scholarly journals Critical conditions and composite Froude numbers for layered flow with transverse variations in velocity

2008 ◽  
Vol 605 ◽  
pp. 281-291 ◽  
Author(s):  
LARRY J. PRATT
Keyword(s):  
Intermediate Layer ◽  
Critical Condition ◽  
Critical Conditions ◽  
Layer System ◽  
Inviscid Flows ◽  
Wave Dynamics ◽  
Long Wave ◽  
Layer Flow ◽  
Layered Flow ◽  
Sluggish Flow

A condition is derived for the hydraulic criticality of a 2-layer flow with transverse variations in both layer velocities and thicknesses. The condition can be expressed in terms of a generalized composite Froude number. The derivation can be extended in order to obtain a critical condition for an N-layer system. The results apply to inviscid flows subject to the usual hydraulic approximation of gradual variations along the channel and is restricted to flows in which the velocity remains single-signed within any given layer. For an intermediate layer with a partial segment of sluggish flow, the long-wave dynamics of the overlying and underlying layers become decoupled.

scholarly journals Physical modeling of resonance phenomena in the long wave dynamics

2016 ◽  
pp. 57-64 ◽  
Author(s):  
Nizar Abcha ◽  
Alexander Ezersky ◽  
Efim Pelinovsky
Keyword(s):  
Physical Modeling ◽  
Wave Dynamics ◽  
Long Wave ◽  
Resonance Phenomena

The Effect of Soft Sub Grade on Train Ride Quality

2015 ◽  
Author(s):  
Yin Gao ◽  
Shelby Stigers ◽  
Hai Huang
Keyword(s):  
Critical Condition ◽  
Critical Speed ◽  
Commercial Vehicle ◽  
Critical Conditions ◽  
Ride Quality ◽  
Vibration Level ◽  
Vehicle Dynamic ◽  
Vehicle Model ◽  
Train Operation ◽  
Speed Effect

Train ride quality plays an important role in train operation. In this paper, the aim is to explore the train ride quality when trains run on soft sub grade at different speeds especially critical conditions and operation safety on the sub grades with different properties. The responses of track and vehicle such as lateral wheel-rail force (L/V ratio), acceleration of vehicle are studied in this research. It is important to note that a critical condition is when train runs on soft sub grade. In this case, the critical speed effect will occur and resonance between vehicle and track could rise up the vibration level which could cause derailment and bad riding experience. In order to measure the track and vehicle responses, it should combine a detailed vehicle model and a track dynamic model. However, most commercial modeling programs do not have the ability to combine both detailed vehicle and track models. In this research, by integrating a computer program with a 2-D track model to a commercial vehicle dynamic program, the responses of vehicle and track can be calculated at the same time. Conclusions and findings will be illustrated in this paper.

scholarly journals Long-Wave Dynamics of Sea Level Variations during Indian Ocean Dipole Events

2009 ◽  
Vol 39 (5) ◽  
pp. 1115-1132 ◽  
Author(s):  
Dongliang Yuan ◽  
Hailong Liu
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Indian Ocean Dipole ◽  
Rossby Waves ◽  
Western Boundary ◽  
Kelvin Wave ◽  
Wave Pulse ◽  
Wave Dynamics ◽  
Long Wave ◽  
Equatorial Rossby Waves

Abstract Long-wave dynamics of the interannual variations of the equatorial Indian Ocean circulation are studied using an ocean general circulation model forced by the assimilated surface winds and heat flux of the European Centre for Medium-Range Weather Forecasts. The simulation has reproduced the sea level anomalies of the Ocean Topography Experiment (TOPEX)/Poseidon altimeter observations well. The equatorial Kelvin and Rossby waves decomposed from the model simulation show that western boundary reflections provide important negative feedbacks to the evolution of the upwelling currents off the Java coast during Indian Ocean dipole (IOD) events. Two downwelling Kelvin wave pulses are generated at the western boundary during IOD events: the first is reflected from the equatorial Rossby waves and the second from the off-equatorial Rossby waves in the southern Indian Ocean. The upwelling in the eastern basin during the 1997–98 IOD event is weakened by the first Kelvin wave pulse and terminated by the second. In comparison, the upwelling during the 1994 IOD event is terminated by the first Kelvin wave pulse because the southeasterly winds off the Java coast are weak at the end of 1994. The atmospheric intraseasonal forcing, which plays an important role in inducing Java upwelling during the early stage of an IOD event, is found to play a minor role in terminating the upwelling off the Java coast because the intraseasonal winds are either weak or absent during the IOD mature phase. The equatorial wave analyses suggest that the upwelling off the Java coast during IOD events is terminated primarily by western boundary reflections.

scholarly journals MORPHOFUNCTIONAL FEATURES OF THE PLACENTA OF NEWBORNS IN BIRTH-INDUCED CRITICAL CONDITIONS: THE RESULTS OF A RETROSPECTIVE COHORT STUDY

2017 ◽  
Vol 14 (3) ◽  
pp. 179-185
Author(s):  
Olga A. Senkevich ◽  
Klaudia E. Popova ◽  
Olga V. Kozharskaia ◽  
Denis V. Musatov
Keyword(s):  
Intensive Care ◽  
Apgar Score ◽  
Critical Condition ◽  
Blood Circulation ◽  
Comparison Group ◽  
Morphological Characteristics ◽  
Critical Conditions ◽  
Pathological Conditions ◽  
Microscopic Studies ◽  
The Relationship

Background.  The placenta condition is the health marker of newborns  and it can be considered  in the early diagnosis  of the development of severe pathological conditions in a child. Objective:  Our aim was to study the relationship between the placenta characteristics and the risk of a birth-induced critical condition in a child and the risk of having children with the APGAR score of < 4 points.Methods. The data of macro- and microscopic studies of the placenta of newborns who have experienced birth-induced critical conditions was retrospectively  analyzed. Birth-induced  critical conditions were the APGAR score at 1 min after birth < 4 points and/or the presence of severe perinatal hypoxia, cerebral ischemia requiring respiratory support and intensive care in the intensive care unit.Results.  We examined 92 placentas of mothers who gave birth to children in a critical condition. Depending on the APGAR score at 1 min after birth, the main group (n = 56, < 4 points) and the comparison  group (n = 36, > 4 points) were singled out. In multivariate analysis, it was established  that the appearance  of a birth-induced  critical condition with the APGAR score < 4 points was associated with pathological attachment of the umbilical cord (odds ratio, OR, 2.8, 95% confidence interval, CI, 1.1–7.0),  placenta weight (OR 5.4, 95% CI 1.9–14.9),  signs of chronic fetoplacental  insufficiency (OR 7.3, 95% CI 2.9–18.8), impaired blood circulation in the placenta (OR 13.7, 95% CI 4.7–39.3), placental hypoplasia (OR 8.9, 95% CI 2.4–32.4), fetal-placental  ratio (OR 8.9, 95% CI 2.4–32.4)  as well as low birth weight of a newborn (OR 2.9, 95% CI 1.2–6.9). Conclusion. Morphological characteristics of the placenta are prognostic markers for the development of critical conditions with the APGAR score at birth < 4 points.

Long wave dynamics for a liquid CO2 lake in the deep ocean

2019 ◽  
Vol 141 ◽  
pp. 144-157
Author(s):  
Krister J. Trandal ◽  
Henrik Kalisch
Keyword(s):  
Deep Ocean ◽  
Wave Dynamics ◽  
Long Wave ◽  
Liquid Co2

Selective withdrawal from a layered fluid

1976 ◽  
Vol 77 (3) ◽  
pp. 581-591 ◽  
Author(s):  
P. J. Bryant ◽  
I. R. Wood
Keyword(s):  
Critical Point ◽  
Critical Points ◽  
Selective Withdrawal ◽  
Long Wave ◽  
External Conditions ◽  
Layer Flow ◽  
Total Discharge ◽  
Theory And Experiment ◽  
Good Agreement ◽  
Layered Fluid

The selective withdrawal of a layered fluid from a reservoir has interesting properties which are not present if the stratification is continuous. The problem investigated is that of finding the ratios of the discharges from each flowing layer when the total discharge from all layers is regulated at the outlet. It is shown that the ratios are determined by the requirement that the flow be smooth at critical points in the flow, each critical point being a point at which the long-wave velocity on one of the interfaces is zero. If there are too many critical points, the flow is over-determined and becomes unsteady. It follows therefore that if the external conditions change slowly, such as in the slow draining of a reservoir, the flow alternates between intervals in which the flow ratios also change slowly and intervals in which the flow ratios oscillate unsteadily. An experiment is described in which the theoretical conclusions were tested for two-layer flow. Good agreement was obtained between theory and experiment.

Open boundary conditions for horizontal 2-D curvilinear-grid long-wave dynamics of a strait

1995 ◽  
Vol 18 (5) ◽  
pp. 267-276 ◽  
Author(s):  
A.A. Androsov ◽  
K.A. Klevanny ◽  
E.S. Salusti ◽  
N.E. Voltzinger
Keyword(s):  
Boundary Conditions ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Wave Dynamics ◽  
Long Wave ◽  
Curvilinear Grid

scholarly journals Review of Long Wave Dynamics over Reefs and into Ports with Implication for Port Operations

2016 ◽  
Vol 4 (1) ◽  
pp. 12 ◽  
Author(s):  
Ap van Dongeren ◽  
Martijn de Jong ◽  
Cock van der Lem ◽  
Alex van Deyzen ◽  
Joost den Bieman
Keyword(s):  
Wave Dynamics ◽  
Port Operations ◽  
Long Wave

scholarly journals Generalized Conditions for Hydraulic Criticality of Oceanic Overflows

2005 ◽  
Vol 35 (10) ◽  
pp. 1782-1800 ◽  
Author(s):  
Larry Pratt ◽  
Karl Helfrich
Keyword(s):  
Critical Condition ◽  
Degrees Of Freedom ◽  
Single Layer ◽  
Direct Calculation ◽  
Dissipative Systems ◽  
Hydraulic Analysis ◽  
Wave Speeds ◽  
Long Wave ◽  
Functional Formulation ◽  
Arbitrary Potential

Abstract Two methods for assessing the hydraulic criticality of an observed or modeled overflow are discussed. The methods are valid for single-layer deep flows with arbitrary potential vorticity and cross section. The first method is based on a purely steady view in which the flow at a given section is divided up into a group of “streamtubes.” A hydraulic analysis requires an extension of Gill’s functional formulation to systems with many degrees of freedom. The general form of the critical condition and associated compatibility condition for such a system are derived and applied to the streamtube model. As an aside, it is shown by example that Gill’s original critical condition can fail to capture all possible critical states, but that this problem is fixed when the multivariable approach is used. It is also shown how Gill’s method can be applied to certain dispersive or dissipative systems. The second method of assessing criticality involves direct calculation of linear, long-wave speeds using a time-dependent version of the streamtube model. This approach turns out to be better suited to the analysis of geophysical datasets. The significance of the local Froude number F is discussed. It is argued that F must take on the value unity at some point across a critical section.

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