522 research outputs found
Modelling high Reynolds number wall-turbulence interactions in laboratory experiments using large-scale free-stream turbulence
No full textData supporting the publication:
Modelling high Reynolds number wall–turbulence interactions in laboratory experiments using large-scale free-stream turbulence
Eda Dogan, R. Jason Hearst, Bharathram Ganapathisubramani
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 2017 375 20160091; DOI: 10.1098/rsta.2016.0091. Published 6 February 2017</span
Dataset for paper titled Robust features of a turbulent boundary layer subjected to high-intensity free-stream turbulence
No full textThis dataset contains a matlab file required to reproduce all the figures in the above mentioned paper. If you use any of the data from this dataset, please cite the following article,
R. Jason Hearst, Eda Dogan and Bharathram Ganapathisubramani, (2018), "Robust features of a turbulent boundary layer subjected to high-intensity free-stream turbulence", Journal of Fluid Mechanics. DOI: 10.1017/jfm.2018.511
Here is further information on the dataset:
The variables contained in the file are:
B = log-law fitting parameter described in equation (1.1)
kappa = log-law fitting parameter described in equation (1.1)
delta = boundary layer thickness (units: meters)
lamb_inf = Taylor microscale in the free-stream (units: meters)
Lu_inf = integral lengthscale in the free-stream (units: meters)
nu = kinematic viscosity (units: m^2/s)
Re_lamb_inf = Taylor microscale based Reynolds number in the free-stream
Re_tau = friction velocity based Reynolds number
Re_theta = momentum thickness based Reynolds number
u2_inf = streamwise velocity variance in the free-stream
(units: m^2/s^2)
U_inf = streamwise mean velocity in the free-stream (units: m/s)
U_tau = mean friction velocity (units: m/s)
uU_inf = free-stream turbulence intensity
Fu = streamwise velocity flatness profiles
Su = streamwise velocity skewness profiles
U = streamwise mean velocity profiles (units: m/s)
u2 = streamwise velocity variance profiles (units: m^2/s^2)
y = wall-normal position for profiles (units: meters)
E11_inf = free-stream spectra
kE11 = pre-multiplied spectra at all wall-normal positions for each case
(units of m^2/s^2)
Gg = global gain function
kpu = wall-unit normalised wavenumber for all spectra
ypu = wall-unit normalised wall-normal position for all spectra
Coh_G = spectral coherence, equation (3.1) of the text, for case G
Coh_H = spectral coherence for case H
Coh_N = spectral coherence for case N
zetap_Coh_G = wall-unit normalised wavelength for spectral coherence case G
zetap_Coh_H = wall-unit normalised wavelength for spectral coherence case H
zetap_Coh_N = wall-unit normalised wavelength for spectral coherence case N
For all variables except for the coherence plots, the data is stored as
"cell" elements in MATLAB where the first element of the cell (index = 1)
is case A, the second element of the cell (index = 2) is case B, and so on.
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Dataset and Matlab Routine
No full textThis file contains the experimental data and the Matlab Routines used in
Luis Blay-Esteban, Eda Dogan, Eduardo Rodríguez-López and Bharathram Ganapathisubramani (2017) Skin friction measurements in a turbulent boundary layer with zero-pressure-gradient under the influence of free-stream turbulence. Experiments in Fluids (2017) 58:115, DOI 10.1007/s00348-017-2397-8
and originally developed in
Eduardo Rodríguez‑López, Paul J. K. Bruce1, Oliver R. H. Buxton (2015)
A robust post‑processing method to determine skin friction in turbulent boundary layers from the velocity profile Exp Fluids (2015) 56:68
DOI 10.1007/s00348-015-1935-5
The dataset contains 28 different cases for various combinations of freestream velocity and freestream turbulence intensity generated with an active grid. All the data are taken using hot-wire anemometry and oil-film interferometry. Then the skin friction obtained by the latter method is compared with the skin friction obtained from a fit to the mean velocity profile.
The data is structured in 28 files corresponding to the various experimental cases. The header of the file is a summary of the experimental conditions (Friction coefficient, freestream turbulence, freestream velocity, wake parameter, boundary layer thickness, Reynolds number, etc.). The same notation of the paper is followed.
Below that header the velocity profile for each case is expressed in wall units (normalized with the viscosity and the friction velocity obtained by the fitting process) </span
Effects of large-scale free stream turbulence on a zero-pressure-gradient turbulent boundary layer
No full textModelling high Reynolds number wall-turbulence interactions in laboratory experiments using large scale free-stream turbulence
No full textA turbulent boundary layer subjected to free-stream turbulence is investigated in order to ascertain the scale interactions that dominate the near-wall region. The results are discussed in relation to a canonical high Reynolds number turbulent boundary layer because previous studies have reported considerable similarities between these two flows. Measurements were acquired simultaneously from four hot-wires mounted to a rake which was traversed through the boundary layer. Particular focus is given to two main features of both canonical high Reynolds numberboundary layers and boundary layers subjected to free-stream turbulence: (i) the footprint of the large scales in the logarithmic region on the near-wall small scales, specifically the modulating interaction between these scales, and (ii) the phase difference in amplitude modulation. The potential for a turbulent boundary layer subjected to free-stream turbulence to “simulate” high Reynolds number wall-turbulence interactions is discussed. The results of this study have encouraging implications for future investigations of the fundamental scale interactions that take place in high Reynolds number flows as it demonstrates that these can be achieved at typical laboratory scales
Interactions of large-scale free-stream turbulence with turbulent boundary layers
No full textData supporting the publication titled "Interactions of large-scale free-stream turbulence with turbulent boundary layers" in Journal of Fluid Mechanics. </span
Interaction layer between a turbulent boundary layer and free-stream turbulence
No full textThe interaction between a turbulent free-stream and a turbulent boundary layer is investigated through particle image velocimetry measurements. An `interaction layer' located between , at the end of the log layer, is identified whereby the kinetic energy in this layer describes the flow above it. Conditional averages about the interaction layer indicate that it is home to peaks in the Reynolds stresses and that it is the location of a change in the vortical structure. Furthermore, the conditional information identifies that low kinetic energy deficit states in the interaction layer result in a more full boundary layer profile due to increased movement of the bulk flow towards the wall
Robust features of a turbulent boundary layer subjected to high-intensity free-stream turbulence
No full textThe influence of the large scale organisation of free-stream turbulence on a turbulent boundary layer is investigated experimentally in a wind tunnel through hot-wire measurements. An active grid is used to generate high-intensity free-stream turbulence with 7.2% ≤ u'_∞ / U_∞ ≤ 13.0% and 302 ≤ Re_λ ,∞ ≤ 760. In particular, several cases are produced with fixed u'_∞ / U_∞ and Re_λ ,∞ , but up to a 65% change in L_u,∞ / δ . It is shown that while qualitatively the spectra at various wall-normal positions in the boundary layer look similar, there are quantifiable differences at the large wavelengths all the way to the wall. Nonetheless, profiles of the longitudinal statistics up to fourth-order are well collapsed between cases at the same u'_∞ / U_∞ . It is argued that a larger separation of the integral scale would not yield a different result, nor would it be physically realisable. Comparing cases across the wide range of turbulence intensities and free-stream Reynolds numbers tested, it is demonstrated that the near-wall spectral peak is independent of the free-stream turbulence, and seemingly universal. The outer peak was also found to be described by a set of global scaling laws, and hence both the near-wall and outer spectral peaks can be predicted a priori with only knowledge of the free-stream spectrum, the boundary layer thickness (δ ) and the frictional velocity U_τ . Finally, a conceptual model is suggested that attributes the increase in U_τ as u'_∞ / U_∞ increases to the build-up of energy at large wavelengths near the wall because that energy cannot be transferred to the universal near-wall spectral peak
Skin-friction measurements in a turbulent boundary layer under the influence of free-stream turbulence
No full textThis experimental investigation deals with the influence of free-stream turbulence (FST) produced by an active grid on the skin-friction of a zero-pressure- gradient turbulent boundary layer. Wall shear stress is obtained by oil-film interferometry (OFI). Additionally, hot-wire anemometry was performed to obtain wall-normal profiles of streamwise velocity. This enables the skin-friction to be deduced from the mean profile. Both methods show remarkable agreement for every test case. Although skin friction is shown to increase with FST; the trend with Reynolds number is found to be similar to cases without FST. Furthermore, once the change in the friction velocity is accounted for, the self-similarity of the logarithmic region and below (i.e. law of the wall) appears to hold for all FST cases investigated
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