Effect of Jet Oscillation on the Maximum Impingement Plate Skin Friction

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Adam Ritcey ◽  
Joseph R. McDermid ◽  
Samir Ziada
Keyword(s):  
Flow Field ◽  
Skin Friction ◽  
Field Measurements ◽  
Friction Reduction ◽  
Gas Jet ◽  
Impingement Plate ◽  
Image Velocimetry ◽  
Skin Friction Reduction ◽  
Jet Oscillation ◽  
Quiescent Fluid

The maximum impingement plate skin friction and flow field is measured for an acoustically forced planar impinging gas jet using oil film interferometry (OFI) and particle image velocimetry (PIV), respectively. The study is performed at a jet Reynolds number of Rejet = 11,000 and an impingement distance H, which is set to eight times the nozzle width W. The planar impinging gas jet is forced at the jet nozzle exit using Strouhal numbers StH = 0.39, 0.76, and 1.1, which are similar to those associated with the jet-plate tones measured in air-knife wiping experiments. The flow-field measurements indicate that the jet column oscillates at the applied forcing frequency, and depending on the forcing frequency, organized vortex structures can be identified in the shear layers that impinge on the plate surface. Both of these jet oscillation features result in a reduction in the time-averaged maximum impingement plate skin friction. This skin friction reduction is attributed to momentum loss at the jet centerline caused by increased levels of fluid entrainment and mixing of the surrounding quiescent fluid.

scholarly journals 3-dimensional particle image velocimetry based evaluation of turbulent skin-friction reduction by spanwise wall oscillation

2020 ◽  
Vol 32 (8) ◽  
pp. 085111
Author(s):  
Kushal U. Kempaiah ◽  
Fulvio Scarano ◽  
Gerrit E. Elsinga ◽  
Bas W. van Oudheusden ◽  
Leon Bermel
Keyword(s):  
Particle Image Velocimetry ◽  
Skin Friction ◽  
Particle Image ◽  
Friction Reduction ◽  
3 Dimensional ◽  
Image Velocimetry ◽  
Wall Oscillation ◽  
Skin Friction Reduction

scholarly journals Skin Friction Reduction Characteristics of Nonsmooth Surfaces Inspired by the Shapes of Barchan Dunes

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Xiao-wen Song ◽  
Ming-xiao Zhang ◽  
Peng-zhe Lin
Keyword(s):  
Skin Friction ◽  
Friction Reduction ◽  
Test Results ◽  
Image Velocimetry ◽  
New Type ◽  
Barchan Dunes ◽  
Reduction Effect ◽  
Skin Friction Reduction ◽  
Reduction Characteristics ◽  
Reduction Percentage

A new type of nonsmooth surface inspired by the shape of barchan dunes has been proposed and is intended to reduce skin friction, a major cause of overall drag. Simulations were carried out to obtain skin friction reduction characteristics for the nonsmooth surface using the commercial computational fluid dynamics software Fluent. A realizable k-ε model was employed to assess the influence of the nonsmooth structure on turbulent flow and velocity fields. The numerical simulation results showed that the new nonsmooth surface possesses the desired skin friction reduction effect and that the maximum skin friction reduction percentage reached 33.63% at a fluid speed of 30 m/s. Various aspects of the skin friction reduction mechanism were discussed, including the distribution of velocity vectors and shear stress contours and the variations in boundary layer thickness. The accuracy of the flow field for the nonsmooth unit was further verified by particle image velocimetry test results. The new bionic nonsmooth surface, which exceeds the limitations of existing nonsmooth bionic structures, can effectively reduce skin friction and should provide insights into engineering applications in the future.

The Maximum Skin Friction and Flow Field of a Planar Impinging Gas Jet

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Adam Ritcey ◽  
Joseph R. McDermid ◽  
Samir Ziada
Keyword(s):  
Flow Field ◽  
Skin Friction ◽  
Turbulence Intensity ◽  
Reynolds Numbers ◽  
Gas Jet ◽  
Potential Core ◽  
Piv Measurements ◽  
Turbulence Transition ◽  
Image Velocimetry ◽  
Plane Jets

The maximum skin friction and flow field are experimentally measured on a planar impinging gas jet using oil film interferometry (OFI) and particle image velocimetry (PIV), respectively. A jet nozzle width of W = 15 mm, impingement ratios H/W = 4, 6, 8, 10, and a range of jet Reynolds numbers Rejet = 11,000–40,000 are tested to provide a parametric map of the maximum skin friction. The maximum skin friction predictions of Phares et al. (2000, “The Wall Shear Stress Produced by the Normal Impingement of a Jet on a Flat Surface,” J. Fluid Mech., 418, pp. 351–375) for plane jets agree within 5% of the current OFI results for H/W = 6, but deviates upward of 28% for other impingement ratios. The maximum skin friction is found to be less sensitive to changes in the impingement ratio when the jet standoff distance is roughly within the potential core length of the jet. PIV measurements show turbulence transition locations moving toward the nozzle exit with increasing Reynolds number, saturation in the downstream evolution of the maximum axial turbulence intensity before reaching a maximum peak upon impingement, followed by sudden damping at the plate surface. As the flow is redirected, there is an orthogonal redistribution of the fluctuating velocity components, and local peaks in both the axial and transverse turbulence intensity distributions at the plate locations of the maximum skin friction.

Endoscopic 2D particle image velocimetry (PIV) flow field measurements in IC engines

2002 ◽  
Vol 33 (6) ◽  
pp. 794-800 ◽  
Author(s):  
U. Dierksheide ◽  
P. Meyer ◽  
T. Hovestadt ◽  
W. Hentschel
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Particle Image ◽  
Field Measurements ◽  
Image Velocimetry ◽  
Ic Engines

Application of Air Microblowing Through a Porous Wall for Skin Friction Reduction on a Flat Plate

2010 ◽  
Vol 5 (3) ◽  
pp. 38-46
Author(s):  
Vladimir I. Kornilov ◽  
Andrey V. Boiko
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Skin Friction ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Porous Wall ◽  
Friction Reduction ◽  
Local Skin ◽  
Skin Friction Reduction

The effect of air microblowing through a porous wall on the properties of a turbulent boundary layer formed on a flat plate in an incompressible flow is studied experimentally. The Reynolds number based on the momentum thickness of the boundary layer in front of the porous insert is 3 900. The mass flow rate of the blowing air per unit area was varied within Q = 0−0.0488 кg/s/m2 . A consistent decrease in local skin friction, reaching up to 45−47 %, is observed to occur at the maximal blowing air mass flow rate studied.

Multiple slot skin friction reduction

1975 ◽  
Vol 12 (9) ◽  
pp. 753-754 ◽  
Author(s):  
F. G. Howard ◽  
J. N. Hefner ◽  
A. J. Srokowski
Keyword(s):  
Skin Friction ◽  
Friction Reduction ◽  
Skin Friction Reduction

Skin friction reduction by large air bubbles in a horizontal channel flow

2007 ◽  
Vol 33 (2) ◽  
pp. 147-163 ◽  
Author(s):  
Yuichi Murai ◽  
Hiroshi Fukuda ◽  
Yoshihiko Oishi ◽  
Yoshiaki Kodama ◽  
Fujio Yamamoto
Keyword(s):  
Skin Friction ◽  
Channel Flow ◽  
Friction Reduction ◽  
Horizontal Channel ◽  
Air Bubbles ◽  
Skin Friction Reduction

Proposal of control laws for turbulent skin friction reduction based on resolvent analysis

2019 ◽  
Vol 866 ◽  
pp. 810-840 ◽  
Author(s):  
Aika Kawagoe ◽  
Satoshi Nakashima ◽  
Mitul Luhar ◽  
Koji Fukagata
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Drag Reduction ◽  
Skin Friction ◽  
Friction Reduction ◽  
Suboptimal Control ◽  
Spectral Space ◽  
Control Laws ◽  
Wall Shear ◽  
Skin Friction Reduction

This paper evaluates and modifies the so-called suboptimal control technique for turbulent skin friction reduction through a combination of low-order modelling and direct numerical simulation (DNS). In a previous study, Nakashima et al. (J. Fluid Mech., vol. 828, 2017, pp. 496–526) employed resolvent analysis to show that the efficacy of suboptimal control was mixed across spectral space when the streamwise wall shear stress (case ST) was used as a sensor signal, i.e. specific regions of spectral space showed drag increment. This observation suggests that drag reduction may be attained if control is applied selectively in spectral space. DNS results presented in the present study, however, do not show a significant effect on the flow with selective control. A posteriori analyses attribute this lack of efficacy to a much lower actuation amplitude in the simulations compared to model assumptions. Building on these observations, resolvent analysis is used to design and provide a preliminary assessment of modified control laws that also rely on sensing the streamwise wall shear stress. Control performance is then assessed by means of DNS. The proposed control laws generate as much as $10\,\%$ drag reduction, and these results are broadly consistent with resolvent-based predictions. The physical mechanisms leading to drag reduction are assessed via conditional sampling. It is shown that the new control laws effectively suppress the near-wall quasi-streamwise vortices. A physically intuitive explanation is proposed based on a separate evaluation of clockwise and anticlockwise vortices.

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