Numerical Study on the Flow Past a Twisted Elliptic Cylinder With Subcritical Reynolds Number

2011 ◽  
Author(s):  
Min Ho Kim ◽  
Jin Woog Lee ◽  
Hyun Sik Yoon ◽  
Man Yeong Ha
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Elliptic Cylinder ◽  
Cross Sectional Area ◽  
Stream Velocity ◽  
Spanwise Direction ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Past ◽  
Smooth Cylinder

Large eddy simulation of flow past a torsional cylinder has been carried out at a Reynolds number of 3900 based on the cylinder diameter and the free stream velocity using finite volume method. The torsional cylinder has been formed by rotating the elliptic cross sectional area along the spanwise direction. For an ellipse, different eccentricities are considered to observe the effect of eccentricity on the flow fields. The excellent comparisons with previous studies for the cases of a smooth cylinder and a wavy cylinder having sinusoidal variation in cross sectional area along the spanwise direction guarantee the accuracy of present numerical methods. The effect of eccentricity on the drag and lift coefficients representing the fluid flow characteristics has been investigated by comparing with those of the smooth cylinder, resulting in enhancement of drag reduction and suppression of vortex-induced vibration. The isosurface of swirling strength has been adopted to identify the vortical structures in the turbulent wake.

scholarly journals Numerical Investigation of a two-inlet PVT air collector

2019 ◽  
Vol 136 ◽  
pp. 05014
Author(s):  
Zhangyang Kang ◽  
Zhaoyang Lu ◽  
Xin Deng ◽  
Qiongqiong Yao
Keyword(s):  
Heat Transfer ◽  
Single Channel ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Thermal Characteristics ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Maximum Heat

A numerical study of heat and mass transfer characteristics of a two-inlet PV/T air collector is performed. The influence of thermal characteristics and efficiency is investigated as the area ratios of inlet and outlet of the single channel with two inlets are changed. The design of the two-inlet PV/T air collector can avoid the poor heat transfer conditions of the single inlet PV/T air collector and improve the total photo-thermal efficiency. When the inlet/outlet cross-sectional area ratio is reduced, the inlet air from the second inlet enhances the convection heat transfer in the second duct and the temperature distribution is more uniform. As the cross-sectional area of the second inlet increase, the maximum heat exchange amount of the two-inlet PV/T air collector occurs between the inlet and outlet cross-sectional area ratio L=0.645 and L=0.562.

scholarly journals Nondimensional translational characteristics of elastomer components

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Andreas Dutzler ◽  
◽  
Christian Buzzi ◽  
Martin Leitner ◽  
◽  
...  
Keyword(s):  
Elastic Properties ◽  
Numerical Study ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Component Size ◽  
Rail Vehicles ◽  
Force Displacement

Elastomer components are used in both primary and secondary spring stages in bogies of rail vehicles. The design of spring components of a bogie requires knowledge of the calculation of the elastic properties of these components. An elastomer spring component is typically analyzed in the dimension to be investigated. Calculated force-displacement curves are directly related to the material and dimension of the component itself. The objective of this paper is to establish generalized or, in other words, universally valid force-displacement characteristics by breaking the entanglement with component size. The advantage of this approach is the extended validity of the results for a specific spring shape of any size. The simulations are performed only once for each shape and may be converted to any other size using the proposed methodology. A numerical study of a layer spring with rectangular cross-sectional area and fixed edges on both top and bottom sides serves as a reference example.

scholarly journals Mass of different snow crystal shapes derived from fall speed measurements

2021 ◽  
Vol 21 (24) ◽  
pp. 18669-18688
Author(s):  
Sandra Vázquez-Martín ◽  
Thomas Kuhn ◽  
Salomon Eliasson
Keyword(s):  
Particle Size ◽  
Reynolds Number ◽  
Empirical Relationship ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Maximum Dimension ◽  
Cross Sectional ◽  
Microphysical Properties ◽  
Ice Particles ◽  
Fall Speed

Abstract. Meteorological forecast and climate models require good knowledge of the microphysical properties of hydrometeors and the atmospheric snow and ice crystals in clouds, for instance, their size, cross-sectional area, shape, mass, and fall speed. Especially shape is an important parameter in that it strongly affects the scattering properties of ice particles and consequently their response to remote sensing techniques. The fall speed and mass of ice particles are other important parameters for both numerical forecast models and the representation of snow and ice clouds in climate models. In the case of fall speed, it is responsible for the rate of removal of ice from these models. The particle mass is a key quantity that connects the cloud microphysical properties to radiative properties. Using an empirical relationship between the dimensionless Reynolds and Best numbers, fall speed and mass can be derived from each other if particle size and cross-sectional area are also known. In this study, ground-based in situ measurements of snow particle microphysical properties are used to analyse mass as a function of shape and the other properties particle size, cross-sectional area, and fall speed. The measurements for this study were done in Kiruna, Sweden, during snowfall seasons of 2014 to 2019 and using the ground-based in situ Dual Ice Crystal Imager (D-ICI) instrument, which takes high-resolution side- and top-view images of natural hydrometeors. From these images, particle size (maximum dimension), cross-sectional area, and fall speed of individual particles are determined. The particles are shape-classified according to the scheme presented in our previous study, in which particles sort into 15 different shape groups depending on their shape and morphology. Particle masses of individual ice particles are estimated from measured particle size, cross-sectional area, and fall speed. The selected dataset covers sizes from about 0.1 to 3.2 mm, fall speeds from 0.1 to 1.6 m s−1, and masses from 0.2 to 450 µg. In our previous study, the fall speed relationships between particle size and cross-sectional area were studied. In this study, the same dataset is used to determine the particle mass, and consequently, the mass relationships between particle size, cross-sectional area, and fall speed are studied for these 15 shape groups. Furthermore, the mass relationships presented in this study are compared with the previous studies. For certain crystal habits, in particular columnar shapes, the maximum dimension is unsuitable for determining Reynolds number. Using a selection of columns, for which the simple geometry allows the verification of an empirical Best-number-to-Reynolds-number relationship, we show that Reynolds number and fall speed are more closely related to the diameter of the basal facet than the maximum dimension. The agreement with the empirical relationship is further improved using a modified Best number, a function of an area ratio based on the falling particle seen in the vertical direction.

Manufacturing Influences on Pressure Losses of Channel Fed Holes

2013 ◽  
Author(s):  
Michael Barringer ◽  
Karen A. Thole ◽  
Vaidyanathan Krishnan ◽  
Evan Landrum
Keyword(s):  
Reynolds Number ◽  
Pressure Loss ◽  
Cross Sectional Area ◽  
Channel Inlet ◽  
Sectional Area ◽  
Exit Hole ◽  
Cross Sectional ◽  
Flow Rates ◽  
Channel Exit ◽  
Loss Coefficients

Variations from manufacturing can influence the overall pressure drop and subsequent flow rates through supply holes in such applications as film-cooling, transpiration cooling, and impingement cooling that are supplied by micro-channels, pipe-flow systems, or secondary air systems. The inability to accurately predict flow rates has profound effects on engine operations. The objective of this study was to investigate the influence of several relevant manufacturing features that might occur for a cooling supply hole being fed by a range of channel configurations. The manufacturing variances included the ratio of hole diameter to channel width, the number of channel feeds (segments), the effect of hole overlap with respect to the channel sidewalls, and channel Reynolds number. Results showed that the friction factors for the typically long channels in this study, were independent of the inlet and exit hole configurations tested. Results also showed that the non-dimensional pressure loss coefficients for the flow passing through the channel inlet holes and through the channel exit holes were found to be independent of the channel flow Reynolds number over the range tested. The geometric scaling ratio of the hole cross-sectional area to the channel cross-sectional area collapsed the pressure loss coefficients the best for both one and two flow segments for both the channel inlet and channel exit hole.

scholarly journals Mass transfer in 3D printed electrolyzers: The importance of inlet effects

2020 ◽  
Author(s):  
Stéphane Weusten ◽  
Luc Murrer ◽  
Matheus de Groot ◽  
John van der Schaaf
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Cross Sectional Area ◽  
Transfer Performance ◽  
Sectional Area ◽  
Entrance Length ◽  
Cross Sectional ◽  
3D Printed ◽  
The Cross

This paper investigates the effect of inlet shape, entrance length and turbulence promoters on mass transfer by using 3D printed electrolyzers. Our results show that the inlet design can promote turbulence and lead to an earlier transition to turbulent flow. The Reynolds number at which the transition occurs can be predicted by the ratio of the cross-sectional area of the inlet to the cross-sectional area of the electrolyzer channel. A longer entrance length results in more laminar behavior and a later transition to turbulent flow. With an entrance length of 550mm, the inlet design did no longer affect the mass transfer performance significantly. The addition of gyroid type turbulence promoters resulted in a factor 2 to 4 increase in mass transfer depending on inlet design, entrance length and the type of promoter. From one configuration to another, there was a minimal variation in pressure drop (<16 mbar).

Manufacturing Influences on Pressure Losses of Channel Fed Holes

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Michael Barringer ◽  
Karen A. Thole ◽  
Vaidyanathan Krishnan ◽  
Evan Landrum
Keyword(s):  
Reynolds Number ◽  
Pressure Loss ◽  
Cross Sectional Area ◽  
Channel Inlet ◽  
Sectional Area ◽  
Exit Hole ◽  
Cross Sectional ◽  
Flow Rates ◽  
Channel Exit ◽  
Loss Coefficients

Variations from manufacturing can influence the overall pressure drop and subsequent flow rates through supply holes in such applications as film-cooling, transpiration cooling, and impingement cooling that are supplied by microchannels, pipe-flow systems, or secondary air systems. The inability to accurately predict flow rates has profound effects on engine operations. The objective of this study was to investigate the influence of several relevant manufacturing features that might occur for a cooling supply hole being fed by a range of channel configurations. The manufacturing variances included the ratio of the hole diameter to the channel width, the number of channel feeds (segments), the effect of hole overlap with respect to the channel sidewalls, and the channel Reynolds number. The results showed that the friction factors for the typically long channels in this study were independent of the tested inlet and exit hole configurations. The results also showed that the nondimensional pressure loss coefficients for the flow passing through the channel inlet holes and through the channel exit holes were found to be independent of the channel flow Reynolds number over the tested range. The geometric scaling ratio of the hole cross-sectional area to the channel cross-sectional area collapsed the pressure loss coefficients the best for both one and two flow segments for both the channel inlet and channel exit hole.

Effects of Masts on the Aerodynamics of Sail Sections

1978 ◽  
Vol 15 (01) ◽  
pp. 35-42
Author(s):  
Jerome H. Milgram
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Limited Range ◽  
Cross Sectional Area ◽  
Water Tunnel ◽  
Two Dimensional ◽  
Sectional Area ◽  
Cross Sectional ◽  
Coefficient Versus

The effects of the addition of masts of varying geometries to two different sail-like two-dimensional airfoil sections were determined by water tunnel tests. Thirteen different mast-sail combinations were tested with four of the sections retested at a different time to confirm repeatability of the data. The results were found to be best presented and best understood by means of graphs of drag coefficient versus lift coefficient for fixed values of d/c(mast diameter/sail chord). The additional drag caused by the addition of a mast was found to be substantial, especially as the ratio d/cbecame relatively large. Results were found to be insensitive to changes in Reynolds number of a factor of two for d/cless than 0.3 for round masts, and 0.2 for elliptical masts (d for an elliptical mast is taken as the diameter of a circle having the same cross-sectional area). Elliptical masts with d/c greater than 0.3 gave results which exhibited a sensitivity to Reynolds number and which, over a limited range of lift coefficients, gave an unexpectedly high value of the ratio of lift coefficient/drag coefficient.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

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