5.7 与物理模拟对比实验¶
图 5.7 单位(cm)¶
备注
~10万颗粒，~13万时步，16核并行(Intel Xeon E5-2650)，耗时 ~3小时 完成计算。
构建了一个典型离散元数值模拟(DEM)试验，对比与构造物理模拟(AM)和差异与相似点。
DEM与AM模拟结果较为一致，基本反映了AM中石英砂的变形行为。AM中材料选取有限（如硅胶、粘土、微玻璃珠等），而DEM材料选取范围大，但其模拟结果依赖参数选取。AM和DEM作为两种独立的方法，有很好的互补性 [Li2021] 。
数值模拟分两步进行：
ex8_dem_am_gen.py生成颗粒，沉积，构建初始模型。ex8_dem_am_push.py给定颜色、粘结参数，挤压。
表 1 颗粒微观参数表. [Li2021]
\(d(mm)\) |
\(k(N \cdot m^{−1})\) |
\(ρ(kg·\cdot m^{−2})\) |
\(g(m·\cdot s^{−2})\) |
\(f\) |
\(μ\) |
\(η(N \cdot s \cdot m^{−1})\) |
\(υ(m·\cdot s^{−1})\) |
|---|---|---|---|---|---|---|---|
0.6 |
7.5e3 |
1.3e3 |
10.0 |
0.4 |
0.3 |
0.04 |
0.04 |
The particle packing consists of four particle sizes, with diameters and quantity ratio of 0.2 mm, 0.4 mm, 0.5 mm, and 0.6 mm and 2:2:1:1, respectively. :math:`d , largest particle diameter. \(ρ\) , particle density. \(g\) , gravitational acceleration. :math: f , safety factor of the time step. \(k\) , stiffness of the contact. \(μ\) , friction coefficient. \(η\) , dynamic viscosity. \(υ\) , velocity of the mobile wall.`
ex8_dem_am_gen.py
######################################
# title: 离散元数值模拟与构造物理模拟对比试验:1 沉积
# date: 2021-05-16
# authors: 李长圣
# E-mail: sheng0619@163.com
# ref: Li et al. (2021) Calibration of the discrete element method and modelling of shortening experiments. Front. Earth Sci. doi: 10.3389/feart.2021.636512
# more info, see www.geovbox.com
#######################################
start
set disk hex
BOX left 0.5e-3 right 615.0e-3 bottom 0.5e-3 height 160.0e-3 kn=1.5e4 ks=1.5e4 fric 0.3
wall id 4, nodes ( 5e-3 158.0e-3) ( 5.0e-3 5.0e-3), kn= 1.5e4 ks= 1.5e4 fric 0.0
wall id 5, nodes ( 5e-3 5.0e-3) (605.0e-3 5.0e-3), kn= 1.5e4 ks= 1.5e4 fric 0.0
wall id 6, nodes ( 605.0e-3 5.0e-3) (605.0e-3 158.0e-3), kn= 1.5e4 ks= 1.5e4 fric 0.0
gen grid idmin 0 rad discrete 0.1e-3 0.1e-3 0.2e-3 0.2e-3 0.25e-3 0.3e-3, x (5.0e-3, 605.0e-3), y (5.0e-3, 155.0e-3), GROUP ball_rand
PROP color red den 1.3e3, fric 0.0, kn 1.5e4, ks 1.5e4 damp 0.4
FIX spin
SET frac 0.4
SET GRAVITY ( 0.0, -10.0 )
SET stepbar 1000
SET save 20000
SET print 20000
SET ps 20000
HIST ID 1 INTERVAL 1000 , kinetic
HIST ID 2 INTERVAL 1000 , step
PLOT hist 2 1
CYC 60000
DEL range x (4.0e-3, 606.0e-3), y (30.0e-3, 1.0),
CYC 20000
#save 2del.sav
EXP ini_xyr.dat
STOP
ex8_dem_am_push.py
######################################
# title: 离散元数值模拟与构造物理模拟对比试验:2 挤压
# date: 2021-05-16
# authors: 李长圣
# E-mail: sheng0619@163.com
# ref: Li et al. (2021) Calibration of the discrete element method and modelling of shortening experiments. Front. Earth Sci. doi: 10.3389/feart.2021.636512
# more info, see www.geovbox.com
#######################################
LOAD ini_xyr.dat
SET disk hex
BOX left 0.5e-3 right 615.0e-3 bottom 0.5e-3 height 110.0e-3 kn=1.5e4 ks=1.5e4 fric 0.3
WALL id 4, nodes ( 5e-3 110.0e-3) ( 5.0e-3 5.0e-3), kn= 1.5e4 ks= 1.5e4 fric 0.0
WALL id 5, nodes ( 5e-3 5.0e-3) (605.0e-3 5.0e-3), kn= 1.5e4 ks= 1.5e4 fric 0.0
WALL id 6, nodes ( 605.0e-3 5.0e-3) (605.0e-3 110.0e-3), kn= 1.5e4 ks= 1.5e4 fric 0.0
PROP color red den 1.3e3, fric 0.0, kn 1.5e4, ks 1.5e4 damp 0.0
FIX spin
SET frac 0.4
SET GRAVITY ( 0.0, -10.0 )
SET stepbar 10000
HIST ID 1 INTERVAL 1000 , kinetic
HIST ID 2 INTERVAL 1000 , step
PLOT 2 1
SET damp lsm 0.04
PROP fric 0.30
PROP color lg
PROP color red , range x 0.0 615.0e-3 y 9.0e-3 10.0e-3
PROP color blue, range x 0.0 615.0e-3 y 14.0e-3 15.0e-3
PROP color red , range x 0.0 615.0e-3 y 19.0e-3 20.0e-3
PROP color blue, range x 0.0 615.0e-3 y 24.0e-3 25.0e-3
PROP color red , range x 0.0 615.0e-3 y 29.0e-3 30.0e-3
wall id 4 fric 0.30 xv 40e-3
wall id 5 fric 0.30
wall id 6 fric 0.30
CYC 1
imple wall id 4 xmove 160e-3 save 20e-3 print 10e-3 ps 10e-3 vtk 10e-3
stop
计算结束后，将得到以下结果：
图 5.8 单位(cm)¶
参考文献