Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session E4: Compressible Flows: General |
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Chair: Roy Baty, Los Alamos National Laboratory Room: 103 |
Sunday, November 22, 2015 4:50PM - 5:03PM |
E4.00001: Group Invariance Properties of the Inviscid Compressible Flow Equations for a Modified Tait Equation of State Scott Ramsey, Roy Baty This work considers the group invariance properties of the inviscid compressible flow equations (Euler equations) under the assumptions of one-dimensional symmetry and a modified Tait equation of state (EOS) closure model. When written in terms of an adiabatic bulk modulus, a transformed version of these equations is found to be identical to that for an ideal gas EOS. As a result, the Lie group invariance structure of these equations – and their subsequent reduction to a lower-order system – is identical to the published results for the ideal gas case. Following the reduction of the Euler equations to a system of ordinary differential equations, a variety of elementary closed-form solutions are derived. These solutions are then used in conjunction with the Rankine-Hugoniot conditions to construct discontinuous shock wave and free surface solutions that are analogous to the classical Noh, Sedov, Guderley, and Hunter similarity solutions of the Euler equations for an ideal gas EOS. The versions of these problems for the modified Tait EOS are found to be semi-analytic in that a transcendental root extraction (and in some cases numerical integration of ordinary differential equations) enables solution of the relevant equations. [Preview Abstract] |
Sunday, November 22, 2015 5:03PM - 5:16PM |
E4.00002: Asymptotic Solutions of Detonation Propagation in a 2D Circular Arc. Mark Short, Chad Meyer, James Quirk The large pressure of the product gas generated by detonating high explosives causes lateral motion of the explosive at the material interface between the explosive and its confinement. In turn, this leads to streamline divergence and curvature of the detonation front (typically in a divergent fashion). The propagation of a detonation front in a given geometry depends on the amount of curvature generated. Here we describe an asymptotic analysis of detonation propagation in a 2D circular arc, examining dependencies of the motion on the size of the inner and outer arc radii, and the relation between the detonation velocity and curvature for different types of explosive. [Preview Abstract] |
Sunday, November 22, 2015 5:16PM - 5:29PM |
E4.00003: Similarity Solutions of the Compressible Flow Equations for a General Equation of State Zachary Boyd, Scott Ramsey, Roy Baty The Euler compressible flow equations admit discontinuous (e.g. shock) solutions regardless of the equation of state (EOS) used to close them. In addition, certain classes of initial conditions and EOS admit special flows known as similarity solutions, including some containing shocks. These are useful (1) as test problems for hydrocodes, (2) as intermediate asymptotic estimates for non-symmetric problems, and (3) in forecasting experimental results. To date, the vast majority of work pertaining to similarity solutions of the Euler equations has been accomplished in the context of the ideal gas EOS; the case where the material is arbitrary is less well-understood. In this work, we classify using Lie-group analysis those materials which admit similarity solutions. We also indicate how such solutions may be found for a variety of materials of interest, including those characterized by particular forms of the Gruneisen EOS. [Preview Abstract] |
Sunday, November 22, 2015 5:29PM - 5:42PM |
E4.00004: Effects of Segmented Slot Blowing at the Leading Edge of a Finite Span Cavity in Supersonic Flow Benjamin George, Lawrence Ukeiley, Louis Cattafesta, Kunihiko Taira In this investigation, the effects of employing segmented slot blowing at the leading edge of a finite span cavity in Mach 1.4 flow are studied. The rectangular cavity under consideration has a length to depth ratio of 6 and width to depth ratio of 2 with an approaching turbulent boundary layer. Qualitative surface flow visualization results reveal changes in the flow characteristics due to the introduction of the sidewalls and multiple slot blowing configurations, as has been previously shown. Quantitatively, unsteady surface pressure measurements and particle image velocimetry (PIV) were utilized to characterize the mechanisms for suppressing surface pressure fluctuations in a three-dimensional flow field. Joint time-frequency analysis using wavelet transformations highlight changes in the tonal and broadband surface pressure fluctuations as a function of time with the different slot configurations. PIV data results from the baseline finite span case were compared with the slot blowing cases to illustrate their effects on the mean flow field properties in the shear layer and recirculation region. Finally, the finite span cavity experimental results are compared with previously acquired data for the full span cavity case to gain some insight into the flow field modifications as the cavity span is altered. [Preview Abstract] |
Sunday, November 22, 2015 5:42PM - 5:55PM |
E4.00005: Viscous Shear Layers Formed by Non-Bifurcating Shock Waves in Shock-Tubes Kevin Grogan, Matthias Ihme Shock-tubes are test apparatuses that are used extensively for chemical kinetic measurements. Under ideal conditions, shock-tubes provide a quiescent region behind a reflected shock wave where combustion may take place without complications arising from gas-dynamic effects. However, due to the reflected shock wave encountering a boundary layer, significant inhomogeneity may be introduced into the test region. The bifurcation of the reflected shock-wave is well-known to occur under certain conditions; however, a viscous shear layer may form behind a non-bifurcating reflected shock wave as well and may affect chemical kinetics and ignition of certain fuels. The focus of this talk is on the development of the viscous shear layer and the coupling to the ignition in the regime corresponding to the negative temperature conditions. [Preview Abstract] |
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