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Convergence to a different maximum

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Old   January 13, 2007, 23:43
Default Convergence to a different maximum
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I'm working on a problem of acoustic scattering of a periodic pressure pulse from a cylinder using Linearized Euler equation.The spatial discretization is a higher order central difference and Runga-Kutta is used for time marching.I have a numerical filter to add stability and a buffer zone at domain outlet to absorb the outgoing waves.Since the problem is symmetric I use just half the cylinder with a symmetry condition.

I ran my code on different grid sizes and the results do not converge.Once the results become periodic the acoustic pressure is just a sine wave of the initial time period T.My results,for different grid sizes attain periodicity with different peak amplitudes.On a 500*500 grid the peak amplitude was 3e-5,4.5e-5 on a 600*600 grid and 3.4e-5 on a 700*700 grid.There is no dispersion error.

I need some advice on what could be the reason for the observed oscillations.

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Old   January 15, 2007, 18:02
Default Re: Convergence to a different maximum
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What makes you think convergence has to be monotonous? Try 800x800. If you get an amplitude around 4e-5, you're closing in...
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