Source code for genesis.engine.materials.SPH.liquid

import gstaichi as ti

from .base import Base


@ti.data_oriented
class Liquid(Base):
    """
    The liquid material class for SPH.

    Parameters
    ----------
    rho: float, optional
        The density (kg/m^3) the material tends to maintain in equilibrium (i.e., the "rest" or undeformed state). Default is 1000.
    stiffness: float, optional
        State stiffness (N/m^2). A material constant controlling how pressure increases with compression. Default is 50000.0.
    exponent: float, optional
        State exponent. Controls how nonlinearly pressure scales with density. Larger values mean stiffer response to compression. Default is 7.0.
    mu: float, optional
        The viscosity of the liquid. A measure of the internal friction of the fluid or material. Default is 0.005
    gamma: float, optional
        The surface tension of the liquid. Controls how strongly the material "clumps" together at boundaries. Default is 0.01
    sampler: str, optional
        Particle sampler ('pbs', 'regular', 'random'). Note that 'pbs' is only supported on Linux x86 for now. Defaults to 'regular' because:
        SPH is sensitive to the initial particle distribution, as it directly determines the initial density and pressure fields.
        To ensure numerical stability, particles must be initialized using a regular sampler that enforces near-uniform spacing.
        Irregular samplers (e.g. pbs, random) introduce local density fluctuations at initialization,
        which lead to large spurious pressure forces and can cause the simulation to become unstable or diverge.
    """

    def __init__(
        self,
        rho=1000.0,
        stiffness=50000.0,
        exponent=7.0,
        mu=0.005,
        gamma=0.01,
        sampler="regular",
    ):
        super().__init__(sampler)

        self._rho = rho
        self._stiffness = stiffness
        self._exponent = exponent
        self._mu = mu  # viscosity
        self._gamma = gamma  # surface tension

    @property
    def rho(self):
        """The density (kg/m^3) the material tends to maintain in equilibrium (i.e., the "rest" or undeformed state)."""
        return self._rho

    @property
    def stiffness(self):
        """State stiffness (N/m^2). A material constant controlling how pressure increases with compression."""
        return self._stiffness

    @property
    def exponent(self):
        """State exponent. Controls how nonlinearly pressure scales with density. Larger values mean stiffer response to compression."""
        return self._exponent

    @property
    def mu(self):
        """The viscosity of the liquid. A measure of the internal friction of the fluid or material."""
        return self._mu

    @property
    def gamma(self):
        """The surface tension of the liquid. Controls how strongly the material "clumps" together at boundaries."""
        return self._gamma