When I use vpasolve I get all variables as [0x1 sym], any input as to what the problem might be would be appreciated!

Question

Malik Awan 2023년 1월 15일

0
링크

이 질문에 대한 바로 가기 링크

https://kr.mathworks.com/matlabcentral/answers/1894475-when-i-use-vpasolve-i-get-all-variables-as-0x1-sym-any-input-as-to-what-the-problem-might-be-woul

댓글: Sulaymon Eshkabilov 2023년 1월 15일

채택된 답변: Sulaymon Eshkabilov

syms M2 M3 beta1 beta2 beta3

M1 = 2.4;

M4 = 1.3;

Gamma = 1.4;

Gamma_P = Gamma+1;

Gamma_M = Gamma-1;

%Mach #'s upstream of normal shock

Mn1 = M1*sind(beta1);

Mn2 = M2*sind(beta2);

Mn3 = M3*sind(beta3);

%Deflection Angles

theta1 = atand(2*(cotd(beta1))*(((M1^2)*(sind(beta1))^2)-1)/((2+((M1^2)*(Gamma+cosd(2*beta1))))));

theta2 = atand(2*(cotd(beta2))*(((M2^2)*(sind(beta2))^2)-1)/((2+((M2^2)*(Gamma+cosd(2*beta2))))));

theta3 = atand(2*(cotd(beta3))*(((M1^2)*(sind(beta3))^2)-1)/((2+((M3^2)*(Gamma+cosd(2*beta3))))));

% Mach #'s

M2x = ((sqrt(((Mn1^2*Gamma_M)+2)/((2*Gamma*Mn1^2)-Gamma_M))))/(sind((beta1)-(theta1)));

M3x = ((sqrt(((Mn2^2*Gamma_M)+2)/((2*Gamma*Mn2^2)-Gamma_M))))/(sind((beta2)-(theta2)));

M4x = ((sqrt(((Mn3^2*Gamma_M)+2)/((2*Gamma*Mn3^2)-Gamma_M))))/(sind((beta3)-(theta3)));

solve = vpasolve([Mn1==Mn2, Mn1==Mn3, M2==M2x, M3==M3x],[beta1 beta2 beta3 M2 M3],[10 20 17 4.2 3.5])

댓글 수: 0
이전 댓글 -2개 표시이전 댓글 -2개 숨기기

댓글을 달려면 로그인하십시오.

이 질문에 답변하려면 로그인하십시오.

Answer 1

Sulaymon Eshkabilov 2023년 1월 15일

0
링크

이 답변에 대한 바로 가기 링크

https://kr.mathworks.com/matlabcentral/answers/1894475-when-i-use-vpasolve-i-get-all-variables-as-0x1-sym-any-input-as-to-what-the-problem-might-be-woul#answer_1149175

The problem here is that you have defined 4 equations and trying to solve for 5 unknowns (beta1, beta2 beta3 M2, M3) that is incompatible. Thus, one of the unknowns to be known/defined. Here is corrected code with this alteration.

syms M3 beta1 beta2 beta3
M1 = 2.4;
M2 = 4.2;              % Defined and M3 remains as unknown
M4 = 1.3;
Gamma = 1.4;
Gamma_P = Gamma+1;
Gamma_M = Gamma-1;
%Mach #'s upstream of normal shock
Mn1 = M1*sind(beta1);
Mn2 = M2*sind(beta2);
Mn3 = M3*sind(beta3);
%Deflection Angles
theta1 = atand(2*(cotd(beta1))*(((M1^2)*(sind(beta1))^2)-1)/((2+((M1^2)*(Gamma+cosd(2*beta1))))));
theta2 = atand(2*(cotd(beta2))*(((M2^2)*(sind(beta2))^2)-1)/((2+((M2^2)*(Gamma+cosd(2*beta2))))));
theta3 = atand(2*(cotd(beta3))*(((M1^2)*(sind(beta3))^2)-1)/((2+((M3^2)*(Gamma+cosd(2*beta3))))));
% Mach #'s
M2x = ((sqrt(((Mn1^2*Gamma_M)+2)/((2*Gamma*Mn1^2)-Gamma_M))))/(sind((beta1)-(theta1)));
M3x = ((sqrt(((Mn2^2*Gamma_M)+2)/((2*Gamma*Mn2^2)-Gamma_M))))/(sind((beta2)-(theta2)));
M4x = ((sqrt(((Mn3^2*Gamma_M)+2)/((2*Gamma*Mn3^2)-Gamma_M))))/(sind((beta3)-(theta3)));
solve = vpasolve([Mn1==Mn2, Mn1==Mn3, M2==M2x, M3==M3x],[beta1 beta2 beta3 M3],[10 20 17 3.5])
solve = struct with fields:
    beta1: 12.42307001044589696233406591853
    beta2: 7.0612666759489129181951376213411
    beta3: 4.5351783118604105328130018107605
       M3: 6.5296692049177007004148130266163