Hello everyone,

     I am having trouble trying to solve a system of differential equations. The modeling was made from the equilibrium equations of a pressure vessel. The set of equations is shown below:

     As you see it is a set of two second-order partial differential equations. So, we need four boundary conditions. This one is the first. It means that the left end of the pressure vessel is fixed.

This one is the second boundary condition. It means that the right end of the pressure vessel is free.

This one is the third boundary condition. It means that the inner surface of the pressure vessel is subject to an external load:

At last, we have the fourth boundary condition. It means that the outer surface of the pressure vessel is free.

     The first test I have been trying to do is the static case. In this case, the time terms (the right side of the two equations shown) is zero.

    The maple commands that I am using are the following:

restart; E := 200*10^9; nu := .33; G := E/(2*(1+nu)); RI := 0.254e-1; RO := 2*RI; p := proc (x) options operator, arrow; 50000000 end proc; sys := [E*(nu*(diff(v(x, r), x))/r+nu*(diff(diff(v(x, r), x), r))+(1-nu)*(diff(diff(u(x, r), x), x)))/(-2*nu^2-nu+1)+G*(diff(diff(u(x, r), r), r)+diff(diff(v(x, r), x), r)+(diff(u(x, r), r))/r+(diff(v(x, r), x))/r) = 0, E*((1-nu)*(diff(diff(v(x, r), r), r))+nu*(diff(diff(u(x, r), x), r))+(1-nu)*(diff(v(x, r), r))/r-(1-nu)*v(x, r)/r^2)/(-2*nu^2-nu+1)+G*(diff(diff(u(x, r), r), x)+diff(diff(v(x, r), x), x)) = 0]; BCs := {E*(nu*v(L, r)/r+nu*(D[2](v))(L, r)+(1-nu)*(D[1](u))(L, r))/(-2*nu^2-nu+1) = 0, E*(nu*v(x, RI)/RI+(1-nu)*(D[2](v))(x, RI)+nu*(D[1](u))(x, RI))/(-2*nu^2-nu+1) = -p(x), E*(nu*v(x, RO)/RO+(1-nu)*(D[2](v))(x, RO)+nu*(D[1](u))(x, RO))/(-2*nu^2-nu+1) = 0, u(0, r) = 0}

sol := pdsolve(sys, BCs, numeric)

I am getting the following error:

Error, (in pdsolve/numeric/process_IBCs) initial/boundary conditions must depend upon exactly one of the independent variables: 0.1459531181e12*v(L, r)/r+0.1459531181e12*(D[2](v))(L, r)+0.2963290579e12*(D[1](u))(L, r) = 0

In this case, my boundary conditions do depend on more than one independent variable. How do I proceed?

Thank you in advance,

Pedro Guaraldi

Is there anyone who has seen maple 2017 provide some details about what new features are being introduced. Is there a platform where we can suggest what features we would like to be added or enhanced?

I'm trying to define some multilinear forms to study differential geometry. What I need is only symbolic. My intention is symplify computations involving multilinear forms.

For example, to create an symbolic inner product "g" I used the command "define" like in this post:

http://www.mapleprimes.com/questions/203480-Define-And-Use-Abstract-Linear-Operator

So I tipped:

define(g, orderless, multilinear);

My doubt is: how can I declare that g(x,y) is always scalar?

With it I would simplify things like g(g(z,w)*x,y) = g(z,w)*g(x,y)

In my case, specifically, I type:

v:=(X,Y,Z)->g(Y,Z)*X-g(X,Z)*Y;

r:=(X,Y,Z,W)->g(v(X,Y,Z),W)-g(Y,T)*g(v(X,T,Z),W)+g(X,T)*g(v(Y,T,Z),W);

expand(r(X,Y,Z,W));

and the result is:

g(W,g(Y,Z)*X)-g(W,g(X,Z)*Y)-g(T,Y)*g(W,g(T,Z)*X)+g(T,Y)*g(W,g(X,Z)*T)+g(T,X)*g(W,g(T,Z)*Y)-g(T,X)*g(W,g(Y,Z)*T)

But I would enjoy that it were:

g(Y,Z)*g(W,X)-g(X,Z)*g(W,Y)-g(T,Z)*g(T,Y)*g(W,X)+g(X,Z)*g(T,Y)*g(W,T)+g(T,Z)*g(T,X)*g(W,Y)-g(Y,Z)*g(T,X)*g(W,T)

Is there a way to declare that g(x,y) is always scalar?

Thanks.

I have a problem using dchange when my variable depend on two (or more variables) and I would like to apply the chain rule.

For example, when I use the command

I would expect something like 

But I get an error saying that the number of new variables and transformation equations must be the same.

Any idea how I could solve it? 

Thanls a lot for your help.

i need to solve for u[i+1] as i attached i wrote the equations but i cant get any answers for it, the delta t is 0.1 and i need to go for ten steps, thank you
 

Download hw_4_structural.mw

Greetings,

currently im working on a project in which i basically have to calcuate and plot a little solar system, using newton mechanic. The work is done, but as it appears, the solution simply cannot be true. In the given example you can see that the planets move in more or less straight lines. I presume that the error is somewhere in the solution of the system of differential equations, but i can't see where it is.

I am grateful for every advice.

PlanetenSpacecurve.mw

I m using the follwing commands for ploting the five differnt values of M

with(plots):
SDfd1 := odeplot(dsol[1], [eta, diff(f(eta), eta)], -1 .. 1, color = green, axes = box);
SDfd2 := odeplot(dsol[2], [eta, diff(f(eta), eta)], -1 .. 1, color = red, axes = box);
SDfd3 := odeplot(dsol[3], [eta, diff(f(eta), eta)], -1 .. 1, color = blue, axes = box);
SDfd4 := odeplot(dsol[4], [eta, diff(f(eta), eta)], -1 .. 1, color = black, axes = box);
SDfd5 := odeplot(dsol[5], [eta, diff(f(eta), eta)], -1 .. 1, color = pink, axes = box);
display([SDfd1, SDfd2, SDfd3, SDfd4, SDfd5], labels = ["η", "f ' (η)"],
    labeldirections = [horizontal, vertical], labelfont = [italic, 16], axes = boxed,
    axesfont = [times, 14], thickness = 3);

But i do not want in colors.....i need graph without colors in different styles. how can ? Moreover i need legend which must be in centre of graph or within the box. It must not on left, right ,up or below. can some one help ?

Find the least number of moves and how many different ways that is achieved to win snakes and ladders with 1 die, with 2 dice, and how about 3 dice.  How to realize this with Maple?

Hi,

I need your help to classify the follwing set {0}, {1} and [0,1] are local attractor or not and in the case of local attractor how can we determine the bassin of attraction. 

ode:=diff(x(t),t)=sqrt(x(t));

how can we prove using maple which of {0}, {1} and [0,1] are local attarctor or not.

Many thanks

How to convert a system of differential equations to a matrix?

can infolevel show this matrix during the process?

Hello, I'd like to generate some data from an audio file, like get the amplitude and the time, so that I can plot it with x = time and y = amplitude, do you know how to do that ?

If algebra use factorise method,

Which method do maple use to dsolve differential equation?

I am trying to perform the following integral:

Which spits the integral back out at me.

I've also tried

Which, again, spits the integral back out at me.

My last attempt was this

Which... Still spit back out the integral.

Is there something special I should be doing for functions I'm integrating with a natural log? I need to get an exact value for this, not an approximation (because I am trying to check the accuracy of an approximation with this!).

Thanks!

hi,

i'am beginers in  the maple programmation, i want to solve the einstien equation in the spherical coordinate,

I have a nested for loop that iterates through a range of values for x and y coordinates to create a 3d surface for illustration of my research. after the x loop there is a y loop, and inside of that y loop is a series of commands to find some eigenvalues of a matrix (which become the z coordinates) and sort them into already open files. This isn't bad when the precision i require is more than .02, but some of my matrices require up to 0.005 or less. The latter precision costs hours of computation time on just one processor. However my laptop has an i7, so I want to see if i can get the for loop to send its next iteration to the next processor in line while it has the previous ones still calculating. Have any tips?