Numerical study on characteristics of flow and thermal fields of offset cylinder arrays in the middle Reynolds number range

2016 ◽  
Vol 65 ◽  
pp. 69-79 ◽  
Author(s):  
Shao-Dong Zhou ◽  
Guan-Nan Xi
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Number Range ◽  
Thermal Fields ◽  
Cylinder Arrays ◽  
Reynolds Number Range

Study on In-Flow Vibration of Cylinder Arrays Caused by Cross Flow

2011 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Keisuke Nishimura ◽  
Yoshiaki Fujita ◽  
Chihiro Kohara
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Thin Plates ◽  
Streamwise Direction ◽  
Number Range ◽  
Direction Transverse ◽  
Drag Forces ◽  
Cylinder Arrays ◽  
Reynolds Number Range

The authors have studied the in-flow vibration phenomena of cylinder arrays caused by cross-flow in the low Reynolds number range around Re=800. This Reynolds number range has been studied because it is the range where symmetric vortex shedding occurs. This report is our first trial to study the in-line fluidelastic vibration of cylinder arrays. In initial tests, the flow velocity was increased up to the maximum achievable level by the test equipment. However, it was found that the array’s cantilever tube supports resulted in large static tube deflections due to static drag forces. The cylinder array tube supports have therefore been replaced by thin plates supported at both ends. The cylinders are set to be flexible both in the streamwise direction and the direction transverse to the flow. The obtained results of these two patterns are also compared with previous cantilevered data. The origin of the observed vibrations whether a self-induced mechanism or vortex shedding is discussed in detail.

An Experimental and Numerical Study of Flow and Heat Transfer in Channels With Pin Fin-Dimple Combined Arrays of Different Configurations

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Yu Rao ◽  
Chaoyi Wan ◽  
Shusheng Zang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Experimental Conditions ◽  
Number Range ◽  
Pin Fin ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Reynolds Number Range

An experimental and numerical study was conducted to investigate the flow and heat transfer characteristics in channels with pin fin-dimple combined arrays of different configurations, where dimples are located transversely or both transversely and streamwisely between the pin fins. The flow structure, friction factor, and heat transfer characteristics of the pin fin-dimple channels of different configurations have been obtained and compared with each other for the Reynolds number range of 8200–50,500. The experimental study showed that, compared to the pin fin channel, depending on the configurations of the pin fin-dimple combined arrays the pin fin-dimple channel can have distinctively further improved convective heat transfer performance by 8.0%–20.0%, whereas lower or slightly higher friction factors over the studied Reynolds number range. Furthermore, three-dimensional and steady-state conjugate computations have been carried out for similar experimental conditions. The numerical computations showed detailed characteristics of the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the pressure loss and heat transfer characteristics in the pin fin-dimple channels of different configurations.

Influence of tubercles’ spanwise distribution on swept wings for unmanned aerial vehicles

2020 ◽  
pp. 095441002091958
Author(s):  
Charalampos Papadopoulos ◽  
Vasilis Katsiadramis ◽  
Kyros Yakinthos
Keyword(s):  
Reynolds Number ◽  
Unmanned Aerial Vehicles ◽  
Numerical Study ◽  
Computational Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Number Range ◽  
Aerial Vehicles ◽  
Reynolds Number Range

In this work, a 3D numerical study on the influence of the spanwise distribution of tubercles on a unmanned aerial vehicle wing is presented. The idea of using tubercles in aeronautics comes from the humpback whale (Megaptera novaeangliae) which has a characteristic flipper, with a spanwise scalloped leading edge, creating an almost sinusoidal shape, consisting of bumps called tubercles. The whale uses this layout in order to achieve high underwater maneuverability. Early experimental research showed a great potential in enhancing the 3D aerodynamic characteristics of a wing. Most of the existing experimental results concern infinite wings (2D) models and are accompanied with substantial loss in lift and increase in drag in pre-stall region. On the other hand, 3D finite models have displayed a better overall aerodynamic performance (increased lift and moment, but also, decreased drag). At a range of Reynolds number between 500,000 and 1,000,000 (based on the mean chord of the flipper), tubercles act as virtual fences, introducing a pair of counter rotating vortices that delays the stall of the flipper, a phenomenon that the whales exploit to perform sharp turns and catch their prey. The aforementioned Reynolds number range is the same as the operational Reynolds number for typical unmanned aerial vehicles. To assess the influence of the tubercles installation on UAV wings, a full 3D computational study is carried-out with the use of CFD tools which at a first phase are validated and calibrated with the available literature experimental data. Then, computations are performed for different spanwise tubercles distributions. The results show that there is a noticeable potential on controlling the flow on the wings of a UAV operating in a Reynolds number range between 500,000 and 1,000,000 (based on UAV’s wing mean chord), which can lead to an aerodynamic performance and efficiency increase.

scholarly journals Numerical 3D study on the influence of spanwise distribution of tubercles on wings for UAV applications

2019 ◽  
Vol 304 ◽  
pp. 02014
Author(s):  
Charalampos Papadopoulos ◽  
Vasilis Katsiadramis ◽  
Kyros Yakinthos
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Computational Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Number Range ◽  
Reynolds Number Range ◽  
Efficiency Increase ◽  
Sinusoidal Shape

In this work, a 3D numerical study on the influence of the spanwise distribution of tubercles for UAV applications is presented. The idea of using tubercles in aeronautics comes from the humpback whale (Megaptera novaeangliae) which has a characteristic flipper, with a spanwise scalloped leading edge, creating an almost sinusoidal shape, consisting of bumps called tubercles. Early experimental research showed a great potential in enhancing the 3D aerodynamic characteristics of a wing. Most of the existing experimental results concern infinite wings (2D) models and are accompanied with substantial loss in lift and increase in drag in pre–stall region. On the other hand, finite models (3D) have displayed a better overall aerodynamic performance (increased lift and moment, but also decreased drag). At a range of Reynolds number between 500,000 and 1,000,000 (based on the mean chord of the flipper), tubercles act as virtual fences, introducing a pair of counter rotating vortices that delays the stall of the flipper, a phenomenon that the whales use to perform sharp turns and catch their prey. The aforementioned Reynolds number range is the same as the operational Reynolds number for typical Unmanned Aerial Vehicles (UAV). To assess the influence of the tubercles installation on UAV wings, a full 3D computational study is carried-out, with the use of CFD tools that at a first phase are validated and calibrated with available in the literature experimental data. Then, computations are performed, for different spanwise tubercles distributions. The results show that there is a noticeable potential on controlling the flow on the wings of a UAV operating in a Reynolds number range between 500,000 and 1,000,000 (based on UAV’s wing mean chord), which can lead to an aerodynamic performance and efficiency increase.

Vortex shedding from a circular cylinder in moderate-Reynolds-number shear flow

1980 ◽  
Vol 101 (4) ◽  
pp. 721-735 ◽  
Author(s):  
Masaru Kiya ◽  
Hisataka Tamura ◽  
Mikio Arie
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Shear Flow ◽  
Vortex Shedding ◽  
Transverse Velocity ◽  
Number Range ◽  
Uniform Shear ◽  
Reynolds Number Range ◽  
Moderate Reynolds Number ◽  
Shear Parameter

The frequency of vortex shedding from a circular cylinder in a uniform shear flow and the flow patterns around it were experimentally investigated. The Reynolds number Re, which was defined in terms of the cylinder diameter and the approaching velocity at its centre, ranged from 35 to 1500. The shear parameter, which is the transverse velocity gradient of the shear flow non-dimensionalized by the above two quantities, was varied from 0 to 0·25. The critical Reynolds number beyond which vortex shedding from the cylinder occurred was found to be higher than that for a uniform stream and increased approximately linearly with increasing shear parameter when it was larger than about 0·06. In the Reynolds-number range 43 < Re < 220, the vortex shedding disappeared for sufficiently large shear parameters. Moreover, in the Reynolds-number range 100 < Re < 1000, the Strouhal number increased as the shear parameter increased beyond about 0·1.

scholarly journals Asymmetrical Split-and-Recombine Micromixer with Baffles

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 844 ◽  
Author(s):  
Wasim Raza ◽  
Kwang-Yong Kim
Keyword(s):  
Reynolds Number ◽  
Geometrical Parameters ◽  
Mixed Species ◽  
Mixing Index ◽  
Number Range ◽  
Mixing Performance ◽  
Curved Channels ◽  
Advection Diffusion Equation ◽  
Advection Diffusion ◽  
Reynolds Number Range

The present work proposes a planar micromixer design comprising hybrid mixing modules of split-and-recombine units and curved channels with radial baffles. The mixing performance was evaluated numerically by solving the continuity and momentum equations along with the advection-diffusion equation in a Reynolds number range of 0.1–80. The variance of the concentration of the mixed species was considered to quantify the mixing index. The micromixer showed far better mixing performance over whole Reynolds number range than an earlier split-and-recombine micromixer. The mixer achieved mixing indices greater than 90% at Re ≥ 20 and a mixing index of 99.8% at Re = 80. The response of the mixing quality to the change of three geometrical parameters was also studied. A mixing index over 80% was achieved within 63% of the full length at Re = 20.

Study of Flow and Convective Heat Transfer in a Simulated Scaled Up Low Emission Annular Combustor

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Sunil Patil ◽  
Teddy Sedalor ◽  
Danesh Tafti ◽  
Srinath Ekkad ◽  
Yong Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat ◽  
Swirling Flow ◽  
Numerical Study ◽  
Swirl Number ◽  
Maximum Heat ◽  
Number Range ◽  
Maximum Heat Transfer ◽  
Annular Combustor

Modern dry low emissions (DLE) combustors are characterized by highly swirling and expanding flows that makes the convective heat load on the gas side difficult to predict and estimate. A coupled experimental–numerical study of swirling flow inside a DLE annular combustor model is used to determine the distribution of heat transfer on the liner walls. Three different Reynolds numbers are investigated in the range of 210,000–840,000 with a characteristic swirl number of 0.98. The maximum heat transfer coefficient enhancement ratio decreased from 6 to 3.6 as the flow Reynolds number increased from 210,000 to 840,000. This is attributed to a reduction in the normalized turbulent kinetic energy in the impinging shear layer, which is strongly dependent on the swirl number that remains constant at 0.98 for the Reynolds number range investigated. The location of peak heat transfer did not change with the increase in Reynolds number since the flow structures in the combustors did not change with Reynolds number. Results also showed that the heat transfer distributions in the annulus have slightly different characteristics for the concave and convex walls. A modified swirl number accounting for the step expansion ratio is defined to facilitate comparison between the heat transfer characteristics in the annular combustor with previous work in a can combustor. A higher modified swirl number in the annular combustor resulted in higher heat transfer augmentation and a slower decay with Reynolds number.

Sign in / Sign up

Export Citation Format

Share Document