有偿找人帮忙Fortran求解微分方程
求visual studio2019版，Fortran2022版求解这种微分方程应该怎么编写代码啊，完全小白一点不懂，想得到s在不同的z(z可以只取总的高度下的几个有代表性的高度就行）下随时间t（t要分的细一点，想要得到的m值多一点）变化的值，我在网上拼拼凑凑瞎写了一下代码好像不能直接识别d和德尔塔，果然错，提示有很多问题，我也不知道咋改，有搜到要用四阶龙格库塔法，但我完全看不懂，球球大神救命！ program Compositionimplicit none
! Variables declaration
real :: ca ! Specific heat capacity of dry air J /kg*k
real :: cv ! specific heat capacity of water vapor J /kg*k
real :: cg ! Specific heat capacity of dry grains J /kg*k
real :: cw ! Specific heat capacity of liquid water J /kg*k
real :: Tem ! Air temperature before drying ℃
real :: H ! Absolute humidity of air before drying g/kg
real :: b! Dry grain capacity kg/m³
real :: G ! Grain weight t
real :: t ! drying time s
real :: z ! Height of grain pile m
real :: r ! heat of vaporization of waterJ/kg
real :: S0 ! Initial moisture content of grainkg/kg
real :: S ! moisture content of grainkg/kg
real :: Se ! Grain Balance Moisture kg/kg
real :: K ! Parameters of the thin-layer drying equation
real :: a ! Parameters of the thin-layer drying equation
!assigning values
ca=1029
cv=1880
cg=3858
cw=4200
Tem=35
H=12.9
b=600
G=100
r=12200
S0=0.03158
z=3.75
!Humidity control equation
dH=-(b/G)*(dS/dt)*dz
!Temperature control equation
dTem=(((cv-cw)*Tem+r)*dS)/((cg++cw*S)+(cw-cv)*dS+(G/b)*(ca+cv*H)*(dt/dz))
!Moisture control equation
(S-Se)/(S0-Se)=exp(-K*(t**a))
!Thin-layer drying equation
dS/dt=-k*(S-Se)
k=0.242261*exp(-2530.2/(Tem+273.15)
！Initial boundary condition
Tem(0,t)=Tem
H(0,t)=H
S(z,0)=S0
write(*,*）"the drying time is: ", t
! output
print *, "End-of-cereal moisture content=", S
end program Composition
我知道我根本没有用到什么微分方程求解的，因为根本看不懂:'(
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