Ventilated Flow in the Unobstructed Space Between Corotating Disks in a Cylindrical Enclosure

1993 ◽  
Vol 115 (3) ◽  
pp. 398-407 ◽  
Author(s):  
D. Gor ◽  
J. A. C. Humphrey ◽  
R. Greif
Keyword(s):  
Flow Characteristics ◽  
Laser Doppler Velocimeter ◽  
Radial Coordinate ◽  
Time Resolved ◽  
Fundamental Interest ◽  
Axial Coordinate ◽  
Disk Storage ◽  
Ventilation Condition ◽  
Potential Impact ◽  
Improved Design

An experimental investigation has been performed for the ventilated flow of air in the unobstructed space between the center pair of four disks corotating in a fixed cylindrical enclosure. This configuration is of fundamental interest and considerable practical utility in the computer industry. Time-resolved and time-averaged measurements of the circumferential velocity component were obtained using a laser-Doppler velocimeter in back-scatter mode. The data were collected along the radial coordinate direction on the midplane between the disks (Z = 0) and along the axial coordinate at two radial locations (R = 0.71 and 0.86). Three values of the Reynolds number (Re = 2.73 × 103, 2.22 × 104, and 2.66 × 105) were investigated for a limited but significant range of the Rossby number (|Ro| < 0.85), including air sucked radially inward (Ro < 0) and air blown radially outward (Ro > 0). The experimental data present a challenging target for numerical procedures purporting to predict this class of flows. In agreement with earlier preliminary calculations performed by Humphrey et al. (1992), the imposition of a radial ventilation condition in the experiments is observed to have a pronounced effect on the inter-disk flow characteristics. However, the predicted results were found to depend strongly on the boundary conditions imposed and present measurements show the importance of knowing these accurately. These and related findings are discussed with special consideration given to their potential impact on the improved design of ventilated disk storage systems.

Ventilated Flow Between Corotating Disks With Large Obstructions in a Fixed Cylindrical Enclosure (Data Bank Contribution)

1994 ◽  
Vol 116 (4) ◽  
pp. 828-834 ◽  
Author(s):  
D. Gor ◽  
J. A. C. Humphrey ◽  
R. Greif
Keyword(s):  
Angular Velocity ◽  
Velocity Component ◽  
Data Bank ◽  
Laser Doppler Velocimeter ◽  
Blockage Ratio ◽  
Time Resolved ◽  
Disk Rotation ◽  
Ventilation Condition ◽  
The Mean ◽  
Flow Case

Time-resolved laser-Doppler velocimeter measurements of the circumferential velocity component were obtained for the flow between the center pair of four disks of common radius R2 corotating at angular velocity Ω in a fixed, cylindrical enclosure. Mean and rms profiles of this velocity component were obtained for two disk rotation speeds (300 and 3600 rpm), two relatively thick tapered obstructions (long and short) placed radially inward midway between each pair of disks, and three ventilation conditions (unventilated, blowing, and sucking) resulting from an imposed inter-disk radial throughflow. The profiles were determined at four circumferential locations downstream of the respective obstructions; radially along the midplane, and axially at selected radial locations. The profiles for the unventilated flow case show that the circumferential component of motion signficantly accelerates near the hub, in the region between the tip of the obstruction and the rotating hub. Elsewhere, this component of motion is significantly decelerated. The presence of ventilation, whether directed radially outward or inward, significantly affects the flow field only in the region immediately around the hub, and far downstream of the obstruction where it increases both the mean and rms velocities. Analysis of the time records suggests that the observed increases in the rms values are due to the circumferentially periodic nature of the radial ventilation condition. These observations are, for the most part, independent of the disk speed of rotation and the length of the obstructions. A comparison of present unventilated flow results with the corresponding results of Usry et al. (1993), who used much thinner obstructions, reveals the extent to which increasing the obstruction blockage ratio induces larger levels of flow unsteadiness.

LDV and PIV Velocity Results in a Thermosiphon

2003 ◽  
Author(s):  
J. Kulman ◽  
D. Gray ◽  
S. Sivanagere ◽  
S. Guffey
Keyword(s):  
Large Scale ◽  
Single Phase ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Flow Patterns ◽  
Laser Doppler Velocimeter ◽  
Mean Velocity ◽  
Developed Turbulence ◽  
The Mean ◽  
Good Agreement

Heat transfer and flow characteristics have been determined for a single-phase rectangular loop thermosiphon. The plane of the loop was vertical, and tests were performed with in-plane tilt angles ranging from 3.6° CW to 4.2° CCW. Velocity profiles were measured in one vertical leg of the loop using both a single-component Laser Doppler Velocimeter (LDV), and a commercial Particle Image Velocimeter (PIV) system. The LDV data and PIV data were found to be in good agreement. The measured average velocities were approximately 2–2.5 cm/s at an average heating rate of 70 W, and were independent of tilt angle. Significant RMS fluctuations of 10–20% of the mean velocity were observed in the test section, in spite of the laminar or transitional Reynolds numbers (order of 700, based on the hydraulic diameter). These fluctuations have been attributed to vortex shedding from the upstream temperature probes and mitre bends, rather than to fully developed turbulence. Animations of the PIV data clearly show these large scale unsteady flow patterns. Multiple steady state flow patterns were not observed.

scholarly journals The Flow Rate Influence on the Interaction of a Radial Pump Impeller and the Diffuser

2004 ◽  
Vol 10 (4) ◽  
pp. 309-317 ◽  
Author(s):  
A. Akhras ◽  
M. El Hajem ◽  
J.-Y. Champagne ◽  
R. Morel
Keyword(s):  
Flow Rate ◽  
Angular Position ◽  
Operating Conditions ◽  
Laser Doppler Velocimeter ◽  
Pump Impeller ◽  
Vaned Diffuser ◽  
Time Resolved ◽  
Flow Investigation ◽  
Rotor Stator Interaction ◽  
Radial Pump

This article presents the results of a detailed flow investigation within a centrifugal pump equipped with a vaned diffuser. The measurements were made with a laser Doppler velocimeter and were carried out at different operating points. The flow was investigated for different rotor–stator relative positions.Unsteady velocity measurements, obtained in phase with the rotor angular position, gave access to the flow inside the impeller channels where three sections were explored. In the diffuser, five sections were studied. Thus, time resolved details of the flow were examined for a better understanding of the complex unsteady flow existing between the two interacting blade rows.Results obtained at different operating conditions show that the rotor-stator interaction is affected by the diffuser position and the flow rate.

scholarly journals A study on intake flow characteristics in a two-cycle engine by a fiber laser Doppler Velocimeter.

1990 ◽  
Vol 56 (521) ◽  
pp. 247-252
Author(s):  
Kihyung LEE ◽  
Yuji IKEDA ◽  
Mitsuyasu HIKOSAKA ◽  
Tsuyoshi NAKAJIMA ◽  
Ryuichi MATSUMOTO ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Flow Characteristics ◽  
Laser Doppler ◽  
Laser Doppler Velocimeter ◽  
Intake Flow

Pressure and Flow Characteristics in a Rotating Two-Pass Square Duct With 45° Angled Ribs

2003 ◽  
Author(s):  
Tong-Miin Liou ◽  
Guang-Yuan Dai
Keyword(s):  
Secondary Flow ◽  
Pressure Coefficient ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Laser Doppler Velocimeter ◽  
Main Stream ◽  
Height Ratio ◽  
Mean Velocity ◽  
Square Duct ◽  
Pressure Transducers

Measurements are presented of the local velocity and wall static-pressure distributions by using laser-Doppler velocimeter and pressure transducers, respectively, in a rotating two-pass square duct with ribs placed on the leading and trailing walls at an angle of 45° to the main stream. The ribs were square in cross-section and in a parallel mode of arrangement. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number Ro ranged from 0 to 0.2. Results are addressed in terms of the evolutions of both main flow and cross-stream secondary flow and the distributions of the pressure coefficient, which are lacking in the published literature for ducts ribbed with 45° ribs and under rotation. In addition, the relationships between the regional averaged Nusselt number, transverse and convective mean velocity component, and turbulent kinetic energy are documented. The 45° ribs are found to reduce the pressure loss to 60% of the 90° ribs for rotating duct under same operating conditions. For CFD reference, the fully developed flow condition is absent for the rotating ducts investigated. The measured evolution of complex secondary flow vortices is believed to be a challenge to numerical simulations.

scholarly journals F-actin Re-organization Mediates Hierarchical Morphogenesis of Swallowtail Butterfly Wing Scale Nanostructures

2020 ◽  
Author(s):  
Kwi Shan Seah ◽  
Vinodkumar Saranathan
Keyword(s):  
Developmental Study ◽  
Butterfly Wing ◽  
Time Resolved ◽  
Fundamental Interest ◽  
Actin Bundles ◽  
Wing Scale ◽  
Nanostructural Organization ◽  
Made In ◽  
Wing Scales

AbstractThe development of color patterning in lepidopteran wings is of fundamental interest in evolution and developmental biology. While significant advances have recently been made in unravelling the cell and molecular basis of lepidopteran pigmentary coloration, the morphogenesis of wing scales, often involved in structural color production, is not well understood. Contemporary research focuses almost exclusively on a few nymphalid model taxa (e.g., Bicyclus, Heliconius), despite an overwhelming diversity across lepidopteran families in the hierarchical nanostructural organization of the scale. Here, we present a time-resolved, comparative developmental study of hierarchical wing scale nanostructure in Parides eurimedes and other papilionid species. Our results uphold the putative conserved role of F-actin bundles in acting as spacers between developing ridges as previously documented in several nymphalid species. While ridges are developing, the plasma membrane manifests irregular crossribs, characteristic of Papilionidae, which delineate the accretion of cuticle into rows of planar disks in between ridges. Once ridges have grown, Arp2/3 appears to re-organize disintegrating F-actin bundles into a reticulate network that supports the extrusion of the membrane underlying the disks into honeycomb-like tubular lattices of air pores in cuticle. Our results uncover a previously undocumented role for F-actin in the morphogenesis of wing scale nanostructures prominently found in Papilionidae. They are also relevant to current challenges in engineering of mesophases, since understanding the diversity and biological basis of hierarchical morphogenesis may offer facile, biomimetic solutions.

scholarly journals PIV measurement of complex flow characteristics in open-cell metal foam replica

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Minsin Kim ◽  
Youngwoo Kim ◽  
Sajjad Hosseini ◽  
Kyung Chun Kim
Keyword(s):  
Reynolds Number ◽  
Metal Foam ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Complex Flow ◽  
Time Resolved ◽  
Open Cell ◽  
Flow Disturbances ◽  
Piv Measurement ◽  
Inlet Conditions

Time-resolved 2-D particle image velocimetry was used to study on turbulent flow characteristics inside an open-cell metal foam under the laminar and turbulent inlet conditions. A study on the effect of Reynolds number was conducted with different three channel Reynolds numbers, 1000, 5000 and 10000. Uniform upstream flow is divided by the pore network of metal foam and it is found that there are flow disturbances induced by metal foam structure even at a laminar inlet condition. It is confirmed that there is a similarity of the preferred flow path flows take regardless of Reynolds number.

Flow Characteristics of a Centrifugal Pump

1994 ◽  
Vol 116 (2) ◽  
pp. 303-309 ◽  
Author(s):  
C. H. Liu ◽  
C. Vafidis ◽  
J. H. Whitelaw
Keyword(s):  
Refractive Index ◽  
Centrifugal Pump ◽  
Radial Flow ◽  
Flow Characteristics ◽  
Secondary Flows ◽  
Laser Doppler Velocimeter ◽  
Suction Surface ◽  
Tip Leakage ◽  
Tip Velocity ◽  
Working Liquid

Measurements of velocity have been obtained in a centrifugal pump in terms of angle-resolved values in the impeller passages, the volute, the inlet and exit ducts and are presented in absolute and relative frames. The pump comprised a radial flow impeller with four backswept blades and a single volute, and the working liquid had the same refractive index as the transparent casing to facilitate the use of a laser-Doppler velocimeter. The flows in the impeller passages were found to depart from the curvature of the blade surfaces at off-design conditions with separation from the suction surface and from the shroud. Secondary flows from the suction to pressure surfaces were dominated by the influences of the relative motion between the shroud and impeller surfaces and the tip leakage. Geometric differences of 0.5 mm and one degree in spacing of the four blades caused differences in passage velocity of up to 6 percent of the impeller tip velocity close to the design flowrate and up to 16 percent at the lowest discharge. The flowrate from each impeller passage varied with volute circumferential position by up to 25 percent at an off-design flowrate. Poor matching of the impeller and volute at off-design conditions caused swirl and separation in the inlet and exit pipes.

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