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plotting problem....

September 18 2012 J4James 175

This question was asked before but because of the curiosity, I 

bring it in the light again. We have a system of odes

restart:with(plots):

a := 1; b := .5; d := 1; omega := .4; h1 := 1+a*cos(x); h2 := -d-b*cos(x+omega);

F := Q-1-d;

de:={alpha*(diff(f(y), y, y, y, y))+G*(diff(theta(y), y, y))+B*(diff(phi(y), y, y))

+6*beta*(diff(f(y), y, y))*(diff(f(y), y, y, y))^2+3*beta*(diff(f(y), y, y, y, y))*

(diff(f(y), y, y))^2 = 0,

Hello every one,

I am trying to solve a system of 5 odes numerically but I get an error

"unable to convert to an explicit first-order system".

Please have a look and guide me through the problem.

Thanks

wprob1.mw

For example 

y'''-y''+2y'=0 ; y(0) = 1, y'(0)=0, y''(0) =0
ode := diff(f(x), x, x, x)-(diff(f(x), x, x))+2*(diff(f(x), x))
ics:=D(f(x))(0)=0,f(0)=1,......
the I.C. for y''(0) =0 is ?
Please give the format.
Thanks.
After numerically solving an ODE, I want to save the solutions as a .dat file. I got this from the internet net for PDES and tried by adapt it to odes using dsolve. But I get this: Error, `sol` does not evaluate to a module 
PDE := diff(u(x, t), t, t)-(diff(u(x, t), x, x))+.2(diff(u(x, t), t))-1/2*(u(x, t)-u(x, t)^3) = 0;
 IBC := {u(-15, t) = -1, u(15, t) = 1, u(x, 0) = tanh(x), (D[2](u))(x, 0) = -1/cosh(x)^2}; sol := pdsolve(PDE, IBC, 'numeric', u(x, t...

I'm trying to use Maple to assist me in my homework.  To me, TI & MsMath are more intuitive than Maple, however, i have a Maple license.  That said, how do i specify an initial condition while trying to solve an ODE using dSolve?  For TI, i would enter:

deSolve(x’=x/25 and x(0)=20,t, x)

... and be done with it.  I suspect that i have to use diff() to assign x/25 as the f(x) of y'.  However, how do i specify the initial condition?

I want to solve a diff eqn, but it is giving absurd answer.

> ode := diff(f(x), x, x) = (Phi(x)-lambda)*f(x);
d / d \
--- |--- f(x)| = (Phi(x) - lambda) f(x)
dx \ dx /
> dsolve(ode);
/ / / d / d \\\ \
f(x) = DESol|{ (-Phi(x) + lambda) _Y(x) + |--- |--- _Y(x)|| }, {_Y(x)}|
I am dealing with a problem in engineering mechanics, but my when using maple to solve the governing nonlinear equation with 4 bcs, I meet with error. 
Error, (in dsolve/numeric/bvp) initial Newton iteration is not converging

my code is :
deq := diff(y(x), `$`(x, 4)) = -.364*(diff(y(x), x))^2*(diff(y(x), `$`(x, 2)))+1.74*10^(-7)
bc := y(0) = 0, (D(y...

I am new to maple. The problem I am facing is to get a non-trivial

solution of a system of odes. But maple gve me only trivial solution.

 

# The system of odequations I am trying to solve is (Please note that in the bcs phi is alpha.)

 

 

# The solution of the above sys of odes is of the form, (note x3=z, its just a typo)

How can I use the command outputs DEtools [convertsys] for solving the system of differential equations? I know that maple can solve the system directly. But most of the examples can be seen in other systems (MathCad, MatLab ..) reduce the system to a system of first order equations. And I would like to implement, "translate" into Maple in this way. Is there a command that allows it? Do I need to implement a procedure?

GRACIAS

Hi

I am a PhD scholar at the University of Queensland. I am reviweing a paper titled as "A similarity solution for laminar thermal boundary layer over a flat plate with a convective surface boundary condition"(the pdf is available online). In this paper the author has written a MAPLE code. I copied the same code in MAPLE but could nt succedded. The author used the Runge Kutta RK5 Method to solve the model.

Please help me to solve the same model...

hi

consider the following ode

eq1:=diff(f(x),x$3)+f(x)*diff(f(x),x$2)+diff(f(x),x$1)^2;

subject to thease boundary condition

f(a)=0,D(f)(b)=0,D(D(f))(0)=0

where

b= infinity (in computational domain b=10 is acceptable )

the exact solution of ode is

f(x)=tanh(x/2)

but when i want to solve it with Dsolve, maple get the zero. how can i use this ode in maple

 

thanks

Hello,

I have a system of two ODEs.  The solutions of the system (U(t) and V(t)) should never take on negative values, but may approach zero.  When using dsolve (numeric) to solve the system and odeplot to plot the system, I can see that dsolve gives slightly negative values to the solutions when close to zero.  This may result in the solutions becomes increasingly negative over time.

How can I prevent dsolve from assigning negative values to...

Solve the equation y"-4y=lnx ?

                                     

hi

i write the followinf code in maple

eq1:= f'''(x) - f'(x)

is this posible in maple that i worte the above command like this

Linear:= d3/d(x) - d/d(x)

eq1:= linear (f)

thanks for youe attention in advance

dsolve,numeric type...

June 12 2012 zari 0

I want to solve a set of ODE equations numerically,there is 5 equations with certain boundary conditions,please help me,what kind of dsolve order could i use? when i use dsolve({sys,bcs}type=numeric) i get an error that say me:system must be entered as a set of equations! how can i solve it?

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