6.4  Subroutines AMBEM2 , AMBEM3 and AMBEMA

SUBROUTINE AMBEM{2 or 3 or A(}

real wavenumber,

description of boundary and set of interior solution points,

homogeneous boundary condition,

validation parameters,

characteristic wavenumbers and their corresponding mode shape at boundary points and at interior solution points (solution),

working space )

The subroutines require input a geometrical description of the boundary of the domain (as covered in Chapter 2) and a list of the points in the interior (from which the values of the f at those points allow us to construct the mode shapes), the homogeneous boundary condition, the subroutine returns the characteristic wavenumbers and their corresponding mode shape at boundary points and at interior solution points. The use of the subroutines are demonstrated by the programs AMBEM2_T , AMBEM3_T and AMBEMA_T in the next Section.

6.4.1  Solution Strategy of the AMBEM* routines

In the subroutines AMBEM2 , AMBEM3 and AMBEMA , the technique employed for deriving the polynomial approximation (6.12) involves computing A_k at the m+1 Chebyshev (¥ norm) interpolation points for any selected wavenumber range [k_A, k_B]. The coefficient matrices A_[0], A_[1], ..., A_[m] in (6.12) are obtained through Newton's divided differences using the value of A_k at the selected values of k in [k_A, k_B].

6.4.2  Subroutine AMBEM2

The subroutine parameters that specify the interior two-dimensional Helmholtz problem must be set up in the main program. Let this be called MAIN.FOR. The following files must be linked together to construct the complete program:

MAIN.FOR (and files containing any user-defined sub-programs),

AMBEM2 .FOR,

H2LC .FOR, the file for computing the discrete operators - see Chapter 3,

FNHANK , the Hankel function - see Appendix 5,

INTEIG .FOR, the file for computing the solution to a linear system - see Appendix 4,

CGEIG .FOR, the file for computing the solution to a linear system - see Appendix 4,

GEOM2D.FOR ,

6.4.3  Subroutine AMBEM3

The subroutine parameters that specify the exterior three-dimensional Helmholtz problem must be set up in the main program. Let this be called MAIN.FOR. The following files must be linked together to construct the complete program:

MAIN.FOR (and files containing any user-defined sub-programs),

AMBEM3 .FOR,

H3LC .FOR, the file for computing the discrete operators - see Chapter 3,

INTEIG .FOR, the file for computing the solution to a linear system - see Appendix 4,

CGEIG .FOR, t

GEOM3D .FOR, the file for 3D geometry - see Appendix 6.

6.4.4  Subroutine AMBEMA

The subroutine parameters that specify the exterior three-dimensional axisymmetric Helmholtz problem must be set up in the main program. Let this be called MAIN.FOR. The following files must be linked together to construct the complete program:

MAIN.FOR (and files containing any user-defined sub-programs),

AMBEMA .FOR,

H3ALC .FOR, the file for computing the discrete operators - see Chapter 3,

INTEIG FOR, the file for computing the solution to a linear system - see Appendix 4,

CGEIG .FOR,

GEOM2D.FOR , the file for 2D geometry - see Appendix 6,

GEOM3D .FOR, the file for 3D geometry - see Appendix 6.