ESTIMATION OF AERODYNAMIC FORCES AND MOMENTS DERIVATIVES WITH RESPECT TO THE ANGULAR VELOCITY COMPONENTS OF THE AIRCRAFT MODEL IN A WIDE RANGE OF ANGLES OF ATTACK

2018 ◽  
Vol 49 (1) ◽  
pp. 43-64
Author(s):  
Mikhail Alekseyevich Golovkin ◽  
Andrey Aleksandrovich Efremov ◽  
Miroslav Sergeevich Makhnev
Keyword(s):  
Angular Velocity ◽  
Aerodynamic Forces ◽  
Aircraft Model ◽  
Wide Range

scholarly journals The magnetorotational instability prefers three dimensions

2020 ◽  
Vol 476 (2233) ◽  
pp. 20190622
Author(s):  
Jeffrey S. Oishi ◽  
Geoffrey M. Vasil ◽  
Morgan Baxter ◽  
Andrew Swan ◽  
Keaton J. Burns ◽  
...  
Keyword(s):  
Shear Rate ◽  
Angular Velocity ◽  
Laboratory Experiments ◽  
Three Dimensional ◽  
Linear Instability ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Magnetorotational Instability ◽  
Dynamo Action ◽  
Wide Range

The magnetorotational instability (MRI) occurs when a weak magnetic field destabilizes a rotating, electrically conducting fluid with inwardly increasing angular velocity. The MRI is essential to astrophysical disc theory where the shear is typically Keplerian. Internal shear layers in stars may also be MRI-unstable, and they take a wide range of profiles, including near-critical. We show that the fastest growing modes of an ideal magnetofluid are three-dimensional provided the shear rate, S , is near the two-dimensional onset value, S c . For a Keplerian shear, three-dimensional modes are unstable above S  ≈ 0.10 S c , and dominate the two-dimensional modes until S  ≈ 2.05 S c . These three-dimensional modes dominate for shear profiles relevant to stars and at magnetic Prandtl numbers relevant to liquid-metal laboratory experiments. Significant numbers of rapidly growing three-dimensional modes remainy well past 2.05 S c . These finding are significant in three ways. First, weakly nonlinear theory suggests that the MRI saturates by pushing the shear rate to its critical value. This can happen for systems, such as stars and laboratory experiments, that can rearrange their angular velocity profiles. Second, the non-normal character and large transient growth of MRI modes should be important whenever three-dimensionality exists. Finally, three-dimensional growth suggests direct dynamo action driven from the linear instability.

SIFs for Radial Cracks in Annular Discs Under Internal and External Shrinkage Pressure and Constant Angular Velocity

2007 ◽  
Author(s):  
A. Sakhaee-Pour ◽  
A. R. Gowhari-Anaraki ◽  
S. J. Hardy
Keyword(s):  
Finite Element ◽  
Angular Velocity ◽  
Constant Angular Velocity ◽  
Coefficient Of Determination ◽  
Linear Elastic ◽  
Crack Configuration ◽  
Wide Range ◽  
Elastic Fracture ◽  
Radial Cracks

Finite element method has been implemented to predict stress intensity factors (SIFs) for radial cracks in annular discs under constant angular velocity. Effects of internal and external uniform pressure on the SIFs have also been considered. Linear elastic fracture mechanics finite element analyses have been performed and results are presented in the form of crack configuration factors for a wide range of components and crack geometry parameters. These parameters are chosen to be representative of typical practical situations. The extensive range of crack configuration factors obtained from the analyses is then used to develop equivalent prediction equations via a statistical multiple non-linear regression model. The accuracy of this model is measured using a multiple coefficient of determination, R2, where 0 ≤ R2 ≤ 1. This coefficient is found to be greater than or equal to 0.98 for all cases considered in this study, demonstrating the quality of the model fit to the data. These equations for the SIFs enable designers to predict fatigue life of the components easily.

A New Control Strategy to Reduce Steering Torque Without Perceptible Vibration for Vehicles Equipped With Electric Power Steering

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Masahiko Kurishige ◽  
Osamu Nishihara ◽  
Hiromitsu Kumamoto
Keyword(s):  
Angular Velocity ◽  
Electric Power ◽  
Control Strategy ◽  
Steering Wheel ◽  
Velocity Control ◽  
Steering Control ◽  
Electric Power Steering ◽  
Power Steering ◽  
Wide Range ◽  
Steering Torque

This paper proposes a new electric power steering control strategy, which significantly reduces the effort needed to change the steering direction of stationary vehicles. Previous attempts to reduce undesirable steering vibration have failed to reduce the steering torque because high-assist gains tend to produce oscillation or increase noise sensitivity. Herein, to eliminate this vibration, a new control strategy was developed based on pinion angular velocity control using a newly developed observer based on a simplified steering model. Tests yielded excellent estimations of the pinion angular velocity, and this made it possible to eliminate vibration at all steering wheel rotation speeds. Experiments with a test vehicle confirmed significant steering torque reduction, over a wide range of steering wheel speeds, without vibration transmission to the driver. The proposed control strategy allowed use of an assist gain more than three times higher than is conventional. Additionally, the proposed control strategy does not require supplemental sensors.

Naval Centrifugal Compressor Design Using CAD Solutions

2014 ◽  
Vol 658 ◽  
pp. 59-64
Author(s):  
Constantin Dumitrache ◽  
Ioan Calimanescu ◽  
Corneliu Comandar
Keyword(s):  
High Flow ◽  
Mean Stress ◽  
Aerodynamic Optimization ◽  
Aerodynamic Forces ◽  
Dynamic Stresses ◽  
Unsteady Aerodynamic ◽  
Wide Range ◽  
Compressor Design ◽  
Blade Vibrations ◽  
Centrifugal Loading

Centrifugal compressors of turbochargersoperate in a wide range of rotational speeds, which depends on the load of the supercharged engine. Current designs of turbocharger compressors exhibit high efficiencies accompanied by high flow capacities [1]. Consequences of aerodynamic optimization are high mean stress values in the blades due to centrifugal loading as well as dynamic stresses due to blade vibrations. Blade vibrations in a turbocharger compressor are assumed to be predominantly excited by unsteady aerodynamic forces [2]. These forces are caused by a variety of sources influencing the flow. Examples include the geometry of the flow channel, elbows, the diffuser vanes or struts. Therefore, an understanding of FSI is essential for further design optimizations.

Particle Resuspension in a Wall-Bounded Turbulent Flow

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
S. C. Fu ◽  
C. Y. H. Chao ◽  
R. M. C. So ◽  
W. T. Leung
Keyword(s):  
Angular Velocity ◽  
Uhlenbeck Process ◽  
Particle Resuspension ◽  
Air Stream ◽  
Safety And Health ◽  
Wide Range ◽  
Resuspension Rate ◽  
Mc Simulation ◽  
Using Data ◽  
Good Agreement

Resuspension is of common occurrence in a wide range of industrial and environmental processes. Excessive resuspension in these processes could have a severe impact on human safety and health. Therefore, it is necessary to develop a practical, yet reasonably accurate model to describe the resuspension phenomenon. It has been identified that rolling is the dominant mechanism for particle resuspension in the presence of an air stream, be it laminar or turbulent. Existing models predict the resuspension rate by regarding particles as being resuspended once they are set in motion; only a few of these models attempt to describe the full scenario, including rolling motion and the effect of turbulence. The objective of this paper is to propose a stochastic model to simulate the resuspension rate in the presence of a near-wall turbulent stream, and where the rolling mechanism is assumed to dominate the resuspension process. The fluctuating part of the angular velocity of a rolling particle is modeled by the Langevin equation (i.e., an Ornstein–Uhlenbeck process); thus, the overall angular velocity is modeled as a diffusion process. A free parameter of the proposed resuspension model is determined using data obtained from a Monte Carlo (MC) simulation of the problem. Once determined, the parameter is found to be universal for different materials and different sizes of particles tested. The modeling results obtained using this parameter are found to be in good agreement with experimental data, and the model performs better compared to other models.

Study on Nozzle Array Structure Fluidic Gyroscope

2012 ◽  
Vol 542-543 ◽  
pp. 727-730
Author(s):  
Chuan Zhi Mei ◽  
Lin Hua Piao ◽  
Quan Gang Yu ◽  
Bao Li Zhang ◽  
Xia Ding ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Sensitive Element ◽  
Impact Resistance ◽  
Measurement Range ◽  
Test Results ◽  
Velocity Difference ◽  
Wide Range ◽  
Array Structure ◽  
The Impact ◽  
Better Than

This paper reports about a nozzle array structure fluidic gyroscope. The gyro used setting sub-nozzle around the main nozzle to inhibit the attenuation which had been caused by the main nozzle jet column spread out and to increase the angular velocity difference of sensitive element in the thermal resistance wire when the jet flow rate had been input, thereby to improve the performance of the jet gyro. The test results showed that: a resolution of better than 0.1°/s nozzle formation jet gyro sensitivity better than 10mv/(0.1°/s), the measurement range is better than ± 60°/s; non-linearity of better than 1%.The impact of the gyroscope impact resistance capability, small size and wide range of applications.

Interpretation of synthetic common‐depth‐point gathers for a single anisotropic layer

Geophysics ◽  
1982 ◽  
Vol 47 (3) ◽  
pp. 323-335 ◽  
Author(s):  
Stuart Crampin ◽  
Barbara J. Radovich
Keyword(s):  
Angular Velocity ◽  
Elastic Constants ◽  
Arrival Time ◽  
Transversely Isotropic ◽  
Orthorhombic Symmetry ◽  
Isotropic Layer ◽  
Anisotropic Layer ◽  
Wide Range ◽  
Velocity Variations ◽  
Anisotropic Layers

Analysis of synthetic traveltime gathers shows that anisotropy may have a large enough effect on P, SH, and SV propagation to alter significantly the interpretation of the subsurface below the anisotropic layers. Consequently, if anisotropy exists below a seismic line, it is important to estimate the anisotropic parameters correctly. We discuss the effects of anisotropy on seismic waves and present a method for estimating the elastic constants of a transversely isotropic layer from P and SH arrival‐time gathers. The technique may be extended to more general anisotropic symmetries by analyzing gathers from several azimuths. To illustrate the possible effect of anisotropy on exploration surveys, P, SH, and SV velocity variations are calculated for several types of anisotropic sedimentary fabrics. Alignments due to bedding, shale lithology, and dry parallel cracks may have similar velocity variations. Fabrics with other configurations of cracks may still possess overall transversely isotropic symmetry, but they have a wide range of angular velocity variations with different polarities and periodicities. Synthetic gather curves are generated for a range of models with an anisotropic layer over an isotropic substrate. They show departures from hyperbolas, and erroneous depth determinations, that depend upon the elastic constants of the anisotropic layer. The elastic constants of the anisotropic layers are estimated from the synthetic gather curves by means of approximate equations for the angular velocity variations, which are linear in the elastic constants. Formulas are developed which relate tangents to the gather curves directly in terms of the elastic constants. These are tested for single‐layer transversely isotropic models and allow the five elastic constants to be estimated by drawing three tangents to P and SH synthetic arrival‐time gathers in [Formula: see text] space. Comparisons of estimated with original elastic constants are good for a number of different types of transversely isotropic fabrics. Gathers are also calculated at two azimuths in an anisotropic layer with orthorhombic symmetry and are analyzed with some success.

Angular velocity measurement with wide range based on dual-comb Sagnac interferometer

2022 ◽  
Author(s):  
Ma Ruyu ◽  
Haoyang Yu ◽  
MA QIUYING ◽  
ZHOU QIAN ◽  
Kai Ni
Keyword(s):  
Angular Velocity ◽  
Velocity Measurement ◽  
Sagnac Interferometer ◽  
Wide Range

II. The angular motion of a freely falling rocket

1964 ◽  
Vol 279 (1379) ◽  
pp. 523-533
Keyword(s):  
Angular Velocity ◽  
Unit Length ◽  
Free Fall ◽  
Axisymmetric Body ◽  
Rigid Bodies ◽  
Angular Motion ◽  
Time Interval ◽  
Angular Momentum Vector ◽  
Centre Of Mass ◽  
Aerodynamic Forces

The motion of a rocket with its propellant exhausted and above the heights where aerodynamic forces can be used to control its motion, can be considered as that of a rigid body in free flight, subjected to small perturbations by weak aerodynamic forces. This permits the separate consideration of the motion of the centre of mass of the rocket along an approximately ‘free fall’ trajectory and the rotation of the rocket about its centre of mass. The rotational motion of free rigid bodies is well known and may be readily visualized by means of Poinsot’s construction (Corben & Stehle 1960). This analysis may be applied to the motion of a rocket with an accuracy which depends on the smallness of the residual aerodynamic forces and the time interval over which the ‘free fall’ approximation is applied. The Skylark rocket vehicle is a long axisymmetric body of approximately uniform mass per unit length. The momental ellipsoid of such a body is a long ellipsoid of revolution with its major axis along the spin axis of the rocket. In this case, the angular motion will consist only of roll and regular precession. In the early stages of the flight the rocket is given some spin motion by aero­dynamic forces on the fins. The angle between the geometrical axis of the rocket and the angular momentum vector is small and can change only slowly because of the aerodynamic forces which are important during the initial stages of the flight. The rate of precession of the rocket axis is much smaller than the rate of spin. In these circumstances, the angular motion will be as shown in figure 11 and can be regarded as roll about the vehicle axis OV with angular velocity ω and precession of this axis about an invariant direction OC with angular velocity Ω. The semi-angle, COV = ρ , of the precession cone is given by cos p = I L / I T ω / Ω , where I L and I T are the moments of inertia about longitudinal and transverse axes passing through the centre of mass.

Javelin Dynamics With Measured Lift, Drag, and Pitching Moment

1984 ◽  
Vol 51 (2) ◽  
pp. 406-408 ◽  
Author(s):  
M. Hubbard ◽  
H. J. Rust
Keyword(s):  
Computer Simulation ◽  
Wind Tunnel ◽  
Angular Velocity ◽  
Initial Velocity ◽  
Center Of Pressure ◽  
Angle Of Attack ◽  
Pitching Moment ◽  
Initial Angle ◽  
Aerodynamic Forces ◽  
Flight Path Angle

Optimal release conditions for the javelin are studied using computer simulation. Included are two important and realistic assumptions: (1) initial velocity attainable by the thrower is dependent on the throwing angle, and (2) the aerodynamic center of pressure moves as a function of angle of attack. Aerodynamic forces and moments, previously measured in wind tunnel tests, are incorporated in the simulation. Range contours are presented in the two-space of initial angle of attack–initial flight path angle, assuming zero initial angular velocity.

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