Flow characteristics and scaling past highly porous wall-mounted fences

Rodríguez-López, Eduardo; Bruce, Paul J.; Buxton, O. R. H.

doi:10.1063/1.4995307

Cited by 5 publications

(4 citation statements)

References 62 publications

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“…The agreement also suggests that the near-wall region is more prone to adapting quickly to a canonical TBL under the tripping impact, which is similar to the previous investigations (Schlatter & Örlü 2012; Rodríguez-López, Bruce & Buxton 2016 a ; Rodríguez-López et al. 2017 b ). On the contrary, a significant difference is observed in the outer layer, showing a progressively repressive wake region with increasing .…”

Section: Experimental Dataset Descriptionsupporting

confidence: 90%

“…For comparison, the inner velocity profile of Musker (1979) is superimposed as a black line, in which the von Kármán constant κ = 0.41 and the constant B = 4.86 (Nagib & Chauhan 2008;Marusic et al 2013;Segalini, Örlü & Alfredsson 2013). The agreement also suggests that the near-wall region is more prone to adapting quickly to a canonical TBL under the tripping impact, which is similar to the previous investigations (Schlatter & Örlü 2012;Rodríguez-López, Bruce & Buxton 2016a;Rodríguez-López et al 2017b). On the contrary, a significant difference is observed in the outer layer, showing a progressively repressive wake region with increasing D c .…”

Section: Experimental Dataset Descriptionsupporting

confidence: 82%

“…On the other hand, the wake-driven mechanism is related to a long adaptation region where the inner structures are reorganized under the influence of highly energetic wake motions. These proposed driven mechanisms have been further confirmed by assessing the geometry parameters of tripping devices, such as aspect ratio, blockage ratio and blockage at the wall (Rodríguez-López, Bruce & Buxton 2017 a , b ; Buxton, Ewenz Rocher & Rodríguez-López 2018).…”

Section: Introductionmentioning

confidence: 74%

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Self-similarity in over-tripped turbulent boundary-layer flows

Tang,

Jiang

2024

J. Fluid Mech.

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The scaling universality of structure functions is studied for artificially thickened turbulent boundary-layer flows in over-tripped impacts by using hot-wire measurement datasets. The self-similarity behaviours in the inner and outer regions are examined from the viewpoint of different flow mechanisms. In the inner region, the relative ratios between structure functions for the energy-containing range of scales exhibit universality behaviour, in accordance with Townsend's attached eddy hypothesis. This universality of the energy-containing range of scales extends further away from the wall by increasing the tripping intensity. On the other hand, the impact of the external intermittency on the self-similarity of small-scale turbulence is examined through the intermittent zone in over-tripped conditions. Towards the boundary-layer edge, the structure functions exhibit a growing departure from self-similarity and analytical prediction, and it is demonstrated that the departure is primarily due to external intermittency. Moreover, based on the conditional statistics concentrated in the turbulent regimes, it is revealed that the small scales in the turbulence regime are homogenized in a self-similar behaviour, which is independent of the current tripping conditions.

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Section: Experimental Dataset Descriptionsupporting

confidence: 90%

Section: Experimental Dataset Descriptionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 74%

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Self-similarity in over-tripped turbulent boundary-layer flows

Tang,

Jiang

2024

J. Fluid Mech.

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“…The final observation is that the strength of the shear layer is particularly strong for the fence trip, significantly higher fluctuations are observed than in the inner peak. This can be attributed to the lack of any gaps in the trip (100% blockage at y = h) leading to a strong shear layer forming as the flow separates from the top edge of the trip, similar to the flows produced by wall mounted fences reported in Rodríguez-López et al (29). The spectral content of the velocity fluctuations is illustrated in figure 5.…”

Section: Mean and Root-mean-square Profilessupporting

confidence: 63%

Influence of strong perturbations on wall-bounded flows

2018

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Single-point hot-wire measurements are made downstream of a series of spanwise repeating obstacles that are used to generate an artificially thick turbulent boundary layer. The measurements are made in the near field, in which the turbulent boundary layer is beginning to develop from the wall-bounded wakes of the obstacles. The recent paper of Rodríguez-López et al. (28) broadly categorised the mechanisms by which canonical turbulent boundary layers eventually develop from wall-bounded wakes into two distinct mechanisms, the wall-driven and wake-driven mechanisms. In the present work we attempt to identify the geometric parameters of tripping arrays that trigger these two mechanisms by examining the spectra of the streamwise velocity fluctuations and the intermittent outer region of the flow. Using a definition reliant upon the magnitude of the velocity fluctuations, an intermittency function is devised that can discriminate between turbulent and non-turbulent flow. These results are presented along with the spectra in order to try to ascertain which aspects of a trip's geometry are more likely to favour the wall-driven or wake-driven mechanism. The geometrical aspects of the trips tested are the aspect ratio, the total blockage and the blockage at the wall. The results indicate that the presence, or not, of perforations is the most significant factor in affecting the flow downstream. The bleed of fluid through the perforations re-energises the mean recirculation and leads to a narrower intermittent region with a more regular turbulent/non-turbulent interface. The near-wall turbulent motions are found to recover quickly downstream of all of the trips with a wall blockage of 50% but a clear influence of the outer fluctuations, generated by the tip vortices of the trips, is observed in the near-wall region for the high total blockage trips. The trip with 100% wall-blockage is found to modify the nature of the inner-wall peak of turbulent kinetic energy.

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