Dissolution finger growth in variable aperture fractures: Role of the tip-region flow field

2002 ◽  
Vol 29 (22) ◽  
pp. 32-1-32-4 ◽  
Author(s):  
Wendy Cheung ◽  
Harihar Rajaram
Keyword(s):  
Flow Field ◽  
Region Flow ◽  
Variable Aperture

scholarly journals Hydrodynamics can determine the optimal route for microswimmer navigation

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Abdallah Daddi-Moussa-Ider ◽  
Hartmut Löwen ◽  
Benno Liebchen
Keyword(s):  
Flow Field ◽  
Hydrodynamic Interactions ◽  
Optimal Trajectories ◽  
Optimal Route ◽  
Active Particles ◽  
Navigation Strategy ◽  
Navigation Strategies

AbstractAs compared to the well explored problem of how to steer a macroscopic agent, like an airplane or a moon lander, to optimally reach a target, optimal navigation strategies for microswimmers experiencing hydrodynamic interactions with walls and obstacles are far-less understood. Here, we systematically explore this problem and show that the characteristic microswimmer-flow-field crucially influences the navigation strategy required to reach a target in the fastest way. The resulting optimal trajectories can have remarkable and non-intuitive shapes, which qualitatively differ from those of dry active particles or motile macroagents. Our results provide insights into the role of hydrodynamics and fluctuations on optimal navigation at the microscale, and suggest that microorganisms might have survival advantages when strategically controlling their distance to remote walls.

Flow Measurements in a Nozzle Guide Vane Passage With a Low Aspect Ratio and Endwall Contouring

2000 ◽  
Author(s):  
Steven W. Burd ◽  
Terrence W. Simon
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Guide Vane ◽  
Flow Measurements ◽  
Vast Number ◽  
Aspect Ratios ◽  
Nozzle Guide Vane ◽  
Endwall Contouring ◽  
Nozzle Guide

The vast number of turbine cascade studies in the literature has been performed in straight-endwall, high-aspect-ratio, linear cascades. As a result, there has been little appreciation for the role of, and added complexity imposed by, reduced aspect ratios. There also has been little documentation of endwall profiling at these reduced spans. To examine the role of these factors on cascade hydrodynamics, a large-scale nozzle guide vane simulator was constructed at the Heat Transfer Laboratory of the University of Minnesota. This cascade is comprised of three airfoils between one contoured and one flat endwall. The geometries of the airfoils and endwalls, as well as the experimental conditions in the simulator, are representative of those in commercial operation. Measurements with hot-wire anemometry were taken to characterize the flow approaching the cascade. These measurements show that the flow field in this cascade is highly elliptic and influenced by pressure gradients that are established within the cascade. Exit flow field measurements with triple-sensor anemometry and pressure measurements within the cascade indicate that the acceleration imposed by endwall contouring and airfoil turning is able to suppress the size and strength of key secondary flow features. In addition, the flow field near the contoured endwall differs significantly from that adjacent to the straight endwall.

scholarly journals Role of Transient Characteristics in Fish Trajectory Modeling

2020 ◽  
Author(s):  
zhu gao ◽  
zu hao zhou ◽  
Helge I Andersson
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Turbulent Flow ◽  
Transient Flow ◽  
Simultaneous Recording ◽  
Fish Locomotion ◽  
Vertical Slot ◽  
Turbulent Flow Structure ◽  
General Method

In this paper, we analyzed the live fish trajectory recorded from an experiment in an experimental vertical slot fishway. Combined with a numerical simulation, we demonstrated that randomness shown in fish trajectory might not merely be attributed to fish's random choices in its swimming, also could be an adaption consequence to the bulk unsteady turbulent flow structure. Simple superposing the fish trajectory on the time-averaged flow field obtained either by interpolating on discrete point measurements or numerical simulation is not an ideal method for fish movement description in fishway engineering. How to model the fish paths in transient flow and the necessity of simultaneous recording of the flow field and the fish locomotion are challenging topics. The suggested spectrum analysis of the flow field may provide a new general method to reproduce the fish trajectory in a complex turbulent flow.

The Role of Vortices and Unsteady Effects During the Hovering Flight of Dragonflies

1979 ◽  
Vol 83 (1) ◽  
pp. 59-77 ◽  
Author(s):  
STUART B. SAVAGE ◽  
BARRY G. NEWMAN ◽  
DENIS T.-M. WONG
Keyword(s):  
Steady State ◽  
Flow Field ◽  
Flow Visualization ◽  
Inviscid Flow ◽  
Physical Explanation ◽  
Hovering Flight ◽  
Wing Motion ◽  
Unsteady Effects ◽  
Animal Flight

Weis-Fogh and Norberg concluded that steady-state aerodynamics is incapable of explaining how the dragonfly supports its weight during hovering. Norberg also concluded that the wing kinematics of Aeschna juncea L., as determined photographically, are incompatible with those proposed by Weis-Fogh for his Flip mechanism. The present paper has proposed an alternative lift-generating mechanism, various aspects of which are novel from the standpoint of animal flight. Flow visualization tests performed in water established the flow field during a complete cycle of the idealized wing motion. Using this information and unsteady inviscid flow theory the forces were analysed. A plausible balance of horizontal forces and more than sufficient lift were obtained. A physical explanation of the theory is provided for those who do not wish to study the mathematical details.

scholarly journals Role of Transient Characteristics in Fish Trajectory Modeling

2020 ◽  
Vol 12 (17) ◽  
pp. 6765
Author(s):  
Gao Zhu ◽  
Zuhao Zhou ◽  
Helge I Andersson
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Transient Flow ◽  
Silver Carp ◽  
Simultaneous Recording ◽  
Trajectory Modeling ◽  
Fish Locomotion ◽  
Vertical Slot ◽  
Ideal Method

In this experiment, we analyzed live fish (silver carp) trajectories recorded in an experimental vertical-slot fishway. Combined with a numerical simulation, we demonstrated that randomness shown in fish trajectories might not merely be attributed to the fish’s random choices in its swimming, but could also be a consequence of adaption to the bulk unsteady turbulent flow structures. Simple superposition of a fish trajectory on the time-averaged flow field obtained either by interpolating on discrete point measurements or numerical simulation data is not an ideal method for description of fish movement. How to model the fish paths in transient flow and the necessity of simultaneous recording of the flow field and the fish locomotion are challenging topics. We also discussed the possible integration of currently existing methods to promote the development of fish trajectory modeling.

The role of the flow pattern in wastewater aeration tanks

2010 ◽  
Vol 61 (2) ◽  
pp. 407-414 ◽  
Author(s):  
M. Gresch ◽  
D. Braun ◽  
W. Gujer
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Compartment Model ◽  
Plant Performance ◽  
Aeration Tank ◽  
Key Factors ◽  
Direct Observations ◽  
Conservative Tracer

Reactor hydraulics is one of the key factors for plant performance and plant control. The residence time distribution is a good but limited indicator of reactor hydraulics. A more detailed view is obtained by direct observations within the reactor. Two different techniques (conservative tracer, reactive tracer) are discussed to detect major anomalies in the flow field of a wastewater aeration tank. Experiments with conservative tracers give valuable information over a very limited period of time making the analysis of the flow field difficult. On the other hand, reactive tracers can be monitored long term which helps identifying the flow pattern provided that a high spatial and temporal resolution of the measurements is applied. Experimental data is used to determine the structure and the parameters of a compartment model that corresponds well with the measurements.

Approximate inviscid, nonadiabatic stagnation region flow field solution

AIAA Journal ◽  
1965 ◽  
Vol 3 (8) ◽  
pp. 1537-1538 ◽  
Author(s):  
G. M. HANLEY ◽  
K. D. KORKAN
Keyword(s):  
Flow Field ◽  
Stagnation Region ◽  
Field Solution ◽  
Region Flow
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