Im trying to solve an equation that have variable on left and right side
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How do I solve this equation? I'm giving the important information also.
depth= 1385.33
por=0.153
Qv=0.980
B=3200
Rw=0.265
m=1.86
n=2.2
Rt=4.05
Sw=(Rw/((por^m)*Rt*(1+(B*Qv*Rw)/Sw)))^(1/n)
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John D'Errico
2020년 5월 23일
편집: John D'Errico
2020년 5월 23일
How is depth relevant to anything here? It does not appear in the expression. Maybe I'm just not thinking very "deeply" today.
If Sw appears on both sides of the equality, surely you can subtract Sw? Just move everything to the same side. WTP?
por=0.153;
Qv=0.980;
B=3200;
Rw=0.265;
m=1.86;
n=2.2;
Rt=4.05;
fun = @(Sw) Sw - (Rw./((por^m)*Rt*(1+(B*Qv*Rw)./Sw))).^(1/n);
Note that for Sw <= 0, you either have a divide by zero at Sw == 0, or a complex result. So If any real solution exists, it must be for positive Sw.
Also note the use of ./ and .^ where necessary in fun. Does a solution exist? PLOT IT!
fplot(fun,[0,0.01])
yline(0);
It looks like a positive solution exists near 0.007.
[Swsol,fval] = fzero(fun,0.007)
Swsol =
0.00698017018548943
fval =
8.67361737988404e-19
We could also do this using symbolic tools. No analytical solution will exist because of the non-integer power.
syms Sw
vpasolve(fun(Sw))
ans =
0.006980170185489425081287353
No other positive root will exist. That should be not too difficult to prove.
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Walter Roberson
2020년 5월 28일
If this is a fitting process to determine the optimal Sw, then you would use different code.
You indicate that you have multiple Rt values; for a fitting you would also need multiple values of some other variable -- you need one more more independent variables and one or more dependent variables.
추가 답변 (3개)
Ameer Hamza
2020년 5월 23일
편집: Ameer Hamza
2020년 5월 23일
This is one of the methods
syms Sw
depth= 1385.33;
por=0.153;
Qv=0.980;
B=3200;
Rw=0.265;
m=1.86;
n=2.2;
Rt=4.05;
eq = Sw==(Rw/((por^m)*Rt*(1+(B*Qv*Rw)/Sw)))^(1/n);
sol = vpasolve(eq, Sw)
Walter Roberson
2020년 5월 23일
depth= 1385.33
por=0.153
Qv=0.980
B=3200
Rw=0.265
m=1.86
n=2.2
Rt=4.05
F = @(Sw) (Sw) - ((Rw/((por^m)*Rt*(1+(B*Qv*Rw)/Sw)))^(1/n));
Sw = fsolve(F, 1.234)
댓글 수: 2
N Sudharshan
2023년 8월 22일
편집: Torsten
2023년 8월 22일
clear all %% solve for SN %%
Z=-1.282;
S=0.5;
PSI=1.9;
M=1000;
W=1000000;
syms SN
eqn = log10(W)==Z*S+9.36*log10(SN+1)-0.20+((log10(PSI/(4.2-1.5)))/(0.40+(1094/(SN+1)^5.19)))+2.32*log10(M)-8.07
solve(eqn)
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