1,721,147 research outputs found
Velocity statistics for rough-wall turbulent boundary layer flow over LEGO roughness elements in different layouts
No full textThis dataset presents 2D PIV experimental data collected over a range of twelve urban roughnesses with different frontal and plan solidities. These are described in:
[1] Placidi, M., & Ganapathisubramani, B. (2015). Effects of frontal and plan solidities on aerodynamic parameters and the roughness sublayer in turbulent boundary layers. Journal of Fluid Mechanics, 782, 541–566. http://doi.org/10.1017/jfm.2015.552
[2] Placidi, M., & Ganapathisubramani, B. (2018). Turbulent Flow Over Large Roughness Elements: Effect of Frontal and Plan Solidity on Turbulence Statistics and Structure. Boundary-Layer Meteorology, 167, 99–121. http://doi.org/10.1007/s10546-017-0317-3
[3] 3] Placidi M. & Ganapathisubramani, B (2019). Velocity statistics for rough-wall turbulent boundary layer flow over LEGO roughness elements in different layouts. DOI: 10.5258/SOTON/D0829.
PLEASE CITE THESE PAPERS AND THIS DATASET DOI WHEN USING THE DATA.
Contact Dr Marco Placidi ([email protected]) or Prof Bharathram Ganapathisubramani ([email protected]) for any queries on the dataset.
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Format of the dataset:
d = Virtual origin [mm]
delta = Boundary layer thickness (delta99 [mm])
deltas = Displacement thickness [mm]
dyn_visc_air = Air dynamic viscosity [Kg/(m s)]
h = Height of the roughness [mm]
K = Acceleration parameter as in [1]
rho_air = Air density [kq/m^3]
run = Case ID as in [1] and [2]
theta = Momentum thickness [mm]
U = Mean streamwise velocity [m/s]
U_edge = Mean streamwise velocity at the edge of the boundary layer [m/s]
utau = Skin friction velocity [m/s] based on drag measurements
uu = Streamwise velocity fluctuations
uv = Reynolds shear stresses
V = Mean wall-normal velocity [m/s]
vv = Wall-normal velocity fluctuations
X = Streamwise coordinate [mm]
Y = Wall-normal coordinate [mm]
y0 = Roughness length [mm]
Additional notes on the dataset:
- The 2D PIV dataset has been averaged across the Field of View in the streamwise direction to obtain 1D profiles.
- utau is measured directly by means of a floating-element drag balance as described in [1].
- y0,d, are obtained via best fitting the velocity profiles as in [1].
- The entire dataset has been filtered to match the local resolution for all cases, as discussed in [1].
- The acceleration parameter is defined in [1], and it is calculated from 2D PIV data across the size of the drag balance sensing element (i.e. 200 mm x200 mm). As such, it is affected by a significant experimental uncertainty. Additional verification of ZPG conditions were obtained via Pitot tube measurements between the inlet and outlet of the tunnel test section. The pressure gradient was considered negligible. </span
Effects of frontal and plan solidarities on aerodynamic parameters and the roughness sublayer in turbulent boundary layers
No full textTurbulent flow over large roughness elements: effect of frontal and plan solidity on turbulence statistics and structure
No full textWind-tunnel experiments were carried out on fully-rough boundary layers with large roughness (δ/h≈10, where h is the height of the roughness elements and δ is the boundary-layer thickness). Twelve different surface conditions were created by using LEGO™ bricks of uniform height. Six cases are tested for a fixed plan solidity (λP) with variations in frontal density (λF), while the other six cases have varying λP for fixed λF. Particle image velocimetry and floating-element drag-balance measurements were performed. The current results complement those contained in Placidi and Ganapathisubramani (J Fluid Mech 782:541–566, 2015), extending the previous analysis to the turbulence statistics and spatial structure. Results indicate that mean velocity profiles in defect form agree with Townsend’s similarity hypothesis with varying λF, however, the agreement is worse for cases with varying λP. The streamwise and wall-normal turbulent stresses, as well as the Reynolds shear stresses, show a lack of similarity across most examined cases. This suggests that the critical height of the roughness for which outer-layer similarity holds depends not only on the height of the roughness, but also on the local wall morphology. A new criterion based on shelter solidity, defined as the sheltered plan area per unit wall-parallel area, which is similar to the ‘effective shelter area’ in Raupach and Shaw (Boundary-Layer Meteorol 22:79–90, 1982), is found to capture the departure of the turbulence statistics from outer-layer similarity. Despite this lack of similarity reported in the turbulence statistics, proper orthogonal decomposition analysis, as well as two-point spatial correlations, show that some form of universal flow structure is present, as all cases exhibit virtually identical proper orthogonal decomposition mode shapes and correlation fields. Finally, reduced models based on proper orthogonal decomposition reveal that the small scales of the turbulence play a significant role in assessing outer-layer similarity
Reproductive isolation in Roio, a pastoral community of the Province of L'Aqila (Abruzzo, Italy)in the period 1800-1965.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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