Role of data uncertainties in identifying the logarithmic region of turbulent boundary layers
2014 (English)In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 55, no 6, 1751- p.Article in journal (Refereed) Published
Composite expansions based on the log-law and the power-law were used to generate synthetic velocity profiles of zero pressure gradient turbulent boundary layers (TBLs) in the range of Reynolds number 800 <= Re-theta <= 860; 000; based on displacement thickness and free-stream velocity. Several artificial errors were added to the velocity profiles to simulate typical measurement uncertainties. The effects of the simulated errors were studied by extracting log-law and power-law parameters from all these pseudo-experimental profiles. Various techniques were used to establish a measure of the deviations in the overlap region. When parameters extracted for the log-law and the power-law are associated with similar levels of deviations with respect to their expected values, we consider that the profile leads to ambiguous conclusions. This ambiguity was observed up to Re-theta 16; 000 for a 4 % dispersion in the velocity measurements, up to Re-theta 8.6 x 10(5) for a 400 mu m uncertainty in probe position (in air flow at atmospheric pressure), and up to Re-theta 32; 000 for 3 % uncertainty in the determination of u(tau): In addition, a new method for the determination of the log-law limits is proposed. The results clearly serve as a further note for caution when identifying either a log or a power-law in TBLs. Together with a number of available studies in the literature, the present results can be seen as a additional reconfirmation of the log-law.
Place, publisher, year, edition, pages
2014. Vol. 55, no 6, 1751- p.
Velocity Distribution, Scaling Laws, Shear Flows, Von Karman, Pipe-Flow
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-148310DOI: 10.1007/s00348-014-1751-3ISI: 000338322400011ScopusID: 2-s2.0-84901574379OAI: oai:DiVA.org:kth-148310DiVA: diva2:736543
QC 201408072014-08-072014-08-052014-08-07Bibliographically approved