Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena最新文献

{"title":"Turbulent pipe flow response to wall changes targeting specific azimuthal modes","authors":"T. Buren, L. Hellström, I. Marusic, A. Smits","doi":"10.1615/tsfp10.880","DOIUrl":"https://doi.org/10.1615/tsfp10.880","url":null,"abstract":"We present an experimental study on the response of turbulent pipe flow at Reτ = 3486 to rapid changes in pipe shape that are designed to manipulate the Large Scale and Very Large Scale Motions in wall-bounded turbulence. Stereo PIV measurements were taken 5 pipe diameters downstream of 3D printed pipe inserts designed to target specific azimuthal Fourier mode numbers m = 3 and 15. Direct manipulation of the flow momentum (vortex generators) and secondary flows induced by Reynolds stresses (sinusoidally varying wall shape) are considered. The designs successfully modified the mean flow to contain structures mimicking the desired Fourier mode shapes. The energy was added directly to the targeted modes, and secondary peaks in energy existed in non-targeted modes indicating nonlinear interactions. At the same time, other modes showed relatively significant losses of energy, indicating that the pipe inserts were gathering energy into predefined flow structure.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"401 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115919691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wind tunnel experiments of flow and dispersion in building arrays","authors":"M. Carpentieri, P. Hayden, A. Robins","doi":"10.1615/tsfp10.760","DOIUrl":"https://doi.org/10.1615/tsfp10.760","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"57 8 Suppl 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115584343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A GLOBAL MODE ANALYSIS OF FLAPPING FLAGS","authors":"Andres Goza, T. Colonius","doi":"10.1615/tsfp10.190","DOIUrl":"https://doi.org/10.1615/tsfp10.190","url":null,"abstract":"We perform a global stability analysis of a flapping flag in the conventional configuration, in which the flag is pinned or clamped at its leading edge, and in the inverted configuration, in which the flag is clamped at its trailing edge. Specifically, we consider fully coupled fluid-structure interaction for two-dimensional flags at low Reynolds numbers. For the conventional configuration, we show that the unstable global modes accurately predict the onset of flapping for a wide range of mass and stiffness ratios. For the inverted configuration, we identify a stable deformed equilibrium state and demonstrate that as the flag becomes less stiff, this equilibrium undergoes a supercritical Hopf bifurcation in which the least damped mode transitions to instability. Previous stability analyses of inverted flags computed the leading mode of the undeformed equilibrium state and found it to be a zero-frequency (non-flapping) mode, which does not reflect the inherent flapping behavior. We show that the leading mode of the deformed equilibrium is associated with a non-zero frequency, and therefore offers a mechanism for flapping. We emphasize that for both configurations the global modes are obtained from the fully-coupled flow-flag system, and therefore reveal both the most dominant flag shapes and the corresponding flow structures that are pivotal to flag flapping behavior. INTRODUCTION Global stability analysis has been used to elucidate important instability-driving mechanisms in a variety of fluid flows, including bluff body flows (Noack & Eckelmann, 1994), jet flows (Bagheri et al., 2009), and boundary layers (Ehrenstein & Gallaire, 2005). Extending this analysis to fully-coupled flow-structure interaction problems with deforming bodies presents several challenges, and (to our knowledge) has not been done before. We present here an analysis of the fully-coupled problem of flow past a deformable flag in both the conventional and inverted configurations, as depicted in figure 1.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116585203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LARGE EDDY SIMULATION OF TURBULENT FLOW OVER A WALL UNDERGOING STREAMWISE TRAVELLING WAVE MOTION","authors":"Wu-Yang Zhang, Weixing Huang, Chunxiao Xu","doi":"10.1615/tsfp10.720","DOIUrl":"https://doi.org/10.1615/tsfp10.720","url":null,"abstract":"Turbulent channel flow with a wall undergoing travelling wave motion in streamwise direction was investigated using large eddy simulations at friction Reynolds number Re*=1000. Phase average and decomposition were used in the analysis of the flow field. Compared to flat wall turbulence, the large-scale motions in the outer layer are significantly enhanced by the traveling wave boundary. Obvious large-scale peaks in outer layer for all the three velocity components could be observed in the spanwise pre-multiplied energy spectra. A strengthened superposition effect of streamwise velocity fluctuation could also be seen in both energy spectra and conditionally averaged flow fields. The analysis of the two-point correlation function transport equation shows that the wave motion of the wall taking effect on the largescale motion in the outer layer is mainly through the wave-induced production. INTRODUCTION The coupling dynamic processes between surface waves and turbulent flow are related to many complicated flow phenomena, such as the effect of the wind-induced wave to momentum flux at the ocean surface, and to the mixing and transport in the upper ocean. A fundamental understanding of the interaction of wave and turbulence is of significance in geophysics and ocean engineering. Existing researches show that turbulent flow over moving boundary has a significant difference with canonical flat plate boundary layer. For instance, Sullivan et al (2000) and Yang & Shen (2010) used the progressive wave wall as the idealized water wave and investigated the influence of wave to the momentum flux and coherence structures of turbulence. In recent years, the large-scale motions scaled by the outer scale in the outer region of wall turbulence were found and confirmed at high Reynolds numbers (Kim & Adrain, 1999; Hutchins & Marusic, 2007a). Moreover, the influence of large-scale motions on near-wall fluctuations could be summarized to the superposition and modulation effects (Hutchins & Marusic, 2007b). In the present work, we studied the turbulent flow over a traveling wavy wall by using large-eddy simulation and focused on the influence of the wavy boundary on the large-scale motions in the outer layer. In order to identify the wave-turbulence interactions, phase average and decomposition (Hussain & Reynolds, 1970) were used in the analysis of the flow field. The significantly enhanced effect on large-scale motions by wavy boundary could be observed in spanwise energy spectra of fluctuating velocity components and conditionally averaged flow fields. We also performed a spectral analysis of the twopoint correlation function transport equation to investigate the mechanism of the wave motion of the wall effecting the large-scale motions in the outer layer. PROBLEM FORMULATION AND NUMERICAL METHOD The problem considered is a fully developed threedimensional turbulent flow in a half channel over a wall undergoing traveling wave motion in the streamwise direction. A s","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129911764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shock-bubble Interaction Near a Compliant Tissue-like Material","authors":"Shucheng Pan, S. Adami, Xiangyu Y. Hu, N. Adams","doi":"10.1615/tsfp10.420","DOIUrl":"https://doi.org/10.1615/tsfp10.420","url":null,"abstract":"In this work, we present numerical simulation results for \u0000shock-induced bubble collapse dynamics near tissue-like compliant \u0000gelatin phase. We use a sharp-interface model for multiple materials \u0000to represent the ambient liquid (water), the non-condensable gas \u0000phase (air) and the gelatin phase. Employing multi-resolution techniques, \u0000we investigate the complex interface dynamics and compare \u0000the results with experimental data from literature. Our aim is \u0000to understand and quantify the mechanisms observed during extracorporeal \u0000shock-wave lithotripsy or sonoporation. Therefore, latestage \u0000dynamics of the bubble collapse and tissue penetration are \u0000presented.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"311 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123478364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"TRANSITIONS IN A SOFT-WALLED CHANNEL","authors":"V. Kumaran, S. Srinivas","doi":"10.1615/tsfp10.590","DOIUrl":"https://doi.org/10.1615/tsfp10.590","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131741683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ON THE ANISOTROPY OF THE LINEAR MECHANISM OF AERODYNAMIC SOUND GENERATION BY VORTICAL PERTURBATIONS IN SHEAR FLOWS","authors":"Janice Hau, M. Oberlack, G. Chagelishvili","doi":"10.1615/tsfp10.1020","DOIUrl":"https://doi.org/10.1615/tsfp10.1020","url":null,"abstract":"We investigate the basics of the linear generation of acoustic waves by vortex modes in homentropic compressible flows with constant shear of velocity, U0 = (Ay,0,0). The mathematical and physical aspects of the generation are grasped by analyzing the dynamics of single, up-shear tilted pure vortex spatial Fourier harmonics (SFHs). The key to comprehending the wave generation process is the possibility of splitting the perturbation field of the considered SFH into its vortex and wave parts at the moment of abrupt wave emergence. Essentially, the linear wave generation mechanism by vortex SFHs in three dimensions (3-D) is similar as in two dimensions (2-D), whereas latter dominates the generation process. The anisotropy of this linear mechanism is also active in 3-D and, thus, confirms the conclusion drawn by Hau et al. (2015) that the anisotropic linear generation mechanism is missed by any formulation of an acoustic analogy as introduced by Lighthill (1952, 1954) due to their topological incompatibility.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134371170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"UNSTEADY CHARACTERISTICS OF TIP-LEAKAGE FLOW IN AN AXIAL FLOW FAN","authors":"Keuntae Park, Haecheon Choi, Seokho Choi, Y. Sa, Oh-kyoung Kwon","doi":"10.1615/tsfp10.1060","DOIUrl":"https://doi.org/10.1615/tsfp10.1060","url":null,"abstract":"An axial flow fan with a shroud generates complicated tip-leakage flow by the interaction of the axial flow with the fan blades and shroud near the blade tips. In this study, large eddy simulation (LES) is performed for tip-leakage flow in a forward-swept axial flow fan inside an outdoor unit of an air-conditioner (Fig. 1), operating at the design condition of the Reynolds number of 547,000 based on the radius of blade tip and the tip velocity. A dynamic global model (Lee et al., 2010) is used for a subgrid-scale model, and an immersed boundary method in a non-inertial reference frame (Kim and Choi, 2006) is adopted. Schematic diagram of the coordinates, computational domain and boundary conditions are shown in Fig. 1(c). The present simulation reveals the evolution of tip-leakage vortex (TLV) near the blade tip. After inception of TLV near the leading edge of the suction-side of the blade tip, it develops downstream, and migrates toward the pressure surface of the following blade (Fig. 2(a)). Along the trajectory of the TLV, the turbulent kinetic energy and pressure fluctuations are high due to the oscillatory feature of the TLV. Energy spectra of the velocity fluctuations near the following blade and the trajectory of the TLV indicate that the TLV shows low-frequency wandering movement (Figs. 2(b)-(d)).","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133309523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SPATIAL DISTRIBUTION OF ENERGY DISSIPATION IN A TURBULENT CYLINDER WAKE","authors":"Jiangang Chen, Yu Zhou, R. Antonia, T. Zhou","doi":"10.1615/tsfp10.840","DOIUrl":"https://doi.org/10.1615/tsfp10.840","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123377950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"INTENSE FOCAL AND REYNOLDS STRESS STRUCTURES OF A SELF-SIMILAR ADVERSE PRESSURE GRADIENT TURBULENT BOUNDARY LAYER","authors":"A. Sekimoto, V. Kitsios, C. Atkinson, J. Jiménez, J. Soria","doi":"10.1615/tsfp10.130","DOIUrl":"https://doi.org/10.1615/tsfp10.130","url":null,"abstract":"The turbulence statistics and structures of a self-similar adverse pressure gradient turbulent boundary layer (APGTBL) are investigated using direct numerical simulation (DNS) of the flow at the verge of separation. The desired self-similar APG-TBL is achieved by a modification of the far-field velocity boundary condition. The required wallnormal velocity in the far-field to produce the necessary adverse pressure gradient was estimated based on the analytical free-stream streamwise velocity distribution for a flow at the point of separation, and the assumption that the streamlines of the outer flow follow the growth of the boundary layer thickness. The APG-TBL develops over a momentum thickness based Reynolds number upto 12000, and achieves a self-similar region of constant friction coefficient, pressure velocity and shape factor. Turbulence statistics in this region show self-similar collapse by using the scaling of the external velocity and the displacement thickness. In this study, the structure of the APG-TBL is investigated using topological methodology and visualisation techniques for a zero pressure gradient turbulent boundary layer (ZPG-TBL) and for the self-similar APG-TBL. The second invariants of the velocity gradient tensor (VGT), which are representative of coherent structures dominated by vortical motions, show a stark difference in the structure and location of coherent vortical structures that exists between the self-similar APGTBL and a ZPG-TBL. Further details based on the structure and distributions of the invariants of VGT and intense Reynolds stress structures of the self-similar APG-TBL are presented.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116282457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}