OffshoreEngineer

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7 years, 147 days

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These are replies submitted by OffshoreEngineer

Thank yuo, that worked!

Thank yuo, that worked!

Thank you, numeric it is indeed possible.

However, when I want to solve an 3-point BVP; dsolve numeric does not work. There are workaround to still solve numerically, but it is also possible to solve symbolically (maybe for a specific range)?

Thank you, numeric it is indeed possible.

However, when I want to solve an 3-point BVP; dsolve numeric does not work. There are workaround to still solve numerically, but it is also possible to solve symbolically (maybe for a specific range)?

@Markiyan Hirnyk I don't really understand how to do it. I have found some examples how to use the shooting method, but nowhere I found an example with multipoint boundary conditions.

@Markiyan Hirnyk I don't really understand how to do it. I have found some examples how to use the shooting method, but nowhere I found an example with multipoint boundary conditions.

I dont think this is the answer to my problem. What I have is 6 coupled differential equation, which have BC's at the points 0, 100 and 150, which makes is a three-point BVP

 

I dont think this is the answer to my problem. What I have is 6 coupled differential equation, which have BC's at the points 0, 100 and 150, which makes is a three-point BVP

 

@JohnS Thank you for your reply. This confirms to me that the solution that Maple finds is correct for these equations. It is not wat I expected, I did not really expected the 2nd derivative to be zero at 0, but certainly I didn't expect it to show a peak to -0.04 like that. 

The theory is the thin-shell theory by kirchhoff-love. I have checked the equations multiple times, but they seem correct. Probably there is a problem in this specific boundary condition or I am making a mathematical mistake.

@JohnS Thank you for your reply. This confirms to me that the solution that Maple finds is correct for these equations. It is not wat I expected, I did not really expected the 2nd derivative to be zero at 0, but certainly I didn't expect it to show a peak to -0.04 like that. 

The theory is the thin-shell theory by kirchhoff-love. I have checked the equations multiple times, but they seem correct. Probably there is a problem in this specific boundary condition or I am making a mathematical mistake.

@JohnS Thanks for your input. I have tried your advice, but this creates the same output I had before.

@JohnS Thanks for your input. I have tried your advice, but this creates the same output I had before.

@Carl Love Yes you a right, I use cylindrical coordinates. My original differential equation is a two dimensional PDE (the r-dimension is small compared to the other dimensions, so is neglegted). I have eliminated the theta-dependence, by using the orthogonality property of the sin and cos function (I know that the input and output on the theta dimension should be a sin or cos function). This gives me a ODE which I can solve quite simple with Maple.

When I change to cartesian, it will be very hard (impossible?) to eliminate dimensions, so I am bound to solving a PDE, which is not preferred.

I could have made a mistake in the elimination of the theta-dependence. Stange thing is that when I calculate a simply supported beam (same ODE, different BC), the result is very good. I am thinking that maybe when I compose the ODE, the assumptions I make do not apply for every BC.

@Carl Love Thank you for the effort, yesterday I also tried to nondimensionalize, which gave no result. Maybe the output that maple gives is correct to this BVP.

Could there be a difference of output when I don't use the numeric version of dsolve? My computer does not have enough computational power to calculate it symbolic, so I cannot try.

And I was thinking, is there another program that can solve differential equations like this, just to confirm the output. I tried Matlab and Mathematica, but both give me problems with this differential equation (they don't solve at all)

 

@Carl Love Thank you for the effort, yesterday I also tried to nondimensionalize, which gave no result. Maybe the output that maple gives is correct to this BVP.

Could there be a difference of output when I don't use the numeric version of dsolve? My computer does not have enough computational power to calculate it symbolic, so I cannot try.

And I was thinking, is there another program that can solve differential equations like this, just to confirm the output. I tried Matlab and Mathematica, but both give me problems with this differential equation (they don't solve at all)

 

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