Ekman Boundary Layers and Energy Dissipation in Rotating Drums During Spin-Down Process

Abstract. Special forecasts from the Global Forecast System (GFS) model were used in this study to evaluate how the intensification process in a tropical cyclone is represented in this model. Several tropical cyclones that developed in 2005 were analyzed in terms of the storm-scale circulation rather than more traditional measures such as maximum wind or minimum central pressure. The primary balance governing the circulation in the planetary boundary layer is between the convergence of environmental vorticity, which tends to spin up the storm, and surface friction, which tends to spin it down. In addition, we employ recently developed ideas about the relationship between precipitation and the saturation fraction of the environment to understand the factors controlling mass, and hence vorticity convergence. The budget of moist entropy is central to this analysis. Two well-known governing factors for cyclone intensification emerge from this study; surface moist entropy fluxes, dependent in the model on sea surface temperature and cyclone-generated surface winds, and ventilation of the system by dry environmental air. Quantitative expressions for the role of these factors in cyclone intensification are presented in this paper.

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Energy dissipation in microfluidic beam resonators

Journal of Fluid Mechanics ◽

10.1017/s0022112009993521 ◽

2010 ◽

Vol 650 ◽

pp. 215-250 ◽

Cited By ~ 30

Author(s):

JOHN E. SADER ◽

THOMAS P. BURG ◽

SCOTT R. MANALIS

Keyword(s):

Energy Dissipation ◽

Boundary Layers ◽

Environmental Changes ◽

Signal To Noise Ratio ◽

Fluid Motion ◽

Microfluidic Channel ◽

Direct Consequence ◽

High Viscosity ◽

Fluid Viscosity ◽

Low Viscosity

The fluid–structure interaction of resonating microcantilevers immersed in fluid has been widely studied and is a cornerstone in nanomechanical sensor development. In many applications, fluid damping imposes severe limitations by strongly degrading the signal-to-noise ratio of measurements. Recently, Burg et al. (Nature, vol. 446, 2007, pp. 1066–1069) proposed an alternative type of microcantilever device whereby a microfluidic channel was embedded inside the cantilever with vacuum outside. Remarkably, it was observed that energy dissipation in these systems was almost identical when air or liquid was passed through the channel and was 4 orders of magnitude lower than that in conventional microcantilever systems. Here, we study the fluid dynamics of these devices and present a rigorous theoretical model corroborated by experimental measurements to explain these observations. In so doing, we elucidate the dominant physical mechanisms giving rise to the unique features of these devices. Significantly, it is found that energy dissipation is not a monotonic function of fluid viscosity, but exhibits oscillatory behaviour, as fluid viscosity is increased/decreased. In the regime of low viscosity, inertia dominates the fluid motion inside the cantilever, resulting in thin viscous boundary layers – this leads to an increase in energy dissipation with increasing viscosity. In the high-viscosity regime, the boundary layers on all surfaces merge, leading to a decrease in dissipation with increasing viscosity. Effects of fluid compressibility also become significant in this latter regime and lead to rich flow behaviour. A direct consequence of these findings is that miniaturization does not necessarily result in degradation in the quality factor, which may indeed be enhanced. This highly desirable feature is unprecedented in current nanomechanical devices and permits direct miniaturization to enhance sensitivity to environmental changes, such as mass variations, in liquid.

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Intensification of tropical cyclones in the GFS model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-17803-2008 ◽

2008 ◽

Vol 8 (5) ◽

pp. 17803-17839

Author(s):

J. C. Marín ◽

D. J. Raymond ◽

G. B. Raga

Keyword(s):

Boundary Layer ◽

Tropical Cyclones ◽

Surface Friction ◽

Sea Surface ◽

Global Forecast System ◽

Forecast System ◽

Gfs Model ◽

Environmental Air ◽

The Relationship

Abstract. Special forecasts from the Global Forecast System (GFS) model were used in this study to evaluate how the intensification process in a tropical cyclone is represented in this model. Several tropical cyclones that developed in 2005 were analyzed in terms of the storm-scale circulation rather than more traditional measures such as maximum wind or minimum central pressure. The primary balance governing the circulation in the planetary boundary layer is between the convergence of environmental vorticity, which tends to spin up the storm, and surface friction, which tends to spin it down. In addition, we employ recently developed ideas about the relationship between precipitation and the saturation fraction of the environment to understand the factors controlling mass, and hence vorticity convergence. The budget of moist entropy is central to this analysis. Two well-known governing factors for cyclone intensification emerge from this study; surface moist entropy fluxes, dependent in the model on sea surface temperature and cyclone-generated surface winds, and ventilation of the system by dry environmental air. Quantitative expressions for the role of these factors in cyclone intensification are presented in this paper.

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Response and Recovery Times of Elastic and Viscoelastic Capsules in Shear Flow

Communications in Computational Physics ◽

10.4208/cicp.2014.m356 ◽

2015 ◽

Vol 17 (5) ◽

pp. 1151-1168 ◽

Cited By ~ 1

Author(s):

John Gounley ◽

Yan Peng

Keyword(s):

Shear Flow ◽

Fluid Viscosity ◽

Membrane Viscosity ◽

Recovery Times ◽

Shear Elasticity ◽

Response And Recovery ◽

Membrane Bending ◽

The Relationship ◽

Spherical Capsule

AbstractAmid the recent interest in the role of membrane viscosity in the deformation of a fluid-filled capsule, we consider the role of various capsule properties (shear elasticity, membrane bending stiffness and viscosity) in determining the response and recovery times of a spherical capsule in shear flow. These times are determined by fitting exponential functions to results for the Taylor deformation parameter Dxy. We focus on the relationship between the membrane and fluid viscosity ratios, as suggested by Diaz et al, and whether adjustments to the fluid viscosity ratio may be used to approximate the effects of membrane viscosity. Based on its ability to reproduce response and recovery times, our results suggest that such an approach holds promise.

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The Origin of Ekman Flow in a Cavity Subject to Impulsive Rotational Motions

International Journal of Rotating Machinery ◽

10.1155/s1023621x0100015x ◽

2001 ◽

Vol 7 (3) ◽

pp. 165-171

Author(s):

Wen-Jei Yang ◽

Hiroshi Ohue ◽

Genshi Kawashima

Keyword(s):

Time History ◽

Light Sheet ◽

Fluid Viscosity ◽

Rotating Drum ◽

Fluid Structure Interactions ◽

Fluid Structure ◽

Real Time Visualization ◽

History Of ◽

Ekman Flow ◽

Rotational Motions

An experimental study is performed to disclose the origin of Ekman flow on the surfaces of a rotating drum resulting from fluid-structure interaction after an impulsive start of motion (referred to as the spin-up process) or an impulsive stop (the spin-down process). Laser Doppler velocimetry (LDV) is employed to determine instantaneous distribution of both the radial and angular velocity components in the flow field inside the rotating drum. From these results, the secondary flow and the time history of the Ekman boundary layer thickness are determined. The tracer/light sheet method is also engaged to enable real-time visualization of flow patterns. Fluid viscosity, drum size and rotational speed are varied to determine their effects on fluid-structure interactions. Results may be applied to cavity flow in rotating machinery.

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Choosing a Markov blanket

Behavioral and Brain Sciences ◽

10.1017/s0140525x19002632 ◽

2020 ◽

Vol 43 ◽

Author(s):

Thomas Parr

Keyword(s):

Markov Blanket ◽

Target Article ◽

The Relationship

Abstract This commentary focuses upon the relationship between two themes in the target article: the ways in which a Markov blanket may be defined and the role of precision and salience in mediating the interactions between what is internal and external to a system. These each rest upon the different perspectives we might take while “choosing” a Markov blanket.

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Staring Down Death

Crisis ◽

10.1027/0227-5910/a000367 ◽

2016 ◽

Vol 37 (3) ◽

pp. 212-217 ◽

Cited By ~ 7

Author(s):

Thomas E. Joiner ◽

Melanie A. Hom ◽

Megan L. Rogers ◽

Carol Chu ◽

Ian H. Stanley ◽

...

Keyword(s):

Suicide Risk ◽

Clinical Utility ◽

Blink Rate ◽

Specific Task ◽

Careful Planning ◽

Eye Blink ◽

Eye Blinks ◽

Potential Clinical Utility ◽

The Relationship

Abstract. Background: Lowered eye blink rate may be a clinically useful indicator of acute, imminent, and severe suicide risk. Diminished eye blink rates are often seen among individuals engaged in heightened concentration on a specific task that requires careful planning and attention. Indeed, overcoming one’s biological instinct for survival through suicide necessitates premeditation and concentration; thus, a diminished eye blink rate may signal imminent suicidality. Aims: This article aims to spur research and clinical inquiry into the role of eye blinks as an indicator of acute suicide risk. Method: Literature relevant to the potential connection between eye blink rate and suicidality was reviewed and synthesized. Results: Anecdotal, cognitive, neurological, and conceptual support for the relationship between decreased blink rate and suicide risk is outlined. Conclusion: Given that eye blinks are a highly observable behavior, the potential clinical utility of using eye blink rate as a marker of suicide risk is immense. Research is warranted to explore the association between eye blink rate and acute suicide risk.

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Parenting Behaviors and Anxiety in Young Adults

Journal of Individual Differences ◽

10.1027/1614-0001/a000169 ◽

2015 ◽

Vol 36 (3) ◽

pp. 170-176 ◽

Cited By ~ 5

Author(s):

Erin N. Stevens ◽

Joseph R. Bardeen ◽

Kyle W. Murdock

Keyword(s):

Effortful Control ◽

Parenting Behaviors ◽

Protective Role ◽

Anxiety Symptoms ◽

Interactive Effects ◽

Parental Overprotection ◽

High Control ◽

Development Of Anxiety ◽

The Relationship

Parenting behaviors – specifically behaviors characterized by high control, intrusiveness, rejection, and overprotection – and effortful control have each been implicated in the development of anxiety pathology. However, little research has examined the protective role of effortful control in the relation between parenting and anxiety symptoms, specifically among adults. Thus, we sought to explore the unique and interactive effects of parenting and effortful control on anxiety among adults (N = 162). Results suggest that effortful control uniquely contributes to anxiety symptoms above and beyond that of any parenting behavior. Furthermore, effortful control acted as a moderator of the relationship between parental overprotection and anxiety, such that overprotection is associated with anxiety only in individuals with lower levels of effortful control. Implications for potential prevention and intervention efforts which specifically target effortful control are discussed. These findings underscore the importance of considering individual differences in self-regulatory abilities when examining associations between putative early-life risk factors, such as parenting, and anxiety symptoms.

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Social Support, Emotional Intelligence, and Posttraumatic Stress Disorder Symptoms

Journal of Individual Differences ◽

10.1027/1614-0001/a000185 ◽

2016 ◽

Vol 37 (1) ◽

pp. 31-39 ◽

Cited By ~ 8

Author(s):

Nicole L. Hofman ◽

Austin M. Hahn ◽

Christine K. Tirabassi ◽

Raluca M. Gaher

Keyword(s):

Social Support ◽

Posttraumatic Stress Disorder ◽

Emotional Intelligence ◽

Protective Factors ◽

Posttraumatic Stress ◽

Stress Disorder ◽

Traumatic Events ◽

Ptsd Symptoms ◽

The Relationship

Abstract. Exposure to traumatic events and the associated risk of developing Posttraumatic stress disorder (PTSD) symptoms is a significant and overlooked concern in the college population. It is important for current research to identify potential protective factors associated with the development and maintenance of PTSD symptoms unique to this population. Emotional intelligence and perceived social support are two identified protective factors that influence the association between exposure to traumatic events and PTSD symptomology. The current study examined the mediating role of social support in the relationship between emotional intelligence and PTSD symptoms. Participants included 443 trauma-exposed university students who completed online questionnaires. The results of this study indicated that social support mediates the relationship between emotional intelligence and reported PTSD symptoms. Thus, emotional intelligence is significantly associated with PTSD symptoms and social support may play an integral role in the relationship between emotional intelligence and PTSD. The current study is the first to investigate the role of social support in the relationship between emotional intelligence and PTSD symptoms. These findings have important treatment and prevention implications with regard to PTSD.

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Coping Humor as a Mediator Between Emotional Intelligence and Job Satisfaction

Journal of Personnel Psychology ◽

10.1027/1866-5888/a000185 ◽

2017 ◽

Vol 16 (3) ◽

pp. 155-159 ◽

Cited By ~ 4

Author(s):

Peizhen Sun ◽

Jennifer J. Chen ◽

Hongyan Jiang

Keyword(s):

Job Satisfaction ◽

Emotional Intelligence ◽

Future Research ◽

Satisfaction Scale ◽

Primary School Teachers ◽

Mediating Role ◽

Regulation Of Emotion ◽

The Relationship ◽

Overall Job Satisfaction

Abstract. This study investigated the mediating role of coping humor in the relationship between emotional intelligence (EI) and job satisfaction. Participants were 398 primary school teachers in China, who completed the Wong Law Emotional Intelligence Scale, Coping Humor Scale, and Overall Job Satisfaction Scale. Results showed that coping humor was a significant mediator between EI and job satisfaction. A further examination revealed, however, that coping humor only mediated two sub-dimensions of EI (use of emotion and regulation of emotion) and job satisfaction. Implications for future research and limitations of the study are discussed.

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