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gradient module. A reverse range of greys was used when creating isolines
to enable better comparison.
The first quasi steady stage of the sharp edge model flow is presented
in Fig. 8. The numerical modelling was performed for the M
= 7
of the
ram air. In area
1
(Fig. 8
a
) the attached shock wave front is clearly visible
which can also be observed in the Schlieren image. In the transition location
of the wedge angular surface (area
2
, Fig. 8
a
) rare faction waves fan is
observed which is not so visible in the shadow image, it can be the result of
the boundary layer and separation flows in this area affecting the shadow
image. In the area
3
(Fig. 8
a
) the attached shock wave fronts intersection
is visible, which can denote the good level of validation for the approach
flow. Near the initial step of the cavity (Fig. 8
a
, area
4
) a series of rare
faction waves is visible, whose outline is also present in the experiment
data. At the end of the cavity (Fig. 8
a
, area
5
) a complex structure of
rarefaction waves is formed, which coincides in some respects with the
shadow image.
The comparison of the experiment Schlieren image with the numerical
simulation results for the second quasi steady sharp-edge flow stage is
presented in Fig. 8
b
, which shows that the high density gradient areas
(areas
1–4
, Fig. 8
b
) are in good agreement. The comparison results of
the flow after the cavity (area
5
, Fig. 8
b
) have also visibly improved,
which may be the consequence of a lower Mach number simulation of
the approach flow and correspondingly more peaked fronts of the wave
structure observed.
The experiment image of the first quasi steady blunt-nose flow stage
is compared to the numerical simulation results in Fig. 9. The experiment
image quality is lower than the one with the sharp edge because the video
camera used had smaller resolution. In the case of the blunt nose wedge,
the detached shock wave (area
1
, Fig. 9) and rare faction waves (area
2
,
Fig. 9) fronts have more blurred boundaries. However, the comparison of
flow structure in this area indicates that the numerical solution adequately
corresponds to the experiment. The majority of density field characteristics
present in the experiment photo image can be observed on the isolines
of the calculated density gradient. It should be noted that the comparison
of Fig. 8
a
and Fig. 9 leads to the conclusion that the blunt edge flow is
somewhat more complicated than sharp edge flow.
Conclusion.
The flow structure for the air intake and ramjet passage
models was investigated experimentally and numerically in “Radiative gas
dynamics” laboratory in the Institute for Problems in Mechanics of RAS.
The change of cold air flows with M
= 7
and 4.5 around sharp and
blunt nose wedge models was recorded with high speed video cameras.
The experiment results are used to test numerical simulation of shockwave
16 ISSN 0236-3941. HERALD of the BMSTU. Series “Mechanical Engineering”. 2015. No. 1