Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session G30: Compressible Flow: Numerical Simulation of Shock Waves and Shock-Boundary Layer InteractionBoundary Layers Compressible
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Chair: Michael Hargather, New Mexico Institute of Mining and Technology Room: 110 |
Monday, November 20, 2017 10:35AM - 10:48AM |
G30.00001: Large-eddy simulation of the passage of a shock wave through homogeneous turbulence N.O. Braun, D.I. Pullin, D.I. Meiron The passage of a nominally plane shockwave through homogeneous, compressible turbulence is a canonical problem representative of flows seen in supernovae, supersonic combustion engines, and inertial confinement fusion. The interaction of isotropic turbulence with a stationary normal shockwave is considered at inertial range Taylor Reynolds numbers, $Re_\lambda=100-2500$, using Large Eddy Simulation (LES). The unresolved, subgrid terms are approximated by the stretched-vortex model (Kosovic et al., 2002), which allows self-consistent reconstruction of the subgrid contributions to the turbulent statistics of interest. The mesh is adaptively refined in the vicinity of the shock to resolve small amplitude shock oscillations, and the implications of mesh refinement on the subgrid modeling are considered. Simulations are performed at a range of shock Mach numbers, $M_s=1.2-3.0$, and turbulent Mach numbers, $M_t=0.06-0.18$, to explore the parameter space of the interaction at high Reynolds number. The LES shows reasonable agreement with linear analysis and lower Reynolds number direct numerical simulations. [Preview Abstract] |
Monday, November 20, 2017 10:48AM - 11:01AM |
G30.00002: Interaction of a Shock Wave with a Homogeneous Field of Acoustic Waves Chao Zhang, Lian Duan Direct numerical simulations (DNS) and linear interaction analysis (LIA) are used to examine significant flow characteristics associated with a homogeneous field of acoustic waves passing through a nominally normal shock wave. The full-fledged nonlinear simulations and the linear analysis are enabled by a pre-cursor numerical database of boundary-layer acoustic radiation that provides incident acoustic fields with high degree of physical realism and applicability. The research contributes to the fundamental understanding of the interaction of a shock wave with a field of turbulence by characterizing its behaviors in the pure dilatational limit and complements existing studies of shock/turbulence interaction with a vorticity-dominated incident turbulent field. [Preview Abstract] |
Monday, November 20, 2017 11:01AM - 11:14AM |
G30.00003: Density Effects on Post-shock Turbulence Structure Yifeng Tian, Farhad Jaberi, Daniel Livescu, Zhaorui Li The effects of density variations due to mixture composition on post-shock turbulence structure are studied using turbulence-resolving shock-capturing simulations. This work extends the canonical Shock-Turbulence Interaction (STI) problem to involve significant variable density effects. The numerical method has been verified using a series of grid and LIA convergence tests, and is used to generate accurate post-shock turbulence data for a detailed flow study. Density effects on post-shock turbulent statistics are shown to be significant, leading to an increased amplification of turbulent kinetic energy (TKE). Eulerian and Lagrangian analyses show that the increase in the post-shock correlation between rotation and strain is weakened in the case with significant density variations (referred to as the ``multi-fluid'' case). Similar to previous single-fluid results and LIA predictions, the shock wave significantly changes the topology of the turbulent structures, exhibiting a symmetrization of the joint PDF of second and third invariant of the deviatoric part of velocity gradient tensor. In the multi-fluid case, this trend is more significant and mainly manifested in the heavy fluid regions. Lagrangian data are also used to study the evolution of turbulence structure away from the shock wave and assess the accuracy of Lagrangian dynamical models. [Preview Abstract] |
Monday, November 20, 2017 11:14AM - 11:27AM |
G30.00004: Shock propagation in media with non-uniform density Daniel Livescu, Yifeng Tian, Farhad Jaberi Flow resolving shock-capturing and shock-resolving simulations are conducted to study the shock propagation in media with non-uniform density. Shock propagation in a simplified one-dimensional configuration is first examined for various types of density profiles. Both shock-capturing and shock-resolving simulations predict the same results, when there is a separation of scales between the shock width and flow scales. The numerical results agree well with theoretical solutions in the case of weak shocks and linearly varying density fields. In the strong shock limit, better agreement with previous results obtained by the method of characteristics is observed when compared with the theoretical solutions. The differences can be attributed to the effects of re-reflected waves immediately behind the shock, which are not considered in the theoretical solutions. For fluctuating density profiles, the numerical results further deviate from the theoretical solutions and exhibit additional long-wavelength oscillations, which are shown to be related to the re-reflected waves. Three dimensional density variations, with and without turbulent velocity fluctuations, are also considered to examine the shock propagation in flows with strongly variable complex density fields. [Preview Abstract] |
Monday, November 20, 2017 11:27AM - 11:40AM |
G30.00005: Analysis of Mixing Layer LES Data with Convective Mach Number 0.9 to 1.3 Clara M. Helm, M. Pino Martin The study of compressible mixing layers is essential to gaining a fundamental physical understanding of the global effects of compressibility on the development of turbulence in shear (Smits \& Dussauge 2006). Research on compressible mixing layers is particularly difficult mainly because of the sensitivity of the mixing layer to initial conditions. A mixing layer occurs naturally in separated shock turbulent boundary layer interactions (STBLIs). We use our STBLI database to study the properties of mixing layers with convective Mach numbers of 0.9, 1.1, and 1.3. We report on the spreading rate, turbulence stress level, vortex shedding frequency, vortex convection velocity, and differences in the three-dimensional form of the vortices. The results are compared with mixing layer data available in literature and evaluated using the various scaling laws that have been proposed over the years. We discuss to what extent the mixing layer in the STBLI represents the canonical case and what additional insight into the is research area it provides. [Preview Abstract] |
Monday, November 20, 2017 11:40AM - 11:53AM |
G30.00006: Effects of non-adiabatic walls on shock/boundary-layer interaction using direct numerical simulations Pedro S. Volpiani, Matteo Bernardini, Johan Larsson The influence of wall thermal conditions on the properties of an impinging shock wave interacting with a turbulent supersonic boundary layer is a research topic that still remains underexplored. In the present study, direct numerical simulations (DNS) are employed to investigate the flow properties of a shock wave interacting with a turbulent boundary layer at free-stream Mach number $M_{\infty}=2.28$ with distinct wall thermal conditions and shock strengths. Instantaneous and mean flow fields, wall quantities and the low-frequency unsteadiness are analyzed. While heating contributes to increase the extent of the interaction zone, wall cooling turns out to be a good candidate for flow control. The distribution of the Stanton number shows a good agreement with prior experimental studies and confirms the strong heat transfer and complex pattern within the interaction region. Numerical results indicate that the changes in the interaction length are mainly linked to the incoming boundary layer as suggested in previous studies (Souverein et al., 2013 and Jaunet et al., 2014). [Preview Abstract] |
Monday, November 20, 2017 11:53AM - 12:06PM |
G30.00007: Stabilizing Effect of Sweep on Low-Frequency STBLI Unsteadiness Michael Adler, Datta Gaitonde A Large-Eddy Simulation database is generated to examine unsteady shock/turbulent boundary-layer-interaction (STBLI) mechanisms in a Mach 2 swept-compression-corner. Such interactions exhibit open separation, with separation relief from the sweep, and lack the closed mean recirculation found in spanwise-homogeneous STBLIs. We find that the swept interaction lacks the low-frequency coherent shock unsteadiness, two-decades below incoming turbulent boundary layer scales, that is a principal feature of comparable closed separation STBLIs. Rather, the prominent unsteady content is a mid-frequency regime that develops in the separated shear layer and scales weakly with the local separation length. Additionally, a linear perturbation analysis of the unsteady flow indicates that the feedback pathway (associated with an absolute instability in spanwise-homogeneous interactions) is absent in swept-compression-corner interactions. This suggests that 1) the linear oscillator is an essential component of low-frequency unsteadiness in interactions with closed separation. 2) Low-frequency control efforts should be focused on disrupting this oscillator. 3) Introduction of 3D effects constitute one mechanism to disrupt the oscillator. [Preview Abstract] |
Monday, November 20, 2017 12:06PM - 12:19PM |
G30.00008: Global modes and transient response of oblique shock/boundary layer interactions at Mach 5.92 Nathaniel Hildebrand, Anubhav Dwivedi, Joseph W. Nichols, Graham V. Candler, Mihailo R. Jovanovic We apply Direct Numerical Simulation (DNS) and global stability analysis to study transitional hypersonic oblique shock/boundary layer interactions. As the incident shock angle increases, 3D instabilities emerge. At the onset of this instability, the global mode is non-oscillatory and selects a spanwise wavenumber that agrees with DNS. Examination of the critical global mode reveals it to be the result of an interaction between small spanwise corrugations at the base of the incident shock, streamwise vortices inside the separation bubble, and spanwise modulation of the bubble strength. Here centrifugal instability plays no role in the self-sustaining mechanism. We use adjoint methods to show how the critical global mode is triggered by disturbances in the impinging shock and the incoming boundary layer. Furthermore, we quantify sensitivity of the critical eigenvalue to base flow modifications by combining direct and adjoint information. Our sensitivity analysis indicates that streamwise vortices inside the separation bubble are crucial to the 3D instability. Although centrifugal instability does not contribute to the critical global mode, it does amplify streamwise streaks downstream of the separation bubble. We quantify this effect through an optimal transient growth analysis. [Preview Abstract] |
Monday, November 20, 2017 12:19PM - 12:32PM |
G30.00009: On the Temporal Evolution in Laminar Separated Boundary Layer Shock- Interaction Flows using DSMC Ozgur Tumuklu, Deborah A. Levin, Vassilis Theofilis Hypersonic laminar boundary layer shock-interactions are characterized by spatial regions with both sub and supersonic flow in various degrees of thermochemical non- equilibrium and multiple length scales. The paper will explore the accurate modeling of such flows in a kinetic framework and address questions related to the role of velocity slip and temperature jump in stability and transition and how these may be influenced by vibrational non-equilibrium. We will discuss recent results that have been obtained with the first ever use of DSMC with linear stability and residuals algorithm analyses to address these questions. Amplitude functions of the least-damped linear global mode for a series of axisymmetric base flows over a double cone will be presented showing the predominant and repeating lambda shock structure at high Reynolds numbers, prior to transition. [Preview Abstract] |
Monday, November 20, 2017 12:32PM - 12:45PM |
G30.00010: Modified geometrical shock dynamics applied to 2D shock wave focusing Heng Liu, Shi Qiu, Veronica Eliasson Shock wave focusing can lead to extreme thermodynamic conditions, and applications have been extended to a variety of areas such as civil engineering and medical treatment. Our current study aims to deepen the understanding of shock focusing process by numerically investigating the interaction of multiple cylindrical shock waves. Solving the inviscid Euler equations can be computationally expensive due to requirements of high resolution at the shock focusing region. Therefore, in this study, the shock focusing scenario is solved using Geometrical Shock Dynamics (GSD) to help reduce the computational cost. The original theory of GSD is based on the assumption that the shock motion is independent from the flow conditions behind the shock front. However, this assumption is not valid for the expansion of cylindrical shock waves. Thus, a modified GSD method is proposed that takes into account the post-shock effects by coupling the post-shock flow conditions obtained from existing data into the original GSD equations. Several comparisons with Euler simulations are performed and the transition from regular to irregular reflection is also discussed. [Preview Abstract] |
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