衝突流体計算の計算手順 - 日本惑星科学会impact/wiki/isale/?c=plugin;...1980年 sale...
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衝突流体計算の計算手順 玄田英典(東工大・ELSI)
完全流体の数値計算方法 オイラー的解法・ラグランジュ的解法 iSALEではどう解いているのか?
弾性体、弾塑性流体 iSALEではどういう 方程式系を解いているのか?
iSALE勉強会(2014年2月5日)
iSALEの歴史 SALE code 1980年 Amsden et al.
ニュートン流体(圧縮性粘性流体)衝撃波も扱える 1種類の物質(ideal or stiffened gas) オイラーモード と ラグランジュモード
SALE code 1992年 Melosh et al. 弾性・塑性モデル、破壊モデルの導入 Tillotson状態方程式の導入(一度に複数種類の物質を扱える) ラグランジュモードのみ
SALEB code 1997年 Ivanov et al. オイラーモード実装(自由表面・物質境界の扱い) ANEOSの導入 弾性・塑性モデル、破壊モデルの改良
コードの並列化、空隙モデル、破壊モデルの改良などなど その後 iSALE code Collins, Wunnemann, Ivanov
ROCK Pressure-‐ and damage-‐dependent strength model for rock-‐like materials. DRPR Drucker-‐Prager Linear pressure-‐dependent strength model for granular material.
LUNDI Ludborg intact: Non-‐linear pressure-‐dependent strength model for intact rock.
LUNDD Lundborg damaged: Non-‐linear pressure-‐dependent strength model for intact rock.
VNMS Von Mises: Constant yield-‐strength model for ducFle materials.
JNCK Johnson and Cook: Strain and strain-‐rate dependent strength model for metals.
LIQU Liquid: Newtonian fluid model
HYDRO Hydrodynamic: Inviscid fluid model
iSALE manual p34
完全流体
iSALEの物質強度モデル
粘性流体
弾性・ 塑性体
破壊モデル(ダメージパラメータ)
Stop
Start
Read input parametersand echo to output file
Restore variables from dump fileif simulation is being restarted
Output data for processing and restart
Compute timestep size
Increment time and cycle number
Artificial viscous stress andAlternate node coupler
Deviatoric stresses
Body forces and pressure gradiants
Update energy and distension
Time to stop?
NoYes
Compute derived quantites
Update pressure, etc.
La
gra
ng
ian
ste
pC
ycle
ad
van
ceP
rob
lem
se
t-u
p
Cyc
le c
om
ple
tion
Generate mesh and setup cell and tracer variables
Allocate memory and decompose domain
Move tracer particles
Ve
loci
ty u
pd
ate
s
Lagrangian/ALE EulerianWhat type of calculation?
Compute new grid coordinates
Compute new cell volumes
Store lagrangian velocities
Compute grid velocities
Advect cell-centered quantities
Construct interfaces in cellswith multiple materials
Compute flux volumes
Compute cell-centered momenta
Update cell density and vertex masses
Update vertex velocities
Compute material velocityrelative to grid
Lagrangian
ALEWhat type of calculation?
iSALE manual p45
iSALE code 計算の流れ
基礎方程式(完全流体) 1次元の場合 ∂Q
∂t+∂E∂x
= 0
Q =
ρ
ρue
!
"
####
$
%
&&&&
連続の式 (質量保存則) 運動方程式
(運動量保存則) エネルギー方程式 (エネルギー保存則)
未知変数4つ(u,ρ,p,e) 方程式4つ必要
状態方程式 P = f ρ,e( )
E =ρu
ρu2 + peu+ pu
!
"
####
$
%
&&&&
数値解法(オイラー的解法)
∂Q∂t
+∂E∂x
= 0
∂Q∂t
=Qi
n+1 −Qin
Δt∂E∂x
=Ei+1n −Ei−1
n
2Δx
時間微分に対して前進差分
空間微分に対して中央差分
Qin+1 =Qi
n −Ei+1n −Ei−1
n
2Δx"
#$
%
&'Δt FTCS Scheme
(Forward in Time and Central difference in Space)
x
i i+1 i-1
Qi Ei
Qi+1 Ei+1
Qi-1 Ei-1
数値解法
∂u∂t+u∂u
∂x= −
1ρ∂p∂x
∂e∂t+u ∂e
∂x= −
Pρ∂u∂x
運動方程式 (運動量保存則)
エネルギー方程式 (エネルギー保存則)
∂ρ∂t+u∂ρ
∂x= −ρ
∂u∂x
基本方程式(別の形式)
連続の式 (質量保存則)
DDt
≡∂∂t+u ∂
∂xラグランジュ微分
数値解法
DuDt
= −1ρ∂p∂x
DeDt
= −Pρ∂u∂x
運動方程式 (運動量保存則)
エネルギー方程式 (エネルギー保存則)
DρDt
= −ρ∂u∂x
基本方程式(ラグランジュ形式)
連続の式 (質量保存則)
DDt
≡∂∂t+u ∂
∂xラグランジュ微分
数値解法(ラグランジュ的解法)
DuDt
= −1ρ∂p∂x
エネルギー方程式 (運動量保存則)
格子点の移動 uin+1 −ui
n
Δt= −
1ρin
pi+1/2n − pi−1/2
n
Δx#
$%
&
'( xi
n+1 = xin +ui
nΔt
uin+1 = ui
n −2
ρi−1/2n + ρi+1/2
n
pi+1/2n − pi−1/2
n
Δx"
#$
%
&'Δt
x
i i+1 i-1
xi ui
i+1/2 i-1/2
ρi+1/2 pi+1/2
数値解法(iSALE-2D) ラグランジュモード
格子点の移動 xin+1 = xi
n +ui, jn Δt
i,j
x
i i+1 i-1
xi ui
i+1/2 i-1/2
ρi+1/2 pi+1/2
pi+1/2,j+1/2
yjn+1 = yj
n + vi, jn Δt
数値解法 オイラー的解法(セミ・ラグランジュ)
iSALEのオイラーモードは 実はセミ・ラグランジュ的な解法
cf. 入力パラメータファイル(asteroid.inp)のALE_MODEを選択する
x i i+1 i-1 step n step n+1 x
x remesh
人工粘性 衝撃波(超音速の波)を捕捉するのに必要
∂u∂t+u∂u
∂x= −
1ρ∂(p+ q)∂x
運動方程式 q
q = −aρCs∂u∂xΔx + bρ ∂u
∂x$
%&
'
()Δx2
0
if ∂u∂x
< 0
if ∂u∂x
≥ 0
+
,--
.--
von Neumann-Richtmyer型の人工粘性
人工粘性 3.1 The iSALE hydrocode 48
0 2 4 6 8 10 12x (mm)
0
10
20
30
40
50
60
Pre
ssure
,P
(GPa)
a1 = 0.0; a2 = 0.0
a1 = 1.0; a2 = 0.0
a1 = 1.0; a2 = 0.1
a1 = 1.0; a2 = 0.2
a1 = 1.0; a2 = 0.5
Figure 3.4: The effect of artificial viscosity on the shock pressure field. Asimple planar impact simulation from iSALE shows that by increasing theconstants a1 and a2, the oscillations are dampened. However, in doing so,the shock is smeared over a number of cells. For example, for a1 = 1.0 anda2 = 0.5, no oscillations exist, but the shock front is smoothed out over > 10computational cells. A balance must be struck between removing oscillationsand how far the shock is smoothed out.
region over which the shock is smoothed and the number and size of theoscillations after the shock. The effect of changing these constants is shownin Figure 3.4. It is usually prudent to experiment with a1 and a2 whenrunning a simulation of a specific impact event to find a suitable balance forthe needs of the calculation. Ideally, the shock front should be smoothedover as few cells as possible (i.e. it should be as sharp as possible), whilststill suppressing any oscillations.
3.1.6 Initial and boundary conditions
For iSALE simulations of collisions between planetesimals, all material inthe planetesimals is assigned an initial velocity according to the desired rel-ative collision velocity. All other cells are vacuum, and hence no velocity is
From Davison (PhD thesis)
ROCK Pressure-‐ and damage-‐dependent strength model for rock-‐like materials. DRPR Drucker-‐Prager Linear pressure-‐dependent strength model for granular material.
LUNDI Ludborg intact: Non-‐linear pressure-‐dependent strength model for intact rock.
LUNDD Lundborg damaged: Non-‐linear pressure-‐dependent strength model for intact rock.
VNMS Von Mises: Constant yield-‐strength model for ducFle materials.
JNCK Johnson and Cook: Strain and strain-‐rate dependent strength model for metals.
LIQU Liquid: Newtonian fluid model
HYDRO Hydrodynamic: Inviscid fluid model
iSALE manual p34
完全流体
iSALEの物質強度モデル
粘性流体
弾性・ 塑性体
破壊モデル(ダメージパラメータ)
弾性体モデル
DuDt
= −1ρ∂p∂x
運動方程式(完全流体)
DuiDt
=1ρ
∂σ ij
∂xi 応力テンソル
σ ij = Kεkkδij + 2G εij −13εkkδij
"
#$
%
&'
構成方程式 εij : ひずみ
G = 3K 1− 2ν2 1+ν( )
体積弾性率 せん断弾性率 iSALEではポアソン比を 入力パラメータとして与える
運動方程式(弾性体)
σ ij = −pδij + sij圧力は状態方程式から計算
εij =12
∂si∂x j
+∂sj∂xi
"
#$$
%
&''
弾性体モデル
σ ij = −pδij + sijDuiDt
=1ρ
∂σ ij
∂xi
sij = 2G εij −13εkkδij
"
#$
%
&'
dsijdt
= 2G εij −13εkkδij
"
#$
%
&'
εij =12∂vi∂x j
+∂vj∂xi
"
#$$
%
&''
εij =12
∂si∂x j
+∂sj∂xi
"
#$$
%
&''
sijn+1 = sij
n +dsij
n
dtΔt
運動方程式(弾性体) 構成方程式
sijの時間微分を使う
偏差応力テンソル
塑性体モデル 応力不変量(J2)がある値(降伏応力Yの2乗)以上に なったら塑性的に振る舞う
s
n+1
ij
= s
n
ij
+ 2G ✏̇ij
�t
G �t
G K
G (p) = 3K (p)
1� 2⌫
2(1 + ⌫)
K (p) ⌫
⌫ =
3K � 2G
2(3K + G )
,
0.1 < ⌫ < 0.4
Y
pJ
2
J
2
J
2
= � (s
xx
s
yy
+ s
yy
s
zz
+ s
zz
s
xx
) + s
2
xy
+ s
2
yz
+ s
2
zx
J
2
=
1
2
�s
2
xx
+ s
2
yy
+ s
2
zz
�+ s
2
xy
+ s
2
yz
+ s
2
zx
J
2
=
1
6
�(s
xx
� s
yy
)
2
+ (s
yy
� s
zz
)
2
+ (s
zz
� s
xx
)
2
�+ s
2
xy
+ s
2
yz
+ s
2
zx
J
2
=
1
6
�(s
1
� s
2
)
2
+ (s
2
� s
3
)
2
+ (s
3
� s
1
)
2
�
J
2
=
1
2
�s
2
1
+ s
2
2
+ s
2
3
�
J
2
=
1
6
�(�
1
� �2
)
2
+ (�2
� �3
)
2
+ (�3
� �1
)
2
�
J
2
=
1
6
�(�
xx
� �yy
)
2
+ (�yy
� �zz
)
2
+ (�zz
� �xx
)
2
�+ �2
xy
+ �2
yz
+ �2
zx
�ij
�k
s
ij
s
k
J
2
=
1
6
�(s
xx
� s
yy
)
2
+ (s
yy
� s✓)2
+ (s✓ � s
xx
)
2
�+ s
2
xy
pJ
2
YpJ
2
= Y Y /p
J
2
Y
Y = Y
d
D + Y
i
(1.� D)
D
Y
d
Y
d
= min(Y
d0
+ µd
p,Y
dm
)
p Y
i
Y
i
= Y
i0
+
µi
p
1 +
µi
p
Y
im
�Y
i0
Y
i0
µi
Y
im
Y
d0
µd
Y
dm
Y
Y = min(Y
0
+ µp,Y
m
)
p
Y
0
µY
m
σ ij = −pδij + sij ×YJ2
J2 >Y の時、
ROCK Pressure-‐ and damage-‐dependent strength model for rock-‐like materials. DRPR Drucker-‐Prager Linear pressure-‐dependent strength model for granular material.
LUNDI Ludborg intact: Non-‐linear pressure-‐dependent strength model for intact rock.
LUNDD Lundborg damaged: Non-‐linear pressure-‐dependent strength model for intact rock.
VNMS Von Mises: Constant yield-‐strength model for ducFle materials.
JNCK Johnson and Cook: Strain and strain-‐rate dependent strength model for metals.
LIQU Liquid: Newtonian fluid model
HYDRO Hydrodynamic: Inviscid fluid model
iSALE manual p34
完全流体
iSALEの物質強度モデル
粘性流体
弾性・ 塑性体
破壊モデル(ダメージパラメータ)
ROCK Pressure-‐ and damage-‐dependent strength model for rock-‐like materials. DRPR Drucker-‐Prager Linear pressure-‐dependent strength model for granular material. LUNDI Ludborg intact: Non-‐linear pressure-‐dependent strength model for intact rock. LUNDD Lundborg damaged: Non-‐linear pressure-‐dependent strength model for intact rock. VNMS Von Mises: Constant yield-‐strength model for ducFle materials.
JNCK Johnson and Cook: Strain and strain-‐rate dependent strength model for metals.
iSALE manual p34
降伏応力モデル
降伏応力(Y)一定モデル
降伏応力(Y)の圧力依存性(線形)
降伏応力(Y)の圧力依存性(非線形)
降伏応力(Y)の圧力依存性(非線形)
降伏応力(Y)のひずみ・ひずみ速度依存性
降伏応力(Y)のダメージパラメータ依存性 Y = YdD + Yi(1-D)
Stop
Start
Read input parametersand echo to output file
Restore variables from dump fileif simulation is being restarted
Output data for processing and restart
Compute timestep size
Increment time and cycle number
Artificial viscous stress andAlternate node coupler
Deviatoric stresses
Body forces and pressure gradiants
Update energy and distension
Time to stop?
NoYes
Compute derived quantites
Update pressure, etc.
La
gra
ng
ian
ste
pC
ycle
ad
van
ceP
rob
lem
se
t-u
p
Cyc
le c
om
ple
tion
Generate mesh and setup cell and tracer variables
Allocate memory and decompose domain
Move tracer particles
Ve
loci
ty u
pd
ate
s
Lagrangian/ALE EulerianWhat type of calculation?
Compute new grid coordinates
Compute new cell volumes
Store lagrangian velocities
Compute grid velocities
Advect cell-centered quantities
Construct interfaces in cellswith multiple materials
Compute flux volumes
Compute cell-centered momenta
Update cell density and vertex masses
Update vertex velocities
Compute material velocityrelative to grid
Lagrangian
ALEWhat type of calculation?
iSALE manual p45
iSALE code 計算の流れ