Combined Simultaneous Flow Visualization/Hot-Wire Anemometry for the Study of Turbulent Flows

1980 ◽  
Vol 102 (2) ◽  
pp. 174-182 ◽  
Author(s):  
R. E. Falco
Keyword(s):  
Pressure Gradient ◽  
Flow Visualization ◽  
Turbulent Flows ◽  
Unsteady Flows ◽  
Gradient Flows ◽  
Hot Wire ◽  
Visual Patterns ◽  
Favorable Pressure Gradient ◽  
Hot Wire Anemometry ◽  
Scattering Light

The measurement of coherent motions in turbulent and unsteady flows is discussed. A technique which discriminates these motions based upon the patterns they create by scattering light from a fog of tiny oil drops is described. It is shown that hot-wire anemometry can be used in this oil fog so that hot-wire data can be conditionally sampled to the visual patterns, giving directly interpretable measures of the importance of the selected features. The three-dimensionality of the coherent motions can also be directly accounted for, using mutually orthogonal sheets of light. Results of step flows, and zero and favorable pressure gradient flows are described.

scholarly journals A predictive inner–outer model for streamwise turbulence statistics in wall-bounded flows

2011 ◽  
Vol 681 ◽  
pp. 537-566 ◽  
Author(s):  
ROMAIN MATHIS ◽  
NICHOLAS HUTCHINS ◽  
IVAN MARUSIC
Keyword(s):  
Pressure Gradient ◽  
Turbulent Flows ◽  
Large Scale ◽  
Adverse Pressure Gradient ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
Gradient Flows ◽  
Streamwise Pressure Gradient ◽  
Logarithmic Region ◽  
Inner Region

A model is proposed with which the statistics of the fluctuating streamwise velocity in the inner region of wall-bounded turbulent flows are predicted from a measured large-scale velocity signature from an outer position in the logarithmic region of the flow. Results, including spectra and all moments up to sixth order, are shown and compared to experimental data for zero-pressure-gradient flows over a large range of Reynolds numbers. The model uses universal time-series and constants that were empirically determined from zero-pressure-gradient boundary layer data. In order to test the applicability of these for other flows, the model is also applied to channel, pipe and adverse-pressure-gradient flows. The results support the concept of a universal inner region that is modified through a modulation and superposition of the large-scale outer motions, which are specific to the geometry or imposed streamwise pressure gradient acting on the flow.

PIV Study of Adverse and Favorable Pressure Gradient Turbulent Flows Over Transverse Ribs

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
M. Agelinchaab ◽  
M. F. Tachie
Keyword(s):  
Pressure Gradient ◽  
Turbulent Flows ◽  
Reynolds Shear Stress ◽  
Adverse Pressure Gradient ◽  
Bottom Wall ◽  
Combined Effects ◽  
Mean Flow ◽  
Turbulent Statistics ◽  
Favorable Pressure Gradient ◽  
The Mean

This paper reports an experimental study of the combined effects of rib roughness and pressure gradient on turbulent flows produced in asymmetric converging and diverging channels. Transverse square ribs with pitch-to-height ratio of 4 were attached to the bottom wall of the channel to produce the rib roughness. A particle image velocimetry technique was used to conduct measurements at several streamwise-transverse planes located upstream, within, and downstream of the converging and diverging sections of the channel. From these measurements, the mean velocities and turbulent statistics at the top plane of the ribs and across the channel were obtained. The data revealed non-negligible wall-normal motion and interaction between the cavities and overlying boundary layers. The different drag characteristics of the rough bottom wall and the smooth top wall produced asymmetric distributions of mean velocity and turbulent statistics across the channel. The asymmetry of these profiles is most extreme in the presence of adverse pressure gradient. Because of the manner in which pressure gradient modifies the mean flow and turbulence production, it was found that the streamwise turbulence intensity and Reynolds shear stress in the vicinity of the ribs are lower in the adverse pressure gradient than in the favorable pressure gradient channel. The results show also that the combined effects of rib roughness and adverse pressure gradient on the turbulent intensity statistics are significantly higher than when roughness and adverse pressure gradient are applied in isolation.

scholarly journals Studies on Wake-Disturbed Boundary Layers Under the Influences of Favorable Pressure Gradient and Free-Stream Turbulence: Part II — Effect of Free-Stream Turbulence

1997 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Takashi Kitazawa ◽  
Kazuyuki Koizumi ◽  
Tadashi Tanuma
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Free Stream ◽  
Transition Model ◽  
Hot Wire ◽  
Time Resolved ◽  
Free Stream Turbulence ◽  
Wire Probe ◽  
Favorable Pressure Gradient ◽  
Probe Measurements

This paper, as Part II of the study on wake-disturbed boundary layer, is aimed at investigation of the effects of free-stream turbulence on wake-induced transition of the boundary layer under a favorable pressure gradient. Hot-wire probe measurements are also made on the wake-disturbed boundary layer to obtain ensemble-averaged shape factor contours on the distance-time diagrams. These data are then used to examine how the favorable pressure gradient and the free-stream turbulence affects time-resolved behaviors of the boundary layer subjected to periodic wakes. In addition, likewise in Part I, the heat transfer data are compared with the transition model proposed by Funazaki (1996) in order to check the capability of the model under the favorable pressure gradient as well as the free-stream turbulence.

Quantification of Mixing Performance in Parallel Jets

Volume 4 ◽  
2004 ◽  
Author(s):  
Nathan E. Bunderson ◽  
Barton L. Smith
Keyword(s):  
Flow Visualization ◽  
Momentum Flux ◽  
Width Ratio ◽  
Hot Wire ◽  
Ambient Fluid ◽  
Jet Mixing ◽  
Mixing Performance ◽  
Flux Condition ◽  
Two Component ◽  
Hot Wire Anemometry

Experiments of unvented parallel planar jets having variable slot widths and velocities are presented. A flow visualization study shows that, for sufficiently large spacing, the jets “flap” and that this motion is maximized for a matched exit momentum flux condition. The extent of the jet mixing with the ambient fluid is investigated using two-component hot wire anemometry. It is demonstrated that the flapping increases mixing of the jets with the ambient. In addition, it is shown that the mixing increases with distance between the jets and with jet-width ratio.

scholarly journals Assessment of uncertainties in hot-wire anemometry and oil-film interferometry measurements for wall-bounded turbulent flows

2018 ◽  
Vol 72 ◽  
pp. 57-73 ◽  
Author(s):  
Saleh Rezaeiravesh ◽  
Ricardo Vinuesa ◽  
Mattias Liefvendahl ◽  
Philipp Schlatter
Keyword(s):  
Turbulent Flows ◽  
Hot Wire ◽  
Oil Film ◽  
Hot Wire Anemometry
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