Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session A35: Compressible Flow I: General Turbulence |
Hide Abstracts |
Chair: Sharath Girimaji, Texas A&M University Room: 2001A |
Sunday, November 23, 2014 8:00AM - 8:13AM |
A35.00001: p-adaption for compressible flow problems using a goal-based error estimator Dirk Ekelschot, David Moxey, Joaquim Peiro, Spencer Sherwin We present an approach of applying p-adaption to compressible flow problems using a dual-weighted error estimator. This technique has been implemented in the high-order h/p spectral element library Nektar$++$. The compressible solver uses a high-order discontinuous Galerkin (DG) discretization. This approach is generally considered to be expensive and that is why the introduced p-adaption technique aims for lowering the computational cost while preserving the high-order accuracy and the exponential convergence properties. The numerical fluxes between the elements are discontinuous which allows one to use a different polynomial order in each element. After identifying and localizing the sources of error, the order of approximation of the solution within the element is improved. The solution to the adjoint equations for the compressible Euler equations is used to weigh the local residual of the primal solution. This provides both the error in the target quantity, which is typically the lift or drag coefficient, and an indication on how sensitive the local solution is to the target quantity. The dual-weighted error within each element serves then as a local refinement indicator that drives the p-adaptive algorithm. The performance of this p-adaptive method is demonstrated using a test case of subsonic flow past a 3D wing geometry. [Preview Abstract] |
Sunday, November 23, 2014 8:13AM - 8:26AM |
A35.00002: 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 The effects of finite span on the control of surface pressures within an open cavity in Mach 1.4 flow are studied. Experiments involve a finite span, rectangular cavity with a length to depth ratio of 6 and width to depth ratio of 2 being characterized using unsteady pressure along the floor and Particle Image Velocimetry (PIV). This data is first compared to measurements taken with a full span cavity of the same length to depth ratio to elucidate the flow phenomena caused by the introduction of sidewalls. Thereafter various leading edge slot configurations are employed and their effects compared to previous experiments involving the finite span cavity to gauge the influence of blowing on the three-dimensional flow field. The effectiveness of the slot blowing to suppress the pressure fluctuations are evaluated by examining reductions in both the tonal and broadband levels of the fluctuating surface pressure spectra. PIV data inside the finite span cavity show changes in the mean properties of the flow field when comparing the baseline to the slot blowing cases. Specifically the interaction of blowing with the flow near the cavity sidewalls, the shear layer, and the recirculation region are of interest. [Preview Abstract] |
Sunday, November 23, 2014 8:26AM - 8:39AM |
A35.00003: On the use of entropy viscosity based high order discontinuous spectral element method for capturing shocks Arnab Chaudhuri, Hesam Abbassi, Gustaaf B. Jacobs, Farzad Mashayek A modified entropy viscosity (EV) based high order discontinuous spectral element method (DSEM) has been proposed to deal with compressible flows involving shocks. Particular attention has been made to control undesired artificial dissipation dictated by entropy generation in shock-free shear dominated regions of the flow-field. A shock sensor based EV switch is used for this purpose. Implementation of the proposed method on an existing 3D parallel DSEM solver is successfully verified and validated with numerous benchmark problems. The effectiveness and applicability of stabiliser filters together with EV switch for various steady and unsteady flow configurations involving flow discontinuities are also tested. Results of simulations of compressible subsonic-to-supersonic flows over ramped cavity geometry, moving shocks over wedge involving regular/irregular Mach reflections are presented. [Preview Abstract] |
Sunday, November 23, 2014 8:39AM - 8:52AM |
A35.00004: DNS and LIA analysis of the shock turbulence interaction Daniel Livescu, Jaiyoung Ryu The interaction between isotropic turbulence and a normal shock wave is studied using Direct Numerical Simulations (DNS), with all flow scales (including the shock width) accurately solved, and the Linear Interaction Analysis (LIA). The turbulence quantities from DNS converge to the LIA solutions as the turbulent Mach number, $M_t$, becomes small, even at low upstream Reynolds numbers. This reconciles a long time open question about the role of LIA and establishes it as a reliable prediction tool for turbulence-shock interaction problems when there is a significant separation between the shock width and turbulence scales and $M_t$ is low, which is encountered in many practical applications. The final LIA formulas are extended to investigate detailed turbulence physics. The extended LIA relations are used to show consistency with the DNS results and study the interaction at high $M_s$, where the resolution requirements make DNS studies unfeasible. The results show that the shock wave significantly changes the topology of the turbulent structures, with a symmetrization of the third invariant of the velocity gradient tensor and ($M_s$ mediated) of the PDF of the longitudinal velocity derivatives, and an $M_s$ dependent increase in the correlation between strain and rotation. [Preview Abstract] |
Sunday, November 23, 2014 8:52AM - 9:05AM |
A35.00005: ABSTRACT WITHDRAWN |
Sunday, November 23, 2014 9:05AM - 9:18AM |
A35.00006: Generation of compressible turbulence using lasers as sources of intense energy Agustin Maqui, Diego Donzis Intense energy from lasers can be used to photo-dissociate molecules, ejecting fragments with extremely high energy. This energy can be in the form of translation (kinetic energy) as well as rotation and vibration for more complex molecular systems. When lasers are used in a flow, ``lines'' of concentrated kinetic and internal energy are generated. It is of fundamental as well as practical interest to know whether this source of energy is sufficient to generate turbulence downstream of a supersonic flow. Direct numerical simulations (DNS) are used to study how the flow evolves past the photo-excitation of molecules. Convergence studies are carried out to understand the numerical challenges associated with the strong gradients imposed by the intense energy fluctuations. A comprehensive analysis of single, as well as two point statistics is performed to understand the development towards realistic turbulence. The perturbations introduced are fully characterized to analyze how they determine the flow evolution and if the conditions can be replicated within a wind tunnel. Further results and consequences for particular cases realizable in laboratories will be discussed. [Preview Abstract] |
Sunday, November 23, 2014 9:18AM - 9:31AM |
A35.00007: Stability of vortical structures of high and low speed mixing layers Mona Karimi, Sharath Girimaji It is known that mixing layers feature spanwise rollers and long streamwise vortices at low Mach numbers. At high speeds, the spanwise rollers are less evident. In this presentation, we attempt to identify the underlying instability mechanisms that ultimately lead to the growth or stabilization of different structures. Specifically, we examine the effect of Mach number and perturbation orientation on vorticity production. The nature of vortex stretching at different Mach numbers is investigated and the change in its character due to the onset dilatational velocity fluctuations is established. It is shown that the dilatational field suppresses spanwise rollers while leaving the streamwise vorticity intact. [Preview Abstract] |
Sunday, November 23, 2014 9:31AM - 9:44AM |
A35.00008: ABSTRACT WITHDRAWN |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700