Maximum Tangential Speed Research Articles

Efficient microspark erosion-assisted machining of a monocrystalline microdiamond stylus using a heat-avoidance path

Monocrystalline diamond possesses covalent bonding making diamond extremely hard and difficult to machine. In this study, a microdiamond stylus typically used in measuring surface roughness is machined to exemplify the proposed ‘microspark erosion-assisted machining with heat-avoidance path’ technique. Based on the high thermal conductivity and weak electrical conductivity of boron-doped monocrystalline diamond, high-frequency pulsed discharge plasma is employed to efficiently perform microspark erosion machining on an extremely hard monocrystalline diamond blank. It was found that the pulse-on time and servo voltage respectively affect erosion plasma length and the erosion gap during diamond machining. Also, the safety distance and safety height of the erosion path dominate heat transfer to filler metal. These factors all affect the firmness of the brazed diamond blank on the substrate. Three mechanisms for removing carbon atoms from the diamond blank surface were observed. They are vaporization, melting, and graphitization of carbon atoms. This graphitized carbon atoms have weak electrical conductivity, which is conducive to inducing the wire-electrode to generate a greater electric field and secondary discharging, facilitating removal of additional carbon atoms. Experimental results indicate that a microdiamond stylus prototype with a tip of 10 μm can be safely formed using a ‘microspark erosion-assisted machining with heat-avoidance path’ technique, creating 93.7% repeatability of the minimum residual stylus diameter. The tangential micro-grinding facilitates the stylus tip to receive grinding from the grinding wheel's maximum tangential speed and create the precision microdiamond stylus with 1 μm in tip-radius. The applied microspark erosion-assisted machining had a diamond material removal rate that was 54% more efficient than conventional grinding of a commercial microdiamond stylus. The formed microdiamond stylus was inspected by Raman spectroscopy and verified by the surface roughness standard gauge to be up to industry standards.

Numerical Simulation of Characteristics of Spray Flow Field on the Conical Surface

Aiming at the gas-liquid two-phase flow process in the spray flow field on the conical outer surface, based on Euler-Euler method a spray film forming model is proposed. A polyhedral mesh was utilized to divide the fluid computing domain and the coupled SIMPLE algorithm was adopted to solve the model. The results of show that the spray shape on the outer surface of the cone is similar to that on the outer surface of the arc, and both are in the shape of an elliptical cone; in the area far away from the wall surface, the difference ofsurface has almost no effect on the spray cone angle. In terms of the spraying speeds of the two spraying methods within the area close to the outer surface of the cone, for the circumferential spraying, the spray normal speed is higher than that of spraying along the busbar, and the maximum tangential speed is lower. Meanwhile, both the two speeds are almost equal to that of spraying the arc surface; for spraying along the busbar, the spray normal speed is higher than that of the arc outer surface, and the maximum tangential speed is lower.

Dynamics and water mass structure of a summertime anticyclonic eddy in Funka Bay, Hokkaido, Japan

The hydrography and flow structure of an anticyclonic eddy are investigated synoptically using conductivity, temperature and depth (CTD) and Acoustic Doppler Current Profiler (ADCP) data for Funka Bay on June 17 and July 23, 1997. In June, the anticyclonic eddy was characterized by a deep concave structure of isopycnal surfaces, with elliptical horizontal shape. The tangential speed of the eddy at 10 m depth approached a maximum of 30 cm s −1 at a radius of about 10 km. In July, the eddy was characterized by a sharp pycnocline with two density fronts around the outer edge of the eddy at a depth of 10 m. The horizontal shape of the eddy became circular, and the maximum tangential speed at 10 m depth decreased to 25 cm s −1 at a radius of about 15 km. The core of the eddy rotated as a rigid body through one cycle approximately once every 2.3 days in June, and every 4.8 days in July. Analysis of the tangential currents at 10 m depth using the gradient flow relationship revealed that the eddy was hydrodynamically balanced between three forces: Coriolis force, centrifugal force and a force due to the horizontal pressure gradient. The vertical and horizontal scales of the eddy changed dramatically between June and July, with the vertical scale of the eddy becoming shallower as the deep concave structure of the isopycnal surfaces was destroyed due to the intrusion of water originating from Tsugaru warm water (TW). The horizontal scale of the eddy also decreased from June to July, related to the formation of two density fronts arising due to coastal upwelling associated with south-southeasterly winds and due to contact of the eddy with water originating from TW in the upper layer. The coastal upwelling not only changed the horizontal structure of the eddy, but also transported nutrients to the surface layers from deeper layers. These nutrients would promote primary production in summer in Funka Bay. The collection of scallop larvae by aquacultural netting at fixed coastal sites would therefore be strongly affected by the eddy, suggesting that the eddy plays an important role in the ecosystem of Funka Bay.

Structure of a Midtropospheric Vortex Induced by a Mesoscale Convective System

On 9 June 1988 a mesoscale (;200-km diameter) convectively generated vortex (MCV) passed through the Colorado wind-profiling network. The generating convective system, which was too small to meet Maddox’s mesoscale convective complex criteria, developed beneath a high-amplitude mid- and upper-level ridge axis. Profiler winds obtained within the stratiform region of the convective system and near the center of the ensuing MCV form the basis of this study. With the addition of satellite (including rapid scan) images and conventional and Doppler radar data, this vortex was well observed over its entire life cycle. The slowly moving vortex was observed by the Flagler 50-MHz profiler for more than 16 h. For a portion of this period the circulation was quasi-steady; hence, the spatial structure of the vortex was depicted by timeto-space conversion of the profiler data. The results show a strong, coherent circulation with maximum tangential speeds greater than 16 m s21 at 6 km above mean sea level (MSL) and at radii of 50‐70 km; corresponding relative vorticity was more than three times as large as the local Coriolis parameter. The long duration and the apparent dominance of vorticity over divergence suggest that the flow in the vortex was in a quasi-balanced state. Hence, the temperature perturbation necessary to support the tangential velocity distribution was computed assuming gradient balance in the radial direction. The resulting estimated temperature structure showed a warm core with a magnitude of 2.38C at 7.3 km MSL and a cold core below 6.3 km MSL. The associated potential vorticity (PV) structure at the vortex center consisted of a lens of high PV with a maximum at 6.3 km MSL and relative minima above and below this height.

Doppler Spectra and Estimated Windspeed of a Violent Tornado

Abstract Presented in this Paper are Doppler spectra of a very large tornado that occurred on 22 May 1981 near Binger, Oklahoma. Tracking of the tornado was accomplished with the help of a novel “polar spectra display.” Bimodal tornado spectral signatures (TSS) were observed in about 40 scans. Direct measurements of maximum velocities from spectral skirts yielded a maximum tangential speed of 80 m s−1 (90 m s−1 relative to ground). A diameter of 1 km at 200 m above ground was deduced from a simplified model. Radial centrifuging of radar targets was estimated to be about 20 m s−1. With simple assumptions for radar target sizes and summation of forces, a beamwidth average convergence value of about 2.5 × 10−2 s−1 was calculated for the tornado boundary layer. Tornado damage to trees and structures was subjectively rated on the Fujita damage scale. The windspeed range associated with the damage scale agreed well with the Doppler-estimated maximum windspeed when the tornado was large (1 km diameter). However,...

Structure of lift-generated rolled-up vortices

Widely used analytical models describing the structure of lift-generate d vortices behind aircraft wings (e.g., models of Betz or Lamb) are generally not in acceptable agreement with experiments. The lack in conservation of vortical dispersion and rotational energy, which is connected with the induced drag of the generating wing, is considered as a reason for this discrepancy. The model of Lamb is modified in a simple way to account for the conservation laws. These modifications yield a reduction in the core radius and a remarkable increase in the maximum tangential speed. A comparison with experiments is made and reasonable agreement is found. For the modification of the vorticity distribution in the Lamb model, the Kirchhoff-Routh function is used. This function is proportional to the rotational energy for a continuously spaced array of point vortices having the proper vorticity. The proposed model can be adapted to arbitrary vorticity distributions and, hence, wing loadings. a c CR De / k, p q r rK s t u vm W 7r, 7 5

Observations of the Union City Tornadic Storm by Plan Shear Indicator

Abstract The storm which spawned the devastating Union City, Okla., tornado of 24 May 1973 was observed by Doppler Plan Shear Indicator (PSI). The PSI, an analog device for display of velocity gradients, had been temporarily mated to the 10 cm Doppler radar operated by the National Severe Storms Laboratory. The first PSI picture showed intense shear at 8–9 km altitude, 45 min before the earliest tornado damage. About 40 min before the tornado struck, a vortex pattern with cyclonic rotation was recognizable at 5–8 km, but the wind field in the storm below 4 km was quite uniform. The base of the flow disturbance as well as the vortex descended and intensified during this early period prior to tornado touchdown. Vortex diameter was as large as 5 km when initially detected but decreased to less than 1 km at the surface when the tornado was on the ground. Maximum tangential speeds of the vortex were generally 10–25 m s−1, with the higher values measured just before and during the period of surface damage. Shea...