scholarly journals OBSERVATIONS OF CANOPY FLOW STRUCTURE AND FRICTIONAL VELOCITY OF CORAL COLONIES IN DONGSHA ATOLL

2018 ◽  
pp. 15
Author(s):  
Zhi-Cheng Huang ◽  
Wen-Yang Hsu ◽  
Jay Yang
Keyword(s):  
Flow Structure ◽  
Morphological Evolution ◽  
Field Measurements ◽  
Flow Structures ◽  
Doppler Velocity ◽  
Benthic Organism ◽  
Boundary Layer Flows ◽  
Canopy Layer ◽  
Drag Forces ◽  
Flow Motion

Understanding the hydrodynamics is important for biological, ecological, and biogeochemical processes in coral reef systems. The near-bed flow motion affects the benthic organism distributions, morphological evolution, larvae settlement, and nutrient uptake. The near-bed flow structures have been characterized as planar boundary-layer flows when the bottom roughness scale created by benthic organisms is much smaller than the water depth. On the other hand, when the bottom roughness scale becomes much larger, the resistance drag forces caused by these canopy elements should be considered (Rosman and Hench, 2011). The form drag of the multiple coral colonies generates turbulent wakes, enhances turbulent mixing, and changes the flow structure (Huang, 2015). Many laboratory and modeling studies have reported the drag parameterization and the flow structure for unidirectional flows through submerged canopy or vegetation (e.g., Finnigan, 2000; among many others). However, the vertical flow structures of the canopy layer caused by coral colonies (bommies) are rarely reported in fields. Here we present field measurements of flow structure over coral colonies using acoustic Doppler velocimetry (ADV) and pulse-coherent Doppler velocity profiler (PCADP) techniques. The measured current profiles and turbulence are used to study the flow dynamics in the canopy-layer created by coral colonies.

Helical Flow Disturbances in a Multi-Nozzle Combustor

2014 ◽  
Author(s):  
Michael Aguilar ◽  
Michael Malanoski ◽  
Gautham Adhitya ◽  
Benjamin Emerson ◽  
Vishal Acharya ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Field Measurements ◽  
Flow Fields ◽  
Helical Flow ◽  
Forced Response ◽  
Flow Structures ◽  
Response Dynamics ◽  
Flow Disturbances ◽  
Nozzle Configuration ◽  
Jet Interactions

This paper describes an experimental investigation of a transversely forced, swirl stabilized combustor. Its objective is to compare the unsteady flow structures in single and triple nozzle combustors and determine how well a single nozzle configuration emulates the characteristics of a multi-nozzle one. The experiment consists of a series of velocity field measurements captured on planes normal to the jet axis. As expected, there are differences between the single and triple-nozzle flow fields, but the differences are not large in the regions upstream of the jet merging zone. Direct comparisons of the time averaged flow fields reveal a higher degree of non-axisymmetry for the flowfields of nozzles in a multi-nozzle configuration. Azimuthal decompositions of the velocity fields show that the transverse acoustic forcing has an important influence on the dynamics, but that the single and multi-nozzle configurations have similar forced response dynamics near the dump plane. Specifically, the axial dependence of the amplitude in the highest energy axisymmetric and helical flow structures is quite similar in the two configurations. This result suggests that the hydrodynamic influence of one swirling jet on the other is minimal and, as such, that jet-jet interactions in this configuration do not have a significant influence on the unsteady flow structures.

Effects of Inclination Angle of Ribs on the Flow Behavior in Rectangular Ducts

2004 ◽  
Vol 126 (4) ◽  
pp. 692-699 ◽  
Author(s):  
Xiufang Gao ◽  
Bengt Sunde´n
Keyword(s):  
Velocity Component ◽  
Flow Direction ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Fluid Flows ◽  
Streamwise Velocity ◽  
Flow Structures ◽  
Local Flow ◽  
Flow Motion ◽  
Streamwise Velocity Component

The flow behavior in rib-roughened ducts is influenced by the inclination of ribs and the effect is investigated in the present study by Particle Image Velocimetry (PIV). The local flow structures between two adjacent ribs were measured. The Reynolds number was fixed at 5800. The flow field description was based on the PIV results in planes both parallel and perpendicular to the ribbed walls at various locations. The rib angle to the main flow direction was varied as 30 deg, 45 deg, 60 deg and 90 deg. The ribs induce three dimensional flow fields. The flow separation and reattachment between adjacent ribs are clearly observed. In addition, the inclined ribs are found to alter the spanwise distribution of the streamwise velocity component. The streamwise velocity component has its highest values at the upstream end of the ribs, and decreases continuously to its lowest values at the downstream end. Strong secondary flow motion occurs over the entire duct cross section for the inclined ribs. The flow structures between two consecutive ribs show that the fluid flows along the ribs from one end of the ribs to the other end, and then turns back at the transverse center. Downwash and upwash flows are observed at the upstream end and downstream end of the ribs, respectively.

scholarly journals Numerical Investigation of the Flow around a Feather Shuttlecock with Rotation

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 28
Author(s):  
John Hart ◽  
Jonathan Potts
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Numerical Investigation ◽  
Computational Fluid Dynamic ◽  
High Reynolds Number ◽  
Fluid Dynamic ◽  
Flow Structures ◽  
Drag Forces ◽  
High Reynolds

This paper presents the first scale resolving computational fluid dynamic (CFD) investigation of a geometrically realistic feather shuttlecock with rotation at a high Reynolds number. Rotation was found to reduce the drag coefficient of the shuttlecock. However, the drag coefficient is shown to be independent of the Reynolds number for both rotating and statically fixed shuttlecocks. Particular attention is given to the influence of rotation on the development of flow structures. Rotation is shown to have a clear influence on the formation of flow structures particularly from the feather vanes, and aft of the shuttlecock base. This further raises concerns regarding wind tunnel studies that use traditional experimental sting mounts; typically inserted into this aft region, they have potential to compromise both flow structure and resultant drag forces. As CFD does not necessitate use of a sting with proper application, it has great potential for a detailed study and analysis of shuttlecocks.

Microscopic Characteristics of Functional Fluid Suspended Diamond Particles Under the High-Voltage Alternating Electric Field

2007 ◽  
Author(s):  
Hiromichi Obara ◽  
Ryousuke Ibata ◽  
Yusuke Kawai ◽  
Yasuaki Matsudair
Keyword(s):  
Electric Field ◽  
Flow Structure ◽  
High Voltage ◽  
Low Frequency ◽  
Flow Structures ◽  
Polishing Process ◽  
Specific Flow ◽  
Micro Particle Image Velocimetry ◽  
Diamond Particles ◽  
Alternating Electric Field

The microscopic characteristics of a functional fluid for a micro polishing process were investigated by microscopic observation and micro particle image velocimetry. This functional fluid, which consists of suspended micro scale diamond particles in insulated silicon oil, has two specific flow structures under a high-voltage alternating electric field. One flow structure consists of a reciprocating flow generated in one direction between the electrodes under low-electric-field and high-frequency conditions. The other flow structure consists of a rotational flow formed under high-electric-field and low-frequency conditions. These specific flow structures contribute actively to a polishing process and to the development of micro fluidic devices in the future. In the present study, the effect of the electric field on specific flow structures and the mechanism of the induced flow are clarified.

Flow Visualization and Acoustic Consequences of the Air Moving Through a Static Model of the Human Larynx

2005 ◽  
Vol 128 (3) ◽  
pp. 380-390 ◽  
Author(s):  
Bogdan R. Kucinschi ◽  
Ronald C. Scherer ◽  
Kenneth J. DeWitt ◽  
Terry T. M. Ng
Keyword(s):  
Flow Visualization ◽  
Flow Structure ◽  
Flow Rate ◽  
Real Life ◽  
Vocal Folds ◽  
Jet Flow ◽  
Scale Model ◽  
Flow Structures ◽  
Human Larynx ◽  
False Vocal

Flow visualization with smoke particles illuminated by a laser sheet was used to obtain a qualitative description of the air flow structures through a dynamically similar 7.5× symmetric static scale model of the human larynx (divergence angle of 10deg, minimal diameter of 0.04cm real life). The acoustic level downstream of the vocal folds was measured by using a condenser microphone. False vocal folds (FVFs) were included. In general, the glottal flow was laminar and bistable. The glottal jet curvature increased with flow rate and decreased with the presence of the FVFs. The glottal exit flow for the lowest flow rate showed a curved jet which remained laminar for all geometries. For the higher flow rates, the jet flow patterns exiting the glottis showed a laminar jet core, transitioning to vortical structures, and leading spatially to turbulent dissipation. This structure was shortened and tightened with an increase in flow rate. The narrow FVF gap lengthened the flow structure and reduced jet curvature via acceleration of the flow. These results suggest that laryngeal flow resistance and the complex jet flow structure exiting the glottis are highly affected by flow rate and the presence of the false vocal folds. Acoustic consequences are discussed in terms of the quadrupole- and dipole-type sound sources due to ordered flow structures.

scholarly journals Three dimensional cyclonic turbulent flow structures at various geometries, inlet-outlet orientations and operating conditions

2018 ◽  
Vol 12 (4) ◽  
pp. 4300-4328
Author(s):  
Pasymi Pasymi ◽  
Y. W. Budhi ◽  
A. Irawan ◽  
Y. Bindar
Keyword(s):  
Flow Structure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Operating Conditions ◽  
Flow Structures ◽  
Ansys Fluent ◽  
Vortex Pattern ◽  
Fluent Software ◽  
Simulation Results ◽  
Vortex Patterns

Flow structure inside a chamber greatly determines the process performances. Therefore, the flow structure inside a chamber are often constructed in such a way as an effort to obtain equipment performances in accordance with the expectations. This study explored flow structure inside several chamber geometries and operating conditions. Three types of chamber, namely; GTC, DTC and TJC were set as the investigated chambers. The Computational Fluid Dynamics technique, supported by some experimental data from the literature, is used as an investigation method. The RANS based models, under Ansys-Fluent software were used in this numerical investigation. Simulation results revealed that the flow structures of GTC and DTC are predominantly created by spiral and vortex patterns. The vortex stabilizer diameter in the GTC affects the vortex pattern, velocity profile and pressure drop. The flow structure of DTC presents the most complex behavior. The flow structure inside TJC, in the case of unconfined outlet boundary, is characterized by the helical and wavy jet pattern. This structure is determined by the initial tangential intensity (IIT) and the inlet aspect ratio (RIA). The structures of vortex, helical, and wavy axial flow are properly constructed and visualized in this paper. There is no a turbulence model which is always superior to the other models, consistently. The standard k-ε model exhibits the realistic and robust performances among  all of investigatied cases.

scholarly journals Fluid Flow in Tree-Shaped Constructal Networks: Porosity, Permeability and Inertial Parameter

2010 ◽  
Vol 297-301 ◽  
pp. 408-412 ◽  
Author(s):  
Antonio F. Miguel
Keyword(s):  
Fluid Flow ◽  
Flow Structure ◽  
Flow Structures ◽  
Hydraulic Permeability ◽  
Flow Networks ◽  
Circular Area ◽  
Ongoing Research ◽  
Inertial Parameter ◽  
Ergun Equation ◽  
Physical Description

This paper aims to contribute to the ongoing research on tree-shaped flow structures. First, it briefly traces the progress made on constructal tree-shaped flow networks. Then, the paper focuses on tree pattern of tubes connecting the centre and the rim of a circular area. It shows that the physical description underlying the classical Darcy-Forchheimer-Ergun equation may provide a legitimate correlation for this kind of flow structure. The porosity, hydraulic permeability and the inertial factor of the flow structure are also presented.

Field measurements of turbulent flow structures over a nebkha

Geomorphology ◽  
2021 ◽  
Vol 375 ◽  
pp. 107555
Author(s):  
Yongcheng Zhao ◽  
Xin Gao ◽  
Jiaqiang Lei ◽  
Shengyu Li
Keyword(s):  
Turbulent Flow ◽  
Field Measurements ◽  
Flow Structures
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