碎屑物沖擊時擋板結構的支護性能模擬

lobby

2022年4月15日 14:21

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0 引言

這里想要嘗試做的是同濟大學黃雨老師的 Computational assessment of baffle performanceagainst rapid granular flows。這篇文章從模擬方面論證了不同擋板結構對碎屑物沖擊的支護性能評價。

1、成樣

這里模擬顆粒運移，所以對初始的模型平衡要求并不是特別高，為了計算省事，只solve到-2次方就停止了，有計算條件的同學可以到-5次方。

我們的模型大概是下面這個樣子：

碎屑物沖擊時擋板結構的支護性能模擬的圖1

（黃雨等，2021）

這里的建模方式是在水平向進行墻體和顆粒區域的構建，然后將其旋轉到指定角度。在初始模型中，顆粒的前端應當是有擋土結構的。

model new

def par    angle=40    rdmin=0.004    rdmax=rdmin*1.5        shiyang_width=0.44    shiyang_height=0.15end@par



geometry set "shiyang"geometry generate box [-2.19-shiyang_width] -2.19 0 0.4 0 @shiyang_heightgeometry rotate angle @angle axis (0,1,0) origin (0,0,0)

model domain extent [(-2.19-shiyang_width)*math.cos(angle*math.pi/180.0)] ...         [(-2.19)*math.cos(angle*math.pi/180.0)+shiyang_height] 0 0.4  [(2.19)*math.sin(angle*math.pi/180.0)-shiyang_height] ...            [(2.19+shiyang_width)*math.sin(angle*math.pi/180.0)+shiyang_height] ...           ball distribute radius @rdmin @rdmax  porosity 0.4 range geometry-space "shiyang" ...    inside 

model domain extent -4 1 -1 1 0 4wall generate id 1 box -3 0 0 0.4 one-wallwall generate id 2 polygon (-2.19,0,0) (-2.19,0.4,0) (-2.19,0.4,0.4) ...        (-2.19,0,0.4) wall rotate axis (0,1,0) point (0,0,0)   angle @angle



    ball attribute density 2.7e3 damp 0.7

contact cmat default type ball-facet model linear method deform emod 100e6 kratio 1.5 property  fric 0contact cmat default type ball-ball model linear method deform emod 100e6 kratio 1.5 property  fric 0.2model cycle 2000 calm 50ball delete range  geometry-space "shiyang" outsidemodel gravity 9.8

model cycle 1model solve ratio-average 1e-2

ball attribute damp 0.2model cycle 1model solve ratio-average 1e-2model save "sample"

生成的模型如圖：

碎屑物沖擊時擋板結構的支護性能模擬的圖2

可以看到在重力影響下，式樣是不能維持一開始的方形。

2 下落

這個事情不難，只需要將初始的擋土結構刪掉，式樣便可以在重力作用下實現下落。需要注意的是，由于一開始我們的方形墻體指定的是onewall，所以無法從wall上面直接拿到沖擊力，需要遍歷面片上的接觸來獲得需要的力。這里是每0.5s保存一個sav文件，共計算了10s。

model restore "sample"model mechanical time-total 0

def wall_init    wp5=wall.facet.find(5)    wp6=wall.facet.find(6)end@wall_init

def jiance    whilestepping    force=0    loop foreach ct wall.facet.contactmap(wp5)        force+=math.mag(contact.force.global(ct))    endloop    loop foreach ct wall.facet.contactmap(wp6)        force+=math.mag(contact.force.global(ct))    endloopend

wall delete walls range id 2[baocunpinlv=0.5][time_record=-10][count=0]def savefile     time=mech.time.total    if time-time_record >= baocunpinlv then        filename=string.build("jieguo%1",count)        command            model save @filename        endcommand        time_record=time        count +=1    endif    end                        fish callback add @savefile -1.0 history id 1 @forcemodel cycle 1model solve time 10model save "result"

3 擋板結構模擬

擋板結構我是寫了一個dat，然后在下落的時候call一下，便可以自動生產擋板了。這里比較的為方形和三角形擋板。

即：

碎屑物沖擊時擋板結構的支護性能模擬的圖3

（黃雨等，2021）

擋板的邏輯和前面類似，也是先在x-y面上定義，然后旋轉到指定角度上。

方形擋板：

[d=0.4/10.0][DBack=0.4/3.0]geometry set "pile_back"geometry generate box [-d*0.5] [d*0.5] [-d*0.5] [d*0.5] 0 0.3geometry translate -0.42 0 0geometry rotate angle @angle axis (0,1,0) origin (0,0,0)





wall import from-geometry "pile_back" name "pile_back_1"def addpile_back    wall_count=2    loop n(1,3)        wall_name=string.build("pile_back_%1",wall_count)        command                         geometry translate 0 @DBack 0             wall import from-geometry "pile_back" name @wall_name        endcommand            wall_count+=1    endloopend@addpile_backgeometry set "pile_front"geometry generate box [-d*0.5] [d*0.5] [-d*0.5] [d*0.5] 0 0.3geometry translate -0.21 [DBack*0.5] 0geometry rotate angle @angle axis (0,1,0) origin (0,0,0)

wall import from-geometry "pile_front" name "pile_front_1"def addpile_front        wall_count=2    loop n(1,2)        wall_name=string.build("pile_front_%1",wall_count)        command                         geometry translate 0 @DBack 0             wall import from-geometry "pile_front" name @wall_name        endcommand            wall_count+=1    endloopend@addpile_front

三角形擋板：

[d=0.4/10.0][DBack=0.4/3.0]geometry set "pile_back"geometry edge create by-position (0,[-d*0.5],0) ([-d*0.5],0,0)  (0,[d*0.5],0) (0,[-d*0.5],0)geometry generate from-edges extrude (0,0,0.3) segments 1geometry triangulate clean geometry translate -0.42 0 0geometry rotate angle @angle axis (0,1,0) origin (0,0,0)





wall import from-geometry "pile_back" name "pile_back_1"def addpile_back    wall_count=2    loop n(1,3)        wall_name=string.build("pile_back_%1",wall_count)        command                         geometry translate 0 @DBack 0             wall import from-geometry "pile_back" name @wall_name        endcommand            wall_count+=1    endloopend@addpile_backgeometry set "pile_front"geometry edge create by-position (0,[-d*0.5],0) ([-d*0.5],0,0)  (0,[d*0.5],0) (0,[-d*0.5],0)geometry generate from-edges extrude (0,0,0.3) segments 1geometry triangulate clean geometry translate -0.21 [DBack*0.5] 0geometry rotate angle @angle axis (0,1,0) origin (0,0,0)

wall import from-geometry "pile_front" name "pile_front_1"def addpile_front        wall_count=2    loop n(1,2)        wall_name=string.build("pile_front_%1",wall_count)        command                         geometry translate 0 @DBack 0             wall import from-geometry "pile_front" name @wall_name        endcommand            wall_count+=1    endloopend@addpile_front