time integration module

[kimsongoik]

Dear Elmer group
I have 2 questions about the ‘time integration module’.
First what is the difference between subroutines ‘NemarkBeta’ and ‘Newmark2ndorder’?
Second what do the words ‘PrevSol0’ and ‘PrevSol1’ and ‘Avarage’ in ‘Newmark2ndorder’ subroutine point to?
Thanks for your kind attention.
Regards,
Kimsongoik

[Juha]

Hi,

the NewmarkBeta() is for first order time derivaritives, Newmark2ndorde for
2nd order time derivatives. The latter is not used anywhere in the solver
proper.

The PrevSol0 and PrevSol1 arrays would be the elementwise nodal values
for the integrated quantitity at timesteps i and i-1.The 'Avarage' flag seems
activate a somewhat altered sceme to the default:

avarage:

Code: Select all

(M/dt^2 + D/(2*dt) + K/3)*u_{i+1} +  (M/dt^2 - D/(2*dt) + K/3)*u_i - (M/(2*dt^2) - K/3)*u_{i-1} = F_{i+1}

default:

Code: Select all

(M/dt^2 + D/(2*dt) + K)*u_{i+1} +  (M/dt^2 - D/(2*dt)) * u_i - M/(2*dt^2) * u_{i-1} = F_{i+1}

M, D & K being the coefficient matrices of the 2nd, 1st, and 0th order time derivative terms.


BR, Juha