scholarly journals Flow Evolution Mechanisms of Lid-Driven Cavities

10.5772/28901 ◽  
2011 ◽  
Author(s):  
Jose Rafael ◽  
Sergio Pedraza
Keyword(s):  
Flow Evolution

scholarly journals A Traffic Flow Evolution Process toward Mixed Equilibrium with Multicriteria of Route Choice Behaviour

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Xiangjun Jiang ◽  
Zhongxiang Huang ◽  
Zhenyu Zhao
Keyword(s):  
Equilibrium State ◽  
Traffic Flow ◽  
Complete Information ◽  
User Equilibrium ◽  
Evolution Model ◽  
Choice Behaviour ◽  
Flow Evolution ◽  
Quantity Adjustment ◽  
Mixed Equilibrium ◽  
Equilibrium Pattern

Based on the price-quantity adjustment behaviour principle of disequilibrium theory, the route choices of travellers are also affected by a quantity signal known as traffic flow, while the route cost is considered as a price signal in economics. Considering the quantity signal’s effect among travellers, a new route comfort choice behaviour criterion and its corresponding equilibrium condition are established. The network travellers are classified into three groups according to their route choice behaviour: travellers in the first group choose the shortest route following the route rapidity behaviour criterion with complete information forming the UE (user equilibrium) pattern, travellers in the second group choose the most comfortable route following the route comfort behaviour criterion with complete information forming the QUE (quantity adjustment user equilibrium) pattern, and travellers in the third group choose a route according to their perceived travel time with incomplete information forming the SUE (stochastic user equilibrium) pattern. The traffic flows of all three groups converge to a new UE-QUE-SUE mixed equilibrium flow pattern after interaction. To depict the traveller-diversified choice behaviour and the traffic flow interaction process, a mixed equilibrium traffic flow evolution model is formulated. After defining the route comfort indicator and the corresponding user equilibrium state, the equilibrium conditions of the three group flows are given under a mixed equilibrium pattern. In addition, an equivalent mathematical programming of the mixed equilibrium traffic flow evolution model is proposed to demonstrate that the developed model converges to the mixed equilibrium state. Finally, numerical examples are examined to evaluate the effect of route comfort proportions on the traffic network flow evolution and analyse the performance of the proposed model.

Evolution and Turbulence Properties of Self-Sustained Transversely Oscillating Flow Induced by Fluidic Oscillator

2007 ◽  
Vol 129 (8) ◽  
pp. 1038-1047 ◽  
Author(s):  
Rong Fung Huang ◽  
Kuo Tong Chang
Keyword(s):  
Stagnation Point ◽  
Vortex Pair ◽  
Transverse Oscillation ◽  
Oscillating Flow ◽  
Near Wake ◽  
Fluidic Oscillator ◽  
Planar Jet ◽  
Oscillation Process ◽  
Gravity Driven ◽  
Flow Evolution

The evolution process and turbulence properties of a transversely oscillating flow induced by a fluidic oscillator are studied in a gravity-driven water tunnel. A planar jet is guided to impinge a specially designed crescent surface of a target blockage that is enclosed in a cavity of a fluidic oscillator. The geometric configuration of the cavity transforms the inherent stability characteristics of the jet from convective instability to absolute instability, so that the jet precedes the persistent back and forth swinging in the cavity. The swinging jet is subsequently directed through two passages and issued alternatively out of the fluidic oscillator. Two short plates are installed near the exits of the alternatively issuing pulsatile jets to deflect the jets toward the central axis. The deflected jets impinge with each other and form a pair of counter-rotating vortices in the near wake of the oscillator with a stagnation point at the impingement point. The stagnation point of the counter-rotating vortex pair moves back and forth transversely because of the phase difference existing between the two issued jets. The merged flow evolving from the counter-rotating vortices formed by the impingement of the two pulsatile jets therefore presents complex behavior of transverse oscillation. The topological models corresponding to the flow evolution are constructed to illustrate the oscillation process of the oscillating flow. Significant momentum dispersion and large turbulence intensity are induced by the transverse oscillation of the merged flow. The statistical turbulence properties show that the Lagrangian integral time and length scales of the turbulence eddies (the fine-scale structure) produced in the oscillating flow are drastically reduced.

scholarly journals Comparison between Dual-Doppler and EnKF Storm-Scale Wind Analyses: Observing System Simulation Experiments with a Supercell Thunderstorm

2012 ◽  
Vol 140 (12) ◽  
pp. 3972-3991 ◽  
Author(s):  
Corey K. Potvin ◽  
Louis J. Wicker
Keyword(s):  
System Simulation ◽  
Radar Data ◽  
Model Errors ◽  
Radar Observations ◽  
Low Level ◽  
Flow Evolution ◽  
Supercell Thunderstorm ◽  
Wind Retrievals ◽  
Observing System Simulation Experiment ◽  
Microphysical Parameterization

Abstract Kinematical analyses of mobile radar observations are critical to advancing the understanding of supercell thunderstorms. Maximizing the accuracy of these and subsequent dynamical analyses, and appropriately characterizing the uncertainty in ensuing conclusions about storm structure and processes, requires thorough knowledge of the typical errors obtained using different retrieval techniques. This study adopts an observing system simulation experiment (OSSE) framework to explore the errors obtained from ensemble Kalman filter (EnKF) assimilation versus dual-Doppler analysis (DDA) of storm-scale mobile radar data. The radar characteristics and EnKF model errors are varied to explore a range of plausible scenarios. When dual-radar data are assimilated, the EnKF produces substantially better wind retrievals at higher altitudes, where DDAs are more sensitive to unaccounted flow evolution, and in data-sparse regions such as the storm inflow sector. Near the ground, however, the EnKF analyses are comparable to the DDAs when the radar cross-beam angles (CBAs) are poor, and slightly worse than the DDAs when the CBAs are optimal. In the single-radar case, the wind analyses benefit substantially from using finer grid spacing than in the dual-radar case for the objective analysis of radar observations. The analyses generally degrade when only single-radar data are assimilated, particularly when microphysical parameterization or low-level environmental wind errors are introduced. In some instances, this leads to large errors in low-level vorticity stretching and Lagrangian circulation calculations. Nevertheless, the results show that while multiradar observations of supercells are always preferable, judicious use of single-radar EnKF assimilation can yield useful analyses.

Blood Flow Velocimetry in a Microchannel During Coagulation Using PIV and wOFV

2020 ◽  
Author(s):  
E. Kucukal ◽  
Y. Man ◽  
U. A. Gurkan ◽  
B. E. Schmidt
Keyword(s):  
Blood Flow ◽  
Blood Cells ◽  
Thrombus Formation ◽  
Blockage Ratio ◽  
Time Decay ◽  
Clotting Time ◽  
White Light Source ◽  
Flow Velocimetry ◽  
Flow Evolution ◽  
Time Decay Rate

Abstract This article describes novel measurements of the velocity of whole blood flow in a microchannel during coagulation. The blood is imaged volumetrically using a simple optical setup involving a white light source and a microscope camera. The images are processed using PIV and wavelet-based optical flow velocimetry (wOFV), both of which use images of individual blood cells as flow tracers. Measurements of several clinically relevant parameters such as the clotting time, decay rate, and blockage ratio are computed. The high-resolution wOFV results yield highly detailed information regarding thrombus formation and corresponding flow evolution that is the first of its kind.

scholarly journals Chaotic Behavior of Traffic-Flow Evolution with Two Departure Intervals in Two-Link Transportation Network

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Shixu Liu ◽  
Lidan Guo ◽  
Said M. Easa ◽  
Wensi Chen ◽  
Hao Yan ◽  
...  
Keyword(s):  
Real Time ◽  
Traffic Flow ◽  
Chaotic Behavior ◽  
Transportation Network ◽  
Dynamic Evolution ◽  
Historical Information ◽  
Flow Evolution ◽  
Types Of Information ◽  
Real Time Information ◽  
Time Information

In this study, the influence of traveler's departure time choice in day-to-day dynamic evolution of traffic flow in a transportation network is investigated. Combining historical information and real-time information, a dynamic evolution model of traffic flow with a study period divided into two intervals is proposed for a simple two-link network. Then, the evolution of network traffic flow is investigated using numerical experiments. Three types of information are considered: (1) only historical information, (2) only real-time information, and (3) both historical and real-time information. The results show that the dynamic evolution of network traffic flow under the three types of information is similar. However, the possibility of chaos occurrence under both historical and real-time information is smaller than that under two individual types of information. When chaos occurs, the chaotic behavior in traffic-flow evolution under only real-time information is relatively less complex than that under the other two types of information.

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