Range Of Rotational Velocities Research Articles

Effect of Rotational Velocity on Mechanical and Corrosion Properties of Friction Stir-Welded SUS301L Stainless Steel.

Friction stir welding was utilized to obtain high-quality SUS301L stainless steel joints, whose mechanical and corrosion properties were thoroughly evaluated. Sound joints were obtained with a wide range of rotational velocities from 400 to 700 rpm. The microstructures of the stir zone primarily consisted of austenite and lath martensite without the formation of detrimental phases. The ultimate tensile strength of the welded joints improved with higher rotational velocities apart from 400 rpm. The ultimate tensile strength reached 813 ± 16 MPa, equal to 98.1 ± 1.9% of the base materials (BMs) with a rotational velocity of 700 rpm. The corrosion resistance of the FSW joints was improved, and the corrosion rates related to uniform corrosion with lower rotational velocities were one order of magnitude lower than that of the BMs, which was attributed to the lower martensite content. However, better anti-pitting corrosion performance was obtained with a high rotational velocity of 700 rpm, which was inconsistent with the uniform corrosion results. It could be speculated that a higher martensitic content had a negative effect on the uniform corrosion performance, but had a positive effect on the improvement of the anti-pitting corrosion ability.

Tracing the evolution of short-period binaries with super-synchronous fast rotators

Context. The initial distribution of rotational velocities of stars is still poorly known, and how the stellar spin evolves from birth to the various end points of stellar evolution is an actively debated topic. Binary interactions are often invoked to explain the existence of extremely fast-rotating stars (vsin i ≳ 200 km s−1). The primary mechanisms through which binaries can spin up stars are tidal interactions, mass transfer, and possibly mergers. However, fast rotation could also be primordial, that is, a result of the star formation process. To evaluate these scenarios, we investigated in detail the evolution of three known fast-rotating stars in short-period spectroscopic and eclipsing binaries, namely HD 25631, HD 191495, and HD 46485, with primaries of masses of 7, 15, and 24 M⊙, respectively, with companions of ∼1 M⊙ and orbital periods of less than 7 days. These systems belong to a recently identified class of binaries with extreme mass ratios, whose evolutionary origin is still poorly understood. Aims. We evaluated in detail three scenarios that could explain the fast rotation observed in these binaries: it could be primordial, a product of mass transfer, or the result of a merger within an originally triple system. We also discuss the future evolution of these systems to shed light on the impact of fast rotation on binary products. Methods. We computed grids of single and binary MESA models varying tidal forces and initial binary architectures to investigate the evolution and reproduce observational properties of these systems. When considering the triple scenario, we determined the region of parameter space compatible with the observed binaries and used a publicly available machine-learning model to determine the dynamical stability of the triple system. Results. We find that, because of the extreme mass-ratio between binary components, tides have a limited impact, regardless of the prescription used, and that the observed short orbital periods are at odds with post-mass-transfer scenarios. We also find that the overwhelming majority of triple systems compatible with the observed binaries are dynamically unstable and would be disrupted within years of formation, forcing a hypothetical merger to happen so close to a zero-age main-sequence that it could be considered part of the star formation process. Conclusions. The most likely scenario to form such young, rapidly rotating, and short-period binaries is primordial rotation, implying that the observed binaries are pre-interaction ones. Our simulations further indicate that such systems will subsequently go through a common envelope and likely merge. These binaries show that the initial spin distribution of massive stars can have a wide range of rotational velocities.

Design and fabrication of a low-cost wireless camera imaging system for centrifugal microfluidics

Centrifugal microfluidic devices offer a robust method for low-volume fluid handling by combining low-cost instrumentation with highly integrated automation. Crucial to the efficacy of Lab-on-a-Disc (LoaD) device operation is the selection of robust valving technology, the design of on-disc fluidic structures, and accurate control of disc spin-speeds (centrifugal force) during operation. The design and refinement of fluidic and valving structures is often guided by inspecting disc operation using high-speed camera systems. This approach involves synchronising image acquisition with disc rotation to visualise liquid flow through a series of images often presented in a video format. Depending on the decisions taken, such systems can cost from €4,000 upwards. This paper outlines the development of a low-cost centrifugal test-stand with an integrated imaging system using a generic wireless camera to record videos directly to a smartphone device. This imaging system can be fabricated using only 3D printers and a low-cost CNC milling machine from widely available materials for approximately €350. High-fidelity imaging of the entire disc for flow visualisation and the recording of real-time colour intensity measurements are facilitated by this standalone device. A vibration analysis study has been performed to determine the rotational velocity range at which the system can be safely operated. Furthermore, the efficacy of the imaging system has been demonstrated by performing real-time colour intensity measurements of dyed water dilutions.

Nonlinear Dynamics of a Blade Rotor with Coupled Rubbing of Labyrinth Seal and Tip Seal

The dynamic response and its stability of a blade rotor with coupled rubbing in the labyrinth seal and tip seal are investigated. The dynamic equations are established based on the Hertz contact rubbing force at the labyrinth seal and the tip rubbing force considering both the contact deformation of the tip seal and the bending deformation of the blade. Numerical simulations show that the coupled rubbing response includes periodic motions, almost periodic motions, and chaotic motions. Compared with the single rubbing fault, coupled rubbing increases the range of rotation velocity of contact. A new continuation shooting method is used in the solution and stability analysis of the periodic response to give the bifurcation diagrams. The paths of the system for entering and exiting chaos are analyzed.

Bubble behaviour in a horizontal high-speed solid-body rotating flow

We study experimentally the behaviour of a bubble injected into a horizontal liquid solid-body rotating flow, in a range of rotational velocities where the bubble is close to the axis of rotation. We first study the stretching of the bubble as a function of its size and of the rotation of the cell. We show that the bubble aspect ratio can be predicted as a function of the bubble Weber number by the model of Rosenthal (J. Fluid Mech., vol. 12, 1962, 358–366) provided an appropriate correction due to the impact of buoyancy is included. We next deduce the drag and lift coefficients from the mean bubble position. For large bubbles straddling the axis of rotation, we show that the drag coefficient $C_D$ is solely dependent on the Rossby number $Ro$, with $C_D \approx 1.5/Ro$. In the same limit of large bubbles, we show that the lift coefficient $C_L$ is controlled by the shear Reynolds number $Re_{shear}$ at the scale of the bubble. For $Re_{shear}$ larger than 3000 we observe a sharp transition, wherein large fluctuations in the bubble aspect ratio and mean position occur, and can lead to the break-up of the bubble. We interpret this regime as a resonance between the periodic forcing of the rotating cell and the eigenmodes of the stretched bubble.

Convective heat transfer analysis of a laminated flux focusing magnetic gearbox

Magnetic machine designers must consider a variety of mechanical and thermal aspects, particularly as the size increases and the air-gaps between rotors and stators decrease. In these instances, increased losses due to eddy currents can create elevated temperatures, which in turn create significant thermal deformation of components that compromises component positioning or magnetic material degradation. Lump capacitance and conduction methods are traditionally used in magnetic machines, but the fluid behavior is ignored. A coupled (conduction/convection) approach, where both convection and conduction heat transfers are considered in the domain, in a 3D flow and conjugate heat transfer analysis, is developed for the fully laminated magnetic gearbox, (1:4.25 gear ratio) to numerically investigate the effect of fluid properties on the thermal results. The numerical results are validated using experimental measurement data. The comparison between the coupled and conduction methods with experimental results shows higher accuracy for the coupled method compared to the conduction method, as the air trapped in the gaps is modeled as a fluid, which is more realistic way compared to the approximation of it with a solid part. This results in the coupled conduction/convection method over-predict the outer rotor temperature by only 2.5 K on average (over 29–123 rpm rotational velocity range), compared to the 5.5 K average over-prediction for the simple conduction method. The eddy current losses created by the travel of magnetic field in the conductive materials inside the active region of a magnetic gear corresponds for the main source of losses in these systems. A detailed loss analysis on the components, followed by the analysis of the structural deformation caused by temperature rise provides the designers with an insight into the material selection and structural design criteria to avoid off-the-range thermal stresses, temperatures and corresponding deformations in such systems.

Research of Dynamics of Gated-Electrical Processes in Simulink

Recent advances in the field of electrical engineering, semiconductor and converter technology, have led to introduction of a new class of electric machines, operating in a wide range of rotational velocities, which are called gate. These machines make it possible to build standalone power supplies on their basis, to ensure the generation of high power with minimum drive unit requirements. A mathematical model of the mechanical synchronous generator with voltage stabilization when changing the drive shaft rotational velocity in a wide range have been implemented in MatLab Simulink package composed of specialist electrical block library. The modeling process in MatLab Simulink functions as a construction scheme of the standard block device package and configure of its individual elements. Obtained results concerning simulation of a gate generator with voltage stabilization based on the example of 32 pole machine with 1 kW showed good ability to generate high electric power over a wide rotational velocity range (90 to 187.5 rpm). Operated intermediate converters are able to maintain the stability of the voltage value at the variable rotational velocity that results in required operation for stand-alone power supplies

Frequency Response of Laser Gyroscopes in a Wide Range of Rotation Velocities

The laser gyro frequency response is studied by means of numerical simulation using a phase equation. The calculation results are compared to the results of experimental measurements on a precision dynamic test-bench. Quantitative relationship between the threshold value of static lock-in zone and frequency response distortions is established. Numerical methods helped to obtain and experimentally confirm the quantitative dependence of frequency response distortion on the amplitude and frequency of meander-shaped dither. It is shown that the dither shape significantly affects the frequency response form. Furthermore, it is demonstrated that frequency-response distortions depend on conditions of its measurement, in particular, on the time. The conducted research allows dither parameters to be optimized with a view to increase the accuracy of measurements using laser gyroscopes.

The KMOS3D Survey: Rotating Compact Star-forming Galaxies and the Decomposition of Integrated Line Widths*

Abstract Using integral field spectroscopy, we investigate the kinematic properties of 35 massive centrally dense and compact star-forming galaxies (SFGs; , , ) at z ∼ 0.7–3.7 within the KMOS3D survey. We spatially resolve 23 compact SFGs and find that the majority are dominated by rotational motions with velocities ranging from 95 to 500 km s−1. The range of rotation velocities is reflected in a similar range of integrated Hα line widths, 75–400 km s−1, consistent with the kinematic properties of mass-matched extended galaxies from the full KMOS3D sample. The fraction of compact SFGs that are classified as “rotation-dominated” or “disklike” also mirrors the fractions of the full KMOS3D sample. We show that integrated line-of-sight gas velocity dispersions from KMOS3D are best approximated by a linear combination of their rotation and turbulent velocities with a lesser but still significant contribution from galactic-scale winds. The Hα exponential disk sizes of compact SFGs are, on average, 2.5 ± 0.2 kpc, 1–2× the continuum sizes, in agreement with previous work. The compact SFGs have a 1.4× higher active galactic nucleus (AGN) incidence than the full KMOS3D sample at fixed stellar mass with an average AGN fraction of 76%. Given their high and centrally concentrated stellar masses, as well as stellar-to-dynamical mass ratios close to unity, the compact SFGs are likely to have low molecular gas fractions and to quench on a short timescale unless replenished with inflowing gas. The rotation in these compact systems suggests that their direct descendants are rotating passive galaxies.

Photospheric carbon and oxygen abundances of F–G type stars in the Pleiades cluster*

Abstract In order to investigate the carbon-to-oxygen ratio of the young open cluster M 45 (Pleiades), the C and O abundances of 32 selected F–G type dwarfs (in the effective temperature range of Teff ∼ 5800–7600 K and projected rotational velocity range of vesin i ∼ 10–110 km s−1) belonging to this cluster were determined by applying the synthetic spectrum-fitting technique to C i 5380 and O i 6156–8 lines. The non-local thermodynamical equilibrium corrections for these C i and O i lines were found to be practically negligible (less than a few hundredths dex).The resulting C and O abundances (along with the Fe abundance) turned out nearly uniform without any systematic dependence upon Teff or vesin i. We found, however, in spite of almost solar Fe abundance ([Fe/H] ∼ 0), carbon turned out to be slightly subsolar ([C/H] ∼ −0.1) while that of oxygen was slightly supersolar ([O/H] ∼ +0.1). This leads to a conclusion that the [C/O] ratio was moderately subsolar (∼ −0.2) in the primordial gas from which these Pleiades stars were formed ∼ 120–130 Myr ago. Interestingly, similarly young B-type stars are reported to show just the same result ([C/O] ∼ −0.2), while rather aged (∼ 1–10 Gyr) field F–G stars of near-solar metallicity yield almost the solar value ([C/O] ∼ 0) on average. Such a difference in the C/O ratio between two star groups of distinctly different ages may be explained as a consequence of the orbit migration mechanism which Galactic stars may undergo over a long time.

Joint representation of translational and rotational components of optic flow in parietal cortex

Terrestrial navigation naturally involves translations within the horizontal plane and eye rotations about a vertical (yaw) axis to track and fixate targets of interest. Neurons in the macaque ventral intraparietal (VIP) area are known to represent heading (the direction of self-translation) from optic flow in a manner that is tolerant to rotational visual cues generated during pursuit eye movements. Previous studies have also reported that eye rotations modulate the response gain of heading tuning curves in VIP neurons. We tested the hypothesis that VIP neurons simultaneously represent both heading and horizontal (yaw) eye rotation velocity by measuring heading tuning curves for a range of rotational velocities of either real or simulated eye movements. Three findings support the hypothesis of a joint representation. First, we show that rotation velocity selectivity based on gain modulations of visual heading tuning is similar to that measured during pure rotations. Second, gain modulations of heading tuning are similar for self-generated eye rotations and visually simulated rotations, indicating that the representation of rotation velocity in VIP is multimodal, driven by both visual and extraretinal signals. Third, we show that roughly one-half of VIP neurons jointly represent heading and rotation velocity in a multiplicatively separable manner. These results provide the first evidence, to our knowledge, for a joint representation of translation direction and rotation velocity in parietal cortex and show that rotation velocity can be represented based on visual cues, even in the absence of efference copy signals.

Effect of Different Operating Conditions on the Corrosion of Carbon Steel in Oxygenated Sodium Sulphate Solution

Carbon steel is a major metal used in manufacturing of the equipments used in petroleum industry and it is subject to different operating conditions causing various corrosion attacks. Corrosion of carbon steel in sodium sulphate solution (Na2SO4) under flow conditions was investigated using rotating cylinder electrode (RCE) for a range of rotation velocity (0 – 2000 rpm) and temperatures (32 - 52 oC). The corrosion rate was determined by using both weight loss method and electrochemical polarization technique (limiting current density). Different salt concentrations were investigated ranged from 0.01 to 0.4 M. The effect of time (or corrosion product formation) and the effect of oxygen concentration through air bubbling in the solution were also investigated and discussed. The results showed that increasing rotational velocity leads to a considerable increase in the corrosion rate represented by limiting current density. The corrosion rate had unstable trend with salt concentrations and temperature. Generally, the corrosion rate decreased appreciably with time due to the formation of corrosion product layer depending on rotational velocity, temperature, and oxygen concentration. It was found that, air pumping through the salt solution leads to a considerable increase in the limiting current density (iL) depending on rotational velocity, temperature, and time.

The effect of temperature and hydrodynamics on carbon steel corrosion and its inhibition in oxygenated acid–salt solution

Corrosion of carbon steel in hydrochloric acid (HCl)–sodium sulphate (Na2SO4) solution mixture was investigated using rotating cylinder electrode (RCE) for a range of rotation velocity, 0–2000rpm, solution temperature of 32–52°C, and different oxygen concentrations. The corrosion rat was determined by using both weight loss method and electrochemical polarization technique. Different acid and salt concentrations were used ranged from 0.01 to 0.2M for salt and 0.5 to 5% for acid. The conjoint effect of increased oxygen concentration and high rotational velocity was studied based on experimental measurements of O2 concentration. The effects of operating conditions on indole and cetyl trimethyl ammonium bromides (CTAB) inhibition efficiency were also studied and discussed. The results showed that increasing the rotational velocity leads to an increase in the corrosion rate depending on the concentration of salt and acid. Increasing the temperature and acid concentrations leads to an increase in the corrosion rate while the corrosion rate exhibited unstable trend with salt concentration leads to change of corrosion. It is found that increasing O2 concentration leads to a considerable increase in the corrosion rates especially at high rotational velocity. Indole and CTAB inhibitors exhibited very good inhibition efficiency in most conditions investigated with the former exhibited better inhibition efficiency arriving up to 87% at low rotational velocities. The inhibition efficiency of both inhibitors was found to decrease with increasing velocity. In addition, indole inhibitor reveals excellent inhibition efficiency even at high temperatures while CTAB efficiency decreased appreciably with temperature increase.

Stress and deformation of rocket gas turbine disc under different loads using finite element modelling

Gas turbine discs have numerous applications in the aerospace industry, such as in liquid rocket engines. In this study, the stresses and deformations of a turbine disc were studied. The goal was to highlight the stress and deformation distribution to assist in the design of a disc as well as to demonstrate the importance of using finite element (FE) analysis in simulating an actual design case. Then, to present the real model, a two-dimensional (2D) axisymmetric model for a non-uniform disc was analysed using FE analysis. The stresses and deformations developed as a result of the disc operating conditions at high rotational speeds and thermal gradients were evaluated using two types of heat transfer modes—conduction and convection, taking into consideration the material behaviour at elevated temperatures. The FE model revealed that the weight of the disc should be reduced optimally by using a non-uniform thickness because this results in a huge increase in the applied stresses. The greatest stresses in the disc result from the thermal load caused by conduction, and they are located at the centre of the disc. In addition, an analytical method was used to evaluate and predict the stresses along the disc, and it gave a good estimate of the stress values compared to the FE model. Based on this estimate, a parametric study was conducted for a range of rotational velocities under high temperature loads for a series of disc radii. Finally, it was found that this method can be used for the preliminary design of different turbines.

Biomechanical investigation into the torsional failure of immature long bone.

Approximately 50% of infant and toddler long bone fractures are attributed to non-accidental trauma; however, differentiating from benign mechanisms is subjective, due to an absence of evidence-based diagnostic tools. Previous studies investigated small ranges of rotational velocities in animal long bone models, although did not report the variation in the spiral fracture angle. This study considered the fracture angle as a potential clinical measure, correlating this data with a wider range of rotational velocities. The spiral fracture angle was measured relative to the long axis, whilst noting the narrowest diaphysial diameter, location of the fracture, and the extent of comminution and periosteal disruption. Twenty-six bones failed in spiral fracture, with the potting material failing in the remaining tests. All spiral fractures centred on the narrowest diaphysial diameter. Slower rotational velocities caused fracture angles approaching 45°, whereas fractures at greater velocities caused fracture angles nearer 30°. A relatively strong trend (R (2)=0.78) is reported when the normalised fracture angle (against the narrowest diaphysial dimension) was plotted against the rotational rate. A relationship has been identified between the angle of spiral fracture and the rotational velocity using the immature bovine metatarsal model. This trend forms a scientific foundation from which to explore developing a diagnostic, evidence-based tool that may ultimately serve to assist differentiating between accidental and non-accidental injury.

Evolution of massive Population III stars with rotation and magnetic fields

[Abridged] We present a new grid of massive population III star models including the effects of rotation on the stellar structure and chemical mixing, and magnetic torques for the transport of angular momentum. Based on the grid, we also present a phase diagram for the expected final fates of rotating massive Pop III stars. Our non-rotating models become redder than the previous models in the literature, given the larger overshooting parameter adopted in this study. In particular, convective dredge-up of the helium core material into the hydrogen envelope is observed in our non-rotating very massive star models (>~200 Msun), which is potentially important for the chemical yields. On the other hand, the stars become bluer and more luminous with a higher rotational velocity. With the Spruit-Tayler dynamo, our models with a sufficiently high initial rotational velocity can reach the critical rotation earlier and lose more mass as a result, compared to the previous models without magnetic fields. The most dramatic effect of rotation is found with the so-called chemically homogeneous evolution (CHE), which is observed for a limited mass and rotational velocity range. CHE has several important consequences: 1) Both primary nitrogen and ionizing photons are abundantly produced. 2) Conditions for gamma-ray burst progenitors are fulfilled for an initial mass range of 13 - 84 Msun. 3) Pair instability supernovae of type Ibc are expected for 84 -190 Msun and 4) Both a pulsational pair instability supernova and a GRB may occur from the same progenitor of about 56 - 84 Msun, which might significantly influence the consequent GRB afterglow. We find that CHE does not occur for very massive stars (> 190 Msun), in which case the hydrogen envelope expands to the red-supergiant phase and the final angular momentum is too low to make any explosive event powered by rotation.

Brouwer’s rotating vessel I: stabilization

The paradox of destabilization of a conservative or non-conservative system by small dissipation, or Ziegler’s paradox (1952), has stimulated an interest in the sensitivity of reversible and Hamiltonian systems with respect to dissipative perturbations. We discuss the motion of a particle in Brouwer’s rotating vessel, a typical gyroscopic system, that has an unstable equilibrium caused by internal damping for a wide range of rotation velocities. Using quasi-periodic averaging-normalization by Mathematica, we find that modulation of the rotation frequency in the cases of single-well and saddle equilibria stabilizes the system for a number of combination resonances, thus producing quenching of the unstable motion.

Basic study of pole change generator for micro windmill generation system

AbstractThis paper proposes a pole change generator for a windmill. Since micro windmill systems generate power from natural energy, power generation characteristics across a wide band are necessary. However, the conventional generator, in which the open voltage is simply proportional to the rotational velocity, encounters difficulty in generating power across a wide range of rotational velocities from low to high, because of the power generation characteristics. To develop a generator with a wide power band suitable for a micro windmill, this paper proposes a technique for switching the status of the generator coil connection. To demonstrate the effectiveness of pole changing, we use a pole‐changing generator with 16 coils as an example. The coils can be connected using four patterns: 16‐pole series, 8‐pole 2‐parallel, 4‐pole 4‐parallel, and 2‐pole 8‐parallel. Theoretical and experimental studies from this point of view demonstrate that this technique is effective. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(1): 28–36, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20873

Effect of rotational sliding velocity on surface friction and wear behavior in Zr-based bulk metallic glass

A Zr 55 Cu 30 Ni 5 Al 10 bulk metallic glass (BMG) with a dimension of 1 mm × 10 mm × 70 mm was prepared by using copper-mold suction casting and the effect of rotational sliding velocity ( RSV ) on the surface dry friction and wear behavior was studied at room temperature. The results showed that the grinding traces of the BMG specimens remain an amorphous structure after friction and wear behavior tests under a load of 5 N with a rotational velocity range of 200–1400 r/min through 8 min. The friction coefficients mainly locate between 0.15 and 0.35. With increasing RSV s, both average friction coefficient and wear weight loss present an upward trend. Obvious molten characteristics can be observed in all grinding traces. At lower RSV s, the wear mechanism tends to a combined action of continuous wear and surface flow, while at higher RSV s, the wear inclines to surface flow. In addition, slight oxidation and adhesion wear accompany during all friction and wear behavior tests.

Temporal Resolution Phantom: A Device and Method for Measurement of a CT Scanner’s Temporal Resolution

A calibration phantom that can be used to measure the temporal resolution of a CT scanner was designed utilizing a deterministic design process. The system was first defined in terms of a set of functional requirements based on parameters of the imaging modality. It was necessary to generate multiple time-varying signals visible to the scanner, each with a pre-determined temporal frequency. Roll-off in the scanner’s ability to resolve the modulation of certain signals would be used to determine the scanner’s temporal resolution. Based on size limitations imposed by the scanning environment, the phantom utilizes multiple planetary gear assemblies, driven by a common shaft, to achieve a wide range of rotational velocities. Results obtained with an alpha prototype agreed with the theory. It was determined that further development of the phantom was necessary to increase the sensitivity of the measurement. The latest prototype phantom has been used to measure the temporal resolution of two different scanners and it was shown that temporal resolution of each is different from the gantry rotation time.