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dataLayout.md

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Test Case I:

attrs:

  • baseArea: Basic Area of a particle (i.e., length in 1D), i.e., $\Delta x$
  • c0: Speed of sound, approximately $10\times u_max$
  • diffusionAlpha: Velocity Diffusion constant for the Price artificial viscosity model (1.0)
  • diffusionBeta: Velocity Diffusion constant for the Price artificial viscosity model (2.0)
  • dt: Fixed Timestep used for the simulation
  • generator: Scheme used to generate the data, perlin and simplex indicates random velocity fields.
  • kappa: Stiffness coefficient for compressible EOS
  • maxDomain: Maximum domain extent (1)
  • minDomain: Minimum domain extent (-1)
  • numParticles: Expected number of particles in a simulation
  • particleRadius: Radius, i.e., half particle spacing $\Delta x$
  • particleSupport: Support radius used during the simulation
  • restDensity: Rest Density of the fluid, 1000 in most cases
  • timesteps: Number of timesteps expected in the simulation
  • xsphConstant: Legacy constant, not used during the simulation

generatorSetting.attrs:

  • freq: Base Frequency of the noise
  • mag: Maximum amplitude of the noise
  • octaves: Number of octaves, i.e., powers of two of the base frequency
  • offset: Constant used to shift the density noise up, needed to avoid zero density
  • r: Implementation specific parameter
  • seed: Seed used for generation (should be included in the file name)

simulationData (no attrs):

  • dudt: Tensor of shape [t,i] containing $\frac{d u}{d t}$
  • dudt_k1, dxdt_k1: Substep information from the RK4 integrator for velocity and position updates
  • dudt_k2, dxdt_k2: Substep information from the RK4 integrator for velocity and position updates
  • dudt_k3, dxdt_k3: Substep information from the RK4 integrator for velocity and position updates
  • dudt_k4, dxdt_k4: Substep information from the RK4 integrator for velocity and position updates
  • fluidAreas: Tensor of shape [t,i] containing area of each particle (constant)
  • fluidDensity: Tensor of shape [t,i] containing the current summation density of each particle
  • fluidPosition: Tensor of shape [t,i] containing the current position of each particle
  • fluidPressure: Tensor of shape [t,i] containing the current pressure of each particle
  • fluidVelocities: Tensor of shape [t,i] containing the current velocity of each particle

Test Case II/III:

attrs:

attribute | example | description | legacy ---|---|--- EOSgamma | 7.0 | Stiffness coefficient for the stiff Tait EOS | yes alphaDiffusion | 0.01 | Diffusion coefficient for the standard velocity | yesdiffusion model boundaryPressureTerm | PBSPH | Method to compute the presssure on the boundary particles if any | yes boundaryScheme | solid | Scheme to sample boundary particles if any | yes c0 | 100 | Speed of sound for the EOS, should be $10\times u_max$ | yes defaultKernel | wendland2 | Kernel function used for the SPH simulation | yes deltaDiffusion | 0.1 | Diffiusion coefficient for the delta-SPH model | yes densityDiffusionScheme | MOG | Density diffusion scheme model, default is MOlteni and coloGrassi | yes densityScheme | continuum | continuum indicates that density is integrated over time, summation means instantenous density | yes device | cuda | Device simulated on | yes fixedDt | True | Indicates if a fixed timestep was used | yes floatprecision | single | Floating point precision used during simulation | yes fluidGravity | [0 0] | Gravity direction and magnitude, if any | no fluidPressureTerm | TaitEOS | Equation of State model used | yes initialDt | 0.001 | Timestep used during the first timestep | yes integrationScheme | RK4 | Temporal integration scheme (RK4 means Runge Kutta 4th Order) | yes kinematicDiffusion | 0.001 | Diffusion coefficient for actual viscosity | yes packing | 0.398825 | Particle Packing $\Delta x$ | yes radius | 0.017781 | Half the packing distance | no restDensity | 998 | Rest density of the fluid | no shiftingEnabled | False | Indicates if Particle Shifting is used | yes shiftingScheme | deltaPlus | Particle Shifting Technique | yes simulationScheme | deltaSPH | Simulation Scheme (either deltaSPH or DFSPH) | yes spacing | 0.398825 | Parameter that is usually identical to the particle packing (might differ for incompressible SPH) | yes staticBoundary | True | Indicates if the boundary particles, if any, are dynamic over time | yes targetNeighbors | 20 | Expected number of neighbors per SPH particle | no velocityDiffusionScheme | deltaSPH | Scheme used for the velocity diffusion | yes

boundaryInformation:

Note that if there are no boundary particles, this node may not exist

  • boundaryArea: Array of shape [b], contains the area of each boundary particle (may be different for the Akinci boundary model)
  • boundaryBodyAssociation: Array of shape [b]: Contains the solid body each particle is associated with
  • boundaryNormals: Array of shape [b,d]: Normal associated with the boundary, points towards the outside of the body
  • boundaryPosition: Array of shape [b,d]: Position of the particle in simulation space
  • boundaryRestDensity: Array of shape [b]: Rest Density of the boundary particle
  • boundarySupport: Array of shape [b]: Support radius of the boundary particle
  • boundaryVelocity: Array of shape [b,d]: Velocity of the boundary particle (0 if static)

simulationExport

Contrary to the 1D data, this group contains a subgroup per frame in the simulation export. The key of each group is the frame in %05d format.

Frame Information:

attrs:

  • dt: Current timestep
  • time: Current time of the simulation (after integration)
  • timestep: Current timestep count of the simulation (after integration)

optional attrs (in new format):

  • CFLNumber:
  • averageCompression:
  • averageDensity:
  • dt_a:
  • dt_c:
  • dt_v:
  • maxCompression:
  • maxNeighborCount:
  • maxShift:
  • medianNeighborCount:
  • minCompression:
  • minNeighborCount:

entries:

  • UID: Array of shape [f]: Contains a unique identifier for each particle to track particles over time, necesssary if inlet/outlet conditions are used
  • boundaryDensity: Array of shape [f]: Density contribution of the boundary to each fluid particle, may not exist
  • finalPosition: Array of shape [f,d]: Position of each particle after integration, may not exist
  • finalVelocity: Array of shape [f,d]: Velocity of each particle after integration, may not exist
  • fluidAcceleration: Array of shape [f,d]: Acceleration of each particle, i.e., du/dt, may not exist
  • fluidArea: Array of shape [f]: Area of each particle, should be constant, may not exist
  • fluidDensity: Array of shape [f]: Current density of each particle, if continuum is used this quantity is integrated over time, otherwise it is recomputed every timestep
  • fluidDpdt: Array of shape [f]: Change of density of a particle, i.e., drho/dt, may not exist
  • fluidPosition: Array of shape [f,d]: Position of each particle before integration
  • fluidPressure: Array of shape [f]: Pressure of each particle based on EOS/pressure Solve, may not exist
  • fluidSupport: Array of shape [f]: Support radius of each particle, should be constant, may not exist
  • fluidVelocity: Array of shape [f,d]: Velocity of each particle before integration
  • fluidShiftAmount: Array of shape [f,d]: Particle Shifting amount, may not exist

Test Case IV:

attrs:

  • dx:
  • jitterAmount:
  • jitterMean:
  • maxDomain:
  • minDomain:
  • numNeighbors:
  • nx:
  • ny:
  • nz:
  • simplexFrequency:
  • simplexScale:
  • support:
  • volume:

simulationData: Contains a list of random seeds as subgroups, each subgroup consists of: attrs:

  • frequency:
  • seed:

and groups:

  • gradRhoDifference:
  • gradRhoNaive:
  • gradRhoSymmetric:
  • jitter:
  • ni:
  • rho:
  • vols:
  • x: