Inverse laplace transform of a periodic function

Hi,

I am trying to solve 1-d transient conduction problem with semi-infinite boundary condition on end (x-->inf) and a periodic heat flux profile at x = 0, using Laplace transform method. I am using invlap.m (<http://www.mathworks.com/matlabcentral/answers/uploaded_files/1034/invlap.m>) function to find the final temperature solution at different time steps.

I am trying to incorporate a unsteady periodic boundary condition at x=0, (like a sawtooth/triangular profile) with a period of ~0.2ms and the total time duration for getting a solution is 3s. However, just as a preliminary test to check if invlap.m would give me correct results for a periodic function, I am trying to find first LT of the function and then inverse LT using invlap.m to see if I can get back the same function of not.

I started with a triangular periodic function and calculated the LT of f(t) within first period (p) and diving by (1-exp(s*p)). However, I found out that using the invlap.m code when I am trying to calculate Linv(G(s)) where, G(s) = LT(f(t)), I am not getting back the same periodic triangular function. The profile is repeated only 3-4 times before it hits a singularity condition and stays constant at a median value between the range specified in the triangular profile. I had been trying to debug the code for since 1 week without any luck.

Could you please comment on applicability of your code on periodic functions. Codes are attached. Any help is highly appreciated!!