Measurement Uncertainty Analysis of a Stitching Linear-Scan Method for the Evaluation of Roundness of Small Cylinders

Influences of angular misalignments of a small cylinder on its roundness measurement by the method referred to as the stitching linear scan method are theoretically investigated. To compensate for the influences, a technique for measuring angular misalignments of a small cylinder by utilizing the linear-scan surface form stylus profilometer, which is employed for roundness measurement, is newly proposed. In addition, for roundness measurement, a holder unit capable of compensating for the angular misalignments of a small cylinder is developed, and the feasibility of the proposed technique is verified in experiments. Furthermore, a measurement uncertainty analysis of the stitching linear-scan method is carried out through numerical calculations based on a Monte Carlo method.

Analysis of the Vertical Driving Performance of Multiple Connected Pipe-Climbing Microrobots with Magnetic Wheels

In this study, we analyzed the vertical driving performance of multiple connected magnetic wheel-driven microrobots when moving up and down a small cylinder that simulated a pipe. The dynamics of pipe climbing by the magnetic wheel-driven microrobot were analyzed considering the magnetic attraction force and slip; a vertical climbing simulator was developed considering the hoop force and external force from the adjacent microrobots to determine the magnetic attraction force required for multiple connected microrobot pipe climbing. A prototype of an independent vertical climbing microrobot, 5 mm long, 9 mm wide, and 6.5 mm high, and prototypes of 10 microrobots were manufactured to evaluate the vertical driving performance. The usefulness was verified by showing that three driving microrobots can move seven non-driving microrobots comprising 60% of their own weight up and down along a small cylinder.

Fourier components of cylindrical illuminance

Fourier analysis is applied to the profile of illuminance around the curved surface of a small cylinder, due to one, two and three point sources of light and due to an extended source. This reveals only one odd harmonic, whose amplitude is equal to half that of the illumination vector. Lighting can also generate a diminishing series of even harmonics. The lighting at any point in open space can be expressed in terms of the harmonics of illuminance around three mutually perpendicular cylinders. Visual discomfort is often associated with the presence of even harmonics. The photometry of cylindrical and semi-cylindrical illuminance, and of cylindrical harmonics, is discussed.

Numerical Investigations of Flow Past a Rotating Stepped Cylinder

Unsteady numerical investigations of flow past a partially rotating stepped cylinder have been performed. The objective of the study was to investigate whether the wake characteristics could be controlled with rotation of one cylinder while the other remains stationary and how partial rotation impacts the aerodynamic forces. The stepped cylinder was 2 m in length where the first meter was a round cylinder 5 cm in diameter followed by a 2:1 step down cylinder. Two round end plates, 0.1 cm thick and 40 cm in diameter, were placed at each end. The end plates were positioned at 5 degrees with respectto the incoming flow to remove the end effect on vortex shedding. All simulations were performed using the Siemens PLM STAR-CCM+ CFD software with K-ω turbulence model. The time step was 0.00083 second to resolve the flow for each 10 degrees rotation. 1200 time steps were used. The investigations were performed with one cylinder rotating while the other remains stationary. Four cases were investigated. When either cylinder was rotating, the RPM was maintained at either 2000 or 4000 while the free stream velocity was maintained at 10 m/sec. The Reynolds number for the large and small cylinders were approximately 32,258 and 16,129, respectively. The corresponding velocity ratios λ for the large cylinder rotating were 0.5 and 1.0, and 0.25 and 1.0 for the small cylinder. Previous investigations have classified vortical structure in the wake of a step cylinder in terms of L-cell (for large cylinder), S-cell (for small cylinder) and N-cell (the region in between). When the large cylinder is rotating, at λ = 1.0, the velocity and vorticity in the wake of the large cylinder is increased. The N-cell initially has a larger velocity than the L-cell and is at a slanted angle. A suction effect was observed in the near wake region, causing the flow in the L-cell to coalesce near its midsection. The vortices originated at the step were connected to the S-cell at a lower speed. The overall lift to drag ratio (L/D) for this case was 1.14. When λ = 0.5, vortex structures were maintained through the three different cells with increased variations in cell frequency across the large cylinder, the L/D was reduced to 0.36. When the small cylinder was rotating, at λ = 0.5, vortex shedding was suppressed within the S-cell and considerable distortion was observed in the vortical structure in the wake of the large cylinder. However, the N-cell had similar structure as when large cylinder was rotating, but connecting to the L-cell at a larger slanted angle. When λ was reduced to 0.25, shedding was observed across the length of the cylinder with increased variations. The corresponding L/D ratios for these cases were both at 0.2.

Effects of Longitudinal Alignments on the Time-Mean Flow Structures of Side-by-Side Circular Cylinders of Diameter Ratio Two

The time-averaged flow characteristics in the regions upstream and downstream of the side-by-side cylinders of diameter ratio two, arranged at different longitudinal alignments and two gap ratios, are studied via particle image velocimetry (PIV). It is found that the locations of forward stagnation point of the large and the small cylinders do change with the longitudinal alignments. Upstream of the large cylinder, the streamwise variations of U* are nearly independent of the longitudinal alignment for both T*=1.5 and 1.0. However, upstream of the small cylinder, the streamwise variations of U* indeed depend on T*. Upstream of the small cylinder, the streamwise variations of V* are strongly affected by T* and, the largest magnitude of V* occurs at CLA for both T*=1.5 and T*=1.0. Also, the locations of the largest magnitude of V* move closer to the small cylinder as the T* reduces. For different T* and L*, the flow rate (or the averaged velocity through the gap) and the gap orientation will be changed at the same Reynolds number (Re=1000). The effect of pressure difference across the gap may be overwhelmed or be counterbalanced by that of the gap orientation leading to quite different flow structures in the downstream region of the cylinder couples. The effects of longitudinal alignment are to (1) change the forward stagnation points of the large and the small cylinders; (2) modify the region of mutual interaction between two wakes. (3) As S* reduces, the gap orientation takes the dominance over the pressure difference across the gap to switch the gap flow so that the wide-wake is formed behind the small cylinder especially for T*=1.0 and TEA.