The Unsteady Aerodynamics of a Finite Supersonic Cascade With Subsonic Axial Flow

1973 ◽  
Vol 40 (3) ◽  
pp. 667-671 ◽  
Author(s):  
J. M. Verdon
Keyword(s):  
Axial Flow ◽  
Unsteady Aerodynamics ◽  
Supersonic Stream ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Combined Use ◽  
Cascade Analysis ◽  
Infinite Array ◽  
Typical Configuration ◽  
Phase Angles

A method is presented for determining the unsteady flow field and the aerodynamic response which occurs when a finite oscillating cascade is placed in a supersonic stream, which has a subsonic velocity component normal to the cascade. Solutions are obtained through the combined use of closed-form and numerical procedures. Computed results indicate that the finite cascade analysis should provide a reasonable indication of the influence of the cascade parameters on the response of the infinite array. A brief parametric study for a typical configuration reveals possible aerodynamic instabilities when the blades perform single-degree-of-freedom pitching oscillations over a broad range of frequencies and interblade phase angles.

Further Developments in the Aerodynamic Analysis of Unsteady Supersonic Cascades—Part 2: Aerodynamic Response Predictions

1977 ◽  
Vol 99 (4) ◽  
pp. 517-525 ◽  
Author(s):  
J. M. Verdon
Keyword(s):  
Free Stream ◽  
Narrow Range ◽  
Axial Flow ◽  
Stable Condition ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Numerical Predictions ◽  
Free Stream Mach Number ◽  
Parameter Values ◽  
Phase Angles

This paper is the second of a two-part report on a theoretical analysis of the aerodynamic response to an oscillating supersonic cascade in subsonic axial flow. Supersonic resonance criteria are discussed and lead to the distinction between subresonant and superresonant cascade motions. Numerical predictions, based on the unsteady solution reported in Part 1, are presented for two typical cascade configurations. These reveal the possibility of both subresonant and superresonant single-degree-of-freedom torsional instabilities. Subresonant instabilities occur over a broad range of frequencies and interblade phase angles, whereas superresonant instabilities occur only over a narrow range of such cascade parameter values. For a given blade motion frequency and free-stream Mach number, it appears that the least stable condition will usually lie in the subresonant region.

scholarly journals A cross-species neural integration of gravity for motor optimization

2021 ◽  
Vol 7 (15) ◽  
pp. eabf7800
Author(s):  
Jeremie Gaveau ◽  
Sidney Grospretre ◽  
Bastien Berret ◽  
Dora E. Angelaki ◽  
Charalambos Papaxanthis
Keyword(s):  
Optimization Strategy ◽  
Motor Patterns ◽  
Activation Patterns ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Neural Integration ◽  
Gravity Effects ◽  
Neural Signature ◽  
Experimental Findings ◽  
Muscular Activation

Recent kinematic results, combined with model simulations, have provided support for the hypothesis that the human brain shapes motor patterns that use gravity effects to minimize muscle effort. Because many different muscular activation patterns can give rise to the same trajectory, here, we specifically investigate gravity-related movement properties by analyzing muscular activation patterns during single-degree-of-freedom arm movements in various directions. Using a well-known decomposition method of tonic and phasic electromyographic activities, we demonstrate that phasic electromyograms (EMGs) present systematic negative phases. This negativity reveals the optimal motor plan’s neural signature, where the motor system harvests the mechanical effects of gravity to accelerate downward and decelerate upward movements, thereby saving muscle effort. We compare experimental findings in humans to monkeys, generalizing the Effort-optimization strategy across species.

Kinematic comparison of single degree-of-freedom robotic gait trainers

2021 ◽  
Vol 159 ◽  
pp. 104258
Author(s):  
Jeonghwan Lee ◽  
Lailu Li ◽  
Sung Yul Shin ◽  
Ashish D. Deshpande ◽  
James Sulzer
Keyword(s):  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Robotic Gait

Analytical Simulation of Dynamically Equivalent Components

1986 ◽  
Vol 108 (4) ◽  
pp. 394-400
Author(s):  
Z. N. Ibrahim
Keyword(s):  
Dynamic Characteristic ◽  
Dynamic Model ◽  
Single Degree Of Freedom ◽  
Residual Mass ◽  
Single Degree ◽  
Modal Synthesis ◽  
Stiffness Matrices ◽  
Analytical Simulation ◽  
Modal Mass ◽  
Residual Stiffness

The inertia concept of modal mass was developed to provide a consistent methodology for establishing an analytically equivalent dynamic model of any discrete section within a complex piping network. The multidegree of freedom system is reduced to several multiple excitation single degree of freedom (SDOF) systems representing its modal masses and modal stiffnesses. The multiple excitation residual mass and residual stiffness matrices were also formulated. The combination of modal mass-modal stiffness SDOF systems and residual mass-residual stiffness matrices can simulate the complete dynamic characteristic of any desired portion of the piping network. This technique was extended to cover substructuring applications, and was proved mathematically to be equivalent to the conventional modal synthesis formulation.

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