The HDYN solver control parameters are specified in the name.iN file:

KMET is the key for the solution method:
$=1$ central difference method (conditionally stable)

KOUT activates the output of solution vectors to the binary file name.PLS, to which the sequence number $\mathtt{ILC}$ then corresponds in the STR2/STR3 program (see name.i5). If the problem was restarted with $\mathtt{KREST}=2$ (see Load case sequence), the name.PLS file is overwritten, i.e., the solution from the previous run must be processed before the restart. The number in parentheses gives the number of solution vectors written:
$=0$ … input data check ($0$)
$=1$ … after each load case ($\mathtt{NCYC}\cdot\mathtt{NLC}$)
$=2$ … after each cycle ($\mathtt{NCYC}$)
$=3$ … only the final solution ($1$)

NINT specifies the subdivision of the integration interval and is related to the accuracy of the solution. It is recommended to set $\mathtt{NINT}=1$.

NGD is the order of numerical integration. $\mathtt{NGD}=1$ activates one-point integration for isoparametric elements. If $\mathtt{NGD}=0$, the integration order $\mathtt{NG}$ assigned to the elements in the name.i1 file is used.

PENAL is specified for contact problems, and the stability and accuracy of the solution depend on its correct choice.

TSTEP is the size of the integration step.

BETA activates a special form of the Rayleigh damping matrix $\mathbf{C}=\beta\mathbf{M}$.

The initial conditions are specified in the name.iN file using one of the following batches:

1) IC set number T KQT R $[X_0]$ defines the initial vector. The number of values must exactly correspond to the number of degrees of freedom of the mesh.

2) IC set number T KQT I IREC reads the initial vector from the $\mathtt{IREC}$-th record in the name.SOL file.

3) IC set number T KQT R $X_0$ $Y_0$ $Z_0$ defines a constant initial vector in the directions of the global coordinate system axes. In 2D problems, $Z_0$ is not written. The initial condition key $\mathtt{KQT}=1$ specifies the initial displacement, and $\mathtt{KQT}=2$ the initial velocity.

Note
If no IC batch is defined, the initial conditions are automatically assumed to be homogeneous.