Impact and Dispersion of Liquid Filled Cylinders

2006 ◽  
Vol 128 (6) ◽  
pp. 1295-1307
Author(s):  
John Borg ◽  
Susan Bartyczak ◽  
Nancy Swanson ◽  
John R. Cogar
Keyword(s):  
Vacuum Chamber ◽  
Early Time ◽  
Impact Dynamics ◽  
Expansion Velocity ◽  
Late Time ◽  
Thin Wall ◽  
Computational Results ◽  
Time Dynamics ◽  
Cylindrical Target ◽  
The Impact

The computational and experimental results of impact loading a thin wall liquid filled cylindrical target within a vacuum chamber are presented. The impact velocity ranges from 2.2 to 4.2km∕s. Both experimental and computational results are presented. It will be shown that impact dynamics and the early time fluid expansion are well modeled and understood. This includes the mass distribution and resulting expansion velocity. However, the late time dynamics, which includes the liquid breakup and droplet formation process of impacted liquid filled cylinders, is not well understood.

Cranioplasty Reverses Dysfunction of the Solutes Distribution in the Brain Parenchyma After Decompressive Craniectomy

Neurosurgery ◽  
2020 ◽  
Vol 87 (5) ◽  
pp. 1064-1069 ◽  
Author(s):  
Alin Borha ◽  
Audrey Chagnot ◽  
Romain Goulay ◽  
Evelyne Emery ◽  
Denis Vivien ◽  
...  
Keyword(s):  
Decompressive Craniectomy ◽  
Early Time ◽  
Brain Parenchyma ◽  
Late Time ◽  
Perivascular Spaces ◽  
Early Time Point ◽  
The Impact ◽  
The Brain ◽  
Brain Homeostasis ◽  
Time Point

Abstract Background Solutes distribution by the intracranial cerebrospinal fluid (CSF) fluxes along perivascular spaces and through interstitial fluid (ISF) play a key role in the clearance of brain metabolites, with essential functions in maintaining brain homeostasis. Objective To investigate the impact of decompressive craniectomy (DC) and cranioplasty (CP) on the efficacy of solutes distribution by the intracranial CSF and ISF flux. Methods Mice were allocated in 3 groups: sham surgery, DC, and DC followed by CP. The solutes distribution in the brain parenchyma was assessed using T1 magnetic resonance imaging after injection of DOTA-Gadolinium in the cisterna magna. This evaluation was performed at an early time point following DC (after 2 d) and at a later time point (after 15 d). We evaluated the solutes distribution in the whole brain and in the region underneath the DC area. Results Our results demonstrate that the global solutes distribution in the brain parenchyma is impaired after DC in mice, both at early and late time-points. However, there was no impact of DC on the solutes distribution just under the craniectomy. We then provide evidence that this impairment was reversed by CP. Conclusion The solute distribution in the brain parenchyma by the CSF and ISF is impaired by DC, a phenomenon reversed by CP.

The Dynamics of Drop Impact

2002 ◽  
Author(s):  
Christophe Josserand
Keyword(s):  
Liquid Layer ◽  
Weber Number ◽  
Stokes Equations ◽  
Early Time ◽  
Mass Conservation ◽  
Viscous Effects ◽  
Time Dynamics ◽  
Similar Solutions ◽  
The Impact

Inkjet printing, rainfall, droplet collision in combustion chambers are different forms of drop impacts. The whole dynamics of these impacts is complex and remains far to be fully understood. In particular the role of the viscosity of the drop liquid is still hard to exhibit. In one hand, the early time of the impact should be considered inviscid, and viscous free calculation give a fair approximation of the short time dynamics. On the other hand, experimental evidences show that the transition between splashing dynamics and deposition is controlled by a so-called splashing parameter K = We · sqrt(Re), where the viscosity enter through the Reynolds number Re (We being the Weber number). Therefore the role of the viscosity for the early time of the impact needs to be elucidated. We will present numerical simulations of the impact of a drop on a liquid layer thanks to a volume of fluid technique (VOF), where the Navier-Stokes equations are solved for both liquid and gas phases. For a given Weber number, we will vary only the viscosity so that viscous effects can be emphasized. The calculation will also determine the relative spreading of the drop inside the liquid layer. For splashing behaviors, a jet is emitted soon after the initiation of the impact; contrarily, no jets are present when deposition happens. The pressure field and the velocity field are studied near the neck of the impact and show no specific dependance on the viscosity. However, viscous effects are observed through the diffusion of the vorticity from the interface into the liquid bulk. Therefore, the viscous length lv = sqrt(vt) controls the gradient fields at the impact and we observe that the width of the emitted jet is determined by this length. Therefore, applying mass conservation to a dynamical solution where a jet of width lv is created, we can estimate the balance between mass ejected by the falling drop with mass coming from a retracting jet. The growth of a jet is thus controlled by this mass balance and the splashing parameter law is retrieved. In particular, the viscous effects appear in the theory as a singular perturbation of the inviscid impact dynamics. Self-similar solutions of the impact are therefore considered in specific gometries. More information at http://www.lmm.jussieu.fr/MEMBRES/JOSSERAND/josserand.html.

scholarly journals On Rayleigh-Taylor and Richtmyer-Meshkov Dynamics With Inverse-Quadratic Power-Law Acceleration

2022 ◽  
Vol 7 ◽  
Author(s):  
D. L. Hill ◽  
S. I. Abarzhi
Keyword(s):  
Initial Conditions ◽  
Density Ratio ◽  
Three Dimensional ◽  
Early Time ◽  
Power Laws ◽  
Future Research ◽  
Continuous Family ◽  
Late Time ◽  
Time Dynamics ◽  
Plane Normal

Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities occur in many situations in Nature and technology from astrophysical to atomic scales, including stellar evolution, oceanic flows, plasma fusion, and scramjets. While RT and RM instabilities are sister phenomena, a link of RT-to-RM dynamics requires better understanding. This work focuses on the long-standing problem of RTI/RMI induced by accelerations, which vary as inverse-quadratic power-laws in time, and on RT/RM flows, which are three-dimensional, spatially extended and periodic in the plane normal to the acceleration direction. We apply group theory to obtain solutions for the early-time linear and late-time nonlinear dynamics of RT/RM coherent structure of bubbles and spikes, and investigate the dependence of the solutions on the acceleration’s parameters and initial conditions. We find that the dynamics is of RT type for strong accelerations and is of RM type for weak accelerations, and identify the effects of the acceleration’s strength and the fluid density ratio on RT-to-RM transition. While for given problem parameters the early-time dynamics is uniquely defined, the solutions for the late-time dynamics form a continuous family parameterised by the interfacial shear and include special solutions for RT/RM bubbles/spikes. Our theory achieves good agreement with available observations. We elaborate benchmarks that can be used in future research and in design of experiments and simulations, and that can serve for better understanding of RT/RM relevant processes in Nature and technology.

scholarly journals Observational constraints on complex quintessence with attractive self-interaction

2021 ◽  
Vol 503 (3) ◽  
pp. 4008-4015
Author(s):  
Belen Carvente ◽  
Víctor Jaramillo ◽  
Celia Escamilla-Rivera ◽  
Darío Núñez
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Early Time ◽  
Mass Term ◽  
Scalar Fields ◽  
Einstein Condensate ◽  
Late Time ◽  
Complex Scalar ◽  
Time Dynamics ◽  
Complex Scalar Field

ABSTRACT In this paper, we consider that dark energy could be described solely by a complex scalar field with a Bose–Einstein condensate-like potential (denoted as CSFDE), that is, with a self-interaction and a mass term. In particular, we analyse a solution that in a fast oscillation regime at late times behaves as a cosmological constant. Our proposal adequately describes the standard homogeneous and flat Fridman dynamics. Furthermore, in this quintessence–complex scalar field scenario, it is possible to mimic the dynamics related to dark energy. However, when the precision cosmological tests are implemented in this landscape, the generic equation of state derived for this model in a restricted regime of ai (which corresponds to the scale factor at which the scalar field turns on) cannot be constrained by late-time current observations, since the analysis constraints solely the scalar field parameters within values ruled out by the theoretical model. This result is a clear hint to consider future CSFDE models with, for instance, two scalar fields in order to study the early-time dynamics of the Universe.

scholarly journals A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear

2021 ◽  
Vol 11 (9) ◽  
pp. 4136
Author(s):  
Rosario Pecora
Keyword(s):  
Numerical Method ◽  
Initial Conditions ◽  
Impact Load ◽  
Numerical Models ◽  
Landing Gear ◽  
Design Stage ◽  
Impact Dynamics ◽  
State Variables ◽  
Adopted Model ◽  
The Impact

Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.

scholarly journals Phase transitions from the fifth dimension

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Kaustubh Agashe ◽  
Peizhi Du ◽  
Majid Ekhterachian ◽  
Soubhik Kumar ◽  
Raman Sundrum
Keyword(s):  
Bubble Dynamics ◽  
Effective Field ◽  
Bubble Nucleation ◽  
Thin Wall ◽  
Black Brane ◽  
Composite Higgs ◽  
Fifth Dimension ◽  
Two Phases ◽  
Holographic Description ◽  
The Impact

Abstract We study the cosmological transition of 5D warped compactifications, from the high-temperature black-brane phase to the low-temperature Randall-Sundrum I phase. The transition proceeds via percolation of bubbles of IR-brane nucleating from the black-brane horizon. The violent bubble dynamics can be a powerful source of observable stochastic gravitational waves. While bubble nucleation is non-perturbative in 5D gravity, it is amenable to semiclassical treatment in terms of a “bounce” configuration interpolating between the two phases. We demonstrate how such a bounce configuration can be smooth enough to maintain 5D effective field theory control, and how a simple ansatz for it places a rigorous lower-bound on the transition rate in the thin-wall regime, and gives plausible estimates more generally. When applied to the Hierarchy Problem, the minimal Goldberger-Wise stabilization of the warped throat leads to a slow transition with significant supercooling. We demonstrate that a simple generalization of the Goldberger-Wise potential modifies the IR-brane dynamics so that the transition completes more promptly. Supercooling determines the dilution of any (dark) matter abundances generated before the transition, potentially at odds with data, while the prompter transition resolves such tensions. We discuss the impact of the different possibilities on the strength of the gravitational wave signals. Via AdS/CFT duality the warped transition gives a theoretically tractable holographic description of the 4D Composite Higgs (de)confinement transition. Our generalization of the Goldberger-Wise mechanism is dual to, and concretely models, our earlier proposal in which the composite dynamics is governed by separate UV and IR RG fixed points. The smooth 5D bounce configuration we introduce complements the 4D dilaton/radion dominance derivation presented in our earlier work.

scholarly journals Transient cell stiffening triggered by magnetic nanoparticle exposure

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Jose E. Perez ◽  
Florian Fage ◽  
David Pereira ◽  
Ali Abou-Hassan ◽  
Sophie Asnacios ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Magnetic Nanoparticles ◽  
Magnetic Nanoparticle ◽  
Early Time ◽  
Population Level ◽  
Short Time Scale ◽  
Initial Contact ◽  
Almost All ◽  
The Impact ◽  
Stiffening Effect

Abstract Background The interactions between nanoparticles and the biological environment have long been studied, with toxicological assays being the most common experimental route. In parallel, recent growing evidence has brought into light the important role that cell mechanics play in numerous cell biological processes. However, despite the prevalence of nanotechnology applications in biology, and in particular the increased use of magnetic nanoparticles for cell therapy and imaging, the impact of nanoparticles on the cells’ mechanical properties remains poorly understood. Results Here, we used a parallel plate rheometer to measure the impact of magnetic nanoparticles on the viscoelastic modulus G*(f) of individual cells. We show how the active uptake of nanoparticles translates into cell stiffening in a short time scale (< 30 min), at the single cell level. The cell stiffening effect is however less marked at the cell population level, when the cells are pre-labeled under a longer incubation time (2 h) with nanoparticles. 24 h later, the stiffening effect is no more present. Imaging of the nanoparticle uptake reveals almost immediate (within minutes) nanoparticle aggregation at the cell membrane, triggering early endocytosis, whereas nanoparticles are almost all confined in late or lysosomal endosomes after 2 h of uptake. Remarkably, this correlates well with the imaging of the actin cytoskeleton, with actin bundling being highly prevalent at early time points into the exposure to the nanoparticles, an effect that renormalizes after longer periods. Conclusions Overall, this work evidences that magnetic nanoparticle internalization, coupled to cytoskeleton remodeling, contributes to a change in the cell mechanical properties within minutes of their initial contact, leading to an increase in cell rigidity. This effect appears to be transient, reduced after hours and disappearing 24 h after the internalization has taken place.

scholarly journals Exogenous Alginate Protects Staphylococcus aureus from Killing by Pseudomonas aeruginosa

2019 ◽  
Vol 202 (8) ◽  
Author(s):  
Courtney E. Price ◽  
Dustin G. Brown ◽  
Dominique H. Limoli ◽  
Vanessa V. Phelan ◽  
George A. O’Toole
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Physical Space ◽  
Late Time ◽  
Protective Effects ◽  
Content Type ◽  
Alginate Production ◽  
The Impact

ABSTRACT Cystic fibrosis (CF) patients chronically infected with both Pseudomonas aeruginosa and Staphylococcus aureus have worse health outcomes than patients who are monoinfected with either P. aeruginosa or S. aureus. We showed previously that mucoid strains of P. aeruginosa can coexist with S. aureus in vitro due to the transcriptional downregulation of several toxic exoproducts typically produced by P. aeruginosa, including siderophores, rhamnolipids, and HQNO (2-heptyl-4-hydroxyquinoline N-oxide). Here, we demonstrate that exogenous alginate protects S. aureus from P. aeruginosa in both planktonic and biofilm coculture models under a variety of nutritional conditions. S. aureus protection in the presence of exogenous alginate is due to the transcriptional downregulation of pvdA, a gene required for the production of the iron-scavenging siderophore pyoverdine as well as the downregulation of the PQS (Pseudomonas quinolone signal) (2-heptyl-3,4-dihydroxyquinoline) quorum sensing system. The impact of exogenous alginate is independent of endogenous alginate production. We further demonstrate that coculture of mucoid P. aeruginosa with nonmucoid P. aeruginosa strains can mitigate the killing of S. aureus by the nonmucoid strain of P. aeruginosa, indicating that the mechanism that we describe here may function in vivo in the context of mixed infections. Finally, we investigated a panel of mucoid clinical isolates that retain the ability to kill S. aureus at late time points and show that each strain has a unique expression profile, indicating that mucoid isolates can overcome the S. aureus-protective effects of mucoidy in a strain-specific manner. IMPORTANCE CF patients are chronically infected by polymicrobial communities. The two dominant bacterial pathogens that infect the lungs of CF patients are P. aeruginosa and S. aureus, with ∼30% of patients coinfected by both species. Such coinfected individuals have worse outcomes than monoinfected patients, and both species persist within the same physical space. A variety of host and environmental factors have been demonstrated to promote P. aeruginosa-S. aureus coexistence, despite evidence that P. aeruginosa kills S. aureus when these organisms are cocultured in vitro. Thus, a better understanding of P. aeruginosa-S. aureus interactions, particularly mechanisms by which these microorganisms are able to coexist in proximal physical space, will lead to better-informed treatments for chronic polymicrobial infections.

scholarly journals NonlinearL2-Gain Analysis of Hybrid Systems in the Presence of Sliding Modes and Impacts

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
T. Osuna ◽  
O. E. Montano ◽  
Y. Orlov
Keyword(s):  
Sliding Mode ◽  
Numerical Study ◽  
Sufficient Conditions ◽  
Disturbance Attenuation ◽  
Sliding Modes ◽  
Time Dynamics ◽  
Attenuation Level ◽  
Disturbance Factor ◽  
Disturbance Attenuation Level ◽  
The Impact

TheL2-gain analysis is extended towards hybrid mechanical systems, operating under unilateral constraints and admitting both sliding modes and collision phenomena. Sufficient conditions for such a system to be internally asymptotically stable and to possessL2-gain less than ana priorigiven disturbance attenuation level are derived in terms of two independent inequalities which are imposed on continuous-time dynamics and on discrete disturbance factor that occurs at the collision time instants. The former inequality may be viewed as the Hamilton-Jacobi inequality for discontinuous vector fields, and it is separately specified beyond and along sliding modes, which occur in the system between collisions. Thus interpreted, the former inequality should impose the desired integral input-to-state stability (iISS) property on the Filippov dynamics between collisions whereas the latter inequality is invoked to ensure that the impact dynamics (when the state trajectory hits the unilateral constraint) are input-to-state stable (ISS). These inequalities, being coupled together, form the constructive procedure, effectiveness of which is supported by the numerical study made for an impacting double integrator, driven by a sliding mode controller. Desired disturbance attenuation level is shown to satisfactorily be achieved under external disturbances during the collision-free phase and in the presence of uncertainties in the transition phase.

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