碎屑物冲击时挡板结构的支护性能模拟

lobby

2022年4月15日 14:21

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0 引言

这里想要尝试做的是同济大学黄雨老师的 Computational assessment of baffle performanceagainst rapid granular flows。这篇文章从模拟方面论证了不同挡板结构对碎屑物冲击的支护性能评价。

1、成样

这里模拟颗粒运移，所以对初始的模型平衡要求并不是特别高，为了计算省事，只solve到-2次方就停止了，有计算条件的同学可以到-5次方。

我们的模型大概是下面这个样子：

碎屑物冲击时挡板结构的支护性能模拟的图1

（黄雨等，2021）

这里的建模方式是在水平向进行墙体和颗粒区域的构建，然后将其旋转到指定角度。在初始模型中，颗粒的前端应当是有挡土结构的。

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"

生成的模型如图：

碎屑物冲击时挡板结构的支护性能模拟的图2

可以看到在重力影响下，式样是不能维持一开始的方形。

2 下落

这个事情不难，只需要将初始的挡土结构删掉，式样便可以在重力作用下实现下落。需要注意的是，由于一开始我们的方形墙体指定的是onewall，所以无法从wall上面直接拿到冲击力，需要遍历面片上的接触来获得需要的力。这里是每0.5s保存一个sav文件，共计算了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 挡板结构模拟

挡板结构我是写了一个dat，然后在下落的时候call一下，便可以自动生产挡板了。这里比较的为方形和三角形挡板。

即：

碎屑物冲击时挡板结构的支护性能模拟的图3

（黄雨等，2021）

挡板的逻辑和前面类似，也是先在x-y面上定义，然后旋转到指定角度上。

方形挡板：

[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

三角形挡板：

[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