|August 2, 2007, 06:57||
error analysis and consistent splitting method
I am trying to solve Navier-Stokes equations with incompressible and laminar flow.
The scheme I have chosen is a consistent splitting method in order to decoupled velocity and pressure.
The temporal scheme is a semi-implicit one; Diffusion matrix is treated implicity and Convection matrix and pressure are treated explicity.
As space discretization I am using finite element method.
As a benchmark I use Kim and Moin problem. And I am calculating the error as the time step decreases in both variables, velocity and pressure.
I calculate the velocity error with Lmax(T=[0,1],L2(space)) and the pressure error with L2(T=[0,1],L2(space))
The weird thing is that I obtain the following errors as the time step value decreases:
incrT=0.03125; error_vel=0.00247964; error_pre=0.00176696
incrT=0.015625; error_vel=0.00262931; error_pre=0.00187242
incrT=0.0078125; error_vel=0.00290054; error_pre=0.00196216
In all cases, the solution I obtain is really similar to the exact solution, but, as you can see, the error is bigger as the time_step_value decreases, something absolutely wrong.
I have checked the code several times and I cannot see the problem, could you give me any advice? Thanks in advance. Isi
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