Fluid-dynamic characteristics of a bristled wing

2002 ◽  
Vol 205 (17) ◽  
pp. 2737-2744 ◽  
Author(s):  
S. Sunada ◽  
H. Takashima ◽  
T. Hattori ◽  
K. Yasuda ◽  
K. Kawachi
Keyword(s):  
Reynolds Number ◽  
Rotational Motion ◽  
Fluid Dynamic ◽  
Angular Acceleration ◽  
Constant Angular Velocity ◽  
Forward Motion ◽  
Motion Patterns ◽  
Dynamic Forces ◽  
Mechanical Models ◽  
Translational Acceleration

SUMMARYThrips fly at a chord-based Reynolds number of approximately 10 using bristled rather than solid wings. We tested two dynamically scaled mechanical models of a thrips forewing. In the bristled design, cylindrical rods model the bristles of the forewing; the solid design was identical to the bristled one in shape, but the spaces between the `bristles' were filled in by membrane. We studied four different motion patterns: (i) forward motion at a constant forward velocity, (ii) forward motion at a translational acceleration, (iii) rotational motion at a constant angular velocity and (iv)rotational motion at an angular acceleration. Fluid-dynamic forces acting on the bristled model wing were a little smaller than those on the solid wing. Therefore, the bristled wing of a thrips cannot be explained in terms of increased fluid-dynamic forces.

Experiments on the lift and drag of spheres suspended in a Poiseuille flow

1964 ◽  
Vol 20 (3) ◽  
pp. 513-527 ◽  
Author(s):  
R. Eichhorn ◽  
S. Small
Keyword(s):  
Reynolds Number ◽  
Poiseuille Flow ◽  
Rotation Speed ◽  
Fluid Dynamic ◽  
Particle Diameter ◽  
Dynamic Forces ◽  
Shear Parameter ◽  
Fluid Properties ◽  
Approach Velocity ◽  
Lift And Drag

An experimental investigation of the fluid dynamic forces on spheres suspended in a Poiseuille flow was performed. Small spheres of polystyrene, nylon, and Lucite, having diameters ranging from 0.061 in. to 0.126 in. were suspended in Poiseuille flows in a 0.419 in. diameter tube. Variations in particle size and density, the fluid properties, and the angle of inclination of the tube, resulted in a sphere Reynolds number (based on particle diameter and approach velocity) ranging from 80 to 250. The results are presented as curves which include the coefficients of lift and drag, and the dimensionless rotation speed plotted versus Reynolds number and a dimensionless shear parameter.

K-1229 Turbulence-Induced Fluid Dynamic Forces Acting on Cross-Shaped Tube Bundle in Cross Flow : Part 2 : Measurement in the High Reynolds Number

2001 ◽  
Vol V.01.1 (0) ◽  
pp. 139-140
Author(s):  
Takashi NISHIHARA ◽  
Nobukazu TANAKA ◽  
Fumio INADA ◽  
Akira YASUO ◽  
Shinichi KAWAMURA ◽  
...  
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Tube Bundle ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Shaped Tube ◽  
Dynamic Forces ◽  
Flow Part ◽  
High Reynolds

Numerical Study on Flow around Three Circular Piers in Tandem Arrangement at a Supercritical Reynolds Number

2012 ◽  
Vol 170-173 ◽  
pp. 1932-1937
Author(s):  
Peng Hao ◽  
Guo Dong Li ◽  
Lan Yang ◽  
Gang Chen
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Two Dimensional ◽  
Lateral Loads ◽  
Dynamic Design ◽  
Tandem Arrangement ◽  
Dynamic Forces ◽  
Les Model ◽  
Supporting Structures

As the support structures of building for crossing river, piers of bridge and/or aqueduct are generally arranged in tandem along the river direction, the fluid dynamic forces are main lateral loads acting on the Piers. Two-dimensional fluid computations have been performed using LES model to investigate the flows around three circular piers in tandem arrangements at a supercritical Reynolds number, Re =8.76×106. Both center-to-center spaces are L/D=2.6. The flows and fluid-dynamic forces obtained from the simulations are analyzed. The results can provide the basis for the dynamic design of the supporting structures of the aqueducts.

High-Resolution Numerical Simulation of Low Reynolds Number Incompressible Flow About Two Cylinders in Tandem

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Sintu Singha ◽  
K. P. Sinhamahapatra
Keyword(s):  
Reynolds Number ◽  
Incompressible Flows ◽  
Fluid Dynamic ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Dynamic Forces ◽  
Low Reynolds ◽  
Volume Method ◽  
Global Parameters

Low Reynolds number steady and unsteady incompressible flows over two circular cylinders in tandem are numerically simulated for a range of Reynolds numbers with varying gap size. The governing equations are solved on an unstructured collocated mesh using a second-order implicit finite volume method. The effects of the gap and Reynolds number on the vortex structure of the wake and on the fluid dynamic forces acting on the cylinders are reported and discussed. Both the parameters have significant influence on the flow field. An attempt is made to unify their influence on some global parameters.

The Effect of Track-Seeking Motion on Off-Track Vibrations of the Head Gimbal Assembly in HDDs

2017 ◽  
Author(s):  
Guoqing Zhang ◽  
Hui Li ◽  
Shengnan Shen ◽  
Tan Trinh ◽  
Frank E. Talke ◽  
...  
Keyword(s):  
Fluid Dynamic ◽  
Angular Acceleration ◽  
Sinusoidal Wave ◽  
Interaction Method ◽  
Square Wave ◽  
Structure Interaction ◽  
Head Gimbal Assembly ◽  
Head Positioning ◽  
Mesh Method ◽  
Simulation Results

The effect of track-seeking on off-track residual vibrations of the head-gimbal assembly (HGA) is investigated for air and helium environments using the so-called “fluid dynamic mesh” method and the “fluid-structure interaction” method. Three different angular acceleration profiles (square wave, triangular wave and sinusoidal wave) are investigated as a function of seek time (10 ms and 5 ms). Results show that smoothening of sharp transitions of the seek profile improves the performance of off-track residual vibrations during track-following and shortens the track-following time of the head positioning servo system. In addition, the effect of lateral flow (windage) on off-track residual vibrations during track-following must be considered for a square wave angular acceleration profile. Simulation results show that helium improves the track-following accuracy compared to air due to the lower windage forces acting on the HGA. We observe that the sinusoidal wave angular acceleration performs best among the three angular acceleration profiles investigated. Furthermore, seek time is found to have only a small effect on off-track residual vibrations during track-following.

Low Pressure Turbine Lapse Rate Study: CFD Model vs. Rig Data

2002 ◽  
Author(s):  
J.-S. Liu ◽  
M. L. Celestina ◽  
G. B. Heitland ◽  
D. B. Bush ◽  
M. L. Mansour ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Fluid Dynamic ◽  
Low Reynolds Number ◽  
Low Pressure ◽  
Lapse Rate ◽  
Bypass Transition ◽  
Blade Row ◽  
Low Reynolds ◽  
Lp Turbine

As an aircraft engine operates from sea level take-off (SLTO) to altitude cruise, the low pressure (LP) turbine Reynolds number decreases. As Reynolds number is reduced the condition of the airfoil boundary layer shifts from bypass transition to separated flow transition. This can result in a significant loss. The LP turbine performance fall-off from SLTO to altitude cruise, due to the loss increase with reduction in Reynolds number, is referred to as a lapse rate. A considerable amount of research in recent years has been focused on understanding and reducing the loss associated with the low Reynolds number operation. A recent 3-1/2 stage LP turbine design completed a component rig test program at Honeywell. The turbine rig test included Reynolds number variation from SLTO to altitude cruise conditions. While the rig test provides detailed inlet and exit condition measurements, the individual blade row effects are not available. Multi-blade row computational fluid dynamics (CFD) analysis is used to complement the rig data by providing detailed flow field information through each blade row. A multi-blade row APNASA model was developed and solutions were obtained at the SLTO and altitude cruise rig conditions. The APNASA model predicts the SLTO to altitude lapse rate within 0.2 point compared to the rig data. The global agreement verifies the modeling approach and provides a high confidence level in the blade row flow field predictions. Additional Reynolds number investigation with APNASA will provide guidance in the LP turbine Reynolds number research areas to reduce lapse rate. To accurately predict the low Reynolds number flow in the LP turbine is a challenging task for any computational fluid dynamic (CFD) code. The purpose of this study is to evaluate the capability of a CFD code, APNASA, to predict the sensitivity of the Reynolds number in LP turbines.

scholarly journals Hemodynamics in the retinal vasculature during the progression of diabetic retinopathy

2017 ◽  
Vol 1 (4) ◽  
pp. 6-15
Author(s):  
Francesco Calivá ◽  
Georgios Leontidis ◽  
Piotr Chudzik ◽  
Andrew Hunter ◽  
Luca Antiga ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Blood Flow ◽  
Diabetic Retinopathy ◽  
Fluid Dynamic ◽  
First Year ◽  
Retinal Vasculature ◽  
Fundus Images ◽  
Parent Vessel ◽  
Last Stage ◽  
Vascular Trees

Purpose: In this study, it is shown that hemodynamic features are applicable as biomarkers to evaluate the progression of diabetic retinopathy (DR). Methods: Ninety-six fundus images from twenty-four subjects were selected. For each patient, four photographs were captured during the three years before DR and in the first year of DR. The vascular trees, which consisted of a parent vessel and two child branches were extracted, and at the branching nodes, the fluid dynamic conditions were estimated. Results: Veins were mostly affected during the last stage of diabetes before DR. In the arteries, the blood flow in both child branches and the Reynolds number in the smaller child branch were mostly affected. Conclusion: This study showed that hemodynamic features can add further information to the study of the progression of DR.

Direct Measurement of Unsteady Fluid Dynamic Forces for a Hovering Dragonfly

AIAA Journal ◽  
2005 ◽  
Vol 43 (12) ◽  
pp. 2475-2480 ◽  
Author(s):  
Manabu Yamamoto ◽  
Koji Isogai
Keyword(s):  
Direct Measurement ◽  
Fluid Dynamic ◽  
Dynamic Forces ◽  
Unsteady Fluid

scholarly journals Flow reduces the amplitude and increases the frequency of lymphatic vasomotion: role of endothelial prostanoids

1999 ◽  
Vol 277 (6) ◽  
pp. R1683-R1689 ◽  
Author(s):  
Akos Koller ◽  
Risuke Mizuno ◽  
Gabor Kaley
Keyword(s):  
Fluid Dynamic ◽  
Intraluminal Pressure ◽  
Perfusate Flow ◽  
Intrinsic Mechanism ◽  
Dynamic Forces ◽  
The Difference ◽  
Induced Changes ◽  
Afferent Lymph ◽  
Oxide Synthase

Fluid dynamic forces have substantial effects on the movement of lymph and activity of lymph vessels. The effect of increases in intraluminal flow on spontaneous pumping activity of isolated collecting lymphatics has not yet been characterized in a condition in which the intraluminal pressure is constant. Thus, in afferent lymph microvessels isolated from rat iliac lymph nodes, changes in maximum (Dmax) and minimum (Dmin) diameter to increases in perfusate flow were investigated in the presence of a constant perfusion pressure of 6 cmH2O. Intraluminal flow was elicited by increases in the difference between outflow and inflow pressures (Pdiff, from 0 to 6 cmH2O). Diameters were measured by videomicroscopy. In response to increases in perfusate flow, Dmax and Dmin of lymphatics decreased from 157.5 ± 6.1 to 90.9 ± 5.6 μm and from 91.9 ± 5.3 to 66.3 ± 3.6 μm, respectively, whereas vasomotion frequency increased from 18.0 ± 0.7 min−1 to 23.4 ± 1.1 min−1 (at Pdiff of 4 cmH2O). Removal of extracellular Ca2+ abolished spontaneous diameter oscillations; under these conditions the passive diameter of lymphatics was 216.0 ± 7.1 μm and did not change in response to increases in perfusion. In the absence of endothelium, flow-induced changes in Dmax, Dmin, and oscillation frequency were eliminated. N ω-nitro-l-arginine methyl ester, an inhibitor of nitric oxide synthase, did not affect flow-induced changes in diameter of lymphatics. In contrast, indomethacin, an inhibitor of prostaglandin synthesis, or SQ-29,548, a PGH2/thromboxane A2(PGH2/TxA2) receptor blocker, inhibited the perfusion-induced reduction of Dmax and Dmin of lymphatics and also the increase in the frequency of vasomotion. These findings suggest that the sensitivity of lymphatic endothelium to increases in intraluminal flow could provide an important local intrinsic mechanism for the control of lymphatic resistance by release of constrictor prostanoids PGH2/TxA2.

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