Stokes Flow Characteristics in a Cylindrical Quadrant Duct With Rotating Outer Wall

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Zongyong Wang ◽  
Jiayu Zhao ◽  
Jianhua Wu
Keyword(s):  
Stokes Flow ◽  
Flow Characteristics ◽  
Outer Wall ◽  
Reynolds Numbers ◽  
Creeping Flow ◽  
Low Reynolds Numbers ◽  
Chaotic Flow ◽  
Rotating Wall ◽  
Analytical Results ◽  
Analytical Expressions

The Stokes flow in a cylindrical quadrant duct with a rotating wall was analytically and numerically studied. Based on mathematics and fluid dynamics theory, the analytical expressions of three velocity components were achieved by solving a Poisson's equation and a biharmonic equation. Especially, a closed-form analytical expression of axial velocity was obtained, which can greatly improve the calculating accuracy and speed in analyzing Stokes flow. The velocity distributions for different Reynolds numbers were investigated numerically to insure the accuracy of the analytical results at low Reynolds numbers and to confirm the error range of the analytic results at higher Reynolds numbers. The conclusion indicates that there exists an infinite sequence of eddies that decrease exponentially in size towards the sectorial vertex. The width of the first eddy region reached 99.4% of the sector radius; the sum of the width of other eddies is only 0.6% of the sector radius, which cannot be easily displayed graphically, while the sequence of eddies contributes to form the chaotic flow. The maximum deviations of the velocity components between the analytical results and simulated ones are all less than 1% when Re < 0.1, which verifies the validity and accuracy of the analytical expressions in the creeping flow regime. The analytical expressions are not only suitable for creeping flow but also for laminar flow with smaller Reynolds number (Re < 50).

scholarly journals Hydrodynamic Entrance Length for Laminar Flow in Microchannels with Rectangular Cross Section

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 240
Author(s):  
Germán Ferreira ◽  
Artur Sucena ◽  
Luís L. Ferrás ◽  
Fernando T. Pinho ◽  
Alexandre M. Afonso
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Creeping Flow ◽  
Low Reynolds Numbers ◽  
Viscous Forces ◽  
Aspect Ratios ◽  
Judicious Choice ◽  
Microsystem Design

This work presents a detailed numerical investigation on the required development length (L=L/B) in laminar Newtonian fluid flow in microchannels with rectangular cross section and different aspect ratios (AR). The advent of new microfluidic technologies shifted the practical Reynolds numbers (Re) to the range of unitary (and even lower) orders of magnitude, i.e., creeping flow conditions. Therefore, accurate estimations of L at Re≤O(1) are important for microsystem design. At such low Reynolds numbers, in which inertial forces are less dominant than viscous forces, flow characteristics become necessarily different from those at the macroscale where Re is typically much larger. A judicious choice of mesh refinement and adequate numerical methods allowed obtaining accurate results and a general correlation for estimating L, valid in the ranges 0≤Re≤2000 and 0.1≤AR≤1, thus covering applications in both macro and microfluidics.

Unsteady numerical investigation of two different corrugated airfoils

2016 ◽  
Vol 231 (13) ◽  
pp. 2423-2437 ◽  
Author(s):  
WH Ho ◽  
TH New
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Mean Flow ◽  
Airfoil Surface ◽  
Low Reynolds Numbers ◽  
Corrugated Surfaces ◽  
Large Scale Flow ◽  
Lift And Drag

An unsteady, two-dimensional numerical study was conducted to investigate the aerodynamic and flow characteristics of two bio-inspired corrugated airfoils at Re = 14,000 and compared with those of a smooth NACA0010 airfoil. Mean aerodynamic results reveal that the corrugated airfoils have better lift performance compared to the NACA0010 airfoil but incur slightly higher drag penalty. Mean flow streamlines indicate that this favourable performance is due to the ability of the corrugated airfoils in mitigating large-scale flow separations and stall. Unsteady flow field results show persistent formations of small recirculating vortices that remain within the corrugations at 10° angle-of-attack or less for one of the corrugated airfoil and below 15° for the other. In contrast, the flow behaviour can be highly turbulent with regular pairings of large-scale flow separation vortices along the upper surface at higher angles-of-attack. This not only disrupts the small recirculating vortices and causes them to detach from the corrugated surfaces, but it gets increasingly dominant at higher angles-of-attack resulting in regular lift and drag oscillations. At the end of each cycle, there is a sudden ejection of flow perpendicular to the airfoil surface and these disruptions manifest themselves as “kinks” in the instantaneous lift and drag of the corrugated airfoils. Therefore instead of regular fluctuations, the lift and drag curves have additional undulations. Despite that, the corrugations are able to produce larger pressure differentials between the upper and lower surfaces than the smooth airfoil. The current study demonstrates the intricate relationships between different sharp surface corrugations and favourable aerodynamic performance. In particular, results from this paper supports earlier investigations that corrugated airfoils may be used to good effects even at low Reynolds numbers, where flow separations are more likely.

scholarly journals Numerical study on the flow characteristics of micro air vehicle wings at low Reynolds numbers

2016 ◽  
Vol 8 (1) ◽  
pp. 29-40 ◽  
Author(s):  
Tianhang Xiao ◽  
Zhengzhou Li ◽  
Shuanghou Deng ◽  
Haisong Ang ◽  
Xinchun Zhou
Keyword(s):  
Numerical Study ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Micro Air Vehicle ◽  
Low Reynolds Numbers ◽  
Air Vehicle ◽  
Low Reynolds

scholarly journals Film flow over strongly undulated bottom profiles at low Reynolds numbers - Analytical results

PAMM ◽  
2003 ◽  
Vol 2 (1) ◽  
pp. 330-331
Author(s):  
Markus Scholle ◽  
Andreas Wierschem ◽  
Nuri Aksel
Keyword(s):  
Film Flow ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Analytical Results ◽  
Low Reynolds

scholarly journals A NUMERICAL SCHEME FOR SOLVING CREEPING FLOWS

2003 ◽  
Vol 2 (2) ◽  
Author(s):  
H. A. Navarro ◽  
V. G. Ferreira
Keyword(s):  
Numerical Scheme ◽  
Fluid Flows ◽  
Reynolds Numbers ◽  
Creeping Flow ◽  
Low Reynolds Numbers ◽  
Alternating Direction Implicit ◽  
Alternating Direction ◽  
Creeping Flows ◽  
Adi Schemes ◽  
Adi Scheme

This work shows an extension of the generalized Peaceman and Rachford alternating-direction implicit (ADI) scheme for simulating two-dimensional fluid flows at low Reynolds numbers. The conservation equations are solved in stream function - vorticity formulation. We compare the ADI and generalized ADI schemes, and show that the latter is more efficient to simulate a creeping flow. Numerical results demonstrating the applicability of this technique are also presented.

scholarly journals T-Shaped Control Plate Effect on Flow past a Square Cylinder at Low Reynolds Numbers

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Maryam Shahab ◽  
Shams Ul-Islam ◽  
Ghazala Nazeer
Keyword(s):  
Passive Control ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Square Cylinder ◽  
Optimum Length ◽  
Low Reynolds Numbers ◽  
Fluid Forces ◽  
Drag Forces ◽  
Control Plate ◽  
Low Reynolds

In this study, the influence of the T-shaped control plate on the fluid flow characteristics around a square cylinder for a low Reynolds numbers flow is systematically presented. The introduction of upstream attached T-shaped control plate is novel of its kind as T-shaped control plate used for the first time rather than the other passive control methods available in the literature. The Reynolds numbers (Re) are chosen to be Re = 100, 150, 200, and 250, and the T-shaped control plate of the same width with varying length is considered. A numerical investigation is performed using the single-relaxation-time lattice Boltzmann method. The numerical results reveal that there exists an optimum length of T-shaped control plate for reducing fluid forces. This optimum length was found to be 0.5 for Re = 100, 150, and 200 and 2 for Re = 250. At this optimum length, the fluctuating drag forces acting on the cylinder are reduced by 134%, 1375, 133%, and 136% for Re = 100, 150, 200, and 250, respectively. Instantaneous and time-averaged flow fields were also presented for some selected cases in order to identify the three different flow regimes around T-shaped control plate and square cylinder system.

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