Statistics and Strusture of Granular Flow through a Vertical Pipe

概要

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Tirne series signals of several flowing patterns of granular particles (rotngh sand) throtrgh avertical pipe have been anarlyzed by the wavelet expansion naethod. Probability distribtrtionftrnctions (PDFs) of wavelet coefficients, xvhich rotughly correspond to the density incretnentsover a given scale, are constrtrcted. It is revealed that PDFs ['or the sparse and trnifortaa flowwere Gatrssian distribution over wide scales. On the other hand, those of trniforzn btnt denseflow were exponential distribtrtions and the titne ser'ies signaxls had strong correlations betweenadjacent length scales. PDFs of' density waves were a little rrnore couaaplex: When the resistancef'orce dtne to the rmedituna air wets xveak, they were Gaussiana. NVhen it becartae strong, however,PDFs of' density waves charnged their shape according to the scales one observes. On large scales,they were Gatrssian. As the length scale becanae sznaller, PDFs were gradtrally defornaed fronaGaussian to exponential. It implies the existence of' intermittent density waves, which remindsus of fully developed turbtrlence.
社団法人日本物理学会の論文
1998-05-15