Stream-barb installations for narrow channel bends — a laboratory study

2004 ◽  
Vol 31 (3) ◽  
pp. 478-486 ◽  
Author(s):  
Troy Matsuura ◽  
Ronald Townsend
Keyword(s):  
Laboratory Study ◽  
Phase 1 ◽  
Rectangular Channel ◽  
Field Tests ◽  
Narrow Channel ◽  
Secondary Currents ◽  
Stream Bank ◽  
Low Profile ◽  
Bank Protection ◽  
Bed Scour

Phase 1 of an ongoing laboratory study of a novel form of stream-bank protection structure is described. "Barbs" are dike-like stone structures designed to protect the (usually unstable) outside-bank regions of channel bends. These low-profile structures point upstream into the flow and typically extend to about 1/4-way across the channel. By disrupting near-bank velocity gradients they promote sediment deposition along the eroding outside-bank region. Their presence also modifies the "helicoidal"-type flow pattern of the bend such that secondary currents, which would otherwise attack the outside-bank, are redirected towards the center of the channel. This novel form of bank protection structure is currently undergoing field tests on selected bends on a number of shallow "wide" streams in Illinois, USA. While initial results are encouraging, additional studies are necessary to develop design criteria for their wider application. In phase 1 of this study, the effectiveness of different arrangements of barb groups, in both 90° and 135° moveable-bed bend sections of a hydraulically "narrow" rectangular channel, are investigated. For each hydraulic condition considered, the channel-bed scour profiles generated by the different barb groups are compared to corresponding "reference" profiles generated in the absence of barbs. Judging the effectiveness of the different barb groups in promoting long-term stability of the outside-bank region is based on two criteria: (i) percent reduction achieved in scouring in the vicinity of the outside-bank and (ii) degree to which the channel thalweg (deepest portion) is moved from the outside-bank region towards the center of the channel.Key words: barb, channel bends, local scouring, bank erosion, bank protection, secondary currents.

A Critical Review of Drag Reduction in Channel Flows and Numerical Study of Forced Convective Transport in a Channel With Conducting-Lubricating (CO-LUB) Surfaces

2015 ◽  
Author(s):  
Jessica Reyes ◽  
Krishna Kota
Keyword(s):  
Heat Transfer ◽  
Drag Reduction ◽  
Liquid Flow ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Narrow Channel ◽  
Convective Transport ◽  
Bulk Liquid ◽  
Frictional Drag ◽  
Ansys Fluent

Addressing the traditionally contradictory problem of obtaining considerable drag reduction without negatively impacting heat transfer as much is an arduous scientific challenge. In this paper, prior efforts on frictional drag reduction and the associated issues are discussed in relevant detail, and the effectiveness of Conducting-Lubricating (CO-LUB) surfaces as one of the potential options to address this challenge for single phase forced convection of liquids is numerically pursued. CO-LUB surfaces have exceptionally high wetting characteristics, and when saturated with a liquid microlayer, provide remarkable lubrication to bulk liquid flow and simultaneously facilitate heat transfer by conduction through the microlayer. In the simulations, the side walls of a high aspect ratio rectangular channel were assumed as CO-LUB surfaces and flow and heat transfer of bulk liquid flow were modeled using ANSYS FLUENT 14.5. Volume-of-Fluid (VOF) method was used to model the two phases with a free surface interface, with water as the microlayer liquid and oil as the bulk liquid, in a narrow channel of 5 mm width and 50 mm length under laminar flow, constant wall heat flux conditions. The results were compared with a regular channel of the same dimensions (without CO-LUB surfaces) and it was found that pressure drop decreased remarkably by ∼23 times for some cases but without any heat transfer attenuation (actually, improved heat transfer performance was observed) leading to highly energy-efficient convective transport.

Correlation of Laboratory and Stripa Field Leaching Studies

1988 ◽  
Vol 127 ◽  
Author(s):  
B. K. Zoitos ◽  
D. E. Clark ◽  
A. R. Lodding ◽  
G. G. Wicks
Keyword(s):  
Laboratory Study ◽  
Secondary Ion Mass Spectrometry ◽  
Field Tests ◽  
Surface Layers ◽  
Infrared Reflection ◽  
Significant Difference ◽  
Field Samples ◽  
Surface Alteration ◽  
Infrared Reflection Spectroscopy ◽  
Secondary Ion

ABSTRACTA variety of surface sensitive techniques has been used to assess surface layers formed on SRL 165 waste glass specimens from the Stripa burial study and from a laboratory study designed to simulate conditions of the Stripa environment. The laboratory study included static and slow flow tests carried out for periods up to 6 and 24 months, respectively. Comparisons of leached layers formed in the two studies are based upon secondary ion mass spectrometry (SIMS), Fourier transform infrared reflection spectroscopy (FTIRRS), and scanning electron microscopy-electron microprobe (SEM-EMP) analysis.Results demonstrate that surface layers having similar trends in elemental profiles were developed in both lab and field tests. It was also found that both sets of samples showed similar changes in FTIRR spectra. One significant difference between the lab and field samples was that surface alteration, as indicated by changes in FTIRR spectra and leached layer thickness (from SIMS), occurred more rapidly in the lab tests.

Experimental Measurements and Numerical Simulations of Two-Phase Stratified, Wavy and Slug Flow in a Narrow Rectangular Channel

2005 ◽  
Author(s):  
Steven P. O’Halloran ◽  
B. Terry Beck ◽  
Mohammad H. Hosni ◽  
Steven J. Eckels
Keyword(s):  
Numerical Simulations ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Measurement Techniques ◽  
Narrow Channel ◽  
Experimental Measurements ◽  
Phase Flow ◽  
Two Phase ◽  
Two Fluids

Flow pattern transitions in two-phase flow are important phenomena for many different types of engineering applications, including heat exchangers. While two-phase flow is not understood as well as single-phase flow, advancements in both measurement techniques and numerical simulations are helping to increase the understanding of two-phase flow. In this paper, stratified/wavy flow is investigated, along with the transition from wavy to slug flow. For the experimental setup, a narrow channel with a length of 600 mm, height of 40 mm, and a width of 15 mm was fabricated using clear acrylic plastic, and water and air were the two fluids used for testing. The water in the channel was initially at rest, and the transition in flow patterns was created by increasing the velocity of air flowing over the water surface. Particle image velocimetry (PIV) was used to measure the velocity of the flow for stratified and wavy flow conditions, and also the velocity at the onset of slug flow. Along with the experimental measurements, computational fluid dynamics (CFD) simulations were conducted on a similar geometry using the volume of fluid (VOF) two-phase model. A commercial CFD software package was used for the simulations, and comparisons were made between the experimental measurements and numerical results. Favorable agreement was found between the experimental measurements and the numerical simulations. In particular, the transition from wavy to slug flow compared well to previously developed two-phase flow transition models, including the slug transition developed by Taitel and Dukler.

Displacement of the Beating Heart with a Low-Profile Suction-Based Apical Positioning Device in a Closed Chest

2007 ◽  
Vol 2 (1) ◽  
pp. 14-19
Author(s):  
James Mykytenko ◽  
Thomas A. Vassiliades ◽  
Jacob Vinten-Johansen
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Arterial Pressure ◽  
Phase 1 ◽  
Beating Heart ◽  
Ventricular Performance ◽  
Baseline Phase ◽  
Closed Chest ◽  
Low Profile ◽  
Cardiac Displacement

Background Off-pump, multivessel, endoscopic coronary artery bypass requires cardiac displacement within an intact chest. The current study evaluated right ventricular performance and systemic hemodynamics while exposing the posterior surface of the heart using a novel, low-profile, apical suction-based cardiac positioner in a closed-chest, beating-heart model. Methods Six pigs underwent instrumentation with continuous monitoring of arterial pressure by fluid-filled transducer and cardiac output and coronary blood flow by ultrasound transit time flow probe. Right ventricular (RV) pressure-volume loops were generated by an impedance catheter. Heart rate was maintained between 80 and 100 beats per minute pharmacologically. The cardiac positioner displaced the heart endoscopically through a port. Data were obtained in 5 sequential phases: (1) baseline/free-beating, (2) positioner coaptation, (3) addition of Trendelenburg, (4) cardiac displacement with Trendelenburg, and (5) cardiac displacement without Trendelenburg. Results Cardiac displacement without Trendelenburg (Phase 5) resulted in a significant (P < 0.05) decrease in cardiac output, coronary blood flow, RV systolic pressure (RVSP), mean arterial pressure, RV end-diastolic volume (RVEDV), and RV end-systolic volume (RVESV) compared with baseline (Phase 1). With Trendelenburg added to cardiac displacement (Phase 4), all parameters improved, but only RVSP, mean arterial pressure, and RVEDV were comparable to baseline (Phase 1). There were no local complications from device coaptation. Conclusions The low-profile endoscopic cardiac positioner is safe and effective in the closed-chest, beating-heart porcine model. Nevertheless, cardiac displacement in a closed chest does cause impairment in ventricular performance that can be ameliorated by the addition of Trendelenburg and further technological progress.

The Evaluation of NHW-1 Type Coated Tubing Abrasion Resistance Performance

2011 ◽  
Vol 189-193 ◽  
pp. 937-942
Author(s):  
Ke Liang Wang ◽  
Yang Liu ◽  
Li Jing Sun ◽  
Chun Bao Sun
Keyword(s):  
Life Cycle ◽  
Laboratory Study ◽  
Oil Recovery ◽  
Abrasion Resistance ◽  
Field Tests ◽  
Current Control ◽  
Control Measures ◽  
Control Technology ◽  
Pumping Wells ◽  
Resistance Performance

The eccentric wear of the sucker rods and tubes has already become the greatest bottleneck restricting the development of oil recovery technology of pumping wells. There is lots of inadaptability of the current control measures. The laboratory study and field tests showed that the NHW-1type coated tubing had a good protection of the rods and tubes of the well pumps. Compared with ordinary tubing, coating can prolong the life cycle of the tubes for more than 2.6 times. At present, the eccentric wear control technology is advanced both at home and abroad.

CFD Study of the Condensation of Water Vapor on the Particles Flow in Rectangular Narrow Channel

2014 ◽  
Author(s):  
Daping Lin ◽  
Tao Zhou ◽  
Xu Yang ◽  
Xiaolu Fang
Keyword(s):  
Phase Transition ◽  
Temperature Field ◽  
Water Vapor ◽  
Liquid Phase ◽  
Liquid Layer ◽  
Rectangular Channel ◽  
Narrow Channel ◽  
Ansys Fluent ◽  
Thermophoretic Force ◽  
Condensation Point

This paper presents a CFD study of the flow and deposition of particles in vapor in a 1000mm by 20mm narrow rectangular channel. The temperature of the wall is set below the condensation point, so the vapor will change into the liquid phase near the wall. The flow and deposition of the particles in the condition when the phase transition of water occurs is simulated by ANSYS Fluent code. The result shows that the condensation of the water vapor will change the temperature field and the velocity of the flow in the channel. The particles will be forced to the wall due to the thermophoretic force. The condensation developing process will enhance the deposition of the particles while the developed liquid layer will stop the particles flow to the wall.

Evaluation and Assessment of Environmentally Sensitive Stream Bank Protection Measures

2016 ◽  
Author(s):  
P. F. Lagasse ◽  
P. E. Clopper ◽  
C. I. Thornton ◽  
F. D. Shields Jr ◽  
J. McCullah ◽  
...  
Keyword(s):  
Protection Measures ◽  
Stream Bank ◽  
Bank Protection ◽  
Environmentally Sensitive ◽  
Evaluation And Assessment

Developing Tactile Maps for Students with Visual Impairments: A Case Study for Customizing Accommodations

2018 ◽  
Vol 112 (2) ◽  
pp. 143-155
Author(s):  
Florian C. Feucht ◽  
Chelsea R. Holmgren
Keyword(s):  
Undergraduate Students ◽  
Low Vision ◽  
Phase 1 ◽  
Field Tests ◽  
Field Testing ◽  
Structured Interviews ◽  
Large Area ◽  
Phase Development ◽  
Tactile Maps ◽  
Phase Process

Introduction The authors of this study evaluated the necessary features of tactile maps to provide independent, efficient, and safe travel across a university campus; and a process for developing tactile maps based on user needs and preferences. Methods Participants who have low vision provided input, through interviews and field tests, regarding which features were critical for a tactile map. The four-phase development and research design process included: phase 1, semi-structured interviews about campus navigation; phase 2, creating draft maps using two different tactile media—microcapsule or braille embossed lines; phase 3, field-testing maps through site visits with participants; and phase 4, finalizing the map. Four undergraduate students with low vision participated in phases 1 and 3 to assess their experiences in navigating a campus; and the collected data were used in phases 2 and 4 to create, revise, and finalize the content, layout, and medium of the map. Results Three of the participants preferred microcapsule lines to braille embossed fines, while one participant stated the usefulness of both media. The four-phase process allowed customization of local maps for individual users. Discussion Map features that contribute to readability and efficacy of use include the medium; the layout; the combination of orientation maps, which provide an “overview” of a large area; and mobility maps, which contain more detail and are designed to help the traveler in unfamiliar areas (James, 1982). Implications for practitioners Colleges and universities should gather data and create tactile campus maps for students with low vision or blindness following the four-phase process used during this study. Although the data show that the map's medium is a matter of personal preference, several features are essential to creating a map with maximum readability.

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