where
()
,
r
=
,
()
11
,
r
=
are scalar functions characterizing surface
properties of the gratings,
u
n
is the derivative of the potential
()
ur
in the direction of
the outer normal
n
to the surface of the conical gratings (a normal derivative),
()
gr
is
the known function;
,
,
R
;
3) the energy limitation condition as the conical structure has the tip and edges
of conical strips:
(
)
22
D
u
u
dV
+
;
4) the infinity condition.
Feasibility of conditions 2)-4) provides uniqueness of the solution of the stated
problem. Let us present the required potential
u
in the form
01
u
u
u
=+
, where
(
)
0
0
0
0
exp
4
u
qr
r
rr
r
=
−
−
−
corresponds to the field of a source (the primary
field), and the potential
1
u
is caused by existence of the gratings and corresponds to
the secondary field.
The purpose and objectives of the study. The work goal is to research the model
problem of wave diffraction by semi-infinite semitransparent circular cone with
longitudinal slots which are periodically cut along generatrices and also development
of a method of the integral singular equations for solving the correspond mathematical
mixed boundary value problem for the Helmholtz equation with the
unclosed conical
geometry.
Particular cases of the considered conical structure are the solid semitransparent
cone, the semitransparent cone with longitudinal slot, the plane angular
semitransparent sector, the symmetrical two plane semitransparent angular sectors
representing model of the p microwave antenna "butterfly" [16]. Perfectly conductive
structures with a conical configuration are obtained from semitransparent by specifying
the value of transparency. The considered conical structure with periodic longitudinal
slots is the model of simple periodic conical gratings with semitransparent strips. The
large number of works [19-21] is devoted to problems of wave diffraction by gratings
those are caused by broad practical application of gratings in various fields.
Assignment of mixed (impedance) conditions for the surfaces of a cone allows to
model a conical metamaterial surface which is effectively used in nanotechnologies
[22,23].
To achieve the goal the following objectives were set:
- to solve the model mixed boundary value problem of the Helmholtz equation
with the unclosed conical geometry utilizing the rigorous method based on applying
the apparatus of the Kontorovich–Lebedev integral transforms and the singular integral
equations (SIE) with the Cauchy integral kernel;
- 1530 -