Effect Of Surface Charge And Rotation Of Sand Particles On Measurement Result By PIV

As the improvement of experimental instrument of research on wind-sand movement, many optical instruments have been used in the research, just as particle image velocimetry(PIV) who is used to meter the velocity and the size of sands. Any influence factors of the optical properties may affect optical instrument measurement result, for instance, the size of sand, surface charge, and the rotation of sand.Base on the electromagnetic scattering model of single spherical sand given by Zhou, The attenuation of electromagnetic wave by a single charged sand/dust particle has been numerically calculated using the finite different time domain in this paper. Then the ratio of attenuation of electromagnetic wave by charged particles to the one by particles without carrying charges are got, and results indicate that attenuation due to the charges carrying by particles is significant, specially when the frequency of electromagnetic wave lower than 200GHz. And it will have a large influence on the communication of electromagnetic wave. The light reflectivity and transmittivity of surface charged sand/dust particle has been numerically calculated using the geometrical optics approach. Then the scattering intensity of single spherical sand and the error's formulas of sand particle diameter and concentration measurement used by PIV are got. It indicates that the maximum error of sand particle diameter measurement by PIV is about 30%, and the maximum error of concentration measurement by PIV could reach 300%. based on the measurement principle of PIV, we analyze the measurement error of PIV. For two frame images of a single sand particle taken by charge-coupled device (CCD) camera at an interval of a pulse time, we calculate the displacement of the mass center of the sand particle and the displacement of the center of image, and calculate the difference between the displacements of the two centers. Then we derive the error's formulas of sand particle velocity and sand particle diameter measurement used by PIV due to the sand particle rotation. It indicates that the velocity error measured by PIV relates to the velocity of sand particles, and the higher is the velocity of sand particles, the larger is the error. The maximum error of velocity measurement by PIV is not beyond 10%, and the measurement error can be decreases by increasing the pulse time.