Highly Sensitive Flow Sensor Based on Flexible Dual-Layer Heating Structures.

Hot film sensors detect the flow shear stress based on the forced convection heat transfer to the fluid. Current hot film sensors have been significantly hindered by the relatively low sensitivity due to the massive heat conduction to the substrate. This paper describes the design, fabrication, simulation, and testing of a novel flow sensor with dual-layer hot film structures. More specifically, the heat conduction was insulated from the sensing heater to the substrate by controlling both sensing and guarding heaters working at the same temperature, resulting in a higher sensitivity. The experiment and simulation results showed that the sensitivity of the dual-layer hot film sensor was significantly improved in comparison to the single-layer sensor. Additionally, the dual-layer sensor was designed and fabricated in an integrated, flexible, and miniaturized manner. Its small size makes it an excellent candidate for flow detection.

Accurate Measurements of Wall Shear Stress on a Plate with Elliptic Leading Edge.

A micro-floating element wall shear stress sensor with backside connections has been developed for accurate measurements of wall shear stress under the turbulent boundary layer. The micro-sensor was designed and fabricated on a 10.16 cm SOI (Silicon on Insulator) wafer by MEMS (Micro-Electro-Mechanical System) processing technology. Then, it was calibrated by a wind tunnel setup over a range of 0 Pa to 65 Pa. The measurements of wall shear stress on a smooth plate were carried out in a 0.6 m × 0.6 m transonic wind tunnel. Flow speed ranges from 0.4 Ma to 0.8 Ma, with a corresponding Reynold number of 1.05 × 106~1.55 × 106 at the micro-sensor location. Wall shear stress measured by the micro-sensor has a range of about 34 Pa to 93 Pa, which is consistent with theoretical values. For comparisons, a Preston tube was also used to measure wall shear stress at the same time. The results show that wall shear stress obtained by three methods (the micro-sensor, a Preston tube, and theoretical results) are well agreed with each other.

5,5'-[(1,4-Phenyl-enedimethyl-ene)bis-(sulfanedi-yl)]bis-(1-methyl-1H-1,2,3,4-tetra-zole).

The title mol-ecule, C(12)H(14)N(8)S(2), has point symmetry [Formula: see text] since it is situated on a crystallographic centre of symmetry. The 1-meth-yl/5-thio groups are in an anti-periplanar conformation. The dihedral angle between the benzene and tetra-zole rings is 84.33 (2)°. In the crystal, C-H⋯N hydrogen bonds link mol-ecules into ladder-like chains running along the b axis. There are also C-H⋯π inter-actions present in the crystal structure.