init. basic examples good.

.gitignore

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+__pycache__
+outputs

configs/inflow.json

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+{
+    "tag": "inflow",
+    "example": "inflow",
+    "N": 256,
+    "dt": 1,
+    "T": 200,
+    "diff": 0,
+    "visc": 0,
+    "draw": "mix",
+    "fps": 20,
+    "save_grids": 0
+}

configs/taylorgreen.json

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+{
+    "tag": "taylorgreen",
+    "example": "taylorgreen",
+    "N": 32,
+    "dt": 0.05,
+    "T": 100,
+    "diff": 0,
+    "visc": 0,
+    "draw": "velocity",
+    "fps": 20,
+    "save_grids": 0
+}

configs/vortexsheet.json

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+{
+    "tag": "vortexsheet",
+    "example": "vortexsheet",
+    "N": 128,
+    "dt": 0.025,
+    "T": 100,
+    "diff": 0,
+    "visc": 0,
+    "draw": "density",
+    "fps": 20,
+    "save_grids": 0
+}

examples/__init__.py

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+import importlib
+
+
+def get_example_setup(name):
+    try:
+        module = importlib.import_module("examples." + name)
+        setup = getattr(module, "setup")
+        return setup
+    except Exception as e:
+        print(e)
+        raise RuntimeError(f"Cannot find example setup. Example name: {name}.")

examples/inflow.py

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+# from https://github.com/GregTJ/stable-fluids/blob/main/example.py
+import numpy as np
+
+
+def create_circular_points(point_dist: float, point_count: int):
+    points = np.linspace(-np.pi, np.pi, point_count, endpoint=False)
+    points = tuple(np.array((np.cos(p), np.sin(p))) for p in points)
+    normals = tuple(-p for p in points)
+    points = tuple(point_dist * p for p in points)
+    return points, normals
+
+
+def inflow_velocity(coords: np.ndarray, vel: float=1. / 250, point_radius: float=0.032, point_dist: float=0.8, point_count: int=4):
+    points, normals = create_circular_points(point_dist, point_count)
+
+    inflow_velocity = np.zeros_like(coords)
+    for p, n in zip(points, normals):
+        mask = np.linalg.norm(coords - p[None, None], 2, axis=-1) <= point_radius
+        inflow_velocity[mask] += n[None] * vel
+    return inflow_velocity
+
+
+def inflow_density(coords: np.ndarray, point_radius: float=0.032, point_dist: float=0.8, point_count: int=4):
+    points, normals = create_circular_points(point_dist, point_count)
+
+    inflow_density = np.zeros(coords.shape[:-1])
+    for p in points:
+        mask = np.linalg.norm(coords - p[None, None], 2, axis=-1) <= point_radius
+        inflow_density[mask] = 1
+    return inflow_density
+
+
+setup = {
+    "domain": [[-1, 1], [-1, 1]],
+    "vsource": inflow_velocity,
+    "dsource": inflow_density,
+    "src_duration": 60
+}

examples/taylorgreen.py

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+import numpy as np
+
+
+def taylorgreen_velocity(coords: np.ndarray):
+    """taylorgreen velocity. domain: [0, 2pi] x [0, 2pi].
+
+    Args:
+        coords (np.ndarray): coordinates of shape (..., 2)
+
+    Returns:
+        velocity: velocity at coordinates
+    """
+    A = 1
+    a = 1
+    B = -1
+    b = 1
+    x = coords[..., 0]
+    y = coords[..., 1]
+    u = A * np.sin(a * x) * np.cos(b * y)
+    v = B * np.cos(a * x) * np.sin(b * y)
+    vel = np.stack([u, v], axis=-1)
+    return vel
+
+
+setup = {
+    "domain": [[0, 2 * np.pi], [0, 2 * np.pi]],
+    "vsource": taylorgreen_velocity,
+    "dsource": None,
+    "src_duration": 1
+}

examples/vortexsheet.py

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+import numpy as np
+
+
+def vortexsheet_velocity(coords: np.ndarray, rigidR=0.5, rate=0.1):
+    """domain: [-1, 1] x [-1, 1]"""
+    w = 1 * 1.0 / rate
+    R = np.linalg.norm(coords, 2, axis=-1)
+    mask = R < rigidR
+    weight = 1
+    u = w * coords[..., 1] * weight
+    v = -w * coords[..., 0] * weight
+    u[~mask] = 0
+    v[~mask] = 0
+    vel = np.stack([u, v], axis=-1)
+    return vel
+
+
+def vortexsheet_density(coords: np.ndarray, rigidR=0.5):
+    R = np.linalg.norm(coords, 2, axis=-1)
+    den = np.zeros(coords.shape[:-1])
+    den[R < rigidR] = 1.0
+    return den
+
+
+setup = {
+    "domain": [[-1, 1], [-1, 1]],
+    "vsource": vortexsheet_velocity,
+    "dsource": vortexsheet_density,
+    "src_duration": 1
+}