No abstract

A simple example using convection heat transfer is used to illustrate the use of uncertainty analysis in PLANNING experiments. Major points made are: (i) the choice of test and data-reduction procedure can have important impact on the accuracy of the results, with one procedure better for some conditions and the other better in other ranges; (ii) it is important to specify carefully the level of replication (what is held constant and what varied in a given test), since otherwise an inappropriate value of uncertainty may be generated; (iii) reliable means for cross-checking and/or externally validating the results of an experiment are necessary if predicted uncertainties are to be confirmed; (iv) in experiments where data are reduced by computer, uncertainty analysis can be done by sequential perturbation, using the main data-reduction program itself.

No abstract

Structural characteristics of transitionally rough and fully rough turbulent boundary layers are presented. These were measured in flows at different roughness Reynolds numbers developing over uniform spheres roughness. Inner regions of the longitudinal component of normal Reynolds stress profiles and log regions of mean profiles continuously change in the transitionally rough regime, as the roughness Reynolds number, Rek, varies. These properties asymptotically approach fully rough behaviour as Rek increases, and smooth behaviour at low Rek Profiles of other Reynolds-stress tensor components, turbulence kinetic energy, turbulence-kinetic-energy production, and the turbulence-kinetic-energy dissipation are also given, along with appropriate scaling variables. Fully rough, one-dimensional spectra of longitudinal velocity fluctuations from boundary-layer inner regions are similar to smooth-wall results for k1 y > 0.2 when non-dimensionalized using distance from the wall y as the lengthscale, and (τ/ρ)½ as the velocity scale, where τ is local shear stress, ρ is static density, and k1 is one-dimensional wavenumber in the flow direction.

No abstract