Boundary handling and porous flow for fluid–hair interactions

Lin, Wei-Chin

doi:10.1016/j.cag.2015.06.005

Cited by 13 publications

(8 citation statements)

References 46 publications

(70 reference statements)

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“…Our choice contrasts with previous work on animating wet hair [Lin 2014[Lin , 2015Rungjiratananon et al 2012], which assumes that liquid flows in the Darcy regime (i.e., porous flow without inertia or convection) inside the entire hair region, including the hair cuticles and the space between hairs.…”

Section: Related Workmentioning

confidence: 92%

A multi-scale model for simulating liquid-hair interactions

et al. 2017

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Fig. 1. Hair is submerged in water and then rapidly flipped, resulting in wet locks and dripping.The diverse interactions between hair and liquid are complex and span multiple length scales, yet are central to the appearance of humans and animals in many situations. We therefore propose a novel multi-component simulation framework that treats many of the key physical mechanisms governing the dynamics of wet hair. The foundations of our approach are a discrete rod model for hair and a particle-in-cell model for fluids. To treat the thin layer of liquid that clings to the hair, we augment each hair strand with a height field representation. Our contribution is to develop the necessary physical and numerical models to evolve this new system and the interactions among its components. We develop a new reduced-dimensional liquid model to solve the motion of the liquid along the length of each hair, while accounting for its moving reference frame and influence on the hair dynamics. We derive a faithful model for surface tension-induced cohesion effects between adjacent hairs, based on the geometry of the liquid bridges that connect them. We adopt an empirically-validated drag model to treat the effects of coarse-scale interactions between hair and surrounding fluid, and propose new volume-conserving dripping and absorption strategies to transfer liquid between the reduced and particle-in-cell liquid representations. The synthesis of these techniques yields an effective wet hair simulator, which we use to animate hair flipping, an animal shaking itself dry, a spinning car wash roller brush dunked in liquid, and intricate hair coalescence effects, among several additional scenarios.

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Section: Related Workmentioning

confidence: 92%

A multi-scale model for simulating liquid-hair interactions

et al. 2017

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“…The saturation of each boundary particle is used to derive the fluid–hair coupling force and the adhesive force between wet hair strands. To further improve stability, Lin incorporated the saturation of each boundary particle into the density computation of the fluid particles at the boundary in the follow‐up studies . By improving the widely used technique of employing stationary boundary particles to satisfy nonpenetration and no‐slip conditions, Bayraktar et al proposed an SPH‐based method of fluid simulation, where boundary conditions are designed in such a way that fluid flow through porous media, pipes, and chokes can be realistically simulated.…”

Section: Related Workmentioning

confidence: 99%

“…h 0 is the initial support radius of water particles. In order to avoid instability induced by very large local density, the position of p is calculated according to Lin's approach . Then, the saturation‐dependent attraction force exerted on p by its neighboring cloth particles is calculated from the following equation to simulate the flows of water drip on the cloth surface:

{boldf}_{p}^{attract E} = \sum_{i} κ^{e} ((), m_{i} + η^{e} S_{i}) normalΨ false(ρ_{0} false) W false(x_{i p}, h_{p} false),

where κ e is a coefficient to adjust the attraction force, Ψ( ρ 0 ) is the function in the work of Akinci et al to consider the relative contribution of neighboring cloth particles, and η e is a user‐defined coefficient to weigh the saturation influence.…”

Section: Nonlinear Cloth Wetting Modelmentioning

confidence: 99%

“…To further improve stability, Lin incorporated the saturation of each boundary particle into the density computation of the fluid particles at the boundary in the follow-up studies. 24 By improving the widely used technique of employing stationary boundary particles to satisfy nonpenetration and no-slip conditions, Bayraktar et al 25 proposed an SPH-based method of fluid simulation, where boundary conditions are designed in such a way that fluid flow through porous media, pipes, and chokes can be realistically simulated. On the basis of Darcy's law, which describes the flow of water in porous materials, several researchers have realistically simulated the wetting phenomena in grid-or particle-based fluid solvers.…”

Section: Wetting Simulationmentioning

confidence: 99%

“…In order to avoid instability induced by very large local density, the position of p is calculated according to Lin's approach. 24 Then, the saturation-dependent attraction force exerted on p by its neighboring cloth particles is calculated from the following equation to simulate the flows of water drip on the cloth surface:…”

Section: Water Emissionmentioning

confidence: 99%

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Position‐based simulation of cloth wetting phenomena

Shao

Wang

2017

Computer Animation & Virtual

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Because of the advantages of high stability and efficiency, position‐based dynamics (PBD) is becoming increasingly popular with game developers and filmmakers. On the basis of the unified adaptive PBD, we present a nonlinear cloth wetting model to simulate visually realistic cloth wetting phenomena, which takes into account the influence of gravity on all aspects of the wetting process. Specifically, in order to model water diffusion in unsaturated cloth, we propose a novel nonlinear saturation constraint of cloth particles, which considers the influence of gravity, and then solve it using PBD to stably smooth the saturation field. The dynamic behaviors of the cloth and the water–cloth coupling during the cloth wetting process are modeled by using PBD. Moreover, a water absorption model and a water emission model are proposed to simulate the unsaturated cloth absorbing water and the oversaturated cloth draining water under the influence of gravity, respectively. The experimental results demonstrate that our novel wetting model provides an efficient way to model more stable and realistic cloth wetting phenomena using PBD.

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