scholarly journals Simulation and analysis of flow patterns around the scleractinian coral Madracis mirabilis (Duchassaing and Michelotti)

2003 ◽  
Vol 358 (1437) ◽  
pp. 1551-1557 ◽  
Author(s):  
Jaap A. Kaandorp ◽  
Evert A. Koopman ◽  
Peter M. A. Sloot ◽  
Rolf P. M. Bak ◽  
Mark J. A. Vermeij ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Flow Patterns ◽  
External Flow ◽  
High Flow ◽  
Low Flow ◽  
Stagnant Region ◽  
Computed Tomography Scanning ◽  
X Ray Computed

Three–dimensional morphologies of Madracis mirabilis were obtained using X–ray computed tomography scanning techniques. The morphologies were used to simulate the flow patterns around the colony. In the simulations, the thin–branching low–flow morph with a relatively larger branch–spacing was compared with the more compact high–flow morph of M. mirabilis . For both morphologies, the inside–colony flow velocities were computed for Reynolds numbers ranging from 154 to 3840. In the high–flow morph, it was found that in the range of investigated Reynolds numbers a stagnant region develops within the colony, whereas in the low–flow morph the stagnant region disappeared. Experiments done under natural conditions suggest that a morph is adapted to a certain external flow velocity and develops a stagnant region below a particular threshold for the external flow velocity. When the external flow velocity exceeds a certain threshold, which is characteristic for the growth form, the core velocity becomes equal to the external velocity. A potential application of a profile of core velocities for a range of Reynolds numbers for a certain morph is the prediction of the optimal external flow velocity for a certain morph, and this can be used to assess the state of the physical (palaeo–) environment.

Corrosion Rate Measurement by Hydrogen Effusion In Dynamic Aqueous Systems At Elevated Temperature and Pressure

CORROSION ◽  
1959 ◽  
Vol 15 (4) ◽  
pp. 29-32
Author(s):  
M. KRULFELD ◽  
M. C. BLOOM ◽  
R. E. SEEBOLD
Keyword(s):  
Elevated Temperature ◽  
Corrosion Rate ◽  
Flow Velocity ◽  
High Flow ◽  
Low Flow ◽  
Aqueous Systems ◽  
Effusion Rates ◽  
Temperature And Pressure ◽  
Effusion Method ◽  
Hydrogen Effusion

Abstract A method of applying the hydrogen effusion method to the measurement of corrosion rates in dynamic aqueous systems at elevated temperature and pressure is described. Data obtained in low carbon steel systems are presented, including (1) reproducibility obtained in measured hydrogen effusion rates at a flow velocity of 1 foot per second at a temperature of 600 F and 2000 psi, and (2) a quantitative comparison between the hydrogen effusion rates in static and in low flow velocity dynamic systems at this temperature and pressure. Some observations are included on corrosion rate measurements in a high flow velocity (30 feet per second) loop by the hydrogen effusion method. Implications of these measurements with regard to the comparison between high flow velocity corrosion and low flow velocity corrosion are mentioned and some data indicating high local sensitivity of the hydrogen effusion method are noted. Some possible difficulties involved in the method are pointed out. 2.3.4

scholarly journals 3T MRI of Peripheral Vascular Malformations: Characteristics and Comparison of Two Fat-Saturated sequences: Short Tau Inversion Recovery Versus Three-Dimensional High-Resolution Volume Interpolated Gradient Recalled Echo

2020 ◽  
Author(s):  
Florentine Höhn ◽  
Simone Hammer ◽  
Claudia Fellner ◽  
Florian Zeman ◽  
Wibke Uller ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
High Resolution ◽  
Vascular Malformations ◽  
Three Dimensional ◽  
High Flow ◽  
Low Flow ◽  
Peripheral Vascular ◽  
Contrast Enhanced ◽  
Hemodynamic Characteristics ◽  
Short Tau Inversion Recovery

Purpose To assess morphological and hemodynamic characteristics of peripheral vascular malformations on 3 T magnetic resonance imaging (MRI) including qualitative comparison of two fat-saturated sequences: short tau inversion recovery (STIR) and three-dimensional high-resolution volume interpolated gradient recalled echo (GRE). Materials and Methods During 9 months, 100 patients with suspected or known vascular malformations were prospectively assessed on a 3 T scanner using T2-weighted STIR and turbo spin echo (TSE), T1-weighted TSE, time-resolved contrast-enhanced magnetic resonance angiography (MRA) with interleaved stochastic trajectories (TWIST) and T1-weighted volume interpolated breath-hold examination (VIBE) after contrast enhancement. The analysis included signal behavior and morphologic and hemodynamic characteristics. Additionally, the image quality of the fat-saturated sequences was evaluated by 2 radiologists. Results 86 patients (14 dropouts; 57 female, 29 male; mean age 26.8 years, age range 1–56) were analyzed. 22 had high-flow and 64 low-flow malformations, including 14 with a lymphatic component. In 21 of 22 patients with high-flow malformations, typical characteristics (flow voids, hyperdynamic arteriovenous fistula, dilated main/feeder-arteries and draining veins) were documented. Patients with low-flow malformations had phleboliths in 35 cases, fluid-fluid levels in 47 and dilated draining veins in 23. Lymphatic malformations showed peripheral contrast enhancement of cyst walls in the volume interpolated GRE. The comparison of fat-saturated sequences showed significantly better results of the volume interpolated GRE in all categories except the presence of artifacts which were significantly reduced in the STIR (p < 0.05). Conclusion 3 T MRI with MRA provides detailed morphological and hemodynamic information of different types of peripheral vascular malformations. Contrast-enhanced high-resolution volume interpolated GRE proved superior to STIR in differentiating morphologic features and to be diagnostic in the differentiation of lymphatic parts and joint involvement. Key Points:  Citation Format

scholarly journals Influence of mineralization and injection flow rate on flow patterns in three-dimensional porous media

2019 ◽  
Vol 21 (27) ◽  
pp. 14605-14611 ◽  
Author(s):  
R. Moosavi ◽  
A. Kumar ◽  
A. De Wit ◽  
M. Schröter
Keyword(s):  
Porous Media ◽  
Flow Field ◽  
Flow Rate ◽  
Three Dimensional ◽  
Flow Patterns ◽  
Low Flow ◽  
Flow Rates ◽  
Injection Flow Rate ◽  
Injection Flow

At low flow rates, the precipitate forming at the miscible interface between two reactive solutions guides the evolution of the flow field.

The Effects of Flushing on Water Quality and Biofilm Biomass in Different Daily Flow Patterns of Distribution System

2014 ◽  
Vol 1030-1032 ◽  
pp. 330-333
Author(s):  
Ze Bing Zhu ◽  
Chen Guang Wu ◽  
Dan Zhong ◽  
Yi Xing Yuan ◽  
Li Li Shan ◽  
...  
Keyword(s):  
Water Quality ◽  
Flow Velocity ◽  
Distribution System ◽  
Distribution Systems ◽  
Heterotrophic Bacteria ◽  
Flow Patterns ◽  
Low Flow ◽  
Biofilm Growth ◽  
Patterns Of Distribution ◽  
Increase Flow Velocity

We studied the effects of flushing on water quality and biofilm biomass in different daily flow patterns of distribution system. After building up steady biofilm layers in two flow velocity (0.25 m/s and 0.65 m/s) distribution systems consisting of PE pipe, then flushed by stepwise increased flow velocity. An increase flow velocity caused an immediate increase in turbidity and heterotrophic bacteria of water as a result of detachment of biofilms in the pipes, especially in low flow patterns distribution system. Three days later after flushing, water quality of two systems were generally lower and more stable than before flushing. Flushing strategies only limited biofilm growth to a certain extent and did not completely eliminate microorganisms from the systems.The low flow velocity distribution system was easily being disturbed by flushing.

Dynamics of a Pipe Subjected to Internal and Confined External Flow

2019 ◽  
Author(s):  
Michael P. Païdoussis ◽  
Ahmed R. Abdelbaki ◽  
M. Faisal Javed Butt ◽  
Kyriakos Moditis ◽  
Arun K. Misra ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Reverse Flow ◽  
Cylindrical Tube ◽  
External Flow ◽  
High Flow ◽  
Analytical Models ◽  
High Flow Velocity ◽  
Cantilevered Pipe ◽  
Flow Configurations ◽  
Theory And Experiment

Abstract We consider a hanging cantilevered pipe conveying water within a water-filled container; the upper portion of the pipe is surrounded by a rigid cylindrical tube of larger diameter, forming an annular fluid-filled region around the pipe. Two flow configurations are investigated : (a) water enters the pipe at its clamped end and flows downwards, discharging at its free end into the container; the fluid exits the container by flowing upwards in the annulus and out; (b) the reverse flow arrangement: water enters the system at the upper end of the annulus and exits by flowing upwards in the pipe. The dynamics of the system is studied theoretically and experimentally for both configurations. The analytical models utilized are outlined and the experiments are described. Theory and experiment find that the system loses stability at sufficiently high flow velocity by flutter or static divergence.

Stability and Dynamic Evolution of Sliding Fluid-Transporting Pipes in Three-Dimensional Sense

2020 ◽  
Vol 20 (03) ◽  
pp. 2050036
Author(s):  
Xiping Sun ◽  
Hao Yan ◽  
Huliang Dai
Keyword(s):  
Flow Velocity ◽  
Three Dimensional ◽  
Flow Speed ◽  
Low Flow ◽  
Single Type ◽  
Dynamic Evolution ◽  
Transient Vibration ◽  
Aerial Refueling ◽  
Dynamic Behaviors ◽  
Conveying Fluid

This paper deals with the stability and dynamic evolution of a sliding pipe conveying fluid in the three-dimensional sense. The pipe is assumed to slide out from a fixed channel so that its free end is moving at the same time, a problem often associated with instabilities in applications of aerial refueling operation. To tackle this problem, the nonlinear governing equations of motion are derived by using the Hamilton’s principle and then reduced to a set of ordinary differential equations by the Galerkin’s method. A parametric study is performed to explore the transient vibration responses of the pipe for different values of flow velocity and sliding rate. Various dynamic behaviors are detected for the pipe in sliding and conveying fluid. The results show that 3-D oscillations of the pipe occur when the flow velocity exceeds a certain value, which can be affected by the sliding rate. For various flow velocities, the evolution of the dynamic characteristics of the sliding pipe can be classified into three typical types of motion. When at low flow velocity, the pipe is mainly subjected to a single type of 3-D motion. When the flow speed increases to high values, multi-type of 3-D motion consisting of three typical types occurs on the pipe. In addition, the pipe can display planar motions, transferring from one plane to the other. The result presented herein is helpful to understand the stabilities and dynamic behaviors of sliding-pipe systems used in aerial refueling applications.

Effect of expiratory flow patterns on lung emptying

1963 ◽  
Vol 18 (1) ◽  
pp. 47-50 ◽  
Author(s):  
A. C. Young ◽  
C. J. Martin ◽  
William R. Pace
Keyword(s):  
Carbon Dioxide ◽  
Flow Pattern ◽  
Body Position ◽  
Volume Ratio ◽  
Flow Patterns ◽  
High Flow ◽  
Low Flow ◽  
Flow Rates ◽  
Single Breath ◽  
Expiratory Flow

Differences in expired alveolar gas concentrations with changes in expiratory flow were studied in single-breath experiments using nitrogen and carbon dioxide meters. High flow rates preferentially emptied lung areas having low ventilation-to-volume ratios and high ventilation-to-perfusion ratios, whereas low flow rates preferentially emptied areas of high ventilation-to-volume and low ventilation-to-perfusion ratios. Selective emptying of different lung areas by varying the expiratory flow pattern was not affected by age, sex, or body position. A model of the lung is proposed to explain how ventilation-to-volume ratio differences can be seen at mouth level during constant slow, varying, and constantly increasing or decreasing expiratory flow. Submitted on May 4, 1962

Studies of Flow Patterns in a Diffuser Designed to Generate Longitudinal Vortices

1989 ◽  
Vol 111 (2) ◽  
pp. 111-117
Author(s):  
L. N. Goenka ◽  
R. L. Panton ◽  
D. G. Bogard
Keyword(s):  
Three Dimensional ◽  
Low Frequency ◽  
Reynolds Numbers ◽  
Flow Patterns ◽  
Three Dimensional Flow ◽  
Low Reynolds Numbers ◽  
Longitudinal Vortices ◽  
Turbulent Vortex ◽  
Transverse Pressure ◽  
High Reynolds

This paper describes flow visualization studies on a three-dimensional diffuser that generates two longitudinal vortices. The premise is that the three-dimensional flow patterns of this diffuser may have attributes that are superior to the two-dimensional flows of conventional diffusers. The diffuser geometry consists of a wide-angle, plane-wall diffuser with a pyramid-shaped insert attached to its expansion wall. The upsweep on the insert upper surface increases the pressure of the incoming flow, which rolls over into the expansion region in the presence of a transverse pressure gradient to form two symmetric, longitudinal vortices. At low Reynolds numbers (below 6000 based on the diffuser inlet height), the flow exhibited three flow patterns with subtle distinctions. The flowfield contained longitudinal vortices that modified and reduced in extent the separated regions that were present along the diffuser expansion wall. At high Reynolds numbers (above 6000), the separated regions along the diffuser expansion wall were replaced by a turbulent vortex. The lack of closed separated regions in the flow implies the absence of low-frequency effects that are characteristic of such regions. In addition, the flowfield exhibited little or no hysteresis with respect to changes in Reynolds number. These flowfield features are desirable in certain applications, such as exhaust diffusers for turbomachinery.

Numerical Simulation of Incompressible Laminar Flow over Three-Dimensional Rectangular Cavities

2004 ◽  
Vol 126 (6) ◽  
pp. 919-927 ◽  
Author(s):  
H. Yao ◽  
R. K. Cooper ◽  
S. Raghunathan
Keyword(s):  
Reynolds Number ◽  
Incompressible Flow ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Cavity Flow ◽  
External Flow ◽  
Cavity Flows ◽  
Recirculating Flow ◽  
Deep Cavity ◽  
Shallow Cavity

This paper presents results of investigations of unsteady incompressible flow past three-dimensional cavities, where there is a complex interaction between the external flow and the recirculating flow inside the cavity. A computational fluid dynamics approach is used in the study. The simulation is based on the solution of the unsteady Navier-Stokes equations for three-dimensional incompressible flow by using finite difference schemes. The cavity is assumed to be rectangular in geometry, and the flow is assumed to be laminar. Typical results of computation are presented, showing the effects of the Reynolds number, cavity geometry, and inflow condition on the cavity flow fields. The results show that high Reynolds numbers, with deep cavity and shallow cavity flows can become unsteady with Kelvin-Helmholtz instability oscillations and exhibiting a three-dimensional nature, with Taylor-Go¨rtler longitudinal vortices on the floor and longitudinal vortex structures on the shear layer. At moderate Reynolds numbers the shallow cavity flow is more stable than deep cavity flows. For a given Reynolds number the flow structure is affected by the thickness of the inflow boundary layer with a significant interaction between the external flow and the recirculating flow inside the cavity.

scholarly journals Flow Characteristics in the Volute and Tongue Region of a Centrifugal Pump

1984 ◽  
Author(s):  
R. B. Brownell ◽  
R. D. Flack
Keyword(s):  
Rotational Speed ◽  
Separation Zone ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
High Flow ◽  
Low Flow ◽  
Flow Rates ◽  
Pressure Profiles ◽  
Instantaneous Position ◽  
Centrifugal Process

A centrifugal process pump was tested at two rotational speeds and five flow rates. Nine piezometer taps around the volute were used to measure time averaged pressure profiles and streak photography was used to visualize the flow patterns near the volute tongue. Flow patterns for four different instantaneous impeller orientations (blade positions) were studied. Nondimensionalized results were independent of rotational speed. At 100% capacity the volute pressures were uniform within 15%. At off-design condition, however, the pressure near the tongue varied by as much as 28% from the average. At 100% capacity the streamlines were smooth and well behaved. At low flow rates the tongue stagnation point moved between the impeller and tongue and a separation zone appeared in the discharge. The instantaneous position of the impeller was seen to affect the streamlines primarily near the impeller, although at high flow rates the separation zone was also seen to depend on the impeller position.

Sign in / Sign up

Export Citation Format

Share Document