Homogeneous cooling state of frictionless rod particles

Rubio-Largo, S.M.; Alonso‐Marroquín, Fernando; Weinhart, Thomas; Luding, Stefan; Hidalgo, R. C.

doi:10.1016/j.physa.2015.09.046

Cited by 26 publications

(44 citation statements)

References 42 publications

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“…These studies showed that as particle aspect ratio increases, the equipartition of granular temperature between the translational and rotational degrees of freedom is achieved. These observations for smooth ellipsoids were found for smooth sphero‐cylinders as well by Rubio‐Largo et al Although this sphero‐cylinder study focused on a single solid‐volume fraction, they found that the collision frequency of elongated particles can be simply correlated through a linear relationship with the collision frequency of spheres.…”

Section: Introductionsupporting

confidence: 72%

“…Frictionless glued‐sphere particles (the blue particles shown in Figure ), ellipsoidal particles, and sphero‐cylindrical particles all have three translational and two rotational degrees of freedom. Particle rotation about the particle major axis does not exist for these particles, due to the fact that the contact force vectors always intersect the particle major axis so that the moment about the major axis is always zero.…”

Section: Simulation Designmentioning

confidence: 99%

“…, the granular temperature

θ

should be replaced by a total granular temperature

θ_{t o t a l} = θ_{t r a n s} + \frac{N_{r o t}}{3} θ_{r o t} = θ_{t r a n s} true(1 + {\frac{N_{normalr normalo normalt}}{3} R}_{θ}^{- 1} true)

in which

R_{θ}

is the ratio of translational to rotational granular temperatures, that is,

R_{θ} = θ_{t r a n s} / θ_{r o t}

. According to previous work, the temperature ratio is constant in the cooling state of HCS simulations and can be determined for elongated particles. The direct implementation of the collisional dissipation rate model would involve replacing

γ

in Eq.…”

Section: Simulation Designmentioning

confidence: 99%

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Using the discrete element method to develop collisional dissipation rate models that incorporate particle shape

2017

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Discrete Element Method simulations of Homogeneous Cooling Systems (HCS) are used to develop a collisional dissipation rate model for non-spherical particle systems that can be incorporated in a two-fluid multiphase flow framework. Two types of frictionless, elongated particle models are compared in the HCS simulations: glued-sphere and true cylinder. Simulation results show that the ratio of translational to rotational granular temperatures is equal to one for the true cylindrical particles with particle aspect ratios (AR) greater than one and glued-sphere particles with AR >1.5, while the temperature ratio is less than one for glued-sphere particles with 1 < AR <1.5. The total collisional dissipation rate, which is associated with both translational and rotational granular temperature change rates, increases linearly with the particle aspect ratio. Thus, a collisional dissipation rate model for the elongated cylinders is developed by a simple modification of the existing spherical particle model.The error bar and extended black dotted lines represent the standard deviation of the measurements from 10 simulations with 100 particles. (Glued-sphere particles, AR 5 4, and a s 5 0.2).

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Section: Introductionsupporting

confidence: 72%

Section: Simulation Designmentioning

confidence: 99%

“…, the granular temperature

θ

should be replaced by a total granular temperature

θ_{t o t a l} = θ_{t r a n s} + \frac{N_{r o t}}{3} θ_{r o t} = θ_{t r a n s} true(1 + {\frac{N_{normalr normalo normalt}}{3} R}_{θ}^{- 1} true)

in which

R_{θ}

is the ratio of translational to rotational granular temperatures, that is,

R_{θ} = θ_{t r a n s} / θ_{r o t}

γ

in Eq.…”

Section: Simulation Designmentioning

confidence: 99%

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Using the discrete element method to develop collisional dissipation rate models that incorporate particle shape

2017

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“…For this reason GPUs become very effective when processing large blocks of data and have emerged as a serious alternative for parallel computing. Our algorithm has already been successfully used in describing the behavior of spherical and nonspherical inert grains [28][29][30].…”

Section: The Modelmentioning

confidence: 99%

Simulating competitive egress of noncircular pedestrians

2017

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We present a numerical framework to simulate pedestrian dynamics in highly competitive conditions by means of a force-based model implemented with spherocylindrical particles instead of the traditional, symmetric disks. This modification of the individuals' shape allows one to naturally reproduce recent experimental findings of room evacuations through narrow doors in situations where the contact pressure among the pedestrians was rather large. In particular, we obtain a power-law tail distribution of the time lapses between the passage of consecutive individuals. In addition, we show that this improvement leads to new features where the particles' rotation acquires great significance.

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“…In addition, the time dependence of the scaling distribution occurs only throught a dimensionless velocity. Similar features are found if grains have different mechanical properties [7,8], are nonspherical [9,10], or even if the model includes other details of the grains, such as roughness/rotations [11,12,13,14], or velocity dependent collision coefficients [15,16,17].…”

Section: Introductionmentioning

confidence: 71%

Generalized time evolution of the homogeneous cooling state of a granular gas with positive and negative coefficient of normal restitution

Khalil¹

2018

J. Stat. Mech.

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The homogeneous cooling state (HCS) of a granular gas described by the inelastic Boltzmann equation is reconsidered. As usual, particles are taken as inelastic hard disks or spheres, but now the coefficient of normal restitution α is allowed to take negative values α ∈ [−1, 1], a simple way of modeling more complicated inelastic interactions. The distribution function of the HCS is studied at the long-time limit, as well as for intermediate times. At the long-time limit, the relevant information of the HCS is given by a scaling distribution function φ s (c), where the time dependence occurs through a dimensionless velocity c. For α −0.75, φ s remains close to the gaussian distribution in the thermal region, its cumulants and exponential tails being well described by the first Sonine approximation. On the contrary, for α −0.75, the distribution function becomes multimodal, its maxima located at c = 0, and its observable tails algebraic. The latter is a consequence of an unbalanced relaxationdissipation competition, and is analytically demonstrated for α ≃ −1 thanks to a reduction of the Boltzmann equation to a Fokker-Plank-like equation. Finally, a generalized scaling solution to the Boltzmann equation is also found φ(c, β). Apart from the time dependence occurring through the dimensionless velocity, φ(c, β) depends on time through a new parameter β measuring the departure of the HCS from its longtime limit. It is shown that φ(c, β) describes the time evolution of the HCS for almost all times. The relevance of the new scaling is also discussed.

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Homogeneous cooling state of frictionless rod particles

Cited by 26 publications

References 42 publications

Using the discrete element method to develop collisional dissipation rate models that incorporate particle shape

Using the discrete element method to develop collisional dissipation rate models that incorporate particle shape

Simulating competitive egress of noncircular pedestrians

Generalized time evolution of the homogeneous cooling state of a granular gas with positive and negative coefficient of normal restitution

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