Unanswered Questions

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Dear Community!

I'm struggleing with a problem long since. I highly appreciate any help with this theme.

The problem is the following:

- I have a set of points, what comes from a numerical solution of a complex, but periodical function. Therefore I have a set of points (X;Y). The points are doesn't matter, but in my case, it look like this:

I want to use the Fourier-method to approximate this points with a function.

The best result I could get is this:

But it is not acceptable due to the high inaccuracy at the starting, and finishing points (there is a diagram inaccuracy %):

I'm feel like, I'm doing something wrong. Unfortunately, I had no time to look deep into the math here. Can somebody tell me, that how can I get a better result, using this method?

Thank you very much for the help in advance.

Best regards

Dávid

Hi guys,

I'm trying to apply boundary condition on the seris i generated using Adomian decomposition. Could some one please check it for me?
 

NULL

u[0] := a1+a2*y:

NULL

NULL

w[0] := a3+a4*y:

theta[0] := a6*y+a5

phi[0] := a8*y+a7

NULL

NULL

``

``

``

``

``

A[1] := R*(diff(u[0], y))+A-Gr*(B*phi[0]+theta[0])/Ree+Ha^2*(alpha*u[0]+beta*w[0])/(alpha^2+beta^2)

R*a2+A-Gr*(a5+a6*y+B*(a7+a8*y))/Ree+Ha^2*(alpha*(a1+a2*y)+beta*(a3+a4*y))/(alpha^2+beta^2)

(1)

u[1] := int(A[1], y = 0 .. y)

(1/2)*(-Gr*(a6+B*a8)/Ree+Ha^2*(alpha*a2+beta*a4)/(alpha^2+beta^2))*y^2+R*a2*y+A*y-Gr*(a5+B*a7)*y/Ree+Ha^2*(alpha*a1+beta*a3)*y/(alpha^2+beta^2)

(2)

u[11] := int(u[1], y = 0 .. y)

(1/3)*(-(1/2)*Gr*(a6+B*a8)/Ree+(1/2)*Ha^2*(alpha*a2+beta*a4)/(alpha^2+beta^2))*y^3+(1/2)*(R*a2+A-Gr*(a5+B*a7)/Ree+Ha^2*(alpha*a1+beta*a3)/(alpha^2+beta^2))*y^2

(3)

u = u[0]+u[11]

u = a1+a2*y+(1/3)*(-(1/2)*Gr*(a6+B*a8)/Ree+(1/2)*Ha^2*(alpha*a2+beta*a4)/(alpha^2+beta^2))*y^3+(1/2)*(R*a2+A-Gr*(a5+B*a7)/Ree+Ha^2*(alpha*a1+beta*a3)/(alpha^2+beta^2))*y^2

(4)

A[2] := R*(diff(w[0], y))-Ha^2*(beta*u[0]-alpha*w[0])/(alpha^2+beta^2)

R*a4-Ha^2*(beta*(a1+a2*y)-alpha*(a3+a4*y))/(alpha^2+beta^2)

(5)

w[1] := int(A[2], y = 0 .. y)

-(1/2)*Ha^2*(beta*a2-alpha*a4)*y^2/(alpha^2+beta^2)+R*a4*y-Ha^2*(beta*a1-alpha*a3)*y/(alpha^2+beta^2)

(6)

w[11] := int(w[1], y = 0 .. y)

-(1/6)*Ha^2*(beta*a2-alpha*a4)*y^3/(alpha^2+beta^2)+(1/2)*(R*a4-Ha^2*(beta*a1-alpha*a3)/(alpha^2+beta^2))*y^2

(7)

``

w = w[0]+w[11]

w = a3+a4*y-(1/6)*Ha^2*(beta*a2-alpha*a4)*y^3/(alpha^2+beta^2)+(1/2)*(R*a4-Ha^2*(beta*a1-alpha*a3)/(alpha^2+beta^2))*y^2

(8)

A[3] := R*Pr*(diff(theta[0], y))-2*Br*((diff(u[0], y))^2+(diff(w[0], y))^2+M^2*C*(u[0]^2+w[0]^2))-gamma*R*Pr*theta[0]

R*Pr*a6-2*Br*(a2^2+a4^2+M^2*C*((a1+a2*y)^2+(a3+a4*y)^2))-gamma*R*Pr*(a5+a6*y)

(9)

theta[1] := int(A[3], y = 0 .. y)

-(2/3)*Br*M^2*C*(a2^2+a4^2)*y^3+(1/2)*(-2*Br*M^2*C*(2*a1*a2+2*a3*a4)-gamma*R*Pr*a6)*y^2+R*Pr*a6*y-2*Br*(a2^2+a4^2+M^2*C*(a1^2+a3^2))*y-gamma*R*Pr*a5*y

(10)

theta[11] := int(theta[1], y = 0 .. y)

-(1/6)*Br*M^2*C*(a2^2+a4^2)*y^4+(1/3)*(-Br*M^2*C*(2*a1*a2+2*a3*a4)-(1/2)*gamma*R*Pr*a6)*y^3+(1/2)*(R*Pr*a6-2*Br*(a2^2+a4^2+M^2*C*(a1^2+a3^2))-gamma*R*Pr*a5)*y^2

(11)

theta = theta[0]+theta[11]

theta = a5+a6*y-(1/6)*Br*M^2*C*(a2^2+a4^2)*y^4+(1/3)*(-Br*M^2*C*(2*a1*a2+2*a3*a4)-(1/2)*gamma*R*Pr*a6)*y^3+(1/2)*(R*Pr*a6-2*Br*(a2^2+a4^2+M^2*C*(a1^2+a3^2))-gamma*R*Pr*a5)*y^2

(12)

``

 

NULL

A[4] := R*Sc*(diff(phi[0], y))-K*Sc*phi[0]

R*Sc*a8-K*Sc*(a7+a8*y)

(13)

phi[1] := int(A[4], y = 0 .. y)

-(1/2)*K*Sc*a8*y^2+R*Sc*a8*y-K*Sc*a7*y

(14)

phi[11] := int(phi[1], y = 0 .. y)

-(1/6)*K*Sc*a8*y^3+(1/2)*(R*Sc*a8-K*Sc*a7)*y^2

(15)

phi = phi[0]+phi[11]

phi = a7+a8*y-(1/6)*K*Sc*a8*y^3+(1/2)*(R*Sc*a8-K*Sc*a7)*y^2

(16)

``


 

Download second_problem.mw

Hi everyone,

Please, I really need your expertise advice(s) on what i am not doing right in the code attached below. I was actually writing the code on Multi-step DTM, but, instead of continuing from the last point, it starting all over again. Please, your expertise will save a soul here. Regard

Thanks

MsDTM3.mw

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N,a, sigma are constants.

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