On spatial resolution issues related to time-averaged quantities using hot-wire anemometry

Örlü, Ramis; Alfredsson, P. Henrik

doi:10.1007/s00348-009-0808-1

Cited by 53 publications

(23 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Uncertainties remain, however, due to the wide range of (dimensionless) sensor lengths used, leading to varying spatial-resolution effects, as recently noted by Ng et al (2011). Spatial averaging when measuring small-scale turbulence is a well-known problem when using hot-wire anemometry, which results in important consequences in studies of wall bounded turbulence (Örlü and Alfredsson, 2010;. Consequently, it is important to make the sensors small compared to the scale of turbulence structures so that local values of the fluctuating flow can be correctly measured (Örlü and Schlatter, 2011).…”

Section: Nonuniform Flow Correctionmentioning

confidence: 94%

Statistical properties of wall shear stress fluctuations in turbulent channel flows

Keirsbulck

Labraga

Gad‐el‐Hak

2012

International Journal of Heat and Fluid Flow

View full text Add to dashboard Cite

Section: Nonuniform Flow Correctionmentioning

confidence: 94%

Statistical properties of wall shear stress fluctuations in turbulent channel flows

Keirsbulck

Labraga

Gad‐el‐Hak

2012

International Journal of Heat and Fluid Flow

View full text Add to dashboard Cite

“…One can notice a fairly good agreement for U + , while (u ) 2 + collapses well on the DNS for y + > 100 only. The strong attenuation of the inner peak of (u ) 2 + may be mainly attributed to spatial integration over the sensing length of the hotwire probe (see for example Wyngaard (1968), Ligrani & Bradshaw (1987), Örlü & Alfredsson (2010) and Philip et al (2013)) but also to various effects such as pressure gradient and wall interferences. Since the RRI is not defined in the boundary layer and the TNTI is rather located in its outer region, probe resolution is good enough for the purposes of this work.…”

Section: Incoming Boundary Layermentioning

confidence: 99%

Scaling of separated shear layers: an investigation of mass entrainment

2017

View full text Add to dashboard Cite

We report an experimental investigation of the separating/reattaching flow over a descending ramp with a $25^{\circ }$ expansion angle. Emphasis is given to mass entrainment through the boundaries of the separated shear layer emanating from the upper edge of the ramp. For this purpose, the turbulent/non-turbulent interface and the separation line inferred from image-based analysis are used respectively to mark the upper and lower bounds of the separated shear layer. The main objective of this study is to identify the physical parameters that scale the development of the separated shear layer, by giving a specific emphasis to the investigation of mass entrainment. Our results emphasise the multiscale nature of mass entrainment through the separated shear layer. The recirculation length $L_{R}$, step height $h$ and free-stream velocity $U_{\infty }$ are the dominant scales that organise the separated flow (and related large-scale quantities as pressure distribution or shear layer growth rate) and set mean mass fluxes. However, local viscous mechanisms seem to be responsible for most of local mass entrainment. Furthermore, it is shown that large-scale mass entrainment is driven by incoming boundary layer properties, since $L_{R}$ scales with $Re_{\unicode[STIX]{x1D703}}$, and in particular by its turbulent state. Surprisingly, the relationships evidenced in this study suggest that these dependencies are established over a large distance upstream of separation and that they might also extend to small scales, at which viscous entrainment is dominant. If confirmed by additional studies, our findings would open new perspectives for designing effective separation control systems.

show abstract

“…Spatial averaging due to the large length of the single-wire is known to reduce the near-wall peak of turbulence intensity [1], but also it could falsify higher order moments, like the skewness and atness factors [11]. It could also reduce the frequency of detected burst events as documented by Johansson and Alfredsson [12].…”

Section: Discussion Of the Resultsmentioning

confidence: 97%

Analysis of hot-wire measurements accuracy in turbulent boundary layer

Dróżdż

Elsner

2015

Open Engineering

View full text Add to dashboard Cite

This paper discusses the issue of measuring velocity uctuations of turbulent boundary layer using hotwire probes. The study highlights the problem of spatial resolution, which is essential when measuring smallscales in wall-bounded ows. Additionally, attention was paid to the inconsistency in streamwise uctuation measurements using single-and X-wire probes. To clarify this problem, the energy spectra using wavelet transformation were calculated. The analysis was performed for turbulent boundary layer ow, which was characterized by Reynolds number based on the friction velocity equal Reτ ≈ .

show abstract

On spatial resolution issues related to time-averaged quantities using hot-wire anemometry

Cited by 53 publications

References 44 publications

Statistical properties of wall shear stress fluctuations in turbulent channel flows

Statistical properties of wall shear stress fluctuations in turbulent channel flows

Scaling of separated shear layers: an investigation of mass entrainment

Analysis of hot-wire measurements accuracy in turbulent boundary layer

Contact Info

Product

Resources

About