Oblique shock

About: Oblique shock is a research topic. Over the lifetime, 6551 publications have been published within this topic receiving 119823 citations.

Shock enhancement and control of hypersonic mixing and combustion

Abstract: The possibility that shock enhanced mixing can substantially increase the rate of mixing between coflowing streams of hydrogen and air has been studied in experimental and computational investigations. Early numerical computations indicated that the steady interaction between a weak shock in air with a coflowing hydrogen jet can be well approximated by the two-dimensional time-dependent interaction between a weak shock and an initially circular region filled with hydrogen imbedded in air. An experimental investigation of the latter process has been carned out in the Caltech 17 Inch Shock Tube in experiments in which the laser induced fluorescence of byacetyl dye is used as a tracer for the motion of the helium gas after shock waves have passed across the helium cylinder. The flow field has also been studied using an Euler code computation of the flow field. Both investigations show that the shock impinging process causes the light gas cylinder to split into two parts. One of these mixes rapidly with air and the other forms a stably stratified vortex pair which mixes more slowly; about 60% of the light gas mixes rapidly with the ambient fluid. The geometry of the flow field and the mixing process and scaling parameters are discussed here. The success of this program encouraged the exploration of a low drag injection system in which the basic concept of shock generated streamwise vorticity could be incorporated in an injector for a Scramjet combustor at Mach numbers between 5 and 8. The results of a substantial computational program and a description of the wind tunnel model and preliminary experimental results obtained in the High Reynolds Number Mach 6 Tunnel at NASA Langley Research Center are given here.

Experimental studies on the lip shock.

Abstract: Lip shock from separation edge of half angle wedge and resultant static pressure recovery distribution along wake

Fluid dynamics of stellar jets in real time: third epoch hubble space telescope images of hh 1, hh 34, and hh 47

Abstract: We present new, third-epoch Hubble Space Telescope H? and [S II] images of three Herbig-Haro (HH) jets (HH?1&2, HH?34, and HH?47) and compare the new images with those from previous epochs. The high spatial resolution, coupled with a time series whose cadence is of order both the hydrodynamic and radiative cooling timescales of the flow, allows us to follow the hydrodynamic/magnetohydrodynamic evolution of an astrophysical plasma system in which ionization and radiative cooling play significant roles. Cooling zones behind the shocks are resolved, so it is possible to identify which way material flows through a given shock wave. The images show that heterogeneity is paramount in these jets, with clumps dominating the morphologies of both bow shocks and their Mach disks. This clumpiness exists on scales smaller than the jet widths and determines the behavior of many of the features in the jets. Evidence also exists for considerable shear as jets interact with their surrounding molecular clouds, and in several cases we observe shock waves as they form and fade where material emerges from the source and as it proceeds along the beam of the jet. Fine structure within two extended bow shocks may result from Mach stems that form at the intersection points of oblique shocks within these clumpy objects. Taken together, these observations represent the most significant foray thus far into the time domain for stellar jets, and comprise one of the richest data sets in existence for comparing the behavior of a complex astrophysical plasma flow with numerical simulations and laboratory experiments.

The use of driver inserts to reduce non-ideal pressure variations behind reflected shock waves

Abstract: Non-ideal shock tube facility effects, such as incident shock wave attenuation, can cause variations in the pressure histories seen in reflected shock wave experiments. These variations can be reduced, and in some cases eliminated, by the use of driver inserts. Driver inserts, when designed properly, act as sources of expansion waves which can counteract or compensate for gradual increases in reflected shock pressure profiles. An algorithm for the design of these inserts is provided, and example pressure measurements are presented that demonstrate the success of this approach. When these driver inserts are employed, near- ideal, constant-volume performance in reflected shock wave experiments can be achieved, even at long test times. This near-ideal behavior simplifies the interpretation of shock tube chemical kinetics experiments, particularly in experiments which are highly sensitive to temperature and pressure changes, such as measurements of ignition delay time of exothermic reactions.