Interference Effect in the Flow Around Two Aligned Cylinders and the Reduction of a Helical Strakes Suppressor Effectiveness

It is well known that the interference effect reduces the effectiveness of vortex induced vibration (VIV) suppressors such as helical strakes. Usually the major concern about structures fitted with VIV suppressors is its own vibration. In this paper it is shown how an upstream structure fitted with helical strakes can induce higher vibrations than bare cylinders in a structure mounted downstream in a tandem configuration. Experiments were conducted in a water channel facility and demonstrate that the vortex wake generated by an cylinder fitted with strakes can induce higher amplitudes of oscillation than a bare cylinder. Particle image velocimetry was employed to measure the velocity field in the wake behind a smooth cylinder and behind a cylinder fitted with strakes. The Reynolds number for the experiments goes from 1000 up to 10.000. The flow field visualization was conducted for fixed cylinder at Re = 10.000.

Classification Inversion Algorithm of Circular Cylinder Particle Size Distribution Based on the Light Extinction Date

Particulate flow is commonly encountered in industries as well as in many other chemical and mechanical engineering applications. The accurate measurement of particle size distribution is of the utmost importance since it decides the physical and chemical characteristic of the particles. The light extinction method can be used for in-line monitoring of particle systems thus providing real time measurements of both particle size distribution and particle concentration. In light extinction particle sizing, a classification inversion algorithm is proposed for the circular cylinder particles. The measured circular cylinder particle system is inversed with different particle distribution functions and classified according to the inversion errors in the dependent model. The simulation experiments illustrate that it is feasible to use the inversion errors of object functions to inverse the circular cylinder particle size distribution in the light extinction particle sizing technique. This classing inversion algorithm can avoid the defects that the type of the size distribution must be assumed beforehand for the light extinction method.