With the aim to characterize the near-wall flow structures and their interaction with large-scale motions in the log-law region, time-resolved planar and volumetric flow field measurements were performed in the near-wall and log-law region of an adverse pressure gradient turbulent boundary layer following a zero pressure gradient turbulent boundary layer at a friction Reynolds number $Re_{\unicode[STIX]{x1D70F}}=5000$ . Due to the high spatial and temporal resolution of the measurements, it was possible to resolve and identify uniform-momentum zones in the region $z/\unicode[STIX]{x1D6FF}<0.15$ or $z^{+}<350$ and to relate them with well known coherent flow motions near the wall. The space–time results confirm that the turbulent superstructures have a strong impact even on the very near-wall flow motion and also their alternating appearance in time and intensity could be quantified over long time sequences. Using the time record of the velocity field, rare localized separation events appearing in the viscous sublayer were also analysed. By means of volumetric particle tracking velocimetry their three-dimensional topology and dynamics could be resolved. Based on the results, a conceptual model was deduced that explains their rare occurrence, topology and dynamics by means of a complex interaction process between low-momentum turbulent superstructures, near-wall low-speed streaks and tilted longitudinal and spanwise vortices located in the near-wall region.

In many situations, 3D velocity measurements in thin (∼1 mm) but wide (∼100 × 100 mm ² ) flow channels is an important task. To resolve the in-plane and out-of-plane velocity gradients properly, a precise calibration is required, since 3D measurement approaches rely strongly on the accuracy of the calibration procedure. It is likely that calibration targets do not fit domains with small depths, due to their size. Furthermore, in fields where such measurements are of interest, the accessibility of the measurement volume is often limited or even impossible. To overcome these drawbacks, this paper introduces an in situ calibrated defocusing particle tracking velocimetry approach for wall-bounded measurement domains with depths in the low millimeter range. The calibration function for the particle depth location is directly derived from the particle image geometries and their displacements between two frames. Employing only a single camera, this defocusing approach is capable of measuring the air flow between two parallel glass plates at a distance of 1 mm with an average uncertainty of 2.43% for each track, relative to the maximum velocity. A tomographic particle tracking velocimetry measurement, serving as a benchmark for the single camera technique, reaches an average uncertainty of 1.59%. Altogether, with its straightforward set-up and without requiring a calibration target, this in situ calibrated defocusing approach opens new areas of application for optical flow velocimetry. In particular, for measurement domains with small optical windows and a lack of accessibility.

Midshaft clavicle fractures comprise up to 15% of all adult upper extremity fractures and account for 76% of all clavicle fractures. The treatment of choice remains controversial. The aim of our retrospective study was to compare the outcome of the surgical and conservative procedure in a trauma care unit (single center study). In a cohort of 151 (mean age 36,1y/male 115/female 36) cases, between 2005 and 2009, 70 patients (46.4%) were treated conservatively (mean age 40.8y) and 81 (53.6%) underwent either surgical treatment with a locking compression plate (n=73/mean age 40.3y) or an intramedullary nail system (n=8, mean age 27.1y). Mean follow up was 15 months. Nine patients (5.9%) were lost to follow-up, due to poor compliance. The clinical outcome was assessed by the Disability of Arm, Shoulder and Hand (DASH) score and the Constant shoulder score. The average DASH score was 7.3 and the Constant score measured 91.7 in the surgical group. The conservative group achieved a DASH score of 11.1 and a Constant score of 88.1. The clinical scores showed a significant superiority for the benefit of the surgical treatment for the DASH (p=0.037) and Constant score (p=0.036). Totally nine patients had a non-union in the conservative group and six a hardware failure in the surgical group which were revised. The treatment options for midshaft clavicle fractures have to be discussed carefully for each patient with regard to the non-union risk, function, cosmesis and revision surgery. Both therapeutic modalities demonstrated comparable efficacy. For active and younger patients we would favour a surgical treatment due to the short time of rehabilitation, the return to sport activities and the high non-union rate after conservative treatment.

Wall roughness induces extra drag in wall-bounded turbulent flows. Mapping any given roughness geometry to its fluid dynamic behaviour has been hampered by the lack of accurate and direct measurements of skin-friction drag. Here, the Taylor–Couette (TC) system provides an opportunity as it is a closed system and allows direct and reliable measurement of the skin-friction. However, the wall curvature potentially complicates the connection between the wall friction and the wall roughness. Here, we investigate a highly turbulent TC flow, with a hydrodynamically fully rough, rotating inner cylinder, while the outer cylinder is kept smooth and stationary. We carry out particle image velocimetry (PIV) measurements in the Twente Turbulent Taylor–Couette (T3C) facility with Reynolds numbers in the range of . Our findings demonstrate that global torque measurements in the TC facility could be well suited to reliably deduce wall-drag properties for any rough surface.