Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session G40: Turbulent Boundary Layers: Curvature and Pressure Gradients I |
Hide Abstracts |
Chair: Antonino Ferrante, University of Washington Room: 6b |
Sunday, November 24, 2019 3:48PM - 4:01PM |
G40.00001: Direct numerical simulation of turbulent flows over curved walls with adverse pressure gradient Abhiram Aithal, Antonino Ferrante Flow separation over curved walls with adverse pressure gradient (APG) occurs in many aerodynamic applications. However, the physical mechanisms of turbulence over curved bodies with APG are not yet well understood and the wall models employed in Reynolds-averaged Navier-Stokes (RANS) and large-eddy simulations (LES) for such flows need to be improved. In order to provide the necessary statistics for the validation of such models and explain the physical mechanisms of such flows, we have performed direct numerical simulations (DNS) over curved walls with APG. First, we have developed a fully-explicit and direct pressure-correction method to solve the incompressible NS equations in orthogonal curvilinear coordinates called FastRK3. FastRK3 is a three-stage, third-order Runge-Kutta projection-method which requires solving the Poisson equation for pressure only once per time step. Then, we have verified and validated FastRK3 with several test-cases and against available experiments. Last, we have performed a DNS study of the turbulent separated flow over a curved ramp and studied the dynamics of its turbulence kinetic energy. [Preview Abstract] |
Sunday, November 24, 2019 4:01PM - 4:14PM |
G40.00002: Non-equilibrium three-dimensional boundary layers at moderate Reynolds numbers Marco G. Giometto, Adrian Lozano-Duran, George I. Park, Parviz Moin Non-equilibrium wall turbulence with mean-flow three-dimensionality is ubiquitous in geophysical and engineering flows. Under these conditions, turbulence may experience a counter-intuitive depletion of the turbulent stresses, which has important implications for modeling and control. Current turbulence theories are established mainly for statistically two-dimensional equilibrium flows and cannot predict such a behavior. In the present work, we propose a multi-scale model explaining the response of non-equilibrium wall-bounded turbulence under the imposition of three-dimensional strain. The analysis is performed via direct numerical simulation of turbulent channels at friction Reynolds numbers up to 1000. We show that scaling properties of the Reynolds stress are consistent with a model comprising momentum-carrying eddies with sizes and time scales proportional to their distance to the wall. We further demonstrate that the reduction in Reynolds stress follows a spatially and temporally self-similar evolution caused by the relative horizontal displacement between the core of the momentum-carrying eddies and the flow layer underneath. [Preview Abstract] |
Sunday, November 24, 2019 4:14PM - 4:27PM |
G40.00003: Characteristics of the so-called uniform momentum zones and vortical fissures in a turbulent boundary layer downstream of an adverse pressure gradient Alireza Ebadi, Christopher White Particle image velocimetry (PIV) data acquired in a turbulent boundary layer downstream of an adverse pressure gradient at high Reynolds number is analyzed to study the characteristics of the so-called uniform momentum zones (UMZs) and vortical fissures (VFs) in the inertial region of the flow (where the viscous forces are subdominant). These characteristics, which include the wall-normal width of the UMZs and VFs, the velocity jump and vorticity across VFs, among others, are compared to those of the zero pressure gradient boundary layer at similar Reynolds number at the same facility. [Preview Abstract] |
Sunday, November 24, 2019 4:27PM - 4:40PM |
G40.00004: A new correlation for predicting transition Reynolds number of varying turbulence intensity with pressure gradient. Wei-Tao Bi, Meng-Juan Xiao, Fan Tang, Zhen-Su She We report a new finding on the correlation predicting the laminar-turbulent transition of a boundary layer for varying incoming turbulence intensity and pressure gradient. The new correlation displays a simple scaling of the transition Reynolds number on the incoming turbulence intensity, much simpler than previously proposed empirical ones, owing to an introduction of a transition central location parameter by our newly proposed symmetry-based description of the laminar-turbulent transition. Excellent agreement between the theory and the measurement/simulation data is found for the skin friction and wall heat flux distributions throughout the transition, as accurately validated by the T3-series flat-plate transition experiment and computation data. Owing to its simplicity, the transition model using the current correlation may have significant engineering interest. Furthermore, the results demonstrate that one may uncover simple similarity law governing the transition onset for both natural and bypass transitions, once relevant (statistical) multilayer structure of TBL is represented. The discovery of such similarity law does not require detailed analysis of complex instability mechanisms of the transition. Future work would be to quantify more transition effects, e.g. those in hypersonic engineering flows, which has been extremely difficult via the traditional approach. [Preview Abstract] |
Sunday, November 24, 2019 4:40PM - 4:53PM |
G40.00005: The effect of concave surface curvature on supersonic turbulent boundary layers Christian Lagares, Kenneth Jansen, Guillermo Araya Unsteady 3D turbulent boundary layers that evolve along the flow direction exhibit a streamwise non-homogeneous condition and pose enormous computational challenges. The reasons are as follows: (i) full spectrum resolution of turbulence, (ii) accurate time-dependent inflow turbulence information, and (iii) compressibility effects. Moreover, accounting for the effects of wall-curvature driven pressure gradient adds significant complexity to the problem. In this presentation, we will show recent Direct Numerical Simulation (DNS) with high spatial/temporal resolution of supersonic spatially-developing turbulent boundary layers (SDTBL) subject to strong concave curvature ($\delta_{inlet}$/R $\approx$ -0.083, R is the curvature radius) and Mach = 2.86, which are of crucial importance in aerospace applications (e.g. unmanned high-speed vehicles and scramjets). The prescribed curved geometry is based on the experimental study by Donovan et al. (J. Fluid Mech., 259, 1-24, 1994). Turbulent inflow conditions are based on extracted data from a previous DNS over a flat plate (precursor). The extensive DNS information will shed important light on the transport phenomena inside turbulent boundary layers subject to strong deceleration or Adverse Pressure Gradient (APG) caused by concave walls. [Preview Abstract] |
Sunday, November 24, 2019 4:53PM - 5:06PM |
G40.00006: ABSTRACT WITHDRAWN |
Sunday, November 24, 2019 5:06PM - 5:19PM |
G40.00007: Adaptive simulations and experiments of the turbulent flow around a NACA 4412 profile at high $Re$ Fermin Mallor, Alvaro Tanarro, Eda Dogan, Agastya Parikh, Nicolas Offermans, Adam Peplinski, Ramis {\"O}rl{\"u}}, Ricardo Vinuesa, Philipp Schlatter Turbulent boundary layers (TBLs) under strong pressure gradients (PG), as appearing on wing surfaces, are still an active research topic. The NACA 4412 has been a benchmark airfoil in the study of PG-TBLs as its surface pressure distribution is only weakly dependent on Reynolds number ($Re$) at moderate angles of attack (AoA). This allows to decouple PG (history) and $Re$ effects affecting the development of the TBL. Using the high-order spectral-element method code Nek5000, large-eddy simulations of a NACA 4412 profile at a $5^o$ AoA are carried out. Adaptive Mesh Refinement (AMR) is used to generate a non-conformal mesh highly refined in the boundary layer and wake regions and avoiding the over-refinement of the far-field typical of structured conformal meshes. A larger domain is used while reducing by a factor of three the number of grid points, allowing to increase $Re$, aiming for 1,640,000 used in the experiments of the 1970s and 80s on the same airfoil. Such well-validated simulation data can then be used to understand better the effect of PG and surface curvature, and allow the calibration of turbulence and wall models. Moreover, an experimental campaign is planned in the MTL wind tunnel at KTH, for which wall liners are designed aiming at reducing blockage effects. [Preview Abstract] |
Sunday, November 24, 2019 5:19PM - 5:32PM |
G40.00008: Measurements in the near-wake of a turbulent wing-body junction J. Klewicki, J.H. Lee, S. Zimmerman, J. Monty Turbulent wing-body junction flows arise from the interaction between a turbulent boundary layer and a surface mounted streamlined obstacle, and are frequently encountered in aerodynamic and hydrodynamic applications. This study uses two-dimensional, three component stereo PIV measurements to investigate the statistical and instantaneous properties of a wing-body near-wake at moderate Reynolds number. The measurements were acquired in an open-return boundary layer wind tunnel at the University of Melbourne. The approach zero pressure gradient boundary layer at $R_{\theta} = 10,000$ interacts with a ‘Rood wing’ composed of a 3:2 elliptical leading edge joined to a NACA 0020 profile, with a chord length C =168mm, maximum thickness T =40mm, and height H = 80mm. The freestream velocity was about 20 m/s. Three component velocity measurements were collected at five different streamwise locations ranging from 0.075C to 1C downstream of the trailing edge of the airfoil, whose angle-of-attack was also varied from -15 to +15 degrees in increments of 5 degrees. Results focus on the three dimensional structure of the near-wake flow and the influence of the necklace vortices that form in front of the body and pass through the wake. Variations with angle of attack are described. [Preview Abstract] |
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