Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session G32: Turbulent Boundary Layers: High Reynolds Numbers and Pressure Gradient Effects |
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Chair: Michel Stanislas, Ecole Centrale de Lille Room: Oregon Ballroom 201 |
Monday, November 21, 2016 8:00AM - 8:13AM |
G32.00001: Large Scale Organization of a Near Wall Turbulent Boundary Layer Michel Stanislas, Raoul Florent Dekou Tiomajou, Jean Marc Foucaut This study lies in the context of large scale coherent structures investigation in a near wall turbulent boundary layer. An experimental database at high Reynolds numbers (Re$\theta =$9830 and Re$\theta =$19660) was obtained in the LML wind tunnel with stereo-PIV at 4 Hz and hot wire anemometry at 30 kHz [1]. A Linear Stochastic Estimation procedure, is used to reconstruct a 3 component field resolved in space and time. Algorithms were developed to extract coherent structures from the reconstructed field. A sample of 3D view of the structures is depicted in Figure 1. Uniform momentum regions are characterized with their mean hydraulic diameter in the YZ plane, their life time and their contribution to Reynolds stresses. The vortical motions are characterized by their position, radius, circulation and vorticity in addition to their life time and their number computed at a fixed position from the wall. The spatial organization of the structures was investigated through a correlation of their respective indicative functions in the spanwise direction. The simplified large scale model that arise is compared to the ones available in the literature. Streamwise low (green) and high (yellow) uniform momentum regions with positive (red) and negative (blue) vortical motions. \textbf{REFERENCES} \\Joel Delville, Patrick Braud, Sebastien Coudert, Jean-Marc Foucaut, Carine Fourment, WK George, Peter BV Johansson, Jim Kostas, Fahrid Mehdi, and Royer. The wallturb joined experiment to assess the large scale structures in a high Reynolds number turbulent boundary layer. In Progress in Wall Turbulence: Understanding and Modeling, pages 65--73. Springer, 2011. [Preview Abstract] |
Monday, November 21, 2016 8:13AM - 8:26AM |
G32.00002: Turbulent Poiseuille \& Couette flows at high $Re$ Myoungkyu Lee, Robert D. Moser We present the results of direct numerical simulation (DNS) of high $Re$ turbulent Poiseuille and Couette flows. Couette flow has been simulated with a streamwise ($x$) domain that is 100$\pi\delta$ long at Reynolds number up to $Re_\tau \approx 500$. In addition Poiseuille flow simulations up to $Re_\tau \approx 5200$ were performed (Lee \& Moser, {\it J. Fluid Mech.}, {\bf 774}, 2015). In Couette flow, extremely large scale motions, which are approximately 50$\pi\delta$ long in the $x$-direction with very strong intensity, have been observed. In this presentation we will focus on a comparison between these two flows in terms of the vorticity-velocity co-spectra, which are interesting because of the relationship between the Reynolds stress and the velocity-vorticity correlation ($\partial_y \langle u'v' \rangle = \langle w'\omega_y' \rangle - \langle v'\omega_z' \rangle$). Also considered will be the spectra of the turbulent transport term in the evolution equation for the turbulent kinetic energy. In both (co)-spectra it is shown that the difference between the two flows at high $Re$ are primarily at large scales. [Preview Abstract] |
Monday, November 21, 2016 8:26AM - 8:39AM |
G32.00003: Evidence of an asymptotic geometric structure to the Reynolds stress motions in turbulent boundary layers Joseph Klewicki, Jimmy Philip, Caleb Morrill-Winter Recent results suggest that the $uv$ motions in turbulent wall-flows asymptotically exhibit self-similar geometric properties. Herein we use time series from high resolution boundary layer experiments up to high Reynolds numbers to discern additional properties associated with the $uv$ signals. Their space filling properties are shown to reinforce previous observations, while the $uv$ skewness profile suggests that the size and magnitude of these motions are correlated on the inertial domain. The size and length scales of the negative $uv$-motions are shown to increase with distance from the wall, while their occurrences decreases. A joint analysis of the signal magnitudes and their corresponding lengths reveals that the length scales that contribute most to $\langle -uv \rangle$ are distinctly larger than their average size. The $u$ and $v$ cospectra, however, exhibit invariance across the inertial region when their wavelengths are normalized by the width distribution, $W(y)$, of the scaling layer hierarchy surmised from analysis of the mean momentum equation. This distribution is associated with scale dependent zero-crossings in the contributions to $\langle -uv \rangle$, and derivative cospectra of $\langle -uv \rangle$ support the existence of this structural detail. [Preview Abstract] |
Monday, November 21, 2016 8:39AM - 8:52AM |
G32.00004: Time resolved, near wall PIV measurements in a high Reynolds number turbulent pipe flow C. Willert, J. Soria, M. Stanislas, O. Amili, G. Bellani, C. Cuvier, M. Eisfelder, T. Fiorini, N. Graf, J. Klinner We report on near wall measurements of a turbulent pipe flow at shear Reynolds numbers up to $Re_\tau = 40000$ acquired in the CICLoPE facility near Bologna, Italy. With 900 mm diameter and 110 m length the facility offers a well-established turbulent flow with viscous length scales ranging from $y^+ = 85\mu$m at $Re_\tau = 5000$ to $y^+ = 11\mu$m at $Re_\tau = 40000$. These length scales can be resolved with a high-speed PIV camera at image magnification near unity. For the measurement the light of a high-speed, double-pulse laser is focused into a $\approx 300\mu$m thin light sheet that is introduced radially into the pipe. The light scattered by $1\mu$m water-glycerol droplet seeding is observed from the side by the camera via a thin high-aspect ratio mirror with a field of view covering 20mm in wall-normal and 5mm in stream-wise direction. Statistically converged velocity profiles could be achieved using 70000 samples per sequence acquired at low laser repetition rates (100Hz). Higher sampling rates of 10 kHz provide temporally coherent data from which frequency spectra can be derived. Preliminary analysis of the data shows a well resolved inner peak that grows with increasing Reynolds number. (Project funding through EuHIT - www.euhit.org) [Preview Abstract] |
Monday, November 21, 2016 8:52AM - 9:05AM |
G32.00005: Two-dimensional energy spectra in a high Reynolds number turbulent boundary layer Dileep Chandran, Rio Baidya, Jason Monty, Ivan Marusic The current study measures the two-dimensional (2D) spectra of streamwise velocity component ($u$) in a high Reynolds number turbulent boundary layer for the first time. A 2D spectra shows the contribution of streamwise ($\lambda_x$) and spanwise ($\lambda_y$) length scales to the streamwise variance at a given wall height ($z$). 2D spectra could be a better tool to analyse spectral scaling laws as it is devoid of energy aliasing errors that could be present in one-dimensional spectra. A novel method is used to calculate the 2D spectra from the 2D correlation of $u$ which is obtained by measuring velocity time series at various spanwise locations using hot-wire anemometry. At low Reynolds number, the shape of the 2D spectra at a constant energy level shows $\lambda_y \sim \sqrt{z\lambda_x}$ behaviour at larger scales which is in agreement with the literature. However, at high Reynolds number, it is observed that the square-root relationship gradually transforms into a linear relationship ($\lambda_y \sim \lambda_x$) which could be caused by the large packets of eddies whose length grows proportionately to the growth of its width. Additionally, we will show that this linear relationship observed at high Reynolds number is consistent with attached eddy predictions. [Preview Abstract] |
Monday, November 21, 2016 9:05AM - 9:18AM |
G32.00006: Structure Functions in Wall-bounded Flows at High Reynolds Number Xiang Yang, Ivan Marusic, Perry Johnson, Charles Meneveau The scaling of the structure function $D_{\mathrm{ij}}=$\textless ($u_{\mathrm{i}}$(\textbf{x}$+$\textbf{r})-$u_{\mathrm{i}}$(x))($u_{\mathrm{j}}$(\textbf{x}$+$\textbf{r})-$u_{\mathrm{j}}$(\textbf{x}))\textgreater (where $i=$1,2,3 and \textbf{r }is the two-point displacement, $u_{i}$ is the velocity fluctuation in the $x_{i}$ direction), is studied in wall-bounded flows at high Reynolds number within the framework of the Townsend attached eddy model. While the scaling of $D_{\mathrm{ij}}$ has been the subject of several studies, previous work focused on the scaling of $D_{\mathrm{11}}$ for \textbf{r}$=(\Delta x$,0,0) (for streamwise velocity component and displacements only in the streamwise direction). Using the Hierarchical-Random-Additive formalism, a recently developed attached-eddy formalism, we propose closed-form formulae for the structure function$ D_{\mathrm{ij}}$ with two-point displacements in arbitrary directions, focusing on the log region$.$ The work highlights new scalings that have received little attention, e.g. the scaling of $D_{\mathrm{ij}}$ for \textbf{r}$=$(0, $\Delta $y, $\Delta $z) and for $i\ne j$. As the knowledge on D$_{ij\thinspace }$leads directly to that of the Reynolds stress, statistics of the filtered flow field, etc., an analytical formula of D$_{ij}$ for arbitrary \textbf{r} can be quite useful for developing physics-based models for wall-bounded flows and validating existing LES and reduced order models. [Preview Abstract] |
Monday, November 21, 2016 9:18AM - 9:31AM |
G32.00007: DNS of self-similar adverse pressure gradient turbulent boundary layer Julio Soria, Vassili Kitsios, Atsushi Sekimoto, Callum Atkinson, Javier Jim\'enez A direct numerical simulation (DNS) of a self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) at the verge of separation has been set-up and carried out. The DNS APG TBL has a displacement thickness based Reynolds number that ranges up to 30,000. The conditions for self-similarity and appropriate scaling will be highlighted, with the first and second order velocity statistical profiles non-dimensionalised using this scaling. The details of the DNS and the required boundary conditions that are necessary to establish this self-similar APG-TBL will be presented. The statistical properties of the self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) DNS will presented, as will the profiles of the terms in the momentum equation, spanwise/wall-normal kinetic energy spectrum and two-point correlations, which will be compared to those of a zero pressure gradient turbulent boundary layer. [Preview Abstract] |
Monday, November 21, 2016 9:31AM - 9:44AM |
G32.00008: Experimental Measurements of a High Reynolds Num- ber Adverse Pressure Gradient Turbulent Boundary Layer Callum Atkinson, Omid Amili, Michel Stanislas, Christophe Cuvier, Jean-Marc Foucaut, Sricharan Srinath, Jean-Philippe Laval, Christian Kaehler, Rainer Hain, Sven Scharnowski, Andreas Schroeder, Reinhard Geisler, Janos Agocs, Anni Roese, Christian Willert, Joachim Klinner, Julio Soria The study of adverse pressure gradient turbulent boundary layers is complicated by the need to characterise both the local pressure gradient and it’s upstream flow history. It is therefore necessary to measure a significant streamwise domain at a resolution sufficient to resolve the small scales features. To achieve this collaborative particle image velocimetry (PIV) measurements were performed in the large boundary layer wind-tunnel at the Laboratoire de Mecanique de Lille, including: planar measurements spanning a streamwise domain of 3.5m using 16 cameras covering 15$\delta$; spanwise wall-normal stereo-PIV measurements, high-speed micro-PIV of the near wall region and wall shear stress; and streamwise wall-normal PIV in the viscous sub layer. Details of the measurements and preliminary results will be presented. [Preview Abstract] |
Monday, November 21, 2016 9:44AM - 9:57AM |
G32.00009: DNS study of wall-pressure fluctuations in a turbulent boundary layer with large pressure gradients Hiroyuki Abe, Yasuhiro Mizobuchi, Yuichi Matsuo DNS data are used to examine the behavior of wall-pressure fluctuations $p_w$ in a turbulent boundary layer with large adverse and favorable pressure gradients, thus involving separation and reattachment. The Reynolds number $Re_\theta$ based on momentum thickness is equal to 300, 600 and 900. Comparison is also made with recent experiment by Weiss et al. (2015) for $Re_\theta=5000$. Particular attention is given to the scaling law focusing on maximum value of each Reynolds stress. It is shown that rms value of $p_w$ normalized by dynamic pressure is about twice larger near separation and reattachment than for zero-pressure gradient. In the former regions, $p_w$ is affected noticeably by outer-layer pressure fluctuations where low pressure regions are closely associated with large-scale motions of negative streamwise velocity fluctuations. Among the scalings, rms value of $p_w$ normalized by maximum Reynolds shear stress (Simpson et al. 1987; Na \& Moin 1998) leads to near plateau in adverse pressure gradient and separated regions, indicating that shear stress makes significant contribution to $p_w$. This scaling also holds reasonably near reattachment where the scaling with maximum wall-normal Reynolds stress, pointed out by Ji \& Wang (2012) for steps, yields better collapse. [Preview Abstract] |
Monday, November 21, 2016 9:57AM - 10:10AM |
G32.00010: The laminarescent region in the quasi-laminarization process: a vorticity dynamics perspective Guillermo Araya, Daniel Rodriguez, Carlos Quinones Incompressible turbulent boundary layers subject to severe acceleration or strong Favorable Pressure Gradient (FPG) might experience a quasi-laminarization or a reversion process characterized by a meaningful depression of Reynolds shear stresses and reduction of turbulent production attributed to the dominance of pressure forces. Direct Numerical Simulation (DNS) of highly accelerated turbulent boundary layers is performed in order to shed some light on the energy redistribution, transport phenomena and vorticity dynamics of the laminarescent stage during the quasi-laminarization process. This region is one of the constituents of “The Island of Ignorance” according to Sreenivasan [Acta Mech. 44, pp1-48, 1982]. In a recent article by Araya, Castillo and Hussain [Journal of Fluid Mechanics, 775, pp189 - 200, 2015], DNS of an initially fully turbulent flow subjected to a very strong FPG has shown reduction of the Reynolds shear stresses with a logarithmic behavior in the mesolayer region, associated with the trend of the wall-normal advection in that region, i.e. $V^{+}\partial U^{+}/\partial y^{+} \sim 1/y^{+}$ $\Big(\sim \partial{\overline{u'v'}^{+}}/\partial{y^+}\Big)$. [Preview Abstract] |
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