@Thomas Richard 

The Lapacian is correct.  https://en.wikipedia.org/wiki/Del_in_cylindrical_and_spherical_coordinates 

For no theta dependency, the term in red above is dropped. Which gives what I wrote because when expanding the first term above gives

expand(1/r*diff(r*diff(f(r,z,t),r),r))

So you see it is the same as what I had (wikipedica uses "f" instead of "u").

I do not like to do as you did, as it can lead to errors. First of all, time "t" is never part of Laplacian, as Laplacian is spatial only, and I could make errors making substitutions afterwords to remove it, so I type the Lapacian by hand, when there is no theta dependency. Same for Laplacian in spherical. I could not figure how to use Maple for this. But I memorized these things by now so no problem.

@Carl Love 

It does not matter if  r<1 or r<a or no assumption at all on "r".

Initially I had the radius as variable "a", then changed it to "1" just to make it simpler, that is all.

The error shows up in all cases.

@Thomas Richard 

Thanks!  Using "u(x,y__0)" to the set the IC is a nice trick which I will try it next when Maple is having hard time with IC.

your hand simplifcation can not be correct. it is easy to see why. You say it has "beta*mu^3" term at the end but if you type "collect(expr,mu)" where "expr" is your expression, Maple gives

And it is clear that the term multiplying "mu^3" is not "beta" and it does not simplify to "beta" either as your hand simplification says. 

@Mariusz Iwaniuk 

"dsolve convert second order ODE to first order ODE(to Abel)."

I am not sure how dsolve will do that, since "y" is not missing in the original ODE. One can convert second order to first order if "y" is missing.

So letting v(t)=y'(t), then what will dsolve replace y(t) by in the ode? integal of v(t)? Then it becomes integral differential equation, not Abel.

Do you have an example of how dsolve does that to look at to help learn how this is done?

@Mariusz Iwaniuk 

"This is Abel diff equation"

But this is second order ODE. Abel differential equation is first order ODE?

@Carl Love 

 that only works when the size is 2. 

Yes ofcourse. I was just answering the question itself which uses 2. Sorry I did not know they wanted it to work for something else.

I will delete my answer now then.

ps.  I can't delete my answer. When I click More... it only shows EDIT. Pease moderator: delete my answer above.

Lets say this can somehow work (which it won't)

v^2:= a^2 + b^2

Then later on, you write v:=5;   Then next you write print(v^2) 

What should Maple print? 

@radaar 

my purpose is to speed up the computation.

if you are using hardware floating points, why do you think if the numbers all have first 10 decimal points not zero, and last 5 are zero, then the calculation will be faster than if all numbers had all 15 decimal points non zero? 

Are you saying the time to do a hardware calculation depends on how many zeros there are in the the  CPU register?

I am not following how less decimal places will make hardware calculations faster?

@Carl Love 

opps, yes, I read it as evalf. Need new glasses. That is why it will be best if OP provides an example, in that case I would have copied it and not made this mistake. But it should still work with evalhf? I mean the truncation part. Will correct

@acer 

Thanks. My question remains the same which you answered. I only added explaining WHY I needed this transformation and where I wanted to use it, that is all. I did not add a new question.

Will try your suggestion on the whole Laplacian now.

Thanks for help

@ecterrab 

V 350 worked for me also, no more error.

Thanks for all your work on this.

@tomleslie 

Thanks for checking.

On "OP suggests issue might be a Windows 10 update??"

No,  I said the above about why I do not install Physics package using the cloud instead of manual download. 

Not related to the error message I get from Maple running the code. I was answering the other reply asking me to try to install Physics package again. May be I should have been more clear.

But I am glad someone other than me is able to produce this error message.

@itsme 

THank you for the suggestion. I tried all these things before. It does not work. This is a known long standing problem.  I am not the only one who seen this

https://www.mapleprimes.com/questions/226651-Why-Still-Not-Able-To-Install-Physics

It might be related to windows 10 professional change in some latest update and due to changing some file permissions.

There is nothing wrong with how I install the physics package. It is something I've been doing the same steps for a year now. I download the physics package itself and put in

Then edit maple.ini in lib folder:

and add the line

libname := "C:\\Maple_updates\\maple_2019\\Physics_Updates_348.maple", libname:

I am following the instruction thanks to Edgardo S. Cheb-Terrab as given in bottom of this post

https://www.mapleprimes.com/questions/226154-Installing-Packages-From-The-Cloud-Hangs

So I am sure I am using Physics package 348. That what Version() says.

As to why I get this error on my Maple, I have no idea. But will be happy to try any suggestion in order to find out why.

@ecterrab 

Thank you for checking. But it does not work for me. I am also using Physics 348 and Maple 2019 on windows 10.

I downloaded version 348 yesterday and followed same steps I always do to use new version. So I do not know why it works for you and not for me. 

If there is something else you like me to check please let me know.

I can't install Maple packages using the CLOUD interface directly, due to a bug somewhere. Maple server crash each time I try, and have to manually download the physics package and then adjust maple.ini to point to new version. This is what I been doing for more than a year now due to this bug in the cloud/windows issue.

Download it_does_not_work_for_me.mw