solve a system of equations.

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Could any one please help me write the code to solve this system of equations?
Fcl=1/(1+0.155*Iclo*h);
hr=4*5.67*0.00000001*0.72*facl*((0.5*(Tcl+To)+273)^3);
To=(hr*Tr+hc*Ta)/h;
Tcl=To+Fcl(Tsk(i)-To);
h=hc+hr;
Unknown: Fcl hr To Tcl h.
Others are known.
I'm a beginner, I follow the format but error always shoot out. Want quick respond thank you.
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jin wang
jin wang 2015-10-12
编辑:jin wang 2015-10-12
What I wrote is like these.
syms Fcl hr To Tcl h
eqn1 = Fcl==1/(1+0.155*Iclo*h);
eqn2 = hr==4*5.67*0.00000001*0.72*facl*((0.5*(Tcl+To)+273)^3);
eqn3 = To==(hr*Tr+hc*Ta)/h;
eqn4 = Tcl==To+Fcl(Tsk(i)-To);
eqn5 = h==hc+hr;
[Fcl,hr,To,Tcl,h] = solve([eqn1,eqn2,eqn3,eqn4,eqn4,eqn5],[Fcl,hr,To,Tcl,hl])

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采纳的回答

Walter Roberson
Walter Roberson 2015-10-12
Is Fcl a function or a value? If it is a value then you need explicit multiplication with respect to (Tsk(i)-To)
Note that by default "i" refers to sqrt(-1) so your Tsk(i) may be trying to index Tsk(sqrt(-1)) unless you have assigned something else to i
The statements you show by themselves are not enough: you need to define numeric values for the other variables or you need to declare them as syms . If you take the syms route then I recommend changing Tsk(i) to just plain Tsk since the indexing does not matter to the solution of the equations.
The solution involves the roots of a polynomial of degree 7 whose leading term is equivalent to
158193*Iclo*facl*(31*Iclo*Ta*hc-31*Iclo*Tr*hc-200*Tr+200*Tsk(i))^3 * x^7
Because it is a 7 degree polynomial, the answer you get is going to be in terms of RootOf() and there is unlikely to be a closed form solution in the standard operations. You are going to need to solve for numeric roots by using vpasolve() or using double()
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jin wang
jin wang 2015-10-12
Exactly, so I should use this 7 sloution matrix to substitute into the following calculation? I keep receiving dimension not match error.
jin wang
jin wang 2015-10-12
Let's say I want to use RC and E which is 7x1 sym in the following code like this. How can I achieve this outcome?
Tsk(1+k,1)=Tsk(k,1)+deltat*(F(5)*(H(5)+(K(4)*(Tvsk(k,1)-Tsk(k,1)))-(RC+E)));

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更多回答(2 个)

John BG
John BG 2015-10-12
Could you please define ranges for each unknown? Be conservative, please define the following: Fcl_min= Fcl_max= hr_min= hr_max= To_min= To_max= Tcl_min= Tcl_max= h_min= h_max=
  1 个评论
jin wang
jin wang 2015-10-12
you mean give them specific value or just write what you have writen in the code. I don't know why to do this.

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John BG
John BG 2016-1-31
Mr Robertson considers as variables parameters that Mr Wang does not want to include as variables. I asked Mr Wang to define ranges because if the symbolic analysis does not help, then having a look at the equations may be useful, let me explain:
Since Mr Wang does not say anything else about the parameters, let me list them
eq1: Iclo assumed constant
eq2: facl and Tc assumed constant
eq3: Tr, Ta and hc assumed constant
eq4: Tsk(i) assumed constant
eq5: as in eq3, hc assumed constant
So, we have 5 variables to solve: Fcl hr To Tcl h
that I rename to: x y z w v
The simplified version of the 5 initial equations is:
eq1: x=1/(1+v)
eq2: y=((1+z)*.5+2)^3
eq3: z=(y+1)/v
eq4: w=z+x*(1-z)
eq5: v=1+y
I have define 5 ranges, that some of them may or may not help solve the system, but at least it's a start point:
x_min=-10;x_max=10;x_step=.1;x_range=[x_min:x_step:x_max]
y_min=-10;y_max=10; y_step=.1; y_range=[y_min:y_step:y_max]
z_min=-10;z_max=10; z_step=.1; z_range=[z_min:z_step:z_max]
w_min=-10;w_max=10; w_step=.1; w_range=[w_min:w_step:w_max]
v_min=-10;v_max=10; v_step=.1; v_range=[v_min:v_step:v_max]
now
v=v_range
x=1./(1+v)
figure(1);plot(v,x);grid on;hold all
z=z_range
y=((1+z)*.5+2).^3
figure(2);plot(z,y);grid on;w=z+x*(1-z)
simplifying some equations is possible:
eq3 and eq5 yield z=(y+1)/(1+y) nearly constant
eq4 with z nearly constant means w shape is w=1+x
I said 'nearly constant' because the simplified equations do not include the the parameters
Including parameters: Iclo facl Tc Tr Ta Tsk(i) hc
renamed: k1 k2 k3 k4 k5 k6 k7
eq1: x=1/(1+k1*v)
eq2: y=k2*((k3+z)*.5+2)^3
eq3: z=(k4*y+k5*k7)/v
eq4: w=z+x*(k6-z)
eq5: v=k7+y
give values to parameters, and find out if the 5 equations have a solution, or if perhaps the only way to solve this equations system is for values of parameters and variables within certain range windows.
Let me know if you progress with anything above explained
John

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