Avalanche statistics of sand heaps

Buchholtz, Volkhard; Pöschel, Thorsten

doi:10.1007/bf02174136

“…Those investigations led to the conclusion that SOC is not as universal as it was claimed. Instead, its validity relies on the dissipation mechanisms of specific systems [30], and also on the way of analysis [31,32]. Thus from the SOC perspective, the ubiquitous f 1 noise is still not completely understood and whether a general theory for f 1 noise exists or not is still unclear.…”

mentioning

confidence: 99%

1/fnoise on the brink of wet granular melting

Huang

¹

2015

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The collective behavior of a two-dimensional wet granular cluster under horizontal swirling motions is investigated experimentally. Depending on the balance between the energy injection and dissipation, the cluster evolves into various nonequilibrium stationary states with strong internal structure fluctuations with time. Quantitative characterizations of the fluctuations with the bond orientational order parameter q 6 reveal power spectra of the form a f with the exponent α closely related to the stationary states of the system. In particular, f 1 type of noise with a » -1 emerges as melting starts from the free surface of the cluster, suggesting the possibility of using f 1 noise as an indicator for phase transitions in systems driven far from thermodynamic equilibrium.

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“…Those investigations led to the conclusion that SOC is not as universal as it was claimed. Instead, its validity relies on the dissipation mechanisms of specific systems [30], and also on the way of analysis [31,32]. Thus from the SOC perspective, the ubiquitous 1/f noise is still not completely understood and whether a general theory for 1/f noise exists or not is still unclear.…”

mentioning

confidence: 99%

$1/f$ noise on the brink of wet granular melting

Huang

2015

Preprint

0

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The collective behavior of a two-dimensional wet granular cluster under horizontal swirling motions is investigated experimentally. Depending on the balance between the energy injection and dissipation, the cluster evolves into various nonequilibrium stationary states with strong internal structure fluctuations with time. Quantitative characterizations of the fluctuations with the bond orientational order parameter q 6 reveal power spectra of the form f α with the exponent α closely related to the stationary states of the system. In particular, 1/f type of noise with α ≈ −1 emerges as melting starts from the free surface of the cluster, suggesting the possibility of using 1/f noise as an indicator for phase transitions in systems driven far from thermodynamic equilibrium. models based on random or point process [20,21] have also been reported to produce 1/f noise.In order to provide a general understanding of 1/f noise, Bak et al. proposed the concept of self-organized criticality (SOC) [22,23], claiming that in spatially extended dissipative systems 1/f noise can be viewed as an indication of self-organized critical state. In contrast to the critical state in equilibrium thermodynamics, the system is self-organized, i.e. no external tuning is needed. Using a cellular automata (CA) model describing the avalanches in a pile of sand, they demonstrated that the scale invariance in time is associated with fractal structures, i.e. scale invariance in space. Triggered by this concept, a tremendous amount of investigations have been conducted to test the universality of SOC [19,24,25]. However, the CA model proposed by BTW was soon found to produce 1/f 2 noise in both one-and two-dimensions [26,27] and thus cannot directly be used to explain 1/f noise. Moreover, contradictory results were found in model experiments on the avalanches of a sandpile [24,28,29]. Those investigations led to the conclusion that SOC is not as universal as it was claimed. Instead, its validity relies on the dissipation mechanisms of specific systems [30], and also on the way of analysis [31,32]. Thus from the SOC perspective, the ubiquitous 1/f noise is still not completely understood and whether a general theory for 1/f noise exists or not is still unclear. Nevertheless, the advance on the relation between the invariance of time and space gives us the hint that noise may provide useful insights into the self-organized stationary states of systems driven far from thermodynamic equilibrium [19].Wet granular matter, such as wet sand used to build sand sculptures, has been drawing more and more interest from both physical and engineering communities in the past decades [33,34,35]. This is not only because of its ubiquity in nature, industries and our daily lives, but also due to the fact that it can be treated as a nonequilibrium model system with granular particles replacing molecules and liquid bridges formed between adjacent particles replacing molecular bonds. Because of the strong energy dissipation associated with wet impacts [36], continuou...

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