77
Fig. 7. The graphs of the dependence between
1
0 2
/ (
)
v h
P c
and
V h
in
the viscous fluid case
Fig. 8. The graphs of the dependence between
1
0 2
/ (
)
v h
P c
and
V h
in the inviscid fluid case
Now we consider the graphs of the dependence between the studied quantities and the velocity
V h
.
These graphs for the stress
22
0
/
T h P
and for velocities
2
0 2
/ (
)
v
h
P c
and
1
0 2
/ (
)
v h
P c
are given in Figs.
5, 6, 7 and 8 which are constructed for various values of the
h
. Under construction of these graphs the
values of the studied
quantities are calculated at
1
0
x h
.
It follows from these graphs that in the case under consideration the influence of the fluid viscosity
on the values of the stress
22
0
/
T h P
is insignificant, but on the values of the fluid flow velocity is very
significant.
Now we consider the results which illustrate the influence of the fluid compressibility on the values
of the studied quantities. We recall that the influence of the fluid compressibility is characterized through the
parameter
1
(7). Numerical results show that the influence of the fluid compressibility on the studied
quantities becomes considerable in the cases where
1
0.25
. However, in the cases where
1
0.25
the
influence of the fluid viscosity on the distribution of the stress
22
0
/
T h P
and velocity
2
0 2
/ (
)
v
h
P c
disappears almost completely. Under obtaining results related to the incompressible fluid model we assume
that
1
0.0
. Basing this reason, we investigate the influence of the fluid compressibility on the values of
the studied quantities within the scope of the inviscid fluid case. Thus, according to the foregoing
discussions, an increase in the values of the velocity must increase the difference between the results
obtained within the scope of the compressible and incompressible fluid models. However, the investigations
shows that there exists such value of the velocity of the moving load under which the absolute values of the
studied quantities become infinite and the resonance type event takes place. Note that the existence of the
critical velocity is characteristic one for dynamics of the moving load acting on the layered medium. The
review of the investigations related to critical velocity of the moving load acting on bi-material elastic
systems was made in a paper [8]. However, up to now, we have not found any investigation on the critical
velocity of the moving load action on the hydro-elastic systems. Consequently, the results related to the
critical velocity, which will be discussed here, are the first attempts on the investigations of the critical
velocity of the moving load acting on the hydro-elastic systems. We introduce a notation
0
cr
V
a
for
illustration of the values of the dimensionless critical velocity. Numerical investigations show that the values
of the
0
cr
V
a
are the same for each studied quantities and for each point, i.e. for each value of the
1
x h
, at
which the values of these quantities are calculated. Numerical investigations also show that the values of
78
0
cr
V
a
do not depend on the plate thickness
h
, but depend on the compressibility or incompressibility of
the fluid. Moreover, it is established that the values of the
0
cr
V
a
depend also on the mechanical
properties of the fluid and of the plate materials. For the selected fluid and plate-layer material we obtain that
0
0.3262
cr
V
a
for the incompressible fluid model case and
0
0.3476
cr
V
a
for the compressible fluid
model case. Consequently, the compressibility of the fluid causes to increase of the values of the critical
velocity.
Fig. 9. The influence
of the fluid compressibility
on the values of the stress
22
0
/
T h P
Now we consider the graphs of the dependence among
22
0
/
T h P
and the velocity
/
V h
constructed
for the compressible and incompressible fluid models in the case where
/
/ .
cr
V h V
h
These graphs are
given in Fig. 9 from which follows that the fluid compressibility causes to decrease of the absolute values of
the pressure acting on the interface plane between the plate and fluid.
With this we restrict ourselves to analysis of the numerical results and note that the
study of the problems
which are similar to that considered here will be continued in the further works by the author of the present
paper.
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97(4), pp. 359 – 390 (2014).
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Journal of Mechanics,
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