Creation and Maintenance of Cavities Under Horizontal Surfaces in Steady and Gust Flows

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
R. E. A. Arndt ◽  
W. T. Hambleton ◽  
E. Kawakami ◽  
E. L. Amromin
Keyword(s):  
Experimental Data ◽  
Scaling Laws ◽  
Substantial Effect ◽  
Low Flow ◽  
Water Tunnel ◽  
Sectional Area ◽  
Cross Sectional ◽  
Air Supply ◽  
Wide Range ◽  
Flow Speeds

An experimental study of air supply to bottom cavities stabilized within a recess under a horizontal surface has been carried out in a specially designed water tunnel. The air supply necessary for creating and maintaining an air cavity in steady and gust flows has been determined over a wide range of speed. Flux-free ventilated cavitation at low flow speeds has been observed. Stable multiwave cavity forms at subcritical values of Froude number were also observed. It was found that the cross-sectional area of the air supply ducting has a substantial effect on the air demand. Air supply scaling laws were deduced and verified with the experimental data obtained.

scholarly journals Adaptive capacity of 2- to 5-month-old infants to the flow, shape, and flexibility of different teats during bottle feeding: a cross-sectional study

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
M. L. J. Lagarde ◽  
N. van Alfen ◽  
S. A. F. de Groot ◽  
A. C. H. Geurts ◽  
L. van den Engel-Hoek
Keyword(s):  
Cross Sectional Study ◽  
Bottle Feeding ◽  
Low Flow ◽  
Complex Activity ◽  
Cross Sectional ◽  
Feeding Difficulties ◽  
Nutritive Sucking ◽  
Healthy Infants ◽  
Wide Range ◽  
Complex Development

Abstract Background Nutritive sucking is a complex activity, the biomechanical components of which may vary in relation to respiratory phase, swallow-rate per minute, suck-swallow ratio, and swallow non-inspiratory flow (SNIF). Quantitative measurement of these components during nutritive sucking in healthy infants could help us to understand the complex development of sucking, swallowing, and breathing. This is important because the coordination between these components is often disturbed in infants with feeding difficulties. The aims of this study were to describe the biomechanical components of sucking and swallowing in healthy 2- to 5-month-old infants during bottle feeding, to assess whether infants adapt to the characteristics of two different teats, and to determine which independent variables influence the occurrence of SNIF. Methods Submental muscle activity, nasal airflow, and cervical auscultation were evaluated during bottle-feeding with two different teats. Results Sixteen term-born infants (6 boys) aged 2–5 months were included. All infants showed variable inhalation and exhalation after swallowing. The swallow rate per minute was significantly higher when infants fed with a higher flow teat (Philips Avent Natural 2.0™). Infants had suck:swallow ratios ranging from 1:1 to 4:1. A suck:swallow ratio of 1:1 occurred significantly more often when infants fed with a higher flow teat, whereas a suck:swallow ratio of 2:1 occurred significantly more often when infants fed with a low-flow teat (Philips Avent Classic+™). A suck:swallow ratio of 1:1 was negatively correlated with SNIF, whereas a suck:swallow ratio of 2:1 was positively correlated with SNIF. Conclusion Healthy infants aged 2–5 months can adapt to the flow, shape, and flexibility of different teats, showing a wide range of biomechanical and motor adaptations.

scholarly journals Representative subsampling of sedimenting blood

2019 ◽  
Vol 475 (2227) ◽  
pp. 20190223
Author(s):  
Bhargav Rallabandi ◽  
Janine K. Nunes ◽  
Antonio Perazzo ◽  
Sergey Gershtein ◽  
Howard A. Stone
Keyword(s):  
Experimental Data ◽  
Entire Range ◽  
Original Sample ◽  
Sectional Area ◽  
Cross Sectional ◽  
Design Considerations ◽  
Simple Tool ◽  
Sedimentation Model ◽  
Practical Challenge ◽  
Larger Sample

It is often necessary to extract a small amount of a suspension, such as blood, from a larger sample of the same material for the purposes of diagnostics, testing or imaging. A practical challenge is that the cells in blood sediment noticeably on the time scale of a few minutes, making a representative subsampling of the original sample challenging. Guided by experimental data, we develop a Kynch sedimentation model to discuss design considerations that ensure a representative subsampling of blood, from a container of constant cross-sectional area, for the entire range of physiologically relevant hematocrit over a specified time of interest. Additionally, we show that this design may be modified to exploit the sedimentation and perform subsampling to achieve either higher or lower hematocrit relative to that of the original sample. Thus, our method provides a simple tool to either concentrate or dilute small quantities of blood or other sedimenting suspensions.

scholarly journals Numerical Study on the Temperature-Dependent Viscosity Effect on the Strand Shape in Extrusion-Based Additive Manufacturing

2020 ◽  
Vol 4 (2) ◽  
pp. 46 ◽  
Author(s):  
Behrouz Behdani ◽  
Matthew Senter ◽  
Leah Mason ◽  
Ming Leu ◽  
Joontaek Park
Keyword(s):  
Experimental Data ◽  
Additive Manufacturing ◽  
Polylactic Acid ◽  
Extrusion Process ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Cross Sectional ◽  
Dependent Viscosity

A numerical model that incorporates temperature-dependent non-Newtonian viscosity was developed to simulate the extrusion process in extrusion-based additive manufacturing. Agreement with the experimental data was achieved by simulating a polylactic acid melt flow as a non-isothermal power law fluid using experimentally fitted parameters for polylactic acid. The model was used to investigate the temperature effect on the flow behavior, the cross-sectional area, and the uniformity of the extruded strand. OpenFOAM, an open source simulation tool based on the finite volume method, was used to perform the simulations. A computational module for solving the equations of non-isothermal multiphase flows was also developed to simulate the extrusion process under a small gap condition where the gap between the nozzle and the substrate surface is smaller than the nozzle diameter. Comparison of the strand shapes obtained from our model with isothermal Newtonian simulation, and experimental data confirms that our model improves the agreement with the experimental data. The result shows that the cross-sectional area of the extruded strand is sensitive to the temperature-dependent viscosity, especially in the small gap condition which has recently increased in popularity. Our numerical investigation was able to show nozzle temperature effects on the strand shape and surface topography which previously had been investigated and observed empirically only.

A One-Dimensional Numerical Model for the Momentum Exchange in Regenerative Pumps

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Francis J. Quail ◽  
Matthew Stickland ◽  
Armin Baumgartner
Keyword(s):  
Experimental Data ◽  
Low Flow ◽  
Correction Factors ◽  
Momentum Exchange ◽  
Pump Design ◽  
Pump Performance ◽  
One Dimensional ◽  
Geometry Model ◽  
Wide Range ◽  
Dimensional Models

The regenerative pump is a rotor-dynamic turbomachine capable of developing high heads at low flow rates and low specific speeds. In spite of their low efficiency, usually less than 50%, they have found a wide range of applications as compact single-stage pumps with other beneficial features. The potential of a modified regenerative pump design is presented for the consideration of the performance improvements. In this paper the fluid dynamic behavior of the novel design was predicted using a one-dimensional model developed by the authors. Unlike most one-dimensional models previously published for regenerative pumps, the momentum exchange is numerically computed. Previous one-dimensional models relied on experimental data and correction factors; the model presented in this paper demonstrates an accurate prediction of the pump performance characteristics without the need for correction with experimental data. The validity of this approach is highlighted by the comparison of computed and measured results for two different regenerative pump standards. The pump performance is numerically assessed without the need of correction factors or other experimental data. This paper presents an approach for regenerative pumps using a physically valid geometry model and by resolving the circulatory velocity in the peripheral direction.

scholarly journals Downstream Morphologic Characteristics of the Alluvial Section of Lower River Ogun, Nigeria

2015 ◽  
Vol 8 (1-2) ◽  
pp. 1-10 ◽  
Author(s):  
Olutoyin A. Fashae ◽  
Adetoye Faniran
Keyword(s):  
Cross Sections ◽  
Morphological Characteristics ◽  
Scientific Basis ◽  
River Channel ◽  
Cross Sectional Area ◽  
Correlation Technique ◽  
Sectional Area ◽  
Cross Sectional ◽  
Wide Range ◽  
Wetted Perimeter

Abstract Rivers constitute an important focus of attention in surface water studies because of their dynamic nature. Therefore, natural rivers develop a wide range of channel forms whose characteristics vary as a function of the position within the fluvial systems. This study examined the river channel morphologic parameters along the alluvial section of River Ogun in South western Nigeria. Data on the channel morphologic variables were collected through field measurement of the bankfull cross sectional characteristics of the river from where the longitudinal characteristics were defined. 48 cross sections were randomly established at bankfull stage along the river channel stretch of 90 km. Bankfull depth and width at each of the cross sections were determined using sonar (electronic sounding machine) that was mounted to a boat. Velocity was measured with the aid of a current meter, while other morphological parameters were estimated from the field data. Analysis of variance revealed that downstream morphological characteristics of the river varies distinctively at each cross section with bedslope as the most significantly varied among all other morphologic parameters (F=91.18; P=0.00). Pearson product moment correlation technique revealed that bankfull width had a correlation of 0.8 and 0.9 with wetted perimeter and cross sectional area respectively while bankfull depth (maximum) had correlations of 0.9, 0.8 and 0.78 with hydraulic radius, wetted perimeter and cross sectional area respectively. The research also revealed that gradient affects the discharge with a positive correlation of 0.9. The study ascertains the extent of variability in the morphologic characteristic of River Ogun which provides scientific basis for river maintenance and management.

scholarly journals Variability of the Suspended Particle Cross-Sectional Area in the Bohai Sea and Yellow Sea

2019 ◽  
Vol 11 (10) ◽  
pp. 1187 ◽  
Author(s):  
Qiong Tang ◽  
Shengqiang Wang ◽  
Zhongfeng Qiu ◽  
Deyong Sun ◽  
Muhammad Bilal
Keyword(s):  
Optical Properties ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Suspended Particles ◽  
Cross Sectional Area ◽  
The Yellow Sea ◽  
Sectional Area ◽  
Cross Sectional ◽  
The Bohai Sea ◽  
Wide Range

A cross-sectional area (CSA) is a key element in the optical properties of suspended particles. The seasonal evolution of CSA has great potential for use in mapping total suspended particles, and such mapping plays an important role in water quality monitoring. In this study, the spatiotemporal variations in CSA in the Bohai Sea and the Yellow Sea were studied using temperature, salinity and chlorophyll-a data collected by four cruises. The CSA field data covered a wide range of spatiotemporal variabilities in the Bohai Sea and the Yellow Sea. The results revealed that the largest CSA (>2 m−1) was found in the coastal area, while the CSA (≤1 m−1) on the outer shelf was much smaller. Large values of CSA (>15 m−1) were observed in winter, whereas the smallest values of CSA (0~2 m−1) were observed in summer. These results suggest that vertical mixing and ocean stratification might be important physical mechanisms that influences the CSA seasonal distribution in the surface layer. The results also showed that phytoplankton played an important role in the CSA, with an R2 value of 0.601. The seasonal patterns of CSA documented in this study provide a fundamental theory for research on optical properties, mapping transparency, and photosynthetically active radiation.

In Vivo Measurement of the Elasticity and Diameter of the Femoral Artery

1985 ◽  
Vol 26 (6) ◽  
pp. 723-726 ◽  
Author(s):  
T. Christensen ◽  
B. Neubauer
Keyword(s):  
Medical Students ◽  
Femoral Artery ◽  
Significant Positive Correlation ◽  
Significant Rise ◽  
Sectional Area ◽  
Cross Sectional ◽  
In Vivo Measurement ◽  
Individual Variations ◽  
Wide Range

The diameter and the elastic properties of the femoral artery were investigated by means of ultrasound M-mode. The nature of individual variations was determined in 27 medical students at the age of 21–23 years. A significant positive correlation was found between height and increasing arterial cross sectional area. The influence of age upon arterial luminal size and elasticity was estimated in a group of 43 persons with a wide range of age. There was a significant rise in stiffness proportional to age, but none in luminal size.

scholarly journals Caecilian jaw-closing mechanics: integrating two muscle systems

2008 ◽  
Vol 5 (29) ◽  
pp. 1491-1504 ◽  
Author(s):  
Thomas Kleinteich ◽  
Alexander Haas ◽  
Adam P Summers
Keyword(s):  
Bite Force ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Lever Arm ◽  
Mandibular Joint ◽  
Wide Range ◽  
Jaw Joint ◽  
Muscle Groups ◽  
Using Data

Caecilians (Lissamphibia: Gymnophiona) are unique among vertebrates in having two sets of jaw-closing muscles, one on either side of the jaw joint. Using data from high-resolution X-ray radiation computed tomography scans, we modelled the effect of these two muscle groups ( mm. levatores mandibulae and m. interhyoideus posterior ) on bite force over a range of gape angles, employing a simplified lever arm mechanism that takes into account muscle cross-sectional area and fibre angle. Measurements of lever arm lengths, muscle fibre orientations and physiological cross-sectional area of cranial muscles were available from three caecilian species: Ichthyophis cf. kohtaoensis ; Siphonops annulatus ; and Typhlonectes natans . The maximal gape of caecilians is restricted by a critical gape angle above which the mm. levatores mandibulae will open the jaw and destabilize the mandibular joint. The presence of destabilizing forces in the caecilian jaw mechanism may be compensated for by a mandibular joint in that the fossa is wrapped around the condyle to resist dislocation. The caecilian skull is streptostylic; the quadrate–squamosal complex moves with respect to the rest of the skull. This increases the leverage of the jaw-closing muscles. We also demonstrate that the unusual jaw joint requires streptostyly because there is a dorsolateral movement of the quadrate–squamosal complex when the jaw closes. The combination of the two jaw-closing systems results in high bite forces over a wide range of gape angles, an important advantage for generalist feeders such as caecilians. The relative sizes and leverage mechanics of the two closing systems allow one to exert more force when the other has a poor mechanical advantage. This effect is seen in all three species we examined. In the aquatic T. natans , with its less well-roofed skull, there is a larger contribution of the mm. levatores mandibulae to total bite force than in the terrestrial I . cf. kohtaoensis and S. annulatus .

scholarly journals The effect of geometry on the surface waves generated by vertical surface–piercing cylinders with a horizontal velocity

2017 ◽  
Vol 233 (1) ◽  
pp. 14-26 ◽  
Author(s):  
Alexander ST Conway ◽  
Dev Ranmuthugala ◽  
Jonathan R Binns ◽  
Martin Renilson
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Free Surface ◽  
Vertical Surface ◽  
Bluff Bodies ◽  
Sectional Area ◽  
Cross Sectional ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy

Bluff bodies advancing through a free surface at high Froude numbers create intricate flow patterns worth further investigation. An example of such flows includes a submarine operating near the free surface which generally will have one or more masts piercing the free surface. These have the potential to produce large wakes at the surface. This article describes the numerical analysis used to investigate possible design modifications to reduce the wake profile of a singular cylindrical mast piercing the free surface. The large eddy simulation model carried out in OpenFOAM computational fluid dynamics software was validated against experimental data obtained by the authors using tow tank experiments. The modifications included the use of a double mast system based on the cylindrical mast and truncated NACA0012 sections. All configurations were performed with a mast cross-sectional area corresponding to a typical submarine snorkel across speeds ranging from two to eight knots. The plume size and mast drag were recorded, and the results show that a 30% reduction in wake profile can be obtained using a double mast system at speeds around eight knots, while at the lower speeds the benefit is not as significant.

A Statistical Study of Metatarsal Anatomy: Toward the Design of Wide-Range Prosthetic Solutions

2017 ◽  
Vol 11 (3) ◽  
pp. 277-287 ◽  
Author(s):  
Yohann Couqueberg ◽  
Romain Augoyard ◽  
Marc Augoyard ◽  
Valérie Berry-Kromer ◽  
Céline Bouby ◽  
...  
Keyword(s):  
Statistical Study ◽  
Metatarsal Head ◽  
Ct Scans ◽  
Sectional Area ◽  
Bone Area ◽  
Characteristic Parameters ◽  
Linear Measurements ◽  
Cross Sectional ◽  
Wide Range ◽  
The Mean

The aim of the study is to provide some characteristic parameters of the anatomy of metatarsals from computed tomography (CT) scans. These data are important for more anatomical metatarsal head resurfacing prosthesis conception. Measures were performed on 20 CT scans from 17 patients with a mean age of 44.35 ± 15.75 years old. The panel was composed of 40% male and 50% left feet. Measurements were divided in 2 distinct categories: linear measurements with length of metatarsal, head radius and head, and diaphysis and base thicknesses, and cross-sectional area measurements, including cortical and cancellous bone area at 10%, 25%, 50%, 60%, 75%, and 90% of the metatarsal’s length. The results included the mean and SD found for each measured value. This study is the first step toward a better understanding of the metatarsal’s anatomy, so as to design a more anatomical range of metatarsal head resurfacing implants. Levels of Evidence: Level IV

Sign in / Sign up

Export Citation Format

Share Document