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Journal articles on the topic 'Streamwise vorticity and turbulent kinetic energy'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Vergine, Fabrizio, Cody Ground, and Luca Maddalena. "Turbulent kinetic energy decay in supersonic streamwise interacting vortices." Journal of Fluid Mechanics 807 (October 19, 2016): 353–85. http://dx.doi.org/10.1017/jfm.2016.611.

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Only a few fundamental studies on the dynamics and interactions of supersonic streamwise vortices have been conducted so far despite the recognized potential of these structures to enhance supersonic mixing. In an effort to shed light on this largely unexplored field, multiple experimental campaigns were conducted in a Mach 2.5 flow to probe the dynamics of turbulence decay in complex flows originating from selected modes of supersonic streamwise vortex interaction. The first part of the manuscript presents the detailed study of two vortex interaction scenarios: one selected to obtain merging

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2

Anderson, William, Julio M. Barros, Kenneth T. Christensen, and Ankit Awasthi. "Numerical and experimental study of mechanisms responsible for turbulent secondary flows in boundary layer flows over spanwise heterogeneous roughness." Journal of Fluid Mechanics 768 (March 6, 2015): 316–47. http://dx.doi.org/10.1017/jfm.2015.91.

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We study the dynamics of turbulent boundary layer flow over a heterogeneous topography composed of roughness patches exhibiting relatively high and low correlation in the streamwise and spanwise directions, respectively (i.e. the roughness appears as streamwise-aligned ‘strips’). It has been reported that such roughness induces a spanwise-wall normal mean secondary flow in the form of mean streamwise vorticity associated with counter-rotating boundary-layer-scale circulations. Here, we demonstrate that this mean secondary flow is Prandtl’s secondary flow of the second kind, both driven and sus

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3

TEIXEIRA, M. A. C., and S. E. BELCHER. "On the distortion of turbulence by a progressive surface wave." Journal of Fluid Mechanics 458 (May 10, 2002): 229–67. http://dx.doi.org/10.1017/s0022112002007838.

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A rapid-distortion model is developed to investigate the interaction of weak turbulence with a monochromatic irrotational surface water wave. The model is applicable when the orbital velocity of the wave is larger than the turbulence intensity, and when the slope of the wave is sufficiently high that the straining of the turbulence by the wave dominates over the straining of the turbulence by itself. The turbulence suffers two distortions. Firstly, vorticity in the turbulence is modulated by the wave orbital motions, which leads to the streamwise Reynolds stress attaining maxima at the wave cr

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4

SHAH, P. N., P. ATSAVAPRANEE, T. Y. HSU, T. WEI, and J. McHUGH. "Turbulent transport in the core of a trailing half-delta-wing vortex." Journal of Fluid Mechanics 387 (May 25, 1999): 151–75. http://dx.doi.org/10.1017/s0022112099004553.

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The development of a turbulent streamwise vortex core in the wake of a half delta wing has been examined using high-resolution DPIV. The objective of this work was to gain understanding of the transport processes at work a short distance downstream of the wing trailing edge as the wake vortex developed. Experiments were conducted in the Rutgers Free Surface Water Tunnel using an in-house DPIV system. A turbulent streamwise vortex was generated by a half delta wing, with 44 cm chord length and 60° sweep angle, mounted at 30° angle of attack. Reynolds number based on chord length was 65 000. Las

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5

BECH, KNUT H., and HELGE I. ANDERSSON. "Turbulent plane Couette flow subject to strong system rotation." Journal of Fluid Mechanics 347 (September 25, 1997): 289–314. http://dx.doi.org/10.1017/s0022112097006691.

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System rotation is known to substantially affect the mean flow pattern as well as the turbulence structure in rotating channel flows. In a numerical study of plane Couette flow rotating slowly about an axis aligned with the mean vorticity, Bech & Andersson (1996a) found that the turbulence level was damped in the presence of anticyclonic system rotation, in spite of the occurrence of longitudinal counter-rotating roll cells. Moreover, the turbulence anisotropy was practically unaffected by the weak rotation, for which the rotation number Ro, defined as the ratio of twice the imposed angula

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6

Sun, Mingbo, Neil D. Sandham, and Zhiwei Hu. "Turbulence structures and statistics of a supersonic turbulent boundary layer subjected to concave surface curvature." Journal of Fluid Mechanics 865 (February 18, 2019): 60–99. http://dx.doi.org/10.1017/jfm.2019.19.

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Supersonic turbulent flows at Mach 2.7 over concave surfaces for two different radii of curvature were investigated and compared with a flat plate turbulent boundary layer using direct numerical simulations. The streamwise velocity reduces in the outer part of the boundary layer due to compression, while it increases near the wall due to curvature, with a higher shape factor for the concave cases. The near-wall spanwise streak spacing reduces compared to the flat plate, with large-scale streaks and turbulence amplification also observed. Streamwise velocity iso-surfaces and streamlines show th

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7

Liou, T. M., Y. Y. Wu, and Y. Chang. "LDV Measurements of Periodic Fully Developed Main and Secondary Flows in a Channel With Rib-Disturbed Walls." Journal of Fluids Engineering 115, no. 1 (1993): 109–14. http://dx.doi.org/10.1115/1.2910091.

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Laser-Doppler velocimeter measurements of mean velocities, turbulence intensities, and Reynolds stresses are presented for periodic fully developed flows in a channel with square rib-disturbed walls on two opposite sides. Quantities such as the vorticity thickness and turbulent kinetic energy are used to characterize the flow. The investigated flow was periodic in space. The Reynolds number based on the channel hydraulic diameter was 3.3×104. The ratios of pitch to rib-height and rib-height to chamber-height were 10 and 0.133, respectively. Regions where maximum and minimum Reynolds stress and

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8

Bech, Knut H., and Helge I. Andersson. "Secondary flow in weakly rotating turbulent plane Couette flow." Journal of Fluid Mechanics 317 (June 25, 1996): 195–214. http://dx.doi.org/10.1017/s0022112096000729.

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As in the laminar case, the turbulent plane Couette flow is unstable (stable) with respect to roll cell instabilities when the weak background angular velocity Ωk is antiparallel (parallel) to the spanwise mean flow vorticity (-dU/dy)k. The critical value of the rotation number Ro, based on 2Ω and dU/dy of the corresponding laminar flow, was estimated as 0.0002 at a low Reynolds number with fully developed turbulence. Direct numerical simulations were performed for Ro = ±0.01 and compared with earlier results for non-rotating Couette flow. At the low rotation rates considered, both senses of r

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9

Pramanik, Shantanu, and Manab Kumar Das. "Computational study of a turbulent wall jet flow on an oblique surface." International Journal of Numerical Methods for Heat & Fluid Flow 24, no. 2 (2014): 290–324. http://dx.doi.org/10.1108/hff-01-2012-0005.

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Purpose – The purpose of the present study is to investigate the flow and turbulence characteristics of a turbulent wall jet flowing over a surface inclined with the horizontal and to investigate the effect of variation of the angle of inclination of the wall on the flow structure of the wall jet. Design/methodology/approach – The high Reynolds number two-equation κ− model with standard wall function is used as the turbulence model. The Reynolds number considered for the present study is 10,000. The Reynolds averaged Navier-Stokes (RANS) equations are used for predicting the turbulent flow. A

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10

YOU, DONGHYUN, MENG WANG, PARVIZ MOIN, and RAJAT MITTAL. "Large-eddy simulation analysis of mechanisms for viscous losses in a turbomachinery tip-clearance flow." Journal of Fluid Mechanics 586 (August 14, 2007): 177–204. http://dx.doi.org/10.1017/s0022112007006842.

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The tip-leakage flow in a turbomachinery cascade is studied using large-eddy simulation with particular emphasis on understanding the underlying mechanisms for viscous losses in the vicinity of the tip gap. Systematic and detailed analysis of the mean flow field and turbulence statistics has been made in a linear cascade with a moving endwall. Gross features of the tip-leakage vortex, tip-separation vortices, and blade wake have been revealed by investigating their revolutionary trajectories and mean velocity fields. The tip-leakage vortex is identified by regions of significant streamwise vel

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11

Antonia, R. A., and J. Kim. "Low-Reynolds-number effects on near-wall turbulence." Journal of Fluid Mechanics 276 (October 10, 1994): 61–80. http://dx.doi.org/10.1017/s0022112094002466.

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Direct numerical simulations of a fully developed turbulent channel flow for two relatively small values of the Reynolds number are used to examine its influence on various turbulence quantities in the near-wall region. The limiting wall behaviour of these quantities indicates important increases in the r.m.s. value of the wall pressure fluctuations and its derivatives, the r.m.s. streamwise vorticity and in the average energy dissipation rate and the Reynolds shear stress. If the normalization is based on the wall shear stress and the kinematic viscosity, these changes are shown to be consist

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12

Neves, João C., Parviz Moin, and Robert D. Moser. "Effects of convex transverse curvature on wall-bounded turbulence. Part 1. The velocity and vorticity." Journal of Fluid Mechanics 272 (August 10, 1994): 349–82. http://dx.doi.org/10.1017/s0022112094004490.

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Convex transverse curvature effects in wall-bounded turbulent flows are significant if the boundary-layer thickness is large compared to the radius of curvature (large γ = δ/a). The curvature affects the inner part of the flow if a+, the cylinder radius in wall units, is small.Two direct numerical simulations of a model problem approximating axial flow boundary layers on long cylinders were performed for γ = 5 (a+ ≈ 43) and γ = 11 (a+ ≈ 21). Statistical and structural data were extracted from the computed flow fields. The effects of the transverse curvature were identified by comparing the pre

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13

Lee, Moon Joo, John Kim, and Parviz Moin. "Structure of turbulence at high shear rate." Journal of Fluid Mechanics 216 (July 1990): 561–83. http://dx.doi.org/10.1017/s0022112090000532.

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The structure of homogeneous turbulence subject to high shear rate has been investigated by using three-dimensional, time-dependent numerical simulations of the Navier–Stokes equations. The instantaneous velocity fields reveal that a high shear rate produces structures in homogeneous turbulence similar to the ‘streaks’ that are present in the sublayer of wall-bounded turbulent shear flows. Statistical quantities such as the Reynolds stresses are compared with those in the sublayer of a turbulent channel flow at a comparable shear rate made dimensionless by turbulent kinetic energy and its diss

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14

Brinkerhoff, Joshua R., and Metin I. Yaras. "Numerical investigation of the generation and growth of coherent flow structures in a triggered turbulent spot." Journal of Fluid Mechanics 759 (October 23, 2014): 257–94. http://dx.doi.org/10.1017/jfm.2014.538.

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AbstractMultiple mechanisms for the regeneration of hairpin-like coherent flow structures in transitional and turbulent boundary layers have been proposed in the published literature, but a complete understanding of the typical topologies of coherent structures observed in the literature has not yet been achieved. To contribute to this understanding, a numerical study is performed of a turbulent spot triggered in a zero-pressure-gradient laminar boundary layer by a pulsed, transverse jet. Two direct numerical simulations (DNS) capture the growth of the spot into a mature turbulent region conta

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15

Chauhan, Kapil, Jimmy Philip, Charitha M. de Silva, Nicholas Hutchins, and Ivan Marusic. "The turbulent/non-turbulent interface and entrainment in a boundary layer." Journal of Fluid Mechanics 742 (February 21, 2014): 119–51. http://dx.doi.org/10.1017/jfm.2013.641.

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AbstractThe turbulent/non-turbulent interface in a zero-pressure-gradient turbulent boundary layer at high Reynolds number ($\mathit{Re}_\tau =14\, 500$) is examined using particle image velocimetry. An experimental set-up is utilized that employs multiple high-resolution cameras to capture a large field of view that extends $2\delta \times 1.1\delta $ in the streamwise/wall-normal plane with an unprecedented dynamic range. The interface is detected using a criteria of local turbulent kinetic energy and proves to be an effective method for boundary layers. The presence of a turbulent/non-turbu

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16

Wang, G., and D. H. Richter. "Modulation of the turbulence regeneration cycle by inertial particles in planar Couette flow." Journal of Fluid Mechanics 861 (December 28, 2018): 901–29. http://dx.doi.org/10.1017/jfm.2018.936.

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Two-way coupled direct numerical simulations are used to investigate the effects of inertial particles on self-sustained, turbulent coherent structures (i.e. the so-called regeneration cycle) in plane Couette flow at low Reynolds number just above the onset of transition. Tests show two limiting behaviours with increasing particle inertia, similar to the results from previous linear stability analyses: low-inertia particles trigger the laminar-to-turbulent instability whereas high-inertia particles tend to stabilize turbulence due to the extra dissipation induced by particle–fluid coupling. Fu

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17

Hong, Jiarong, Joseph Katz, Charles Meneveau, and Michael P. Schultz. "Coherent structures and associated subgrid-scale energy transfer in a rough-wall turbulent channel flow." Journal of Fluid Mechanics 712 (September 27, 2012): 92–128. http://dx.doi.org/10.1017/jfm.2012.403.

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AbstractThis paper focuses on turbulence structure in a fully developed rough-wall channel flow and its role in subgrid-scale (SGS) energy transfer. Our previous work has shown that eddies of scale comparable to the roughness elements are generated near the wall, and are lifted up rapidly by large-scale coherent structures to flood the flow field well above the roughness sublayer. Utilizing high-resolution and time-resolved particle-image-velocimetry datasets obtained in an optically index-matched facility, we decompose the turbulence into large (${\gt }\lambda $), intermediate ($3\text{{\ndas

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18

Wang, Lei, Jiri Hejcik, and Bengt Sunden. "PIV Measurement of Separated Flow in a Square Channel With Streamwise Periodic Ribs on One Wall." Journal of Fluids Engineering 129, no. 7 (2007): 834–41. http://dx.doi.org/10.1115/1.2742723.

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In this study, particle image velocimetry (PIV) is used to investigate the physical process of separated flow in a square channel roughened with periodically transverse ribs on one wall. The ribs obstruct the channel by 15% of its height and are arranged 12 rib heights apart. The Reynolds number, based on the bulk-mean velocity and the corresponding hydraulic diameter of the channel, is fixed at 22,000. Assuming flow periodicity in the streamwise direction, the investigated domain is between two consecutive ribs. The emphasis of this study is to give some insight into the turbulence mechanism

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19

MELVILLE, W. KENDALL, FABRICE VERON, and CHRISTOPHER J. WHITE. "The velocity field under breaking waves: coherent structures and turbulence." Journal of Fluid Mechanics 454 (March 10, 2002): 203–33. http://dx.doi.org/10.1017/s0022112001007078.

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Digital particle image velocimetry (DPIV) measurements of the velocity field under breaking waves in the laboratory are presented. The region of turbulent fluid directly generated by breaking is too large to be imaged in one video frame and so an ensemble-averaged representation of the flow is built up from a mosaic of image frames. It is found that breaking generates at least one coherent vortex that slowly propagates downstream at a speed consistent with the velocity induced by its image in the free surface. Both the kinetic energy of the flow and the vorticity decay approximately as t−1. Th

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20

Spicer, Preston, and Kimberly Huguenard. "Observations of Near-Surface Mixing Behind a Headland." Journal of Marine Science and Engineering 8, no. 2 (2020): 68. http://dx.doi.org/10.3390/jmse8020068.

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Field observations were collected near the mouth of the Bagaduce River, Maine, in order to understand how complex features affect the intratidal and lateral variability of turbulence and vertical mixing. The Bagaduce River is a low-inflow, macrotidal estuary that features tidal islands, tidal flats and sharp channel bends. Profiles of salinity, temperature, and turbulent kinetic energy dissipation (ε) were collected for a tidal cycle across the estuary with a microstructure profiler. Lateral distributions of current velocities were obtained with an acoustic doppler current profiler. Results sh

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21

Bettencourt, João H., and Frédéric Dias. "Wall pressure and vorticity in the intermittently turbulent regime of the Stokes boundary layer." Journal of Fluid Mechanics 851 (July 25, 2018): 479–506. http://dx.doi.org/10.1017/jfm.2018.520.

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In this paper we study the wall pressure and vorticity fields of the Stokes boundary layer in the intermittently turbulent regime through direct numerical simulation (DNS). The DNS results are compared to experimental measurements and a good agreement is found for the mean and fluctuating velocity fields. We observe maxima of the turbulent kinetic energy and wall shear stress in the early deceleration stage and minima in the late acceleration stage. The wall pressure field is characterized by large fluctuations with respect to the root mean square level, while the skewness and kurtosis of the

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22

Namgyal, L., and J. W. Hall. "Reynolds stress distribution and turbulence generated secondary flow in the turbulent three-dimensional wall jet." Journal of Fluid Mechanics 800 (July 13, 2016): 613–44. http://dx.doi.org/10.1017/jfm.2016.404.

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The lateral half-width of the turbulent three-dimensional wall jet is typically five to eight times larger than the vertical half-width normal to the wall. Although the reason for this behaviour is not fully understood, it is caused by mean secondary flows that develop in the jet due to the presence of the wall. The origin of the secondary flow has been associated previously with both vorticity reorientation and also gradients in the Reynolds stresses, although this has not been directly quantified as yet. The present investigation focuses on a wall jet formed using a circular contoured nozzle

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23

Loucks, Richard B., and James M. Wallace. "Velocity and velocity gradient based properties of a turbulent plane mixing layer." Journal of Fluid Mechanics 699 (April 16, 2012): 280–319. http://dx.doi.org/10.1017/jfm.2012.103.

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AbstractExperiments were carried out in a turbulent mixing layer designed to match, as closely as possible, the conditions of the temporally evolving direct numerical simulation of Rogers & Moser (Phys. Fluids, vol. 6, 1994, pp. 903–922). Two Reynolds numbers, based on the local momentum thickness in the self-similar region of the mixing layer, were investigated:${R}_{\theta } = 1792$and$2483$. Measurements were also made in the mixing layer in the pre-mixing transition region where${R}_{\theta } = 432$. The three velocity components and their cross-stream gradients were measured with a sm

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24

Sreedhar, Madhu, and Fred Stern. "Prediction of Solid/Free-Surface Juncture Boundary Layer and Wake of a Surface-Piercing Flat Plate at Low Froude Number." Journal of Fluids Engineering 120, no. 2 (1998): 354–62. http://dx.doi.org/10.1115/1.2820655.

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Results are reported of a RANS simulation investigation on the prediction of turbulence-driven secondary flows at the free-surface juncture of a surface-piercing flat plate at low Froude numbers. The turbulence model combines a nonlinear eddy viscosity model and a modified version of a free-surface correction formula. The different elements of the model are combined and the model constants calibrated based on the premises that the anisotropy of the normal stresses is mainly responsible for the dynamics of the flow in the juncture region, and an accurate modeling of the normal-stress anisotropy

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25

Jeong, J., F. Hussain, W. Schoppa, and J. Kim. "Coherent structures near the wall in a turbulent channel flow." Journal of Fluid Mechanics 332 (February 1997): 185–214. http://dx.doi.org/10.1017/s0022112096003965.

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Coherent structures (CS) near the wall (i.e.y+ ≤ 60) in a numerically simulated turbulent channel flow are educed using a conditional sampling scheme which extracts the entire extent of dominant vortical structures. Such structures are detected from the instantaneous flow field using our newly developed vortex definition (Jeong & Hussain 1995) - a region of negativeλ2, the second largest eigenvalue of the tensorSikSkj+ ΩikΩkj- which accurately captures the structure details (unlike velocity-, vorticity- or pressure-based eduction). Extensive testing has shown thatλ2correctly captures vorti

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26

VUKASINOVIC, B., Z. RUSAK, and A. GLEZER. "Dissipative small-scale actuation of a turbulent shear layer." Journal of Fluid Mechanics 656 (June 2, 2010): 51–81. http://dx.doi.org/10.1017/s0022112010001023.

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The effects of small-scale dissipative fluidic actuation on the evolution of large- and small-scale motions in a turbulent shear layer downstream of a backward-facing step are investigated experimentally. Actuation is applied by modulation of the vorticity flux into the shear layer at frequencies that are substantially higher than the frequencies that are typically amplified in the near field, and has a profound effect on the evolution of the vortical structures within the layer. Specifically, there is a strong broadband increase in the energy of the small-scale motions and a nearly uniform de

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27

Chen, J. G., T. M. Zhou, R. A. Antonia, and Y. Zhou. "Comparison between passive scalar and velocity fields in a turbulent cylinder wake." Journal of Fluid Mechanics 813 (January 26, 2017): 667–94. http://dx.doi.org/10.1017/jfm.2016.868.

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This work compares the enstrophy with the scalar dissipation rate, as well as the passive scalar variance with the turbulent kinetic energy, in the presence of coherent Kármán vortices in the intermediate wake of a circular cylinder. Measurements are made at$x/d=10$, 20 and 40, where$x$is the streamwise distance from the cylinder axis and$d$is the cylinder diameter, with a Reynolds number of$2.5\times 10^{3}$based on the cylinder diameter and the free-stream velocity. A probe consisting of eight hot wires (four X-wires) and four cold wires is used to measure simultaneously the three components

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28

PRIYADARSHANA, P. J. A., J. C. KLEWICKI, S. TREAT, and J. F. FOSS. "Statistical structure of turbulent-boundary-layer velocity–vorticity products at high and low Reynolds numbers." Journal of Fluid Mechanics 570 (January 3, 2007): 307–46. http://dx.doi.org/10.1017/s0022112006002771.

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The mean wall-normal gradients of the Reynolds shear stress and the turbulent kinetic energy have direct connections to the transport mechanisms of turbulent-boundary-layer flow. According to the Stokes–Helmholtz decomposition, these gradients can be expressed in terms of velocity–vorticity products. Physical experiments were conducted to explore the statistical properties of some of the relevant velocity–vorticity products. The high-Reynolds-number data (Rθ≃O(106), where θ is the momentum thickness) were acquired in the near neutrally stable atmospheric-surface-layer flow over a salt playa un

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29

Yu, S. C. M., Y. X. Hou, and S. C. Low. "The flow characteristics of a confined square jet with mixing tabs." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 212, no. 2 (1998): 63–76. http://dx.doi.org/10.1243/0954410981532144.

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The flow characteristics of a confined square jet with mixing tabs have been determined by measurements obtained using a two-component laser Doppler anemometer at a Reynolds number of 1.026 × 105 (based on the exit hydraulic diameter, DH = 60 mm, and bulk mean velocity, Ur, of the stream at 1.71 m/s). Both tabs of rectangular and triangular shapes are considered with the same height-breadth ratio ( h/b = 1.35) and with their apex leaning downstream. Altogether four tabs have been used, with one tab each located at the centre of each side wall at the exit plane. Each tab is found to produce a d

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30

Mohammed-Taifour, Abdelouahab, and Julien Weiss. "Unsteadiness in a large turbulent separation bubble." Journal of Fluid Mechanics 799 (June 23, 2016): 383–412. http://dx.doi.org/10.1017/jfm.2016.377.

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The unsteady behaviour of a massively separated, pressure-induced turbulent separation bubble (TSB) is investigated experimentally using high-speed particle image velocimetry (PIV) and piezo-resistive pressure sensors. The TSB is generated on a flat test surface by a combination of adverse and favourable pressure gradients. The Reynolds number based on the momentum thickness of the incoming boundary layer is 5000 and the free stream velocity is$25~\text{m}~\text{s}^{-1}$. The proper orthogonal decomposition (POD) is used to separate the different unsteady modes in the flow. The first POD mode

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Barnes, Andrew, Daniel Marshall-Cross, and Ben Richard Hughes. "Validation and comparison of turbulence models for predicting wakes of vertical axis wind turbines." Journal of Ocean Engineering and Marine Energy 7, no. 4 (2021): 339–62. http://dx.doi.org/10.1007/s40722-021-00204-z.

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AbstractVertical axis wind turbine (VAWT) array design requires adequate modelling of the turbine wakes to model the flow throughout the array and, therefore, the power output of turbines in the array. This paper investigates how accurately different turbulence models using 2D computational fluid dynamics (CFD) simulations can estimate near and far wakes of VAWTs to determine an approach towards accurate modelling for array design. Three experiments from the literature are chosen as baselines for validation, with these experiments representing the near to far wake of the turbine. Five URANS tu

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Amador, António, Martí Sánchez-Juny, and Josep Dolz. "Characterization of the Nonaerated Flow Region in a Stepped Spillway by PIV." Journal of Fluids Engineering 128, no. 6 (2006): 1266–73. http://dx.doi.org/10.1115/1.2354529.

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The development of the roller-compacted concrete (RCC) as a technique of constructing dams and the stepped surface that results from the construction procedure opened a renewed interest in stepped spillways. Previous research has focused on studying the air-water flow down the stepped chute with the objective of obtaining better design guidelines. The nonaerated flow region enlarges as the flow rate increases, and there is a lack of knowledge on the hydraulic performance of stepped spillways at high velocities that undermines its use in fear of cavitation damage. In the present, study the deve

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Wei, Maoxing, Nian-Sheng Cheng, Yee-Meng Chiew, and Fengguang Yang. "Vortex Evolution within Propeller Induced Scour Hole around a Vertical Quay Wall." Water 11, no. 8 (2019): 1538. http://dx.doi.org/10.3390/w11081538.

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This paper presents an experimental study on the characteristics of the propeller-induced flow field and its associated scour hole around a closed type quay (with a vertical quay wall). An “oblique particle image velocimetry” (OPIV) technique, which allows a concurrent measurement of the velocity field and scour profile, was employed in measuring the streamwise flow field (jet central plane) and the longitudinal centerline scour profile. The asymptotic scour profiles obtained in this study were compared with that induced by an unconfined propeller jet in the absence of any berthing structure,

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Landahl, Marten T. "Algebraic Growth and Streak Formation in Shear Flows." Applied Mechanics Reviews 43, no. 5S (1990): S218. http://dx.doi.org/10.1115/1.3120810.

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By examination of the long-term behavior of an initial three-dimensional and localized disturbance in an inflection-free shear flow a detailed study of the algebraic instability mechanism of an inviscid shear flow (Landahl, 1980) is carried out. It is shown that the vertical velocity component will tend to zero at least as fast as 1/t whereas, as a result of a nonzero liftup of the fluid elements, the streamwise disturbence velocity component will tend to a limiting finite value in a convected frame of reference. For an initial disturbence having a nonzero net vertical momentum along a streaml

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XANTHOS, SAVVAS, MINWEI GONG, and YIANNIS ANDREOPOULOS. "Velocity and vorticity in weakly compressible isotropic turbulence under longitudinal expansive straining." Journal of Fluid Mechanics 584 (July 25, 2007): 301–35. http://dx.doi.org/10.1017/s002211200700674x.

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The response of homogeneous and isotropic turbulence to streamwise straining action provided by planar expansion waves has been studied experimentally in the CCNY shock tube research facility at several Reynolds numbers. The reflection of a propagating shock wave at the open endwall of the shock tube generated an expansion fan travelling upstream and interacting with the induced flow behind the incident shock wave which has gone through a turbulence generating grid.A custom-made hot-wire vorticity probe was designed and developed capable of measuring the time-dependent highly fluctuating three

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36

Karp, Michael, and Jacob Cohen. "Tracking stages of transition in Couette flow analytically." Journal of Fluid Mechanics 748 (May 9, 2014): 896–931. http://dx.doi.org/10.1017/jfm.2014.203.

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AbstractThe current study focuses on a transition scenario in which the linear transient growth mechanism is initiated by four decaying normal modes. It is shown that the four modes, the initial structure of which corresponds to counter-rotating vortex pairs, are sufficient to capture the transient growth mechanism. More importantly, it is demonstrated that the kinetic energy growth of the initial disturbance is not the key parameter in this transition mechanism. Rather, it is the ability of the transient growth process to generate an inflection point in the wall-normal direction and consequen

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Mohaghar, Mohammad, John Carter, Gokul Pathikonda, and Devesh Ranjan. "The transition to turbulence in shock-driven mixing: effects of Mach number and initial conditions." Journal of Fluid Mechanics 871 (May 24, 2019): 595–635. http://dx.doi.org/10.1017/jfm.2019.330.

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The effects of incident shock strength on the mixing transition in the Richtmyer–Meshkov instability (RMI) are experimentally investigated using simultaneous density–velocity measurements. This effort uses a shock with an incident Mach number of 1.9, in concert with previous work at Mach 1.55 (Mohaghar et al., J. Fluid Mech., vol. 831, 2017 pp. 779–825) where each case is followed by a reshock wave. Single- and multi-mode interfaces are used to quantify the effect of initial conditions on the evolution of the RMI. The interface between light and heavy gases ($\text{N}_{2}/\text{CO}_{2}$, Atwoo

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Mohand Kaci, Hakim, Thierry Lemenand, Dominique Della Valle, and Hassan Peerhossaini. "Effects of embedded streamwise vorticity on turbulent mixing." Chemical Engineering and Processing: Process Intensification 48, no. 10 (2009): 1459–76. http://dx.doi.org/10.1016/j.cep.2009.08.002.

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UKEILEY, L., L. CORDIER, R. MANCEAU, J. DELVILLE, M. GLAUSER, and J. P. BONNET. "Examination of large-scale structures in a turbulent plane mixing layer. Part 2. Dynamical systems model." Journal of Fluid Mechanics 441 (August 15, 2001): 67–108. http://dx.doi.org/10.1017/s0022112001004803.

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The temporal dynamics of large-scale structures in a plane turbulent mixing layer are studied through the development of a low-order dynamical system of ordinary differential equations (ODEs). This model is derived by projecting Navier–Stokes equations onto an empirical basis set from the proper orthogonal decomposition (POD) using a Galerkin method. To obtain this low-dimensional set of equations, a truncation is performed that only includes the first POD mode for selected streamwise/spanwise (k1/k3) modes. The initial truncations are for k3 = 0; however, once these truncations are evaluated,

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Gregory-Smith, D. G., C. P. Graves, and J. A. Walsh. "Growth of Secondary Losses and Vorticity in an Axial Turbine Cascade." Journal of Turbomachinery 110, no. 1 (1988): 1–8. http://dx.doi.org/10.1115/1.3262163.

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The growth of losses, secondary kinetic energy, and streamwise vorticity have been studied in a high turning rotor cascade. Negative vorticity associated with the passage vortex agreed well with predictions of classical secondary flow theory in the early part of the blade passage. However, toward the exit, the distortion of the flow by the secondary velocities rendered the predictions inaccurate. Areas of positive vorticity were associated with the feeding of loss into the bulk flow and have been related to separation lines observed by surface flow visualization.

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Gustavsson, L. Hårkan. "Energy growth of three-dimensional disturbances in plane Poiseuille flow." Journal of Fluid Mechanics 224 (March 1991): 241–60. http://dx.doi.org/10.1017/s002211209100174x.

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The development of a small three-dimensional disturbance in plane Poiseuille flow is considered. Its kinetic energy is expressed in terms of the velocity and vorticity components normal to the wall. The normal vorticity develops according to the mechanism of vortex stretching and is described by an inhomogeneous equation, where the spanwise variation of the normal velocity acts as forcing. To study specifically the effect of the forcing, the initial normal vorticity is set to zero and the energy density in the wavenumber plane, induced by the normal velocity, is determined. In particular, the

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WU, XIAOHUA, and KYLE D. SQUIRES. "Prediction and investigation of the turbulent flow over a rotating disk." Journal of Fluid Mechanics 418 (September 10, 2000): 231–64. http://dx.doi.org/10.1017/s0022112000001117.

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Large-eddy simulation (LES) has been used to predict the statistically three-dimensional turbulent boundary layer (3DTBL) over a rotating disk. LES predictions for six parameter cases were compared to the experimental measurements of Littell & Eaton (1994), obtained at a momentum thickness Reynolds number of 2660. A signal-decomposition scheme was developed by modifying the method of Spalart (1988) to prescribe time-dependent boundary conditions along the radial direction, entrainment towards the disk surface was prescribed by satisfying global mass conservation. Predictions of the mean ve

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Gorski, J. J., and P. S. Bernard. "Vorticity Transport Analysis of Turbulent Flows." Journal of Fluids Engineering 117, no. 3 (1995): 410–16. http://dx.doi.org/10.1115/1.2817277.

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Turbulence closure for the Reynolds averaged Navier-Stokes equations based on vorticity transport theory is investigated. General expressions for the vorticity transport correlation terms in arbitrary two-dimensional mean flows are derived. Direct numerical simulation data for flow in a channel is used to evaluate the modeled terms and set unknown scales. Results are presented for a channel, flat plate boundary layer, and flow over a hill. The computed mean flow and kinetic energy compares well with numerical and physical experiments. The vorticity transport model appears to perform better tha

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Vukoslavcevic, Petar, and James Wallace. "On the accuracy of measurement of turbulent velocity gradient statistics with hot-wire probes." Thermal Science 21, suppl. 3 (2017): 533–51. http://dx.doi.org/10.2298/tsci160210116v.

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A very high resolution minimal channel flow direct numerical simulation was used to examine, virtually, the ability of various multi-sensor hot-wire probe configurations to measure the statistics of velocity gradient components. Various array and sensor configurations and the spatial resolution of probes with these configurations were studied, building on designs and investigations of various authors. In contrast to our previous studies, which focused on turbulent vorticity, vorticity-velocity correlations, dissipation and production rate, here the measurement accuracy of each component of the

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Sutherland, Peter, and W. Kendall Melville. "Measuring Turbulent Kinetic Energy Dissipation at a Wavy Sea Surface." Journal of Atmospheric and Oceanic Technology 32, no. 8 (2015): 1498–514. http://dx.doi.org/10.1175/jtech-d-14-00227.1.

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AbstractWave breaking is thought to be the dominant mechanism for energy loss by the surface wave field. Breaking results in energetic and highly turbulent velocity fields, concentrated within approximately one wave height of the surface. To make meaningful estimates of wave energy dissipation in the upper ocean, it is then necessary to make accurate measurements of turbulent kinetic energy (TKE) dissipation very near the surface. However, the surface wave field makes measurements of turbulence at the air–sea interface challenging since the energy spectrum contains energy from both waves and t

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Dairay, T., M. Obligado, and J. C. Vassilicos. "Non-equilibrium scaling laws in axisymmetric turbulent wakes." Journal of Fluid Mechanics 781 (September 16, 2015): 166–95. http://dx.doi.org/10.1017/jfm.2015.493.

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We present a combined direct numerical simulation and hot-wire anemometry study of an axisymmetric turbulent wake. The data lead to a revised theory of axisymmetric turbulent wakes which relies on the mean streamwise momentum and turbulent kinetic energy equations, self-similarity of the mean flow, turbulent kinetic energy, Reynolds shear stress and turbulent dissipation profiles, non-equilibrium dissipation scalings and an assumption of constant anisotropy. This theory is supported by the present data up to a distance of 100 times the wake generator’s size, which is as far as these data exten

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Lee, Yu-Tai, William K. Blake, and Theodore M. Farabee. "Modeling of Wall Pressure Fluctuations Based on Time Mean Flow Field." Journal of Fluids Engineering 127, no. 2 (2004): 233–40. http://dx.doi.org/10.1115/1.1881698.

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Time-mean flow fields and turbulent flow characteristics obtained from solving the Reynolds averaged Navier-Stokes equations with a k‐ε turbulence model are used to predict the frequency spectrum of wall pressure fluctuations. The vertical turbulent velocity is represented by the turbulent kinetic energy contained in the local flow. An anisotropic distribution of the turbulent kinetic energy is implemented based on an equilibrium turbulent shear flow, which assumes flow with a zero streamwise pressure gradient. The spectral correlation model for predicting the wall pressure fluctuation is obta

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Wei, Tie. "Integral properties of turbulent-kinetic-energy production and dissipation in turbulent wall-bounded flows." Journal of Fluid Mechanics 854 (September 10, 2018): 449–73. http://dx.doi.org/10.1017/jfm.2018.578.

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Turbulent-kinetic-energy (TKE) production $\mathscr{P}_{k}=R_{12}(\unicode[STIX]{x2202}U/\unicode[STIX]{x2202}y)$ and TKE dissipation $\mathscr{E}_{k}=\unicode[STIX]{x1D708}\langle (\unicode[STIX]{x2202}u_{i}/x_{k})(\unicode[STIX]{x2202}u_{i}/x_{k})\rangle$ are important quantities in the understanding and modelling of turbulent wall-bounded flows. Here $U$ is the mean velocity in the streamwise direction, $u_{i}$ or $u,v,w$ are the velocity fluctuation in the streamwise $x$- direction, wall-normal $y$- direction, and spanwise $z$-direction, respectively; $\unicode[STIX]{x1D708}$ is the kinema

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LIU, Z., R. J. ADRIAN, and T. J. HANRATTY. "Large-scale modes of turbulent channel flow: transport and structure." Journal of Fluid Mechanics 448 (November 26, 2001): 53–80. http://dx.doi.org/10.1017/s0022112001005808.

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Turbulent flow in a rectangular channel is investigated to determine the scale and pattern of the eddies that contribute most to the total turbulent kinetic energy and the Reynolds shear stress. Instantaneous, two-dimensional particle image velocimeter measurements in the streamwise-wall-normal plane at Reynolds numbers Reh = 5378 and 29 935 are used to form two-point spatial correlation functions, from which the proper orthogonal modes are determined. Large-scale motions – having length scales of the order of the channel width and represented by a small set of low-order eigenmodes – contain a

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ORLANDI, P., and M. FATICA. "Direct simulations of turbulent flow in a pipe rotating about its axis." Journal of Fluid Mechanics 343 (July 25, 1997): 43–72. http://dx.doi.org/10.1017/s0022112097005715.

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Flow in a circular pipe rotating about its axis, at low Reynolds number, is investigated. The simulation is performed by a finite difference scheme, second-order accurate in space and in time. A non-uniform grid in the radial direction yields accurate solutions with a reasonable number of grid points. The numerical method has been tested for the non-rotating pipe in the limit ν→0 to prove the energy conservation properties. In the viscous case a grid refinement check has been performed and some conclusions about drag reduction have been reached. The mean and turbulent quantities have been comp

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