Environmental Engineering Reference
In-Depth Information
Remark 2 . To apply Eqs. (2.44) and (2.45), we must determine M mn , the normal
square of eigenfunction sets. Here we develop expressions of M mn for three cases of
boundary conditions.
Rewrite Eq. (2.41) into
r d R
d r
n 2
r R
d
d r
k 2 rR
+
=
.
(2.46)
Multiplying Eq. (2.46) by rR and integrating over
[
0
,
a 0 ]
yields
a 0
a 0
k 2 a 0
0
rR rR d r
n 2 RR d r
r 2 RR d r
+
=
,
0
0
or
2
2 R 2
k 2 a 0 r 2 d R 2
2
a 0
0 =
a 0
0 +
n 2
1
2 (
rR )
k 2 r 2 R 2
2
M mn
a 0
0
=
.
Thus
(
a 0
0 .
2
rR )
2
2
rR
)
+ (
(
nR
)
M mn =
(2.47)
2 k 2
2 k 2
2
1. Boundary Condition of the First Kind
Since R
(
a 0 )=
0and R
(
0
)=
J n (
0
)=
0
(
n
=
1
,
2
, ··· )
, Eq. (2.47) becomes
J n
2
2 k mn k mn J n (
a 0
k mn a 0 ) 2
a 0
2
μ ( n )
M mn =
=
m
2 J n 1
2 J n + 1
a 0
a 0
μ ( n )
μ ( n )
=
=
,
m
m
2 J n (
2 n
x J n (
where J n 1 (
x
)
J n + 1 (
x
)=
x
)
and J n 1 (
x
)+
J n + 1 (
x
)=
x
)
have been used.
2. Boundary Condition of the Second Kind
For this case, R (
a 0
)=
0and R
(
0
)=
J n
(
0
)=
0
(
n
=
1
,
2
, ··· )
. Eq. (2.47) reduces to
2
n
μ ( n )
J n
a 0
2
μ ( n )
1
M mn =
.
m
m
 
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