[求助]加载热流密度后，求解显示温度没有变化？各位大侠看看

hunterma

就是在两层的夹层处加热流密度，结果模型显示为红色，没有任何结果。
我的命令流如下：hflux=15.27
/prep7  
keyw,pr_therm,1
blc4,,,1,0.08   
blc4,,,1,-0.45  

nummrg,all  

mp,ex,1,160000  
mp,prxy,1,0.22  
mp,kxx,1,0.157  
mp,dens,1,2.4e-3
mp,c,1,700
mp,ex,2,63000   
mp,prxy,2,0.2   
mp,kxx,2,1.13
mp,dens,2,2.23e-3  
mp,c,2,800
et,1,plane55
KEYOPT,1,3,1
lesize,1,,,40   
lesize,1,,,20   
lesize,1,,,40   
lesize,2,,,4
lesize,6,,,20   
mshkey,1
mat,1
amesh,1
mat,2
amesh,2
finish
/SOL

nsel,s,,,1
nsel,s,,,3
nsel,s,,,4
sf,all,HFLUX,hflux

allsel
ANTYPE,4
NSUBST,50,100,20
AUTOTS,1
KBC,0   
LNSRCH,1
TIME,1000   
solve

hunterma

是不是热流密度的加载方法有误啊？

iomega

Just several advices on your model and how to know if the analysis is correct or not quickly:

1. Thermal property values are not correct.
>mp,dens,2,2.23e-3
>mp,c,2,800
The heat capacity based on your number is Cp = 2.23e-3*800= 1.784J/m^3-K
NO material in the world has such heat capacity value. Combined with the k = 1.13 W/m-K, you ended up with a material of thermal diffusivity alf beyond the best heat conductor in the world...    alf = k/Cp
typical c*dens should be order of 10^6 J/m^3-K

2. you only have heat put in, but no boundary conditions to let heat dissipate out -> temperature keep increase forever.

3. your dimension is order of L=1m -> thermal diffusion time = L^2/alf ~ 1s for your problem, which means in seveal seconds your temperature distribution will be unifrom everywhere in the domain. While your calculation time is ~1000s.

hunterma

谢谢，iomega给予的帮助
由于我的疏忽，我没有说明我用的单位制是mm，g，ms，所以我定义的材料属性是没有问题的
按照你的提示，我施加了对流的边界条件，但还是显示温度没有变化
求解的时间也按照你所给的公式设为了600ms
修改后的命令流如下：
hflux=15.27
/prep7  
keyw,pr_therm,1
blc4,,,1,0.08   
blc4,,,1,-0.45  

nummrg,all  

mp,ex,1,160000  
mp,prxy,1,0.22  
mp,kxx,1,0.157  
mp,dens,1,2.4e-3
mp,c,1,700

mp,ex,2,63000   
mp,prxy,2,0.2   
mp,kxx,2,1.13
mp,dens,2,2.23e-3  
mp,c,2,800
et,1,plane55
KEYOPT,1,3,1
lesize,1,,,40   
lesize,2,,,4
lesize,6,,,20   
mshkey,1
mat,1
amesh,1
mat,2
amesh,2
finish
/SOL
ANTYPE,trans
timint,on
time,600
deltim,10,2,200
autots,on
outres,,all
nsel,s,,,1
nsel,s,,,3
nsel,s,,,4
sf,all,HFLUX,hflux ！夹层处加热流密度
allsel
lsel,s,,,4
lsel,s,,,8
lsel,s,,,2
lsel,s,,,6
nsll,s,1
sf,all,conv,12.5e-6,20  ！两边加对流载荷
allsel
tunif,20
solve
结果还是有问题，希望大侠在给予指点，谢谢了

hunterma

温度梯度显示也有问题

iomega

Why use the non-standard units for calculation. Remember you also have to consider the unit change for Watt because it is J/s and J = F*m...

What's the unit of your heat flux? it maybe be so small.

suggest you to use m s and kg to draw the dimension - it's easy for you to debug...

>nsll,s,1  
>sf,all,conv,12.5e-6,20 ！两边加对流载荷
you type wrong, should be nsel...

200802172

xuexi le hendujo le