tiSPHi

An accurate, stable, fast, extendable fluid-solid coupling SPH solver.

For old documents about SPH, please find the doc.

News

06 Feb. 2023 - Still problems in all simulations!

Demos

Water dambreak

Fig. Water dambreak at 1.6s, 2D colored by pressure and 3D colored by velocity (very slow and wrong of 3D).

Granular column collapse

Fig. Granular column collapse at 0.61s (under μ(I) model), 2D colored by accumulated equivalent total strain. You could find pairing instability problem in the left-bottom side.

Runtime

Run

1. Creat or change a .\data\scenes\***.json, through which you can design a simulation case.
2. run python run_simulation.py --scene_file .\data\scenes\test1_db_water.json.

Hot key

• SPACE: control the pause/run of simulation.
• ESC: stop and exit the simulation.
• P: make a screenshot and save to the folder "screenshots".
• V: restore the initiate view.
• Press Q, E to move down and up the camera, press W, A, S, D to move forward, left, back, right the camera.
• Move the slider in Control panel to control the moving speed of camera (lcoked when equals to zero) or change the drawing radius of particles.

Scene file

• Configuration

    "Configuration":
    {
        "GPUmemoryPercent": 0.25,		// percentage of GPU memory used in CUDA backend
        "is2D": true,				// `true` means the simulation is 2d. `false` means 3d
        "domainStart": [0.0, 0.0, 0.0],		// the left-down-backward corner of the domain
        "domainEnd": [3.22, 1.6, 0.5],		// the right-up-forward corner of the domain
        "gravitation": [0.0, -9.81, 0.0],	// vector to define the gravitational acceleration
        "particleRadius": 0.005,		// the radius of the particles in the simulation (all have the same radius)
        "kappa": 2.0,				// smoothing length multiplier
        "kh": 1.5,				// supporting radius multiplier

        "simulationMethod": 1,			// 1: WCSPH, 2: µ(I)SPH, 3: DPSPH
        "timeStepSizeMin": 1e-4,		// the initial (and minimum) time step size used for the time integration
        "boundary": 2,				// 0: No boundary, 1: enforced collision bdy, 2: dummy particle bdy, 3: repulsive particle bdy, 4: repulsive+dummy particle bdy (CD-SBT)
        "kernel": 1,				// 0: cubic-spline kernel, 1: Wendland C2 kernel
        "kernelCorrection": 0,			// 0: no kernel gradient correction, 1: CSPM correction
        "timeIntegration": 2,			// 1: 1st order Symplectic Euler (SE), 2: 2nd order Leap-Frog (LF), 4: 4th order Runge-Kutta (RK)
        "xsph": false,				// `true` means using XSPH method to update the position

        "colorTitle": 7,			// colored variable, see `eng/ui_sim.py`
	"colorGroup": 0,			// colored particle group, 0: flow, 1: flow and rigid, 2: flow, rigid and bdy
	"comment": "sd, Fd",			// comment shown in GUI
        "stepsPerRenderUpdate": 10,		// number of simulation steps per rendered frame
        "pauseAtStart": true,			// `true` means pause simulation at beginning
        "stopEveryStep": 8000,			// pause simulation at every given step value
        "stopAtStep": 0,			// stop simulation at given step
        "exitAtStep": 0,			// exit simulation at given step and make a screenshot
        "stopAtTime": 0,			// stop at given time
        "exitAtTime": 2.4,			// exit at given time and make a screenshot
        "showBdyPts": true,			// `true` means show the bdy particles (both dummy and repulsive particles)
        "kradius": 1.15,			// drawing radius multiplier
        "givenMax": 5886,			// maximum value in drawing (`-1` means not set)
        "givenMin": -1,				// minimum value in drawing (`-1` means not set)
        "fixMax": 1,				// `1` (true) means set the maximum value as constant, otherwise it will change until the real value is bigger than `givenMax`
        "fixMin": 0,				// `1` (true) means set the minimum value as constant, otherwise it will change until the real value is smaller than `givenMin`

	"exportEveryTime": 0.001,		// save frame in every specific time.
	"exportEveryRender": 0,			// save frame in specific steps. `5` means every `5 × stepsPerRenderUpdate` step will be saved in a new folder
	"exportFrame": false,			// save png files
	"exportVTK": false,			// save vtu files
	"exportCSV": false			// save csv files
    },

• Materials

    "Materials": [
        {
            "matId": 0,				// id of the current material
            "matType": 1,			// 1: water or fluid
            "color": [50, 100, 200],		// default drawing color
            "density0": 1000,			// rest density, kg/m3
            "viscosity": 0.005,			// coefficient for the viscosity force computation
            "stiffness": 50000,			// stiffness coefficient of the equation of state
            "exponent": 7			// exponent in the equation of state
        },
        {
            "matId": 1,
            "matType": 2,			// 2: sand or granular material
            "color": [180, 100, 24],
            "density0": 2040,
            "cohesion": 0,			// cosition, Pa
            "friction": 21.9,			// friction, DEG
            "EYoungMod": 5.84e6,		// Young's modulus, Pa
            "poison": 0.3,			// Poison ratio
            "dilatancy": 0			// dilatancy angle, DEG
        }
    ],

• Blocks

    "FluidBlocks": [
        {
            "objectId": 0,			// id of the current object
            "size": [1.2, 0.6, 0.2],		// cube size in x, y, z direction
            "translation": [0, 0, 0],		// cube left-down-backward coner position
            "velocity": [0.0, 0.0, 0.0],	// the initial velocity is set for all particles in the fluid model
            "materialId": 0			// the material id of current object
        }
    ]

Ambition