Experimental studies in magnetofluid dynamics - Pipe flow through a solenoid of finite length

Liquid sodium tunnel for magneto-fluid-dynamic flow

A Simple Observational Technique for the Investigation of Boundary Layer Stability and Turbulence

A dense suspension of aluminum flakes in a fluid has many advantages as a flow-visualization method, and has been used to study circular Couette flow and Benard instability, among others. In the present contribution the scientific and pedagogical merits of the technique are examined further for three different cases: (a) Stability of Poiseuille flow; (b) Stability of the side-wall boundary layers created when a fluid-filLed, rotating container is suddenly brought to rest; (b) Stability of the boundary layer beneath a concentrated vortex. The technique is also useful in other cases, especially when fundamentals of fluid flow are to be demonstrated in the classroom. Several of these further possibilities are briefly discussed

Do Study Guides Improve Text Comprehension?

Although there are many types of study guides, the theoretical assumptions underlying them are the same. They are structures designed to improve reading comprehension (Armstrong, Patberg and Dewitz, 1988)

Hydrodynamic Impulse in a Compressible Fluid

A suitable expression for hydrodynamic impulse in a compressible fluid is deduced. The development of appropriate impulse formulation for compressible Euler equations confirms the propriety of the hydrodynamic impulse expression for a compressible fluid given here. Implications of the application of this formulation to a compressible vortex ring are pointed out. A variational characterization for an axisymmetric vortex system moving steadily in an ideal, compressible fluid is discussed

Can Middle School Students Summarize?

One frequently needed study skill is summarization. Summarizing text information is a valuable study activity which helps students understand and remember important ideas. In order to summarize, students must reduce the text to its main points. This requires an ability to analyze text structure and discard inessential information

Experimental Studies of the Interaction Between a Parallel Shear Flow and a Directionally-Solidifying Front

It has long been recognized that flow in the melt can have a profound influence on the dynamics of a solidifying interface and hence the quality of the solid material. In particular, flow affects the heat and mass transfer, and causes spatial and temporal variations in the flow and melt composition. This results in a crystal with nonuniform physical properties. Flow can be generated by buoyancy, expansion or contraction upon phase change, and thermo-soluto capillary effects. In general, these flows can not be avoided and can have an adverse effect on the stability of the crystal structures. This motivates crystal growth experiments in a microgravity environment, where buoyancy-driven convection is significantly suppressed. However, transient accelerations (g-jitter) caused by the acceleration of the spacecraft can affect the melt, while convection generated from the effects other than buoyancy remain important. Rather than bemoan the presence of convection as a source of interfacial instability, Hurle in the 1960s suggested that flow in the melt, either forced or natural convection, might be used to stabilize the interface. Delves considered the imposition of both a parabolic velocity profile and a Blasius boundary layer flow over the interface. He concluded that fast stirring could stabilize the interface to perturbations whose wave vector is in the direction of the fluid velocity. Forth and Wheeler considered the effect of the asymptotic suction boundary layer profile. They showed that the effect of the shear flow was to generate travelling waves parallel to the flow with a speed proportional to the Reynolds number. There have been few quantitative, experimental works reporting on the coupling effect of fluid flow and morphological instabilities. Huang studied plane Couette flow over cells and dendrites. It was found that this flow could greatly enhance the planar stability and even induce the cell-planar transition. A rotating impeller was buried inside the sample cell, driven by an outside rotating magnet, in order to generate the flow. However, it appears that this was not a well-controlled flow and may also have been unsteady. In the present experimental study, we want to study how a forced parallel shear flow in a Hele-Shaw cell interacts with the directionally solidifying crystal interface. The comparison of experimental data show that the parallel shear flow in a Hele-Shaw cell has a strong stabilizing effect on the planar interface by damping the existing initial perturbations. The flow also shows a stabilizing effect on the cellular interface by slightly reducing the exponential growth rate of cells. The left-right symmetry of cells is broken by the flow with cells tilting toward the incoming flow direction. The tilting angle increases with the velocity ratio. The experimental results are explained through the parallel flow effect on lateral solute transport. The phenomenon of cells tilting against the flow is consistent with the numerical result of Dantzig and Chao

Preventing Self-Harm Among Adolescent Victims of Adverse Child Experiences Integrated Review

Background: Evidence shows a clear connection between adverse childhood experiences (ACEs) and mental health disorders in adolescence. If not treated, adolescent victims of ACEs could develop maladaptive behaviors such as self-mutilation and suicidal ideation. The standard therapies to treat this population are psychotropic medications or cognitive behavior therapy. Search Methodology: Ten studies from a literature search on CINAHL, PubMed, APA PsychInfo, and Joanna Briggs databases were selected, appraised, and reviewed. Integrated Review: Studies were grouped into six types: (a) screening for ACEs, (b) usual care and alternative therapies, (c) ineffectiveness of usual care, (d) comprehensive treatment that included trauma-informed therapy, (e) provider satisfaction through comprehensive trauma-informed therapy, and (f) clinical guidelines of TF-CBT. Synthesis of Literature: Trauma-focused cognitive-behavioral therapy (TF-CBT) emerged from the studies reviewed as an effective evidence-based approach to care for adolescents\u27 victims of ACEs with self-harming behavior Implications for Practice: Policy changes are needed to require psychiatric mental health nurse practitioners to obtain adequate training in screening and treating adolescents for ACEs. Such changes would facilitate early identification and treatment of adolescents’ ACE victims. Conclusion: TF-CBT is an evidence-based method to treat adolescents’ victims of ACEs with self-harming behavior. Few studies were identified that connected ACEs and specific self-harming behaviors. As such, future studies include self-harm behaviors such as substance use disorder and eating disorders to determine the effectiveness of TF-CBT. Keywords: ACE, teen, mental health, trauma-informed therapy, self-harm, holistic care, medication, and CBT care

Interaction of acoustic waves with flame front propagation

International audienceThe mechanisms of laminar premixed flame propagation have been intensively studied over the last century. Numerous authors have highlighted intrinsic phenomena in flame propagation such as Darrieus-Landau instability and Rayleigh-Taylor instability. Rayleigh-Taylor instability is often linked to the interaction between the flame front and an acoustic wave. To better characterize the interaction between a flame and aerodynamic conditions, we designed a special vertical closed tube apparatus. Our analysis focused on the behavior of a flame that propagates in a uniform stoichiometric mixture of H2 and O2 diluted with nitrogen. The experimental investigation revealed that acoustic waves emitted as the flame formed near the ignition point could increase the flame front surface by a factor of 10. An acoustic node with an amplitude of 1.3 m was identified and seemed to be responsible for the disappearance of one of the acoustic modes and for a reduction in the average flame surface. This could explain why the flame trajectory had two distinct parts: one corresponding to propagation at a high speed in the lower part of the tube, and the other with a slower speed in the upper part of the tube. The flame surface seemed to depend primarily on the frequencies of vibration and marginally on the nature of the reactive components. Propagation velocities, obtained by multiplying these flame surfaces by the fundamental burning velocity, strongly depended on the mixture reactivity

Vortex String Dynamics in an External Antisymmetric Tensor Field

We study the Lund-Regge equation that governs the motion of strings in a constant background antisymmetric tensor field by using the duality between the Lund-Regge equation and the complex sine-Gordon equation. Similar to the cases of vortex filament configurations in fluid dynamics, we find various exact solitonic string configurations which are the analogue of the Kelvin wave, the Hasimoto soliton and the smoke ring. In particular, using the duality relation, we obtain a completely new type of configuration which corresponds to the breather of the complex sine-Gordon equation.Comment: 20 pages, 9 figure