The transition to Taylor vortices in a closed rapidly rotating cylindrical annulus

1980 ◽  
Vol 372 (1749) ◽  
pp. 201-218 ◽  
Keyword(s):  
Flow Pattern ◽  
Shear Layers ◽  
Vertical Shear ◽  
Taylor Vortices ◽  
Cylindrical Annulus ◽  
Ekman Layers ◽  
Angular Velocities ◽  
The Difference

The effects of the end walls on the flow in a rapidly rotating cylindrical annulus are considered. When the difference in the angular velocities of the cylindrical walls is small the flow is described in terms of Ekman layers and vertical shear layers but for larger values the Ekman layers are non­linear and a flow pattern corresponding to Taylor vortices may be resonated.

Rotating flow over a step

1971 ◽  
Vol 50 (4) ◽  
pp. 675-687 ◽  
Author(s):  
Don L. Boyer
Keyword(s):  
Horizontal Plane ◽  
Free Stream ◽  
Rotation Axis ◽  
Plane Surface ◽  
Shear Layers ◽  
Vertical Shear ◽  
Step Width ◽  
Ekman Layers ◽  
The Right ◽  
Good Agreement

The flow of a rotating homogeneous incompressible fluid over a step is investigated. In the physical system considered the rotation axis is vertical and the step, which is assumed to be infinitely long, is located on a horizontal plane surface. Upstream of the step the fluid is in a uniform free stream motion at an angle α to a line perpendicular to the step axis. The analysis is restricted by the following: E [Lt ] 1, Ro ∼ E½, h/D ∼ E½, H/D ∼ E0, and cos α ∼ E0 where Ro and E are the Rossby and Ekman numbers and h/D and H/D are the step height to step width and water depth to step width ratios respectively. The flow field is shown to consist of interior geostrophic regions, Ekman layers on the horizontal surfaces and vertical shear layers located in the vicinity of vertical planes defined by the edges of the step. In the vertical layers there is a balance between the inertial, Coriolis, and pressure terms in the momentum equations while the effects of viscosity are found to be negligible. Downstream of the step the streamlines are shifted to the right (positive or Northern Hemisphere rotation) of their upstream locations by a distance of S = 2½(h/D) E−½ cos α. Experiments are presented which are in good agreement with the theory advanced.

Study on cyclic variation rate of fuel flow in the nozzle during fuel injection

2021 ◽  
Vol 13 (2-3) ◽  
pp. 113-123
Author(s):  
Wen Hua ◽  
Zhang Xin-yu ◽  
Jiang Yu-long ◽  
Zhao Ling-yao
Keyword(s):  
Diesel Engine ◽  
Flow Pattern ◽  
Working Condition ◽  
Fuel Injection ◽  
Injection Pressure ◽  
Cyclic Variation ◽  
Injection Nozzle ◽  
Fuel Flow ◽  
Variation Rate ◽  
The Difference

The fuel flow pattern in the fuel injection nozzle of diesel engine is a complex and changeable phenomenon, which is easily affected by various factors, bringing the differences of flow patterns between multiple injection cycles. To solve the above problem, a visual experimental platform of fuel injection nozzle was built, in which the 100 injection cycles of diesel engine on the same working condition were photographed via shadowgraphy to study the difference in fuel flow pattern in the nozzle by ensemble average processing method. The cyclic variation rate K of fuel flow pattern is defined. Results demonstrate that the fuel flow pattern tends to be the same in multiple fuel injection cycles, but there is a strong randomness at the starting of injection and after ending of injection; the K can be reduced by decreasing the injection pressure and the inclination angle of orifice, so that the fuel flow pattern in the nozzle tends to be consistent.

DETERMINATION OF WIND SHEAR AND TURBULENCE INTENSITY ACCORDING TO YAK42-D “ROSHYDROMET” RESEARCH AIRCRAFT DATA

2021 ◽  
pp. 117-129
Author(s):  
V. V. VOLKOV ◽  
◽  
M. A. STRUNIN ◽  
A. M. STRUNIN ◽  
◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Shear ◽  
Vertical Shear ◽  
Horizontal Shear ◽  
S 100 ◽  
Research Aircraft ◽  
The Difference ◽  
Wind Shears ◽  
Aircraft Data

The results of the development and comparative analysis of methods for determining wind shear in the atmosphere (regression and difference ones) based on research aircraft data are presented. It is shown that shear calculation by the regression method gives the error of 0.002-0.006 (m/s)/km (depending on the length of the measurement sections) for horizontal shears and 0.04-0.12 (m/s)/100 m for vertical shears; the respective error of the difference method is 0.007 (m/s)/km and 0.07 (m/s)/100 m. Based on the Yak-42D “Roshydromet” research aircraft data, the values of shears of two horizontal components of wind speed in three directions (two horizontal and vertical) were calculated. According to the data of two research aircraft flights, the maximum values of the horizontal shear of wind speed components were reached above the boundary layer and were equal to 0.2 (m/s)/km, and the vertical shear was 1.2 (m/s)/100 m. The energy profiles of horizontal and vertical turbulent pulsations are constructed, it is shown that intense turbulence smooths wind shears in the convective atmospheric boundary layer.

On the flow properties of a fluid between concentric spheres

1971 ◽  
Vol 47 (4) ◽  
pp. 799-809 ◽  
Author(s):  
S. G. H. Philander
Keyword(s):  
Outer Sphere ◽  
Azimuthal Velocity ◽  
Ekman Layer ◽  
Shear Layers ◽  
The Other ◽  
Axial Motion ◽  
Flow Properties ◽  
Axis Of Rotation ◽  
Concentric Spheres ◽  
Angular Velocities

Proudman (1956) and Stewartson (1966) analyzed the dynamical properties of a fluid occupying the space between two concentric rotating spheres when the angular velocities of the spheres are slightly different, in other words, when the motion relative to a reference frame rotating with one of the spheres is due to an imposed azimuthal velocity which is symmetric about the equator. The consequences of forcing motion across the equator are explored here. Whereas the flow inside the cylinder [Cscr ] circumscribing the inner sphere and having generators parallel to the axis of rotation is similar to that which results when the driving is symmetric, the flow outside [Cscr ] is quite different. The Ekman layer on the outer sphere persists outside [Cscr ] - its dynamics is modified in the vicinity of the equator - and is instrumental in transferring fluid from one hemisphere to the other. The divergence of this Ekman layer causes slow, axial motion in the inviscid region outside [Cscr ]. On [Cscr ], two shear layers of thicknessO(R−2/7) andO(R−1/3) (whereRis the Reynolds number, assumed large) remove discontinuities in the flow field and return fluid from one hemisphere to the other (rather than one Ekman layer to the other as is the case when the driving is azimuthal).

scholarly journals Correction of the Koenig Formula for the Kinetic Energy of a Rotating Solid

2021 ◽  
Author(s):  
Yuriy Alyushin
Keyword(s):  
Kinetic Energy ◽  
Superposition Principle ◽  
The Body ◽  
Initial State ◽  
Moments Of Inertia ◽  
Lagrange Form ◽  
Joint Plane ◽  
Angular Velocities ◽  
The Difference ◽  
Cyclic Changes

An exact solution is obtained for the kinetic energy in the general case of the spatial motion of solids with arbitrary rotation, which differs from the Koenig formula by three additional terms with centrifugal moments of inertia. The description of motion in the Lagrange form and the superposition principle are used, which provides a geometric summation of the velocities and accelerations of the joint motions in the Lagrange form for any particle at any time. The integrand function in the equation for kinetic energy is represented by the sum of the identical velocity components of the joint plane-parallel motions. The moments of inertia in the Koenig formula do not change during movement and can be calculated from the current or initial state of the body. The centrifugal moments change and turn to 0 when rotating relative to the main central axes only for bodies with equal main moments of inertia, for example, for a ball. In other cases, the difference in the main moments of inertia leads to cyclic changes in the kinetic energy with the possible manifestation of precession and nutation, the amplitude of which depends on the angular velocities of rotation of the body. An example of using equations for a robot with one helical and two rotational kinematic pairs is given.

scholarly journals Comparison of strength and depth cut with scalpel on porcine gingival tissues

Duazary ◽  
2020 ◽  
Vol 17 (1) ◽  
pp. 19-26
Author(s):  
Arnulfo Taron-Dunoyer ◽  
Antonio Díaz-Caballero ◽  
Eliana Ávila-Martínez ◽  
Efren Castellar-Vásquez
Keyword(s):  
Shear Force ◽  
Vertical Shear ◽  
Gingival Tissue ◽  
Anterior Section ◽  
Posterior Section ◽  
Significant Difference ◽  
Convenience Sampling ◽  
The Difference ◽  
Cut Depth ◽  
Experimental Trials

The composition of the gums confers some physical characteristics that make it resistant to mechanical stimulation.  The objective of the study was to compare the difference of the utilized forces when performing cuts in the anterior and posterior sections of porcine gingival tissue, measuring the depth of the tissue. A comparative descriptive study was performed with a non-probability convenience sampling, sectioned pig mandibles were used. The experimental trials were performed with an EZ-S SHIMADZU texture analyzer. All of the samples were submitted to a vertical shear force, thus identified the force level used to perform the incision and its depth. the necessary force to perform a cut in porcine gingival tissue was evaluated, comparing the posterior section (39.3571 Newton and 2.160 mm)  and  with the anterior ( 37.8424 newton and 1.747 mm), just as the depth of said cut, showing a statistical difference on the depth, (p=0.022 p< 0.59); regarding the force, no statistically significant difference was found. In the analyzed samples where the shear force in the posterior and anterior section were compared, no difference was found in both groups; as for the cut depth, this was greater in the posterior section than in the anterior.

Experimental Verification of a New Model for Transition Flow of Thin Films in Long Journal Bearings

2010 ◽  
Author(s):  
Dingfeng Deng ◽  
Minel J. Braun
Keyword(s):  
Experimental Verification ◽  
Journal Bearing ◽  
Flow Behavior ◽  
Journal Bearings ◽  
Turbulent Regime ◽  
Transition Flow ◽  
New Model ◽  
Taylor Vortices ◽  
The Difference ◽  
Good Agreement

A new model for predicting the flow behavior in long journal bearing films in the transition regime (Taylor and wavy vortex regimes) was previously proposed by the authors. This paper presents the experimental verification. A comparison between the experimental and numerical results of the Torque–Speed graphs is presented with good agreement between the numerical and experimental data for the Couette, Taylor and pre-wavy regimes. In the wavy and turbulent regime, the magnitude of the numerically obtained data is larger than the corresponding measured torques, but the difference is confined to below 14%. A comparison between experimental and numerical flow patterns is also presented. The results match well in general, except that experimentally, a pre-wavy regime was identified. The latter is characterized by the disappearance of the Taylor vortices, while numerically the Taylor vortices are only distorted and the wavy vortices are formed in this regime.

Yawed Effect on Wind Turbine Near Wake

2014 ◽  
Author(s):  
Yuntian Ge ◽  
Xiuling Wang
Keyword(s):  
Wind Turbine ◽  
Flow Pattern ◽  
Wind Turbines ◽  
Air Flow ◽  
Aerodynamic Performance ◽  
Wake Flow ◽  
Near Wake ◽  
Rotation Plane ◽  
The Difference ◽  
Ansys Workbench

Wind turbines rotation was motivated by the force of wind. In reality, wind doesn’t moving vertically to the wind turbine rotation plane, but in random directions instead. Therefore, the yawed effect has to be taken into consideration when study wind turbine aerodynamic performance. The purpose of this study is to compare the difference between the wind turbine near wake flow with yawed effect and without yawed effect aerodynamically. The research uses CFD technology to simulate the rotation movement and air flow pattern, which is completed in software Ansys Workbench.

Numerical Simulation on Fluid-Solid Coupling of Gate with Different Structure Types of Hemline in Deep Hole

2013 ◽  
Vol 444-445 ◽  
pp. 239-243
Author(s):  
Jun Xing Wang ◽  
Li Qiang Chen ◽  
Yu Ting Chen
Keyword(s):  
Numerical Simulation ◽  
Dynamic Response ◽  
Flow Pattern ◽  
Natural Vibration ◽  
Vibration Characteristics ◽  
Deep Hole ◽  
Flow Induced Vibration ◽  
Type D ◽  
The Difference ◽  
Natural Vibration Characteristics

Although there are some achievements of flow-induced vibration of plane steel gate, few is about the influence on gate caused by the difference of structure types of gates hemline. This paper studies on the flow pattern, natural vibration characteristics and dynamic response of four typical types of gates hemline in deep hole of Kajiwa Hydropower Stations service gate. Based on model test and numerical simulation and considering the flow pattern under the gate and in the gate slot, the natural vibration characteristics and the gates dynamic response, it is suggested to use an anteversion angle and a caster angle (type D for short) for the hemline of the type II gate slot. The optimal factors of a gates hemline in a concrete project can be optimized by numerical simulation.

scholarly journals Fabric along the NEEM ice core, Greenland, and its comparison with GRIP and NGRIP ice cores

2014 ◽  
Vol 8 (4) ◽  
pp. 1129-1138 ◽  
Author(s):  
M. Montagnat ◽  
N. Azuma ◽  
D. Dahl-Jensen ◽  
J. Eichler ◽  
S. Fujita ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Vertical Shear ◽  
Deformation Pattern ◽  
Bottom Part ◽  
Viscosity Change ◽  
The Core ◽  
Climatic Transition ◽  
The Difference

Abstract. Fabric (distribution of crystallographic orientations) along the full NEEM ice core, Greenland was measured in the field by an automatic ice texture analyzer every 10 m, from 33 m down to 2461 m depth. The fabric evolves from a slightly anisotropic fabric at the top, toward a strong single maximum at about 2300 m, which is typical of a deformation pattern mostly driven by uniaxial compression and simple shearing. A sharp increase in the fabric strengthening rate is observed at the Holocene to Wisconsin (HW) climatic transition. From a simple model we estimate that this depth is located at a transition from a state dominated by vertical compression to a state dominated by vertical shear. Comparisons are made to two others ice cores drilled along the same ridge; the GRIP ice core, drilled at the summit of the ice sheet, and the NGRIP ice core, drilled 325 km to the NNW of the summit along the ridge, and 365 km upstream from NEEM. This comparison tends to demonstrate that the ice viscosity change with the HW climatic transition must be associated with the shear-dominated state to induce the abrupt fabric strengthening observed at NEEM. This comparison therefore reflects the increasing role of shear deformation on the coring site when moving NW along the ridge from GRIP to NGRIP and NEEM. The difference in fabric profiles between NEEM and NGRIP also evidences a stronger lateral extension associated with a sharper ridge at NGRIP. Further along the core, centimeter scale abrupt texture (fabric and microstructure) variations are observed in the bottom part of the core. Their positions are in good agreement with the observed folding layers in Dahl-Jensen et al. (2013).

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