Impulsive Rotation Research Articles

Application of One-Axis-Controlled Magnetic Bearing With a Hollow Shaft to Noncontact Rotation Drive

A rotor is supported using a magnetic bearing, which consists of permanent magnets and electromagnets in the axial direction without mechanical contacts. In this paper, a new mechanism with a hollow shaft structure in the center of the rotor and the stator for levitation control is proposed. A test device is made according to the results of analysis. Moreover, some experiments about impulse response, step response, levitation, and rotation are performed. In this paper, static characteristics and dynamic characteristics about the test device are discussed, and the new mechanism with a hollow shaft structure is also discussed.

Influences of Patellofemoral Pain and Fatigue in Female Dancers during Ballet Jump-Landing.

This study investigated the influence of patellofemoral pain (PFP) and fatigue on lower-extremity joint biomechanics in female dancers during consecutive simple ground échappé. 3-dimensional joint mechanics were analyzed from the no-fatigue to fatigue conditions. 2-way mixed ANOVAs were used to compare the differences of the kinematic and kinetic variables between groups and conditions. Group main effects were seen in increased jump height (p=0.03), peak vertical ground reaction force (p=0.01), knee joint power absorption (p=0.04), and patellofemoral joint stress (PFJS, p=0.04) for PFP group. Fatigue main effects were found for decreased jump height (p<0.01), decreased ankle plantarflexion at initial foot-ground contact (p=0.01), and decreased ankle displacement (p<0.01). Hip external rotation impulse and hip joint stiffness increased (both p<0.01) while knee extension and external rotation moment, and ankle joint power absorption decreased (p<0.01, p=0.02, p<0.01, respectively) after fatigue. The peak PFJS also decreased after fatigue (p<0.01). Female ballet dancers with PFP sustained great ground impact and loads on the knee probably due to higher jump height compared to the controls. All dancers presented diminished knee joint loading for the protective mechanism and endurance of ankle joint musculature required for the dissipation of loads and displayed a distal-to-proximal dissipation strategy after fatigue.

Dynamic transition from Mach to regular reflection of shock waves in a steady flow

AbstractThe steady, two-dimensional transition criteria between regular and Mach reflection are well established. Little has been done on the dynamic effect on transition due to a rapidly rotating wedge. Results from experiments and computations done on steady and unsteady shock wave transition from Mach reflection to regular reflection, MR $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\rightarrow $ RR, are described. The measured motion and the initial shock incidence was used to mimic the experiment with a two-dimensional numerical code. The maximum rotation speed achieved at transition was approximately $2500^\circ \ {\mathrm{s}}^{-1}$. Rapid wedge rotation was shown to have a significant measurable effect on transition. The code was also applied to the dependence of dynamic MR $\rightarrow $ RR transition on other variables in the parameter space. These include rotation about the leading or trailing edge, initial incidence and rotation speed at two free-stream conditions. Impulsively started rotation in these cases was used with the rotation specified by $M_E = \omega c/a_{\infty }$ where $\omega $ is constant angular velocity (negative anticlockwise), $c$ the distance from the edge considered to the pivot point and $a_{\infty }$ the free-stream sound speed. For the Mach numbers and range of rotation speeds tested, both the wedge and shock angle at transition decreased with increased rotation speed. The sensitivity of the transition angle to changing the rotation point from the trailing edge to the experimental model pivot point was investigated briefly at a free-stream Mach number of $M = 2.98$ with $M_E = -0.1$. The wedge angle at transition increased by 1.5° and the shock angle at transition decreased by 1.5°, a significant variation. The effect of the initial incidence was also investigated. By reducing the initial wedge angle from 24.5 to 23.5° for these initial conditions the shock angle at transition decreased by approximately 1.8°, also a marked sensitivity. The flow field development for impulsive rotation about the wedge trailing and leading edges at $M = 1.93$ for $M_E = -0.075$ was analysed in some detail. The flow field development is very sensitive to the rotation centre, more especially at large rotation rates. Four phases of the Mach stem development were identified in both cases. For rotation about the wedge leading edge the Mach stem height remains constant until the expansion waves arrive at the triple point. This is followed by an increase in Mach stem height, which then remains constant for a short period after which it decreases until transition to RR. For rotation about the wedge trailing edge the impulsive start generates a disturbance on the incident wave which propagates down the wave, through the triple point and down the Mach stem. The stem height is constant until the arrival of the incident wave disturbance. This causes a sudden decrease in Mach stem height. Subsequently, the Mach stem height remains constant for a short time, before it decreases until transition to RR. Similar effects in the variation of stem height with wedge angle occur at the higher Mach number of 2.98. It was demonstrated that MR can be maintained for a while at zero wedge incidence with a sufficiently large rotation rate of $M_E = -0.1$, with $M=1.93$, for both leading and trailing edge pivot points.

A numerical investigation of flow around octopus-like arms: near-wake vortex patterns and force development

The fluid dynamics of cephalopods has so far received little attention in the literature, due to their complexity in structure and locomotion. The flow around octopuses, in particular, can be complicated due to their agile and dexterous arms, which frequently display some of the most diverse mechanisms of motion. The study of this flow amounts to a specific instance of the hydrodynamics problem for rough tapered cylinder geometries. The outstanding manipulative and locomotor skills of octopuses could inspire the development of advanced robotic arms, able to operate in fluid environments. Our primary aim was to study the hydrodynamic characteristics of such bio-inspired robotic models and to derive the hydrodynamic force coefficients as a concise description of the vortical flow effects. Utilizing computational fluid dynamic methods, the coefficients were computed on realistic morphologies of octopus-like arm models undergoing prescribed solid-body movements; such motions occur in nature for short durations in time, e.g. during reaching movements and exploratory behaviors. Numerical simulations were performed on translating, impulsively rotating, and maneuvering arms, around which the flow field structures were investigated. The results reveal in detail the generation of complex vortical flow structures around the moving arms. Hydrodynamic forces acting on a translating arm depend on the angle of incidence; forces generated during impulsive rotations of the arms are independent of their exact morphology and the angle of rotation; periodic motions based on a slow recovery and a fast power stroke are able to produce considerable propulsive thrust while harmonic motions are not. Parts of these results have been employed in bio-inspired models of underwater robotic mechanisms. This investigation may further assist elucidating the hydrodynamics underlying aspects of octopus locomotion and exploratory behaviors.

An Innovative Method for Rotor Inertia Emulation at Wind Turbine Test Benches

Recently wind industry paid a lot of attention to nacelle test benches in the multi MW class, which allow overall tests of wind turbine systems, including the control strategy. For several reasons the rotors of such turbines are dismounted at test benches, through which the dynamic properties of the system are changed significantly. This results in the challenge of having to emulate the missing rotational inertia for realistic wind turbine controller tests.In this paper an innovative method is proposed, which allows the emulation of the missing rotational inertia. The idea of the proposed method is to balance the inertia related torque by controlling the rotational impulse of the wind turbine's drive train. This has the advantage, that compared to a baseline approach, this method does not require a rigid drive train at the test bench to accurately emulate the rotor inertia. For this reason the proposed method reproduces the drive train's dynamics more accurately than the baseline approach and thereby allows for stable operation of the wind turbine controller. An experimental verification of the method was conducted at the world-wide first nacelle test bench.

Transient force generation during impulsive rotation of wall-mounted panels

AbstractSquare and triangular shape actuator panels mounted on the wall of a wind tunnel beneath an air flow have been impulsively rotated with an angular velocity between 3 and $26~\mathrm{rad} ~{\mathrm{s} }^{- 1} $. A custom-designed balance was used to measure the time-dependent lift and drag forces during the deployment of the actuator, the position of which was monitored by a digital encoder. The measured forces have been compensated for inertia effects which are significant. The results indicated that all lift and drag force coefficients during the transient deployment are different than the corresponding coefficients under stationary conditions at the same deployment angle. It was found that these dynamic effects are augmented with increasing velocity ratio $\mathit{Str}$. The square actuator was found to have better aerodynamic performance than the triangular ones. Additional experiments within different boundary layers reveal that the generated unsteady forces on the moving panels are affected by the characteristics of the incoming boundary layers. The results showed that the thinner the boundary layer is the higher the forces are. Time-resolved flow visualization studies indicated that during the deployment of the panel the upstream turbulent boundary layer structures and the free stream fluid are decelerated and squeezed in the longitudinal direction as they approach the moving plate. A very thin and highly sheared wall layer develops over the moving panel, it generates a substantial amount of vorticity and it subsequently separates from the three edges of the panel to form a large-scale ring-like vortical structure which is responsible for the transient augmentation of the aerodynamic forces. This structure consists of wrapped around separated shear layers which contain pockets of compressed eddies and free stream fluid originated in the upstream incoming boundary layer and free stream. A horseshoe vortex starts to form over the moving plate and during the final stages of deployment it has been moved upstream while the incoming boundary layer turbulent structures are pushed and diverted upwards.

Fiber transport and deposition in human upper tracheobronchial airways

Using a multi-level asymmetric lung bifurcation model, transport and deposition of ellipsoidal fibers in the human upper airways were analyzed. The first three generations (G0–G3) of the tracheobronchial tree were included in the study. The focus of this research is airflow simulation and fiber motion prediction in the multi-level human airway bifurcation model. The laryngeal jet at the trachea entrance was modeled as an equivalent turbulence generator, and downstream in the lower level of the bronchi a laminar flow model was used. Lagrangian simulation of ellipsoidal fiber transport and deposition was performed where the effects of coupled hydrodynamic drag and torque, shear induced lift, gravitational sedimentation, inertial impaction, turbulence diffusion were included in the analysis. The study showed that the multi-level asymmetric lung bifurcation model was flexible, easy to use, and computationally highly efficient. The particle simulation results showed that the elongated fibers were aligned with the main flow direction most of the time, but occasionally they experienced impulsive rotation along their pathway. The rotational motion was dependent on the fiber geometry and the local flow patterns. Fiber deposition pattern and deposition rate in the human upper airways were evaluated. The simulation results were compared with the experimental data. The equivalent sphere model for fiber transport and deposition was also discussed.

Turning the Corner in Quadrupedal Arboreal Locomotion: Kinetics of Changing Direction While Running in the Siberian Chipmunk (Tamias sibiricus)

Arboreal animals frequently change directions during locomotion on tree branches, trunks, or twigs. Linear and rotational impulses required to change direction and rotate the body while running are largely unexplored. We trained Siberian chipmunks (Tamias sibiricus) to run on narrow cylindrical trackways. The first trackway was straight and the second had a 45° bend to the right. A force pole collected substrate reaction forces and torques, and linear and rotational impulses were calculated. When the chipmunks ran and jumped across the bend, they exerted strong impulses to the left, pushing the body to the right. Before the bend the substrate reaction yaw angular impulse rotated the animal to the new heading. After passing over the 45° bend in the trackway, opposing yaw angular impulses were exerted to stop the body's rotation. Rolling angular impulses were mostly similar between straight and turning trials. We conclude that mediolateral forces are more important than craniocaudal forces to change direction in locomotion. Yaw angular impulse is necessary to start and stop the rotation of the body around the center of mass. To avoid rolling during turns, the chipmunks relied on banking rather than exerting rolling torques.

Laboratory Evaluation of the Pivot-Shift Phenomenon with Use of Kinetic Analysis

Currently, a suitable and reliable noninvasive method to evaluate rotational stability in vivo in anterior cruciate ligament-deficient knees, particularly during sports movements, does not exist. We speculated that if there is a rotational instability, the patient would avoid reaching a high pivoting moment during pivoting activities as a defense mechanism, and that the ground reaction moment, as registered by dynamometric platforms, would be reduced. On the basis of this hypothesis, we developed a study using kinetic analysis to evaluate rotational stability under dynamic loading. Thirty recreationally active athletes, including fifteen healthy subjects and fifteen with an anterior cruciate ligament-deficient knee, were recruited for this study. Patients performed jumping with pivoting with internal tibial rotation and external tibial rotation on the dynamometric platform with both the healthy and the injured limb. The quantitative results were graphically plotted, and the following parameters were evaluated: loading moment, pivoting moment, torque amplitude, loading slope, pivoting slope, percentage of pivoting with load, loading impulse, pivoting impulse, and maximum body rotation angle. There were no significant differences between the dominant and nondominant knees in the control group during the jumping with pivoting and external tibial rotation test with regard to the pivoting moment (p = 0.805), pivoting slope (p = 0.716), pivoting impulse 2 (p = 0.858), and pivoting impulse 3 (p = 0.873). In patients with a chronic tear of the anterior cruciate ligament, there was a significant decrease of the pivoting moment (p = 0.02), pivoting slope (p = 0.005), pivoting impulse 2 (p = 0.006), and pivoting impulse 3 (p = 0.035) during the jumping with pivoting and external tibial rotation test in the anterior cruciate ligament-deficient knee compared with the healthy, contralateral knee. Kinetic analysis with use of a dynamic platform can objectively detect alterations of rotational stability in anterior cruciate ligament-deficient knees, which may allow this to be a useful research tool for evaluating treatment strategies in patients with anterior cruciate ligament injuries.

Effects of physiotherapy treatment on knee osteoarthritis gait data using principal component analysis

Background Interpreting gait data is challenging due to intersubject variability observed in the gait pattern of both normal and pathological populations. The objective of this study was to investigate the impact of using principal component analysis for grouping knee osteoarthritis (OA) patients' gait data in more homogeneous groups when studying the effect of a physiotherapy treatment. Methods Three-dimensional (3D) knee kinematic and kinetic data were recorded during the gait of 29 participants diagnosed with knee OA before and after they received 12 weeks of physiotherapy treatment. Principal component analysis was applied to extract groups of knee flexion/extension, adduction/abduction and internal/external rotation angle and moment data. The treatment's effect on parameters of interest was assessed using paired t-tests performed before and after grouping the knee kinematic data. Findings Increased quadriceps and hamstring strength was observed following treatment ( P < 0.05). Except for the knee flexion/extension angle, two different groups (G 1 and G 2) were extracted from the angle and moment data. When pre- and post-treatment analyses were performed considering the groups, participants exhibiting a G 2 knee moment pattern demonstrated a greater first peak flexion moment, lower adduction moment impulse and smaller rotation angle range post-treatment ( P < 0.05). When pre- and post-treatment comparisons were performed without grouping, the data showed no treatment effect. Interpretation The results of the present study suggest that the effect of physiotherapy on gait mechanics of knee osteoarthritis patients may be masked or underestimated if kinematic data are not separated into more homogeneous groups when performing pre- and post-treatment comparisons.

Effect of Ankle Taping on Knee and Ankle Joint Biomechanics in Sporting Tasks

Prophylactic taping is commonly used to prevent ankle injuries during sports. However, unnatural constraint of the ankle joint may increase the risk of injury to proximal joints such as the knee. The association between ankle taping and knee joint loading during open sporting tasks has not been quantified. This research aimed to measure changes in knee and ankle kinetics and kinematics during dynamic athletic activities undertaken with and without ankle taping. A kinematic and inverse dynamics model was used to determine ankle and knee joint motion and loading in 22 healthy male participants undertaking running and sidestepping tasks. Both tasks were randomized to planned and unplanned conditions and undertaken with and without the use of ankle tape. At the knee, peak internal rotation moments (P < 0.001) and peak varus moments (P < 0.05) were significantly reduced during all running and sidestepping trials (planned and unplanned) when undertaken with ankle tape. Internal rotation impulse (P < 0.001) was reduced for sidestepping tasks. Varus impulse during unplanned sidestepping maneuvers (P = 0.04) was reduced with the use of ankle tape. However, there was a trend toward increased valgus moments and impulse for planned sidestepping trials undertaken with ankle tape(P = 0.056). Taping reduced the range of motion at the ankle in all three planes (P < 0.05). Peak inversion (P < 0.001) was reduced for running trials only. Average eversion and peak dorsiflexion moments were significantly reduced in sidestepping tasks by use of taping. By limiting motion at the ankle, taping increased mechanical stability at this joint. Ankle taping also provided protective benefits to the knee via reduced internal rotation moments and varus impulses during both planned and unplanned maneuvers. Medial collateral and anterior cruciate ligament injuries may, however, occur through increased valgus impulse during sidestepping undertaken with ankle tape.

Transient moment to rotate inner walls of vertical concentric annuli in the natural convection regime

Purpose – The paper seeks to focus on obtaining the transient torque required to rotate the inner cylinder in open ended vertical concentric annuli for a fluid of Pr = 0.7 in the laminar natural convection flow regime over a wide range of the controlling parameter Gr2/Ta. The inner wall is heated and subjected to an impulsive rotation while the outer one is stationary and maintained adiabatic.Design/methodology/approach – The governing transient boundary‐layer equations are numerically solved using an iterative linearized finite‐difference scheme.Findings – The transient induced flow rate and absorbed heat for different annulus heights are presented. High rotational speed (i.e. low values of Gr2/Ta) increases the flow rate and heat absorbed in short annuli. However, for considerably tall annuli, Gr2/Ta has slight effect on the flow and heat absorbed. The steady‐state time is tangibly influenced by Gr2/Ta in considerably short annuli and very slightly affected for considerably tall annuli.Practical implica...

Axial invariance of rapidly varying diffusionless motions in the Earth’s core interior

Geostrophic jets propagating as Alfvén waves are shown to arise in a rapidly rotating spherical shell permeated by a magnetic field among the transient motions set up by an impulsive rotation of the inner core. These axially invariant motions evolve on a time-scale which is short compared to the magnetic diffusion time. The numerical study is taken as illustrative of a more general point: on such a fast time-scale the dimensionless number appropriate to compare the rotation and magnetic forces is independent of the magnetic diffusivity in contrast with the often used Elsasser number. Extension of the analysis to non-axisymmetrical motions is supported by published studies of dynamo models and magnetic instabilities.

Transient, powerful pressures are generated in the brain by a rotational acceleration impulse to the head

A rotational acceleration impulse to a head, as occurs at traffic accidents, sport injuries, assaults and falls, induces a diffuse brain damage that eventually could result in persistent neuropsychiatric deficits and neurodegeneration. Emphasis has been concentrated on the relative motion of the brain inside the skull during head impact, whereas less attention has been paid to whether intracranial pressure changes are generated and, if so, the implications thereof. In the present experimental study we investigated in an animal model system, based on rabbits, if a sagittal, anterior-posterior rotational acceleration of a head generated intracranial pressure changes, recorded by fibre optic pressure sensors, inserted ipsilaterally in the parieto-temporal and the occipital lobes. Two levels of rotational acceleration were used in the experiments; one higher, corresponding to the threshold limit for moderate diffuse brain injury, and one lower, close to being noninjurious. Several pressure recordings were performed in each rabbit at the two acceleration levels. The pressure recordings invariably revealed the same general characteristics of rapid, positive and negative pressures within the brain, with variations in amplitude and duration, lasting for up to 10 ms. A major finding was the generation of powerful negative pressures, as low as 0.3 bars in absolute pressure. The most prominent difference in amplitudes of the negative peak pressures between the two applied acceleration levels was demonstrated at the parieto-temporal location. The presented pressure recordings are the first to disclose the generation of transient, powerful intracerebral pressures at rotational acceleration of the head, which must be considered in studies of brain injury generation and distribution as well as prevention.

Vestibular function at the end of intratympanic gentamicin treatment of patients with Ménière's disease

The aim of this study is to analyze the effects of intratympanic gentamicin injections on vestibular function in 33 patients with unilateral Meniere's Disease (according to AAO-HNS guidelines 1995) that had been unresponsive to medical therapy for at least one year. In such patients, the results of bedside examination of vestibular function vestibular examination is compared to those from laboratory tests. Intratympanic gentamicin injections (27 mg/ml) were performed at weekly intervals until symptoms or signs of vestibular hypofunction developed in the treated ear. Vestibular function was evaluated in two different rotatory chair tests. The parameters that were specifically considered were the time constant of the vestibulo-ocular reflex (VOR) after impulse rotation with a peak chair velocity of 100 degrees s(-1), and the phase and gain of the VOR after the sinusoidal harmonic acceleration (SHA) test with a peak chair velocity of 50 degrees s(-1). After treatment, both the time constant of the VOR after rotation towards the treated side and the gain in the SHA test were significantly reduced. These reductions were in accordance with the number of additional signs observed upon bedside examination at the end of the treatment. The changes observed in the VOR correlate well with the results of bedside examination of vestibular function, which in turn reflects the damage induced by intratympanic gentamicin injection.

Influence of impact direction on the human head in prediction of subdural hematoma.

The objective of the present study was to analyze the effect of different loading directions following impact, and to evaluate existing global head injury criteria. Detailed and parameterized models of the adult human head were created by using the Finite Element Method (FEM). Loads corresponding to the same impact power were imposed in different directions. Furthermore, the Head Injury Criterion (HIC) and the recently proposed Head Impact Power (HIP) criterion were evaluated with respect to the relative motion between the skull and the brain, as well as the strain in the bridging veins. It was found that the influence of impact direction had a substantial effect on the intracranial response. The largest relative skull-brain motion and strain in the bridging veins occurred with the anterior-posterior (AP) and posterior-anterior (PA) rotational impulses. HIC was unable to predict consequences of a pure rotational impulse while HIP needed individual scaling coefficients for the different terms to account for difference in load direction. When using the proposed scaling procedure, a better prediction of subdural hematoma (SDH) was obtained. It is thus suggested that an evaluation of the synergistic terms is necessary to further improve the injury prediction. These variations should be considered when developing new head injury criteria.

Effects of unilateral vestibular deafferentation on the linear vestibulo-ocular reflex evoked by impulsive eccentric roll rotation.

The effects of unilateral vestibular deafferentation (UVD) on the linear vestibulo-ocular reflex (LVOR) were studied by measuring three-dimensional eye movements in seven UVD subjects evoked by impulsive eccentric roll rotation while viewing an earth-fixed target at 200, 300, or 600 mm and comparing their responses to 11 normal subjects. The stimulus, a whole-body roll of approximately 1 degrees, with the eye positioned 815 mm eccentric to the rotation axis, produced an inter-aural linear acceleration of approximately 0.5 g and a roll acceleration of approximately 360 degrees /s(2). The responses generated by the LVOR comprise horizontal eye rotations. Horizontal eye velocity at 100 ms from stimulus onset in UVD subjects was significantly lower than in normal subjects for all viewing distances, with no significant difference between ipsilesional and contralesional responses. LVOR acceleration gain, defined as the slope of actual horizontal eye velocity divided by the slope of ideal horizontal eye velocity during a 30-ms period starting 70 ms from stimulus onset, was bilaterally significantly reduced in UVD subjects at all viewing distances. Acceleration gain from all viewing distances was 1.04 +/- 0.28 in normal subjects, and in UVD subjects was 0.49 +/- 0.23 for ipsilesional and 0.63 +/- 0.27 for contralesional acceleration. LVOR enhancement in the first 100 ms by near viewing was still present in UVD subjects. LVOR latency in UVD subjects (approximately 39 ms) was not significantly different from normal subjects (approximately 36 ms). After UVD, LVOR is bilaterally and largely symmetrically reduced, but latency remains unchanged and modulation by viewing distance is still present.

A merging criterion for two-dimensional co-rotating vortices

We propose a quantitative criterion for the merging of a pair of equal two-dimensional co-rotating vortices. A cross-validation between experimental and theoretical analyses is performed. Experimental vortices are generated by the roll-up of a vortex sheet originating from the identical and impulsive rotation of two plates. The phenomenon is then followed up in time until a rapid pairing transition occurs for which critical parameters are measured. In the theoretical approach, the nonlinear Euler solution representing a pair of equal vortices is computed for various nonuniform vorticity distributions. The stability analysis of such a configuration then provides critical values for the onset of merging. From this data set, a criterion depending on global impulse quantities is extracted for different shapes of the vorticity distribution. This theoretical statement agrees well with our experimentally based criterion.

Motorized head impulse stimulator to determine angular horizontal vestibulo-ocular reflex

The objective of the current study was to develop a computer-controlled mechanical system for the generation of impulsive head rotations to measure eye movements induced by angular horizontal vestibulo-ocular reflex. This is a clinical eye movement test recently introduced for the usage of otoneurological balance laboratories. We built the system and modified our prior computer software developed for other types of eye movement tests. Motor controlled stimulation has fulfilled the requirement of more uniform and constant acceleration stimulation than obtained with manually administrated impulses. After having executed preliminary experiments at our balance laboratory we found the system to be efficient, reliable and secure.

Unsteady flow of thin liquid film on a disk under nonuniform rotation

Development of thin liquid film under nonuniform rotation has been studied numerically by using finite difference technique under the assumption of planar interface. For impulsive rotation of the disk an anomalous behavior of the rate of film thinning with the variation of the Reynolds number is observed in a different time zone. It is also shown that the azimuthal velocity field develops into the entire depth faster with the smaller impulsive rotation. A physical explanation for the above observation is provided. Further it is found that faster rate of thinning can be obtained if the spinner starts impulsively and then increases its spinning rate continuously.