scholarly journals Results of W-87/Mk21 Deployment Separation Shock Tests

1999 ◽  
Author(s):  
C A Avalle
Keyword(s):  
Separation Shock ◽  
Deployment Separation

scholarly journals Numerical Analysis of Side-loads Reduction in a Sub-scale Dual-bell Rocket Nozzle

2021 ◽  
Author(s):  
M. Cimini ◽  
E. Martelli ◽  
M. Bernardini
Keyword(s):  
Inflection Point ◽  
Pressure Ratio ◽  
Mean Value ◽  
Detached Eddy Simulation ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Separation Shock ◽  
Delayed Detached Eddy Simulation ◽  
Controlled Flow ◽  
Dual Bell

AbstractA calibrated delayed detached eddy simulation of a sub-scale cold-gas dual-bell nozzle flow at high Reynolds number and in sea-level mode is carried out at nozzle pressure ratio NPR = 45.7. In this regime the over-expanded flow exhibits a symmetric and controlled flow separation at the inflection point, that is the junction between the two bells, leading to the generation of a low content of aerodynamic side loads with respect to conventional bell nozzles. The nozzle wall-pressure signature is analyzed in the frequency domain and compared with the experimental data available in the literature for the same geometry and flow conditions. The Fourier spectra in time and space (azimuthal wavenumber) show the presence of a persistent tone associated to the symmetric shock movement. Asymmetric modes are only slightly excited by the shock and the turbulent structures. The low mean value of the side-loads magnitude is in good agreement with the experiments and confirms that the inflection point dampens the aero-acoustic interaction between the separation-shock and the detached shear layer.

scholarly journals Numerical Study of Separation Characteristics of Piston-Type Explosive Bolt

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Yanhua Li ◽  
Jingcheng Wang ◽  
Shihui Xiong ◽  
Li Cheng ◽  
Yuquan Wen ◽  
...  
Keyword(s):  
Numerical Study ◽  
Separation Process ◽  
Tensile Fracture ◽  
Shock Source ◽  
Separation Time ◽  
Separation Shock ◽  
High Shock ◽  
Release Device ◽  
Shock Response ◽  
The Impact

An explosive bolt is a simple, highly reliable, and efficient pyrotechnic release device widely used in spacecraft and rocket launchers. High shock transient response is generated during the separation of a release device, which tends to damage the nearby micromechanism and hardware. The purpose of this article is to predict the shock response of an explosive bolt. In this paper, the separation process of a piston-type explosive bolt is simulated by using a hydrocode named AUTODYN and the influence of the charge amount on separation time, separation speed, and separation shock is analyzed. Results show that piston-type explosive bolts obey a tensile fracture mechanism and that the critical charge amount for separation is 354–398 mg of PETN. The separation shock of such an explosive bolt mainly includes two aspects: the shock caused by explosive detonations and the impact of the piston at the end of the stroke. As the charge amount increases, the separation time decreases, the speed of the piston and screw increases first and then decreases, and the separation shock first increases and then stabilizes. On a simple aluminum plate, the shock response decreases as the distance from the shock source increases, obeying the power function attenuation law.

A simple model for low-frequency unsteadiness in shock-induced separation

2009 ◽  
Vol 629 ◽  
pp. 87-108 ◽  
Author(s):  
S. PIPONNIAU ◽  
J. P. DUSSAUGE ◽  
J. F. DEBIÈVE ◽  
P. DUPONT
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Particle Image ◽  
Mixing Layer ◽  
Low Frequency ◽  
Oblique Shock Wave ◽  
Separation Shock ◽  
Image Velocimetry ◽  
Boundary Layer Interaction ◽  
Aerodynamic Parameters

A model to explain the low-frequency unsteadiness found in shock-induced separation is proposed for cases in which the flow is reattaching downstream. It is based on the properties of fluid entrainment in the mixing layer generated downstream of the separation shock whose low-frequency motions are related to successive contractions and dilatations of the separated bubble. The main aerodynamic parameters on which the process depends are presented. This model is consistent with experimental observations obtained by particle image velocimetry (PIV) in a Mach 2.3 oblique shock wave/turbulent boundary layer interaction, as well as with several different configurations reported in the literature for Mach numbers ranging from 0 to 5.

scholarly journals Two-dimensional unsteadiness map of oblique shock wave/boundary layer interaction with sidewalls

2019 ◽  
Vol 871 ◽  
Author(s):  
P. K. Rabey ◽  
S. P. Jammy ◽  
P. J. K. Bruce ◽  
N. D. Sandham
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Low Frequency ◽  
Oblique Shock ◽  
Oblique Shock Wave ◽  
Pressure Measurements ◽  
Wave Boundary Layer ◽  
Reflected Shock ◽  
Separation Shock ◽  
Wave Boundary

The low-frequency unsteadiness of oblique shock wave/boundary layer interactions (SBLIs) has been investigated using large-eddy simulation (LES) and high-frequency pressure measurements from experiments. Particular attention has been paid to off-centreline behaviour: the LES dataset was generated including sidewalls, and experimental pressure measurements were acquired across the entire span of the reflected shock foot. The datasets constitute the first maps of low-frequency unsteadiness in both streamwise and spanwise directions. The results reveal that significant low-frequency shock motion (with $St\approx 0.03$) occurs away from the centreline, along most of the central separation shock and in the corner regions. The most powerful low-frequency unsteadiness occurs off-centre, likely due to the separation shock being strengthened by shocks arising from the swept interactions on the sidewalls. Both simulation and experimental results exhibit asymmetry about the spanwise centre. In simulations, this may be attributed to a lack of statistical convergence; however, the fact that this is also seen in experiments is indicative that some SBLIs may exhibit some inherent asymmetry across the two spanwise halves of the separation bubble. There is also significant low-frequency power in the corner separations. The relation of the unsteadiness in the corner regions to that in the centre is investigated by means of two-point correlations: a key observation is that significant correlation does not extend across the attached flow channel between the central and corner separations.

scholarly journals Oscillation of separation shock wave ahead of forward-facing steps.

1988 ◽  
Vol 54 (498) ◽  
pp. 230-235
Author(s):  
Ryuichiro YAMANE ◽  
Myeongkwan PARK ◽  
Shuzo OSHIMA
Keyword(s):  
Shock Wave ◽  
Separation Shock
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