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empty sym error, how to solve

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esat gulhan
esat gulhan on 20 Aug 2020
Commented: Adam Danz on 22 Aug 2020
syms P1 P2 V1 V2 z1 z2 g p debi Wpump Wturb Eloss Wpumpshaft npump nturb alfa1 alfa2
g=9.807
p=1000
V1=0
z1=0
alfa1=1;
P2=0
V2=1
z2=0
alfa2=1;
debi=70 %kg/sn
Wpumpshaft=20100
npump=0.683074626865671
Wpump=Wpumpshaft*npump
Wturb=0;
nturb=1
Eloss=0;
ar=((P1/p+V1^2/(2)*alfa1+z1*g)*debi+Wpump==(P2/p+V2^2/(2)*alfa2+z2*g)*debi+Wturb*nturb+Eloss);
vpa(solve(ar,P1),8)
when i try to solve this it give error. it is ridiculuous. Where is the error.

  1 Comment

Adam Danz
Adam Danz on 22 Aug 2020
When I run this, I do not get an error.

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Accepted Answer

Alan Stevens
Alan Stevens on 22 Aug 2020
You could use fzero:
P10 = -100;
P1 = fzero(@fn, P10);
function F = fn(P1)
g=9.807;
p=1000;
V1=0;
z1=0;
alfa1=1;
P2=0;
V2=1;
z2=0;
alfa2=1;
debi=70; %kg/sn
Wpumpshaft=20100;
npump=0.683074626865671;
Wpump=Wpumpshaft*npump;
Wturb=0;
nturb=1;
Eloss=0;
F = ((P1/p+V1^2/(2)*alfa1+z1*g)*debi+Wpump ...
- (P2/p+V2^2/(2)*alfa2+z2*g)*debi+Wturb*nturb+Eloss);
end

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