(Received 31 March 2005 and in revised form 29 July 2005) Data from the near-wall-turbulent region of the high-Reynolds-number atmospheric surface layer are used to analyse the attached-eddy model of wall turbulence. All data were acquired during near-neutral conditions at the Surface Layer Turbulence and Environmental Science Test (SLTEST) facility located in the western Utah Great Salt Lake Desert. Instantaneous streamwise and wall-normal components of velocity were collected with a wall-normal array of two-component hot wires within the first 2 m above the surface of the salt flats. Streamwise and wall-normal turbulence intensities and spectra are directly compared to corresponding laboratory data and similarity formulations hypothesized from the attached-eddy model of wall turbulence. This affords the opportunity to compare results with Reynolds numbers varying over three orders of magnitude. The wall-normal turbulence-intensity similarity formulation is extended. The results show good support for the similarity arguments forwarded by the attached-eddy model as well as Townsend’s (1956) Reynolds-number similarity hypothesis and lack of the ‘inactive’ motion influence on the wall-normal velocity component. The effects of wall roughness and the spread in the convection velocity due to this roughness are also discussed. An experimental investigation of the near-wall-turbulent (logarithmic) region of the high-Reynolds-number turbulent boundary layer was conducted. The main purpose of this work is to use these data to investigate the attached-eddy model of wallbounded turbulence at high Reynolds numbers. (A good review of the importance of understanding high-Reynolds-number wall-bounded flow is given by Gad-el-Hak & Bandyopadhyay 1994.) The attached-eddy model essentially provides a kinematic description for wall-bounded turbulence. The foundation of the model, which is based on the attached-eddy hypothesis of Townsend (1976), is the observation that wallbounded turbulence contains a collection of coherent structures or eddies. Therefore, the model proposes that the statistical features of wall-bounded turbulence can be modelled by a linear superposition of such eddies. The model has been refined and developed over the past three decades on the data of low-to-moderate Reynoldsnumber wall-bounded turbulence experiments (e.g. pipe and boundary-layer flow) and has led to a number of similarity laws. For a complete review of the attached-eddy model see Perry & Marusic (1995) and the references therein.

/pdf/study-of-the-near-wall-turbulent-region-of-the-high-reynolds-2fwl85x4v5.pdf

An experimental study of the high Reynolds number turbulent boundary layer

Study of the near-wall-turbulent region of the high-Reynolds-number boundary layer using an atmospheric flow

A collaborative experimental effort employing the minimally perturbed atmospheric surface-layer flow over the salt playa of western Utah has enabled us to map coherence in turbulent boundary layers at very high Reynolds numbers, \({Re_{\tau}\sim\mathcal{O}(10^6)}\) . It is found that the large-scale coherence noted in the logarithmic region of laboratory-scale boundary layers are also present in the very high Reynolds number atmospheric surface layer (ASL). In the ASL these features tend to scale on outer variables (approaching the kilometre scale in the streamwise direction for the present study). The mean statistics and two-point correlation map show that the surface layer under neutrally buoyant conditions behaves similarly to the canonical boundary layer. Linear stochastic estimation of the three-dimensional correlation map indicates that the low momentum fluid in the streamwise direction is accompanied by counter-rotating roll modes across the span of the flow. Instantaneous flow fields confirm the inferences made from the linear stochastic estimations. It is further shown that vortical structures aligned in the streamwise direction are present in the surface layer, and bear attributes that resemble the hairpin vortex features found in laboratory flows. Ramp-like high shear zones that contribute significantly to the Reynolds shear-stress are also present in the ASL in a form nearly identical to that found in laboratory flows. Overall, the present findings serve to draw useful connections between the vast number of observations made in the laboratory and in the atmosphere.

/pdf/towards-reconciling-the-large-scale-structure-of-turbulent-zrzpp2f8q0.pdf

Towards Reconciling the Large-Scale Structure of Turbulent Boundary Layers in the Atmosphere and Laboratory

University of Minnesota Ph.D. dissertation. February 2010. Major: Aerospace Engineering and Mechanics. Advisors: Ellen K. Longmire, Ivan Marusic. 1 computer file (PDF); xxi, 223 pages, appendices A-F.

An experimental study of the high Reynolds number turbulent boundary layer

Citations

Study of the near-wall-turbulent region of the high-Reynolds-number boundary layer using an atmospheric flow

Towards Reconciling the Large-Scale Structure of Turbulent Boundary Layers in the Atmosphere and Laboratory

Studies in wall turbulence using dual plane particle image velocimetry and direct numerical simulation data

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