled water motion and salinity for idealized well-mixed estuaries and prognostically investigate the influence of each physical mechanism on the residual salt transport. As a study case, a schematized estuary with an exponentially converging width and a channel–shoal structure is considered. The temporal correlation between horizontal tidal velocities and tidal salinities is the dominant process for the landward residual salt transport. The residual salt transport induced by residual circulation is locally significant, but the induced salt transport integrated over the cross section is small. The impacts of the estuarine geometry, Coriolis force, and bathymetry on the salt dynamics are studied using three dedicated experiments, in which the impact of each of these factors is studied separately. To assess the impact of width convergence, a convergent estuary without bathymetric variations or Coriolis force is considered. In this experiment, the temporal correlation between tidal velocities and salinities is the only landward salt transport process. In the second experiment, Coriolis effects are included. This results in a significant residual salt transport cell due to the advection of the tidally averaged salinity by residual circulation, with salt imported into the estuary from the left side and exported on the right (looking seaward). In the last experiment, a lateral channel–shoal structure is included while the Coriolis effects are excluded. This results in a significant landward salt transport through the deeper channel and a seaward salt transport over the shoals due to the advection of the tidally averaged salinity by residual circulation.

scholarly journals Random and systematic set-up errors in three-dimensional conformal radiotherapy – impact on planning target volume margins: the experience of the Radiation Oncology Centre of Sassari

2013 ◽  
Vol 13 (2) ◽  
pp. 166-179
Author(s):  
Matteo Tamponi ◽  
Angela Poggiu ◽  
Maria F. Dedola ◽  
Rossella Madeddu ◽  
Antonella Carnevale ◽  
...  
Keyword(s):  
Planning Target Volume ◽  
Three Dimensional ◽  
Conformal Radiotherapy ◽  
Target Volume ◽  
Patient Specific ◽  
Geometric Uncertainties ◽  
Three Dimensional Conformal Radiotherapy ◽  
Set Up ◽  
Oncology Centre ◽  
The Impact

AbstractPurposeGeometric uncertainties limit the accuracy of three-dimensional conformal radiotherapy treatments. This study aims to evaluate typical random and systematic set-up errors and analyse the impact of no action level (NAL) correction protocol on systematic set-up errors and clinical target volume (CTV)–planning target volume (PTV) margins.Materials and methodsA total 668 pairs of orthogonal electronic portal images were compared with digitally reconstructed radiographs from computed tomography planning scans for 100 patients consecutively treated during 2011. Patients were divided into groups depending on the treated anatomical region. Patient-specific and population random and systematic set-up errors were calculated. Impact of application of NAL correction protocol on systematic set-up errors and CTV–PTV expansions were evaluated.ResultsPopulation set-up errors resulted from about 1 mm in head and neck to 2–3 mm in prostate, rectum, lung, breast and gynaecological districts. Patient-specific systematic set-up errors were higher for breast and gynaecological districts and application of NAL correction protocol gave significant reductions, even higher than 30%. Calculated CTV–PTV margins ranged from 10 mm on left–right direction for prostate to 20 mm on superior–inferior direction for lung.ConclusionsSet-up errors resulted reasonably controlled and application of NAL correction protocol could further improve the level of accuracy. However, the NAL application alone did not seem to add any substantial benefit on CTV–PTV total margins without the adoption of corrective strategies to reduce other important uncertainties limiting accuracy of three-dimensional conformal radiotherapy.

scholarly journals The magic hand: Plasticity of mental hand representation

2018 ◽  
Vol 71 (11) ◽  
pp. 2314-2324 ◽  
Author(s):  
Gianna Cocchini ◽  
Toni Galligan ◽  
Laura Mora ◽  
Gustav Kuhn
Keyword(s):  
Mental Representation ◽  
Three Dimensional ◽  
Sensory Information ◽  
Body Part ◽  
Hand Position ◽  
Proprioceptive Information ◽  
Body Parts ◽  
Motor Information ◽  
The Impact

Internal spatial body configurations are crucial to successfully interact with the environment and to experience our body as a three-dimensional volumetric entity. These representations are highly malleable and are modulated by a multitude of afferent and motor information. Despite some studies reporting the impact of sensory and motor modulation on body representations, the long-term relationship between sensory information and mental representation of own body parts is still unclear. We investigated hand representation in a group of expert sleight-of-hand magicians and in a group of age-matched adults naïve to magic (controls). Participants were asked to localise landmarks of their fingers when their hand position was congruent with the mental representation (Experiment 1) and when proprioceptive information was “misleading” (Experiment 2). Magicians outperformed controls in both experiments, suggesting that extensive training in sleight of hand has a profound effect in refining hand representation. Moreover, the impact of training seems to have a high body-part specificity, with a maximum impact for those body sections used more prominently during the training. Interestingly, it seems that sleight-of-hand training can lead to a specific improvement of hand mental representation, which relies less on proprioceptive information.

The Impact of Torsion on the Bending Curve during 3D Bending of Thin-Walled Tubes - A Case Study on Forming Helices

2015 ◽  
Vol 651-653 ◽  
pp. 1595-1601 ◽  
Author(s):  
Daniel Staupendahl ◽  
Christoph Becker ◽  
A. Erman Tekkaya
Keyword(s):  
Analytical Model ◽  
Lightweight Design ◽  
Three Dimensional ◽  
Forming Process ◽  
Direct Production ◽  
Transportation Sector ◽  
Structural Parts ◽  
Set Up ◽  
The Impact

Chassis or cabin designs in the transportation sector are currently manufactured out of several single structural elements. To save handling steps and energy intensive joining processes and furthermore support lightweight design, bending processes can be used that offer the direct production of structural parts that incorporate the functionality of several single elements. In recent years, several processes for the kinematic bending of three-dimensional tubes and profiles have been developed. Additionally, three-roll push bending has gained in importance in manufacturing three-dimensional tubes. In this kinematic process, three-dimensional bending is achieved by continuously changing the bending plane relative to the workpiece during the forming process. Several studies exist that investigate the mechanisms that lead to three-dimensional bending contours. These were, however, based on the generation of empirical models, e.g. characteristic maps. Up until now, no analytical model exists, which describes the process of bending three-dimensional tubes in a comprehensive manner, especially taking into account tube torsion. In the following case study, the tube rotation needed to produce helices is measured and compared to helix radii and helix height. The results were subsequently used to set up an analytical model, which, first of all, describes the tube rotation needed to produce the torsion of the investigated helices and, more importantly, can be generalized to describe the tube rotation needed for the torsion of arbitrary bending curves.

scholarly journals Turbulent wake past a three-dimensional blunt body. Part 1. Global modes and bi-stability

2013 ◽  
Vol 722 ◽  
pp. 51-84 ◽  
Author(s):  
M. Grandemange ◽  
M. Gohlke ◽  
O. Cadot
Keyword(s):  
Time Scales ◽  
Three Dimensional ◽  
Body Part ◽  
The Body ◽  
Recirculation Region ◽  
Stream Velocity ◽  
Lateral Direction ◽  
Reduction Strategies ◽  
Long Time ◽  
The Impact

AbstractThe flow around the three-dimensional blunt geometry presented in the work of Ahmed, Ramm & Faitin (Tech. Rep., 1984) is investigated experimentally at $\mathit{Re}= {U}_{0} H/ \nu = 9. 2\times 1{0}^{4} $ (where ${U}_{0} $ is free-stream velocity, $H$ the height of the body and $\nu $ viscosity). The very large recirculation on the base responsible for the dominant part of the drag is characterized. The analyses of the coherent dynamics of the wake reveal the presence of two very distinctive time scales. At long time scales ${T}_{l} \sim 1{0}^{3} H/ {U}_{0} $, the recirculation region shifts between two preferred reflectional-symmetry-breaking positions leading to a statistically symmetric wake; the sequence of these asymmetric states is random. This bi-stable behaviour is independent of the Reynolds number but occurs only above a critical value of ground clearance. At short time scales ${T}_{s} \sim 5H/ {U}_{0} $, the wake presents weak coherent oscillations in the vertical and lateral directions. They are respectively associated with the interaction of the top/bottom and lateral shear layers; when normalized by the height and width of the body, the Strouhal numbers are close to 0.17. These results suggest an alternate shedding associated with the vertical oscillation and a one-sided vortex shedding in the lateral direction with an orientation linked to the current asymmetric position. Finally, the impact of these coherent wake motions on the base pressure is discussed to motivate further drag reduction strategies.

scholarly journals PHOTOGRAMMETRIC MODELING OF SUBTERRANEAN FEATURES THROUGH THREE-DIMENSIONAL SOFTWARE ANALYSIS

2020 ◽  
Vol XLIV-M-2-2020 ◽  
pp. 95-98
Author(s):  
J. Sepulveda ◽  
J. Capps ◽  
K. Johnson ◽  
C. Parada ◽  
A. Garcia ◽  
...  
Keyword(s):  
Point Cloud ◽  
Three Dimensional ◽  
Point Cloud Data ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Cloud Data ◽  
Software Analysis ◽  
Cave System ◽  
Set Up ◽  
The Impact

Abstract. LiDAR is a popular and accurate method for mapping that can be utilized for three-dimensional model analysis. However, the equipment set-up and usage can become tedious, and ultimately impractical when applied to locations that are remote and confined in nature. In this investigation, three-dimensional analysis was conducted within a cave system. With this, limitations of LiDAR technology in these conditions become prominent; mapping non-planar surfaces can cause a potential decrease of the quality of the point cloud data. In all, a LiDAR application would be an inefficient use of methodology to conduct this investigation. This prompted a need to set-up and conduct a photogrammetric based evaluation. With this, smartphone camera technology was used in conjunction with free-to-use software and three-dimensional modeling applications. Through the use of photogrammetric concepts and structure from motion software, a three-dimensional model of the cave can be generated. Long term, this model can also be utilized to document the impact and health of the cave system. For the methodology, the on-sight portion of the investigation relied heavily on smartphone camera technology. The procedure draws parallels to drone paths; specifically, two flight-plans were developed to evaluate different perspectives within a 15 by 15 meter space in the cave. Within each flight path, the use of photo overlapping techniques established a denser and more fluid point cloud model. Once the data was processed, two different three-dimensional models of the cave were created. From those models, the point cloud data was extracted in order to merge the two separate models. Afterwards, the models underwent several format conversions in order to import it into the Unity game engine. The final result is an accurate three-dimensional model of the cave that is viewable and playable in a simple video game platform.

Analyzing the Impact of X-Ray Tomography on the Reliability of Integrated Circuits

2015 ◽  
Author(s):  
Halit Dogan ◽  
Md Mahbub Alam ◽  
Navid Asadizanjani ◽  
Sina Shahbazmohamadi ◽  
Domenic Forte ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Integrated Circuit ◽  
3D Imaging ◽  
Three Dimensional ◽  
Serial Sectioning ◽  
Promising Technique ◽  
Flash Memories ◽  
X Ray ◽  
3D Information ◽  
The Impact

Abstract X-ray tomography is a promising technique that can provide micron level, internal structure, and three dimensional (3D) information of an integrated circuit (IC) component without the need for serial sectioning or decapsulation. This is especially useful for counterfeit IC detection as demonstrated by recent work. Although the components remain physically intact during tomography, the effect of radiation on the electrical functionality is not yet fully investigated. In this paper we analyze the impact of X-ray tomography on the reliability of ICs with different fabrication technologies. We perform a 3D imaging using an advanced X-ray machine on Intel flash memories, Macronix flash memories, Xilinx Spartan 3 and Spartan 6 FPGAs. Electrical functionalities are then tested in a systematic procedure after each round of tomography to estimate the impact of X-ray on Flash erase time, read margin, and program operation, and the frequencies of ring oscillators in the FPGAs. A major finding is that erase times for flash memories of older technology are significantly degraded when exposed to tomography, eventually resulting in failure. However, the flash and Xilinx FPGAs of newer technologies seem less sensitive to tomography, as only minor degradations are observed. Further, we did not identify permanent failures for any chips in the time needed to perform tomography for counterfeit detection (approximately 2 hours).

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