tfirst implementaiton of grain-wall interaction - Granular.jl - Julia package for granular dynamics simulation
(HTM) git clone git://src.adamsgaard.dk/Granular.jl
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---
(DIR) commit 6e8adb0d8a14aa77aaa516f197c72bbe242a9fbb
(DIR) parent ccd9921a7fd354df82bcfcfb115844cc26278beb
(HTM) Author: Anders Damsgaard <andersd@riseup.net>
Date: Tue, 14 Nov 2017 16:12:33 -0500
first implementaiton of grain-wall interaction
Diffstat:
M src/interaction.jl | 42 +++++++++++++++++++++++++++++++
M src/simulation.jl | 5 ++++-
M src/wall.jl | 15 +++++++++------
3 files changed, 55 insertions(+), 7 deletions(-)
---
(DIR) diff --git a/src/interaction.jl b/src/interaction.jl
t@@ -5,6 +5,9 @@ export interact!
interact!(simulation::Simulation)
Resolve mechanical interaction between all particle pairs.
+
+# Arguments
+* `simulation::Simulation`: the simulation object containing the grains.
"""
function interact!(simulation::Simulation)
for i=1:length(simulation.grains)
t@@ -28,6 +31,45 @@ function interact!(simulation::Simulation)
nothing
end
+
+"""
+ interactWalls!(sim)
+
+Find and resolve interactions between the dynamic walls (`simulation.walls`) and
+the grains. The contact model uses linear elasticity, with stiffness based on
+the grain Young's modulus `grian.E` or elastic stiffness `grain.k_n`. The
+interaction is frictionless in the tangential direction.
+
+# Arguments
+* `simulation::Simulation`: the simulation object containing the grains and
+ dynamic walls.
+"""
+function interactWalls!(sim::Simulation)
+
+ δ_n::Float64 = 0.0
+ k_n::Float64 = 0.0
+
+ for iw=1:length(sim.walls)
+ for i=1:length(sim.grains)
+
+ # get overlap distance by projecting grain position onto wall-normal
+ # vector
+ δ_n = dot(sim.walls[iw].normal, sim.grains[i].lin_pos) -
+ sim.walls[iw].pos - sim.grains[i].contact_radius
+
+ if sim.grains[i].youngs_modulus > 0.
+ k_n = sim.grains[i].youngs_modulus *
+ sim.grains[i].thickness
+ else
+ k_n = sim.grains[i].contact_stiffness_normal
+ end
+
+ sim.walls[iw].force += k_n * abs(δ_n)
+ sim.grains[i].force += k_n * abs(δ_n) * sim.grains[iw].normal
+ end
+ end
+end
+
export interactGrains!
"""
interactGrains!(simulation::Simulation, i::Int, j::Int, ic::Int)
(DIR) diff --git a/src/simulation.jl b/src/simulation.jl
t@@ -248,13 +248,16 @@ function disableGrain!(simulation::Simulation, i::Int)
end
export zeroForcesAndTorques!
-"Sets the `force` and `torque` values of all grains to zero."
+"Sets the `force` and `torque` values of all grains and dynamic walls to zero."
function zeroForcesAndTorques!(simulation::Simulation)
for grain in simulation.grains
grain.force .= grain.external_body_force
grain.torque = 0.
grain.pressure = 0.
end
+ for wall in simulation.walls
+ wall.force = 0.
+ end
nothing
end
(DIR) diff --git a/src/wall.jl b/src/wall.jl
t@@ -13,7 +13,9 @@ The only required arguments are
# Arguments
* `simulation::Simulation`: the simulation object where the wall should be
added to.
-* `normal::Vector{Float64}`: 2d vector denoting the normal to the wall [m].
+* `normal::Vector{Float64}`: 2d vector denoting the normal to the wall [m]. The
+ wall will only interact in the opposite direction of this vector, so the
+ normal vector should point in the direction of the grains.
* `pos::Float64`: position along axis parallel to the normal vector [m].
* `bc::String="fixed"`: boundary condition, possible values are `"fixed"`
(default), `"normal stress"`, or `"velocity"`.
t@@ -52,11 +54,11 @@ Granular.addWallLinearFrictionless!(sim, [0., 1.], 1.5,
vel=-0.5)
```
-To create a wall parallel to the *x* axis with a constant normal stress of 100
-kPa:
+To create a wall parallel to the *y* axis pushing downwards with a constant
+normal stress of 100 kPa, starting at a position of y = 3.5 m:
```julia
-Granular.addWallLinearFrictionless!(sim, [1., 0.], 3.5,
+Granular.addWallLinearFrictionless!(sim, [0., -1.], 3.5,
bc="normal stress",
normal_stress=100e3)
```
t@@ -78,11 +80,12 @@ function addWallLinearFrictionless!(simulation::Simulation,
"$normal)")
end
- if !(normal ≈ [1., 0.]) && !(normal ≈ [0., 1.])
+ if !(normal ≈ [1., 0.]) && !(normal ≈ [0., 1.]) &&
+ !(normal ≈ [-1., 0.]) && !(normal ≈ [0., -1.])
error("Currently only walls with normals orthogonal to the " *
"coordinate system are allowed, i.e. normals parallel to the " *
"x or y axes. Accepted values for `normal` " *
- "are [1., 0.] and [0., 1.]. The passed normal was $normal")
+ "are [±1., 0.] and [0., ±1.]. The passed normal was $normal")
end
# if not set, set wall mass to equal the mass of all grains.