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The demand of air bearings is increasing for those applications that require precision linear movements or high-speed rotations. In particular in this paper air pads for air motion technology are studied. The paper analyses the effect of a circumferential groove machined on the pad surface on pressure distribution, air flow consumption and stiffness. Two geometries are investigated and compared: one with three supply orifices and the other with a circumferential groove as well. The static characteristics of the pads are experimentally determined with also the pressure distributions under the pads along the radial and circumferential directions. The experimental pressure distributions are compared with the simulated ones, obtained with a numerical program at the purpose developed. The numerical model considers a general formulation of the supply holes discharge coefficient that can be used also in presence of a circumferential groove.

The paper presents an experimental co mparison of three types of static micro mixer. Efficiencies of a split and recomb ination micro mixer (SAR) based on plate symmet rical modules (PSM) and basic T-type and O-type mixers are examined. Experimental tests were carried out in the laminar flow reg ime with a lo w Reynolds number range, 0.083 ≤ Re ≤ 4.166 and image-based techniques were used to evaluate mixing efficiency. Experimental results illustrate that the micro mixers with splitting and recombination have outstanding mixing efficiency than those of without SAR process. Indeed split and reco mbine (SA R) structures of the flow channels result in the reduction of the d iffusion distance of two fluids and optimize the diffusion process and after a short distance fro m inlet high mixing efficiency can be achieved. A lso, experimental data show that the SAR PSM mixer is up to 99% efficient, and that efficiency reaches 90% in a short distance, demonstrating this type of mixer's high mixing performance and the effect of splitting and recombination on the degree of mixing and the efficiency of the mic ro mixer.