Two-degrees-of-freedom linear system response of structures

2009 ◽  
pp. 266-304
Author(s):  
S. Rajasekaran
Keyword(s):  
Linear System ◽  
Degrees Of Freedom ◽  
System Response ◽  
Two Degrees Of Freedom

Two Degrees of Freedom Vortex-Induced Vibrations of a Rigid Circular Cylinder With Varying Natural Frequencies in the X and Y Directions

2009 ◽  
Author(s):  
Arnaud Sanchis
Keyword(s):  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Local Maximum ◽  
Classical Case ◽  
System Response ◽  
Two Degrees Of Freedom ◽  
Vortex Induced Vibrations ◽  
Vertical Displacements ◽  
New Apparatus ◽  
Low Mass Ratio

VIV experiments in two degrees of freedom are performed with a new apparatus designed to achieve a very low mass ratio and structural damping (ζ = 0.01). We investigated the influence of the ratio between the natural frequencies in the horizontal (fx) and vertical (fy) directions on the system response. Experiments were conducted at fx/fy = 0.42, 0.87, 1.16, 1.36 and 1.44 with mx* = 2.87 and my* = 1.65. For fx/fy < 1, the amplitude and frequency response were found to be similar to the classical case where fx/fy = 1, except in the transition zone between the upper and lower branches. For fx/fy > 1 however, radical changes were observed in the system response in amplitude, frequency and phase θ between the horizontal and vertical displacements. The most obvious is the appearance of a local maximum of Ay* in the middle of the upper branch. Secondly, the nature of the transition between the upper and lower branches changes from intermittent switching to a hysteretic one. The shape of the figure-of-eights describing the cylinder trajectory is also affected so that the cylinder is moving upstream at the top of its trajectory instead of downstream, indicating a profound modification of the interaction between the two degrees of freedom. Lastly, the range of reduced velocities over which stable, two-degrees-of-freedom oscillations were recorded is greatly increased up to 3.8 < U* < 8.4.

The scientific bases of autocontrol with vibration phase for a resonance beating-vibration system with two degrees of freedom driven by debalances

1996 ◽  
Vol 18 (2) ◽  
pp. 43-48
Author(s):  
Tran Van Tuan ◽  
Do Sanh ◽  
Luu Duc Thach
Keyword(s):  
Degrees Of Freedom ◽  
Regulation System ◽  
Vibration System ◽  
Two Degrees Of Freedom ◽  
System Operating

In the paper it is introduced a method for studying dynamics of beating-vibrators by means of digital calculation with the help of the machine in accordance with the needs by the helps of an available auto regulation system operating with high reability.

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