2 Some Properties of the Kernel Functions
The results given in this section are extracted mainly from references
[8], [9],
and [14]. In the following r = p - q
and r = |r|, Gk = Gk(p,q), G0 = G0(p,q).
2.1 Derivatives of G0 with respect to r
In two dimensions we have
In three dimensions we have
2.2 Derivatives of Gk (k ¹ 0) with respect to r
In two dimensions we have
where H1(1) is the spherical Hankel function of the first kind and of
order one and
|
|
¶2 Gk
¶r2
|
= |
i
4
|
k2 ( |
H1(1)
kr
|
-H0(1) ) . |
| (17) |
In three dimensions we have
|
|
¶Gk
¶r
|
= |
eikr
4 pr2
|
( ikr - 1 ) , |
| (18) |
|
|
¶2 Gk
¶r2
|
= |
eikr
4 pr3
|
( 2 -2ikr -k2 r2 ) . |
| (19) |
2.3 Expressions for the normal derivatives of Gk
The following expressions hold in both two and three dimensions
and for all k:
|
|
¶Gk
¶nq
|
= |
¶Gk
¶r
|
|
¶r
¶nq
|
, |
| (20) |
|
|
¶Gk
¶vp
|
= |
¶Gk
¶r
|
|
¶r
¶vp
|
, |
| (21) |
|
|
¶2 Gk
¶vp ¶nq
|
= |
¶Gk
¶r
|
|
¶2 r
¶vp ¶nq
|
+ |
¶2 Gk
¶r2
|
|
¶r
¶vp
|
|
¶r
¶nq
|
. |
| (22) |
2.4 Expressions for the normal derivative of r
The derivatives of r with respect to vp and nq may be
written as follows:
|
|
¶2 r
¶vp ¶nq
|
= - |
1
r
|
( vp.nq + |
¶r
¶vp
|
|
¶r
¶nq
|
) . |
| (25) |
2.5 Expressions for
¶2 G0/ ¶vp ¶nq
The following results can be derived from the substitution of
(25) and (12),(13) or
(14),(15) into (22) with k = 0:
|
|
¶2 G0
¶vp ¶nq
|
= |
1
2 pr2
|
( vp.nq + 2 |
¶r
¶vp
|
|
¶r
¶nq
|
) in two dimensions, |
| (26) |
|
|
¶G0
¶vp ¶nq
|
= |
1
4 pr3
|
( vp.nq + 3 |
¶r
¶vp
|
|
¶r
¶nq
|
) in three dimensions. |
| (27) |
2.6 Asymptotic Properties
In the following results, p, q Î G
where G is a surface and G is
smooth at p:
|
|
lim
q ® p
|
( Gk(p,q) -G0(p,q) ) = O(r0) , |
| (28) |
|
|
lim
q ® p
|
|
¶Gk
¶vp
|
(p,q) = O(r0) , |
| (29) |
|
|
lim
q ® p
|
|
¶Gk
¶nq
|
(p,q) = O(r0) , |
| (30) |
|
|
lim
q ® p
|
( |
¶2 Gk
¶vp ¶nq
|
(p,q) - |
¶2 G0
¶vp ¶nq
|
(p,q) + |
1
2
|
k2 Gk(p,q) ) = O(r0) . |
| (31) |