5. Obstacles

Obstacles are solid bodies placed inside the simulation domain. They are registered in the set_obstacles block before the simulation starts. Each operator adds one obstacle to the list and requires a unique integer id. Obstacle surfaces enforce the no-slip condition through wall_bounce_back in pre_stream_bcs.

pre_stream_bcs:
  - wall_bounce_back

5.1. Solid Wall

  • Operator Name: register_solid_wall

  • Description: Registers an axis-aligned box (AABB) as a solid obstacle.

  • Parameters:

    • id: Unique integer identifier for this obstacle.

    • bounds: Axis-aligned bounding box [[xmin, ymin, zmin], [xmax, ymax, zmax]].

YAML example:

set_obstacles:
  - register_solid_wall:
     id: 0
     bounds: [[0.048, 0, 0], [0.052, 0.1, 0.08]]

5.2. Solid Ball

  • Operator Name: register_solid_ball

  • Description: Registers a spherical obstacle defined by a center and a radius.

  • Parameters:

    • id: Unique integer identifier for this obstacle.

    • center: Position of the sphere center [x, y, z].

    • radius: Radius of the sphere.

YAML example:

set_obstacles:
  - register_solid_ball:
     id: 0
     center: [0.1, 0.05, 0.1]
     radius: 0.013

5.3. Quadric Surface

  • Operator Name: register_quadrics

  • Description: Registers a quadric surface obstacle. A quadric is defined by a named canonical shape and an optional sequence of geometric transforms (scale and/or translate) that are composed in order. A point p is inside the obstacle if Q(T⁻¹ p) ≤ 0 where Q is the canonical quadric matrix and T is the composed transform.

  • Parameters:

    • id: Unique integer identifier for this obstacle.

    • quadrics: Name of the canonical quadric shape. Available shapes:

      • sphere: unit sphere (also used as ellipsoid via non-uniform scaling)

      • cyly: cylinder aligned along the Y axis

      • cylx: cylinder aligned along the X axis

      • cylz: cylinder aligned along the Z axis

      • conez: cone aligned along the Z axis

    • transform (optional): List of transforms applied in order. Each entry is either:

      • scale: [sx, sy, sz]

      • translate: [tx, ty, tz]

YAML example:

set_obstacles:
  - register_quadrics:
     id: 0
     quadrics: cyly
     transform:
       - scale:     [ 0.05, 1,    0.05 ]
       - translate: [ 0.15, 0.1,  0.1  ]
  - register_quadrics:
     id: 1
     quadrics: sphere
     transform:
       - scale:     [ 0.05, 0.08, 0.05 ]
       - translate: [ 0.35, 0.1,  0.15 ]
  - register_quadrics:
     id: 2
     quadrics: conez
     transform:
       - scale:     [ 0.05, 0.05, 0.05 ]
       - translate: [ 0.55, 0.1,  0.25 ]
../_images/quadrics.png