tUse Young's modulus and Poisson's ratio by default for contact mechanics - Gra… | |
git clone git://src.adamsgaard.dk/Granular.jl | |
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--- | |
commit 7fe5b27334a798544f5a5ae76b8c259026d37e65 | |
parent b4856096f45707589baa494ad735de2128f7ec35 | |
Author: Anders Damsgaard <[email protected]> | |
Date: Wed, 24 May 2017 15:09:43 -0400 | |
Use Young's modulus and Poisson's ratio by default for contact mechanics | |
Diffstat: | |
M src/icefloe.jl | 5 +++-- | |
M src/interaction.jl | 70 ++++++++++++++++++++---------… | |
M src/temporal.jl | 19 +++++++++++++++---- | |
M test/collision-2floes-oblique.jl | 22 ++++++++++++---------- | |
M test/vtk.jl | 2 +- | |
5 files changed, 77 insertions(+), 41 deletions(-) | |
--- | |
diff --git a/src/icefloe.jl b/src/icefloe.jl | |
t@@ -21,13 +21,14 @@ function addIceFloeCylindrical(simulation::Simulation, | |
ang_acc::float = 0., | |
torque::float = 0., | |
density::float = 934., | |
- contact_stiffness_normal::float = 1.e6, | |
+ contact_stiffness_normal::float = 1e7, | |
contact_stiffness_tangential::float = 0., | |
contact_viscosity_normal::float = 0., | |
contact_viscosity_tangential::float = 0., | |
contact_static_friction::float = 0.4, | |
contact_dynamic_friction::float = 0.4, | |
- youngs_modulus::float = 2e9, # Hopkins 2004 | |
+ youngs_modulus::float = 2e7, | |
+ #youngs_modulus::float = 2e9, # Hopkins 2004 | |
poissons_ratio::float = 0.185, # Hopkins 2004 | |
tensile_strength::float = 500e3, # Hopkins 2004 | |
compressive_strength_prefactor::float = 1285e3,… | |
diff --git a/src/interaction.jl b/src/interaction.jl | |
t@@ -33,9 +33,14 @@ end | |
export interactIceFloes! | |
""" | |
+ interactIceFloes!(simulation::Simulation, i::Int, j::Int, ic::Int) | |
+ | |
Resolve an grain-to-grain interaction using a prescibed contact law. This | |
function adds the compressive force of the interaction to the ice floe | |
`pressure` field of mean compressive stress on the ice floe sides. | |
+ | |
+The function uses the macroscopic contact parameterization based on Young's | |
+modulus and Poisson's ratio if Young's modulus is a positive value. | |
""" | |
function interactIceFloes!(simulation::Simulation, i::Int, j::Int, ic::Int) | |
t@@ -80,19 +85,37 @@ function interactIceFloes!(simulation::Simulation, i::Int,… | |
abs(delta_n)/2. | |
# Contact mechanical parameters | |
- k_n_harmonic_mean = | |
- harmonicMean(simulation.ice_floes[i].contact_stiffness_normal, | |
- simulation.ice_floes[j].contact_stiffness_normal) | |
- | |
- k_t_harmonic_mean = | |
- harmonicMean(simulation.ice_floes[i].contact_stiffness_tangential, | |
- simulation.ice_floes[j].contact_stiffness_tangential) | |
+ if simulation.ice_floes[i].youngs_modulus > 0. && | |
+ simulation.ice_floes[j].youngs_modulus > 0. | |
+ | |
+ E = harmonicMean(simulation.ice_floes[i].youngs_modulus, | |
+ simulation.ice_floes[j].youngs_modulus) | |
+ ν = harmonicMean(simulation.ice_floes[i].poissons_ratio, | |
+ simulation.ice_floes[j].poissons_ratio) | |
+ | |
+ # Contact area | |
+ A_ij = R_ij*min(simulation.ice_floes[i].thickness, | |
+ simulation.ice_floes[j].thickness) | |
+ | |
+ # Effective normal and tangential stiffness | |
+ k_n = E*A_ij/R_ij | |
+ #k_t = k_n*ν # Kneib et al 2016 | |
+ k_t = k_n*2.*(1. - ν^2.)/((2. - ν)*(1. + ν)) # Obermayr et al … | |
+ | |
+ else # Micromechanical parameterization: k_n and k_t set explicitly | |
+ k_n = harmonicMean(simulation.ice_floes[i].contact_stiffness_norma… | |
+ simulation.ice_floes[j].contact_stiffness_normal) | |
+ | |
+ k_t = | |
+ harmonicMean(simulation.ice_floes[i].contact_stiffness_tangentia… | |
+ simulation.ice_floes[j].contact_stiffness_tangentia… | |
+ end | |
- gamma_n_harmonic_mean = harmonicMean( | |
+ gamma_n = harmonicMean( | |
simulation.ice_floes[i].contact_viscosity_normal, | |
simulation.ice_floes[j].contact_viscosity_normal) | |
- gamma_t_harmonic_mean = harmonicMean( | |
+ gamma_t = harmonicMean( | |
simulation.ice_floes[i].contact_viscosity_tangential, | |
simulation.ice_floes[j].contact_viscosity_tangential) | |
t@@ -100,28 +123,28 @@ function interactIceFloes!(simulation::Simulation, i::In… | |
simulation.ice_floes[j].contact_dynamic_friction) | |
# Determine contact forces | |
- if k_n_harmonic_mean ≈ 0. && gamma_n_harmonic_mean ≈ 0. | |
+ if k_n ≈ 0. && gamma_n ≈ 0. | |
force_n = 0. | |
- elseif k_n_harmonic_mean > 0. && gamma_n_harmonic_mean ≈ 0. | |
- force_n = -k_n_harmonic_mean*delta_n | |
+ elseif k_n > 0. && gamma_n ≈ 0. | |
+ force_n = -k_n*delta_n | |
- elseif k_n_harmonic_mean > 0. && gamma_n_harmonic_mean > 0. | |
- force_n = -k_n_harmonic_mean*delta_n - gamma_n_harmonic_mean*vel_n | |
+ elseif k_n > 0. && gamma_n > 0. | |
+ force_n = -k_n*delta_n - gamma_n*vel_n | |
if force_n < 0. | |
force_n = 0. | |
end | |
else | |
- error("unknown contact_normal_rheology (k_n = $k_n_harmonic_mean,"… | |
- " gamma_n = $gamma_n_harmonic_mean") | |
+ error("unknown contact_normal_rheology (k_n = $k_n," * | |
+ " gamma_n = $gamma_n") | |
end | |
- if k_t_harmonic_mean ≈ 0. && gamma_t_harmonic_mean ≈ 0. | |
+ if k_t ≈ 0. && gamma_t ≈ 0. | |
# do nothing | |
- elseif k_t_harmonic_mean ≈ 0. && gamma_t_harmonic_mean > 0. | |
- force_t = abs(gamma_t_harmonic_mean * vel_t) | |
+ elseif k_t ≈ 0. && gamma_t > 0. | |
+ force_t = abs(gamma_t * vel_t) | |
if force_t > mu_d_minimum*abs(force_n) | |
force_t = mu_d_minimum*abs(force_n) | |
end | |
t@@ -129,19 +152,18 @@ function interactIceFloes!(simulation::Simulation, i::In… | |
force_t = -force_t | |
end | |
- elseif k_t_harmonic_mean > 0. | |
+ elseif k_t > 0. | |
- force_t = -k_t_harmonic_mean*delta_t - gamma_t_harmonic_mean*vel_t | |
+ force_t = -k_t*delta_t - gamma_t*vel_t | |
if abs(force_t) > mu_d_minimum*abs(force_n) | |
force_t = mu_d_minimum*abs(force_n)*force_t/abs(force_t) | |
- delta_t = (-force_t - gamma_t_harmonic_mean*vel_t)/ | |
- k_t_harmonic_mean | |
+ delta_t = (-force_t - gamma_t*vel_t)/k_t | |
end | |
else | |
error("unknown contact_tangential_rheology (k_t = " * | |
- "$k_t_harmonic_mean, gamma_t = $gamma_t_harmonic_mean") | |
+ "$k_t, gamma_t = $gamma_t") | |
end | |
end | |
simulation.ice_floes[i].contact_parallel_displacement[ic] = delta_t*t | |
diff --git a/src/temporal.jl b/src/temporal.jl | |
t@@ -99,13 +99,24 @@ function findLargestIceFloeStiffness(simulation::Simulatio… | |
i_n_max = -1 | |
i_t_max = -1 | |
for i in length(simulation.ice_floes) | |
+ | |
icefloe = simulation.ice_floes[i] | |
- if icefloe.contact_stiffness_normal > k_n_max | |
- k_n_max = icefloe.contact_stiffness_normal | |
+ | |
+ if icefloe.youngs_modulus > 0. | |
+ k_n = icefloe.youngs_modulus*icefloe.thickness # A = h*r | |
+ k_t = k_n*2.*(1. - icefloe.poissons_ratio^2.)/ | |
+ ((2. - icefloe.poissons_ratio)*(1. + icefloe.poissons_ratio)) | |
+ else | |
+ k_n = icefloe.contact_stiffness_normal | |
+ k_t = icefloe.contact_stiffness_tangential | |
+ end | |
+ | |
+ if k_n > k_n_max | |
+ k_n_max = k_n | |
i_n_max = i | |
end | |
- if icefloe.contact_stiffness_tangential > k_t_max | |
- k_t_max = icefloe.contact_stiffness_tangential | |
+ if k_t > k_t_max | |
+ k_t_max = k_t | |
i_t_max = i | |
end | |
end | |
diff --git a/test/collision-2floes-oblique.jl b/test/collision-2floes-oblique.jl | |
t@@ -13,6 +13,8 @@ sim = SeaIce.createSimulation(id="test") | |
SeaIce.addIceFloeCylindrical(sim, [0., 10.], 10., 1., verbose=verbose) | |
SeaIce.addIceFloeCylindrical(sim, [19., 0.], 10., 1., verbose=verbose) | |
sim.ice_floes[1].lin_vel[1] = 0.1 | |
+sim.ice_floes[1].contact_dynamic_friction = 0. | |
+sim.ice_floes[2].contact_dynamic_friction = 0. | |
sim.ice_floes[2].fixed = true | |
E_kin_lin_init = SeaIce.totalIceFloeKineticTranslationalEnergy(sim) | |
t@@ -68,6 +70,8 @@ sim = SeaIce.createSimulation(id="test") | |
SeaIce.addIceFloeCylindrical(sim, [0., 10.], 10., 1., verbose=verbose) | |
SeaIce.addIceFloeCylindrical(sim, [19.0, 0.], 10., 1., verbose=verbose) | |
sim.ice_floes[1].lin_vel[1] = 0.1 | |
+sim.ice_floes[1].contact_dynamic_friction = 0. | |
+sim.ice_floes[2].contact_dynamic_friction = 0. | |
E_kin_lin_init = SeaIce.totalIceFloeKineticTranslationalEnergy(sim) | |
E_kin_rot_init = SeaIce.totalIceFloeKineticRotationalEnergy(sim) | |
t@@ -229,7 +233,7 @@ E_kin_rot_final = SeaIce.totalIceFloeKineticRotationalEner… | |
info("Testing kinetic energy conservation with Two-term Taylor scheme") | |
sim = deepcopy(sim_init) | |
SeaIce.setTimeStep!(sim, epsilon=0.007) | |
-tol = 0.02 | |
+tol = 0.04 | |
info("Relative tolerance: $(tol*100.)%") | |
SeaIce.run!(sim, temporal_integration_method="Two-term Taylor", | |
verbose=verbose) | |
t@@ -242,7 +246,7 @@ E_kin_rot_final = SeaIce.totalIceFloeKineticRotationalEner… | |
info("Testing kinetic energy conservation with Three-term Taylor scheme") | |
sim = deepcopy(sim_init) | |
SeaIce.setTimeStep!(sim, epsilon=0.07) | |
-tol = 0.02 | |
+tol = 0.04 | |
info("Relative tolerance: $(tol*100.)% with time step: $(sim.time_step)") | |
SeaIce.run!(sim, temporal_integration_method="Three-term Taylor", | |
verbose=verbose) | |
t@@ -292,7 +296,7 @@ E_kin_rot_final = SeaIce.totalIceFloeKineticRotationalEner… | |
info("Testing kinetic energy conservation with Two-term Taylor scheme") | |
sim = deepcopy(sim_init) | |
SeaIce.setTimeStep!(sim, epsilon=0.007) | |
-tol = 0.02 | |
+tol = 0.04 | |
info("Relative tolerance: $(tol*100.)%") | |
SeaIce.run!(sim, temporal_integration_method="Two-term Taylor", | |
verbose=verbose) | |
t@@ -305,7 +309,7 @@ E_kin_rot_final = SeaIce.totalIceFloeKineticRotationalEner… | |
info("Testing kinetic energy conservation with Three-term Taylor scheme") | |
sim = deepcopy(sim_init) | |
SeaIce.setTimeStep!(sim, epsilon=0.07) | |
-tol = 0.02 | |
+tol = 0.04 | |
info("Relative tolerance: $(tol*100.)% with time step: $(sim.time_step)") | |
SeaIce.run!(sim, temporal_integration_method="Three-term Taylor", | |
verbose=verbose) | |
t@@ -325,8 +329,6 @@ sim = SeaIce.createSimulation(id="test") | |
SeaIce.addIceFloeCylindrical(sim, [0., 0.], 10., 1., verbose=verbose) | |
SeaIce.addIceFloeCylindrical(sim, [19.0, -10.], 10., 1., verbose=verbose) | |
sim.ice_floes[2].lin_vel[1] = -0.1 | |
-sim.ice_floes[1].contact_viscosity_tangential = 1e4 | |
-sim.ice_floes[2].contact_viscosity_tangential = 1e4 | |
E_kin_lin_init = SeaIce.totalIceFloeKineticTranslationalEnergy(sim) | |
E_kin_rot_init = SeaIce.totalIceFloeKineticRotationalEnergy(sim) | |
t@@ -355,7 +357,7 @@ E_kin_rot_final = SeaIce.totalIceFloeKineticRotationalEner… | |
info("Testing kinetic energy conservation with Two-term Taylor scheme") | |
sim = deepcopy(sim_init) | |
SeaIce.setTimeStep!(sim, epsilon=0.007) | |
-tol = 0.02 | |
+tol = 0.04 | |
info("Relative tolerance: $(tol*100.)%") | |
SeaIce.run!(sim, temporal_integration_method="Two-term Taylor", | |
verbose=verbose) | |
t@@ -368,7 +370,7 @@ E_kin_rot_final = SeaIce.totalIceFloeKineticRotationalEner… | |
info("Testing kinetic energy conservation with Three-term Taylor scheme") | |
sim = deepcopy(sim_init) | |
SeaIce.setTimeStep!(sim, epsilon=0.07) | |
-tol = 0.02 | |
+tol = 0.04 | |
info("Relative tolerance: $(tol*100.)% with time step: $(sim.time_step)") | |
SeaIce.run!(sim, temporal_integration_method="Three-term Taylor", | |
verbose=verbose) | |
t@@ -424,7 +426,7 @@ E_kin_rot_final = SeaIce.totalIceFloeKineticRotationalEner… | |
info("Testing kinetic energy conservation with Two-term Taylor scheme") | |
sim = deepcopy(sim_init) | |
SeaIce.setTimeStep!(sim, epsilon=0.007) | |
-tol = 0.02 | |
+tol = 0.04 | |
info("Relative tolerance: $(tol*100.)%") | |
SeaIce.run!(sim, temporal_integration_method="Two-term Taylor", | |
verbose=verbose) | |
t@@ -437,7 +439,7 @@ E_kin_rot_final = SeaIce.totalIceFloeKineticRotationalEner… | |
info("Testing kinetic energy conservation with Three-term Taylor scheme") | |
sim = deepcopy(sim_init) | |
SeaIce.setTimeStep!(sim, epsilon=0.07) | |
-tol = 0.03 | |
+tol = 0.04 | |
info("Relative tolerance: $(tol*100.)% with time step: $(sim.time_step)") | |
SeaIce.run!(sim, temporal_integration_method="Three-term Taylor", | |
verbose=verbose) | |
diff --git a/test/vtk.jl b/test/vtk.jl | |
t@@ -26,7 +26,7 @@ else | |
end | |
icefloechecksum = | |
-"4885bc7c0eccc5e43a77d370295841fae710465c8bcc120a13681a0947ffbd53 " * | |
+"de1ee347a6a15c665d3fa122c73092b3aa200bf8180007303f43f71396094d8d " * | |
"test.icefloes.1.vtu\n" | |
oceanchecksum = |