Sinusoidal disturbance effect

This test is particularly useful for disturbances such as steps and pulses because their full impact is felt immediately. However, the test is not restricted to these disturbances and may also be used to consider the initial effect of sinusoids, ramps, or other disturbances. 

The RTD for a given reactor and flow rate can be established from response-type experiments. In these experiments the concentration of an inert tracer is disturbed in the feed stream and its effect on the effluent stream is measured. The three most common perturbations are a step function, a pulse (square wave), and a sinusoidal wave. The relationships between the observed concentration-vs-time curves and the RTD are examined here for step functions and pulses. The analysis of sinusoidal perturbations is more complex but is available in the literature. ... 

Consider a small-amplitude sinusoidal plane wave of length A and amplitude a propagating along an air-water interface in the positive x direction with wave speed c, as sketched in Fig. 10.4.1. The water is taken to be incompressible with viscosity and other dissipative effects neglected so that the wave amplitude at the interface remains unchanged. The vertical displacement of the disturbed surface, f, may be written... 

The first theoretical analysis of the breakup of a Newtonian thread in a quiescent Newtonian matrix was performed over a century ago by Rayleigh [284]. The disturbances that initiate the breakup process are often referred to as Rayleigh disturbances. Rayleigh analyzed only the effect of surface tension, neglecting the viscosities of the two phases. This work was extended by Tomotika [285] by including the effect of viscosity. The analysis considers a sinusoidal liquid cylinder the radius as a function of axial distance z is ... 

Here we have to mention that at the VTB-2 instmment sometimes there was another form of temperature instability. This instability appeared in a long period (150 - 180 sec) sinusoidal signal variation. This periodic perturbation appeared both on the heterodyne and the local signals. This effect was disturbing only at low cl values, and this perturbation appears as a systematic error in our results at low cl. The origin of this slow variation of the lasers has not been clarified. 

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