Low reynolds number motion of two drops submerged in an unbounded arbitrary velocity field

1978 ◽  
Vol 4 (1) ◽  
pp. 1-17 ◽  
Author(s):  
G. Hetsroni ◽  
S. Haber
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Low Reynolds Number ◽  
Low Reynolds ◽  
Arbitrary Velocity

Vortex Shedding Analysis in the Wake of a Flat Plate at Low Incidence and Low Reynolds Number

2021 ◽  
Author(s):  
Bastav Borah ◽  
Anand Verma ◽  
Vinayak Kulkarni ◽  
Ujjwal K. Saha
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Flat Plate ◽  
Vortex Shedding ◽  
Low Reynolds Number ◽  
General Tendency ◽  
Flat Plates ◽  
Trailing Edge ◽  
Low Reynolds ◽  
Low Incidence

Abstract Vortex shedding phenomenon leads to a number of different features such as flow induced vibrations, fluid mixing, heat transfer and noise generation. With respect to aerodynamic application, the intensity of vortex shedding and the size of vortices play an essential role in the generation of lift and drag forces on an airfoil. The flat plates are known to have a better lift-to-drag ratio than conventional airfoils at low Reynolds number (Re). A better understanding of the shedding behavior will help aerodynamicists to implement flat plates at low Re specific applications such as fixed-wing micro air vehicle (MAV). In the present study, the shedding of vortices in the wake of a flat plate at low incidence has been studied experimentally in a low-speed subsonic wind tunnel at a Re of 5 × 104. The velocity field in the wake of the plate is measured using a hot wire anemometer. These measurements are taken at specific points in the wake across the flow direction and above the suction side of the flat plate. The velocity field is found to oscillate with one dominant frequency of fluctuation. The Strouhal number (St), calculated from this frequency, is computed for different angles of attack (AoA). The shedding frequency of vortices from the trailing edge of the flat plate has a general tendency to increase with AoA. In this paper, the generation and subsequent shedding of leading edge and trailing edge vortices in the wake of a flat plate are discussed.

scholarly journals Microscopic velocity field measurements inside a regular porous medium adjacent to a low Reynolds number channel flow

2019 ◽  
Vol 31 (4) ◽  
pp. 042001 ◽  
Author(s):  
A. Terzis ◽  
I. Zarikos ◽  
K. Weishaupt ◽  
G. Yang ◽  
X. Chu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Porous Medium ◽  
Velocity Field ◽  
Channel Flow ◽  
Low Reynolds Number ◽  
Field Measurements ◽  
Low Reynolds

The unsteady force on a body at low Reynolds number; the axisymmetric motion of a spheroid

1988 ◽  
Vol 189 ◽  
pp. 463-489 ◽  
Author(s):  
C. J. Lawrence ◽  
S. Weinbaum
Keyword(s):  
Reynolds Number ◽  
Exact Solutions ◽  
Stokes Flow ◽  
High Frequency ◽  
Low Reynolds Number ◽  
Frequency Parameter ◽  
Inverse Laplace Transform ◽  
Fourth Term ◽  
Low Reynolds ◽  
Arbitrary Velocity

In a recent paper by Lawrence & Weinbaum (1986) an unexpected new behaviour was discovered for a nearly spherical body executing harmonic oscillations in unsteady Stokes flow. The force was not a simple quadratic function in half-integer powers of the frequency parameter λ2 = −ia2ω/ν, as in the classical solution of Stokes (1851) for a sphere, and the force for an arbitrary velocity U(t) contained a new memory integral whose kernel differed from the classical t−½ behaviour derived by Basset (1888) for a sphere. A more general analysis of the unsteady Stokes equations is presented herein for the axisymmetric flow past a spheroidal body to elucidate the behaviour of the force at arbitrary aspect ratio. Perturbation solutions in the frequency parameter λ are first obtained for a spheroid in the limit of low- and high-frequency oscillations. These solutions show that in contrast to a sphere the first order corrections for the component of the drag force that is proportional to the first power of λ exhibit a different behaviour in the extreme cases of the steady Stokes flow and inviscid limits. Exact solutions are presented for the middle frequency range in terms of spheroidal wave functions and these results are interpreted in terms of the analytic solutions for the asymptotic behaviour. It is shown that the force on a body can be represented in terms of four contributions; the classical Stokes and virtual mass forces; a newly defined generalized Basset force proportional to λ whose coefficient is a function of body geometry derived from the perturbation solution for high frequency; and a fourth term which combines frequency and geometry in a more general way. In view of the complexity of this fourth term, a relatively simple correlation is proposed which provides good accuracy for all aspect ratios in the range 0.1 < b/a < 10 where exact solutions were calculated and for all values of λ. Furthermore, the correlation has a simple inverse Laplace transform, so that the force may be found for an arbitrary velocity U(t) of the spheroid. The new fourth term transforms to a memory integral whose kernel is either bounded or has a weaker singularity than the t−½ behaviour of the Basset memory integral. These results are used to propose an approximate functional form for the force on an arbitrary body in unsteady motion at low Reynolds number.

Characterization of Low Reynolds Number Wind Turbine Aerodynamics by BEM Theory and PIV Measurements

2010 ◽  
Author(s):  
A. Villegas Vaquero ◽  
Y. Cheng ◽  
V. del Campo ◽  
F. J. Di´ez
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Wind Turbine ◽  
Low Reynolds Number ◽  
Water Channel ◽  
Horizontal Axis Wind Turbine ◽  
Thrust Coefficient ◽  
Wind Turbine Aerodynamics ◽  
Image Velocimetry ◽  
Low Reynolds

In this study, low Reynolds number wind turbine aerodynamics was considered. The overall goal was to characterize the flow in order to optimize the power output of the system. First, BEMT theory (Blade Element Momentum Theory) was formulated for this flow where Prandtl’s tip- and hub-loss corrections were included, as well as Glauert’s thrust coefficient correction. The theory was validated with experimental data from National Renewable Energy Laboratory (NREL) for larger scale wind turbines. Also, a physical model of a low Reynolds number horizontal-axis wind turbine (HAWT) was built. Particle Image Velocimetry (PIV) was used to calculate the velocity field around the HAWT. This allowed for planar measurements of the velocity field at different location in the wake of the rotor. The measurements were performed in a water channel allowing for better control of PIV seeding and improved flow visualization. PIV results allowed observation of the velocity field and vorticity field in the wake of the rotor. This data is currently being compared to BEMT theory suggesting good agreement.

Experimental Investigation on Blunt-Edged UTM Delta Wing VFE-2 Configurations at Low Reynolds Number

2018 ◽  
Vol 12 (3) ◽  
pp. 255
Author(s):  
Muhammad Zal Aminullah Daman Huri ◽  
Shabudin Bin Mat ◽  
Mazuriah Said ◽  
Shuhaimi Mansor ◽  
Md. Nizam Dahalan ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Delta Wing ◽  
Low Reynolds Number ◽  
Low Reynolds
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