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

{"title":"SCALING AND CORRELATION OF FLUCTUATING VORTICITY IN TURBULENT WALL LAYERS","authors":"R. Panton","doi":"10.1615/tsfp8.640","DOIUrl":"https://doi.org/10.1615/tsfp8.640","url":null,"abstract":"Asymptotic expansions for the profiles of fluctuating vorticity in boundary layers are proposed based on DNS data. The inner region requires two terms with different scalings; < ! i ! i > /(U 0 u \" 3 / # 2 ) and < ! i ! i > /(u \" 4 / # 2 ) . The first term decays exponentially and needs no matching term in the outer region. The second term has an overlap behavior of ~ C / y . To match the outer region this requires a third scaling for the outer expansion < ! i ! i > /(u \" 3 / #$ ) . This scaling turns out to be the Kolmogorov time scale. INTRODUCTION From a mathematical viewpoint the theory of turbulent wall layers is a singular perturbation problem for large Reynolds numbers. Profiles are expressed as matched asymptotic expansions. There are three parts; an expansion for the outer region, an expansion for the inner region, and a common part that matches the two. The velocity profile is a well-known example. For the outer region the profile has an expansion consisting of two terms.","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128052108","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":"COMPARISON OF NEAR-FIELD EVENTS AND THEIR FAR-FIELD ACOUSTIC SIGNATURES IN EXPERIMENTAL AND NUMERICAL HIGH SPEED JETS","authors":"P. Kan, J. Lewalle, G. Daviller","doi":"10.1615/tsfp8.1410","DOIUrl":"https://doi.org/10.1615/tsfp8.1410","url":null,"abstract":"Two different approaches are applied to near-field (NF) velocity field and far-field (FF) pressure signals to gain better understanding of the flow structures that contribute to high speed jet noise. We use laboratory data from a 10kHz TRPIV experiment data of Mach 0.6 jet and numerical data from an 80kHz LES database at Mach 0.9 jet. From the NF, over 20 representative diagnostics are extracted as time traces, of which about half give high correlation with the far-field. Utilizing cross-correlation and wavelet analysis, we locate the frequency band where information is transferred from NF to FF. Furthermore we identify excerpts in time and frequency domain that act as major correlation contributors. The lists of events based on FF only (acoustic footprints) and on NF-FF correlations are compared and show good similarity, which validates both techniques. Finally, the lists of events are separated into categories based on their properties, including magnitude, frequency, and axial and transverse location. INTRODUCTION The noise sources of high speed jet was initially assumed to be random, until the discovery of turbulent coherent structures offered another view to understanding the dynamics. Coherent structures are firstly found to be in part responsible for the occurrence of acoustic spectrum peak (Mollo-Christensen, 1967; Crow and Champagne, 1971). The frequency range associated with the loudest noise was found to be 0.1 < St < 0.7 (Michalke, 1977). Coherent structures are more amenable to flow control toward noise reduction, and related studies dominate the literature. The level of coherence was important for jet noise production since a periodic shear layer would not generate farfield noise. Also, it was shown by Michalke and Fuchs (1975) that while the first few azimuthal modes were associated with far-field noise, the axisymmetric mode is not the most efficient. This was related to the coherence level of the velocity field, defined as the ratio of the size of the source to that of the eddies. From the research of Wei and Freund (2006), the more ordered propagation of near-field structures was related with the far-field noise reduction. Cavalieri et al. (2011b) showed that the far-field pressure reFigure 1. Experimental facilities of jet flow measurement (courtesy K.R. Low). sulted from the near-field wave packets propagating through a modeled flow field had good correspondence with the experimental data. What we observe in this paper adds to the coherent part of analysis. DATA DESCRIPTION In this study, we use two sets of data, one experimental and the other numerical. Our two algorithms, distinct for far-field and near-field processing, are applied to both databases, providing validation of the procedures in spite of the different Mach numbers. Experimental Data The experiment was performed in a large-scale (approximately 8000 f t3) anechoic chamber in Syracuse University. The data we use for this paper is for a cold jet with Ma = 0.6 and i","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"36 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":"116679981","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":"QUANTIFYING UNCERTAINTIES IN TURBULENT FLOW SIMULATIONS","authors":"G. Iaccarino, M. Emory","doi":"10.1615/tsfp8.1660","DOIUrl":"https://doi.org/10.1615/tsfp8.1660","url":null,"abstract":"The Reynolds averaged Navier-Stokes equations represent an attractive alternative to direct numerical simulation of turbulence due to their simplicity and reduced computational expense. In the literature it is well established that structure of Reynolds averaged turbulence models are fundamentally limited in their ability to represent the turbulent processes introducing epistemic model-form uncertainty into the predictions. Sensitivity analysis and probabilistic approaches have been used to address these uncertainties, however there is no well established framework within the turbulence modeling community to quantify this important source of error. This work introduces a new approach for addressing epistemic uncertainty which is then demonstrated for the ow over a 2D transonic bump configuration. The well known SST k-ω turbulence model is considered. The reported quantities are the wall pressure, separation location, and reattachment location along the bottom wall of the domain. The results show the new method is able to introduce bounding behavior on the numerical and experimental predictions for these quantities.","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth 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":"117144297","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":"MODELING OF TURBULENCE EFFECT ON RADAR REFLECTIVITY FACTOR IN CLOUDS","authors":"K. Matsuda, R. Onishi, Masaaki Hirahara, Keiko Takahashi, R. Kurose, S. Komori","doi":"10.1615/tsfp8.1110","DOIUrl":"https://doi.org/10.1615/tsfp8.1110","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"55 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":"115061825","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 THE NEAR WAKE OF A HEATED SPHERE AT RE=10,000","authors":"M. Stadler, S. Sarkar","doi":"10.1615/tsfp8.1780","DOIUrl":"https://doi.org/10.1615/tsfp8.1780","url":null,"abstract":"Large eddy simulation is used to numerically simulate flow past a heated sphere at Re=10,000. A second order accurate in space and time, semi-implicit finite difference code is used with the immersed boundary to represent the sphere in a Cartesian domain. Visualizations of the vorticity field and temperature field are provided together with profiles of the temperature and velocity fields at various locations in the wake. The laminar separated shear layer was found to efficiently transport temperature from the hot sphere surface to the cold fluid in the wake. Pronounced Kelvin-Helmholtz induced rollers are formed which destabilize the separated shear layer and promote mixing. Calculations of the wake dimensions showed that the wake dimensions of the velocity field and the temperature field differ by 10% in the developed region behind the re-circulating region.","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth 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":"115220823","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":"SPECTRAL PROPERTIES OF THE TURBULENT FLOW OF A VISCOELASTIC FLUID FOR REDUCED DRAG","authors":"L. Thais, T. Gatski, G. Mompean","doi":"10.1615/tsfp8.1350","DOIUrl":"https://doi.org/10.1615/tsfp8.1350","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"78 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":"116386871","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":"SPATIO-TEMPORAL 3D CORRELATIONS OF FLUCTUATING PRESSURE AND VELOCITY IN A HIGH REYNOLDS NUMBER TURBULENT BOUNDARY LAYER","authors":"Y. Naka, S. Coudert, J. Foucaut, M. Stanislas","doi":"10.1615/tsfp8.470","DOIUrl":"https://doi.org/10.1615/tsfp8.470","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth 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":"122602042","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":"DNS ON MULTISCALE-GENERATED GRID TURBULENCE USING A CLASSICAL GRID","authors":"H. Suzuki, K. Nagata, Y. Sakai, T. Hayase, Y. Hasegawa, T. Ushijima","doi":"10.1615/tsfp8.1910","DOIUrl":"https://doi.org/10.1615/tsfp8.1910","url":null,"abstract":"We carry out direct numerical simulation of experimental grid turbulence, for which the mesh Reynolds number is 2500. The grid is directly constructed in the computational domain. The streamwise computational domain size is >100 times the mesh size. The value of the decay exponentn is estimated asn ≈ 1.36 by using a ratio defined by the turbulent kinetic energy and its dissipation. The prevailing perspective is that the memory of the turbulence cannot be considered as short. In this paper, we propose a promoter that focuses on the generation of turbulence using the grid, not on the shape of the grid, as addressed in previous studies (Hurst & Vassilicos (2007); Krogstad & Davidson (2011)), from a multiscale perspective and investigate the effects of the turbulence-generating method on the decay exponent n. Specifically,n is increased ton ≈ 1.53 and 1.41 because of the changes in the initial conditions. INTRODUCTION Grid turbulence is the most fundamental type of turbulent flow and has been studied extensively (Pope (2000)). Grid turbulence usually becomes highly homogeneous in the downstream region (Hinze (1975)). Its decay follows a power law, which includes a decay coefficient, the virtual origin, and the decay exponent (Mohamed & LaRue (1990); Pope (2000)) applicable in the region. The decay exponent is directly related to the fundamental characteristics of the decaying grid turbulence. If the grid turbulence is modeled by the Saffman turbulence (Hinze (1975)), the decay exponent will be close to 6 /5 (Krogstad & Davidson (2010)) when the turbulent Reynolds number is sufficiently high. Mohamed & LaRue (1990) proposed a method in which a search is performed for the fit that gives the smallest variance between the data and the form of the decay power law. Wang & George (2002) proposed an indirect means of obtaining the power law through the Taylor microscale. In this work, we employ another method to estimate the decay exponent and the virtual origin by focusing on a principal relation in grid turbulence. Wakes produced by the grid are significantly affected by the grid configuration (Mohamed & LaRue (1990); Lavoieet al. (2005)). The prevailing perspective is that the memory of the generated turbulence cannot be considered to be short (Davidson (2004)). In addition, scatter of the decay exponent among experiments may reflect the dependence of the decay exponent on initial conditions (George (1992)). In recent previous studies (mainly Hurst & Vassilicos (2007)), the turbulence generated by using a grid of a specific fractal shape has been investigated. However, in these previous studies, the concept of multiscale generation of turbulence was added to the generation of turbulence by focusing on the shape of the grid, not on the generation of turbulence by the grid. In this paper, we propose a promoter that focuses on the generation of turbulence using the grid, not on the shape of the grid, and we investigate the effects of the initial conditions o","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"33 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":"123006495","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":"CHARACTERIZATION OF STRUCTURES ASSOCIATED WITH LOW-AND HIGH-SHEAR REGIONS IN EXPERIMENTAL AND NUMERICAL TURBULENT CHANNEL FLOWS","authors":"O. Amili, Y. Mizuno, N. Buchmann, C. Atkinson, J. Soria","doi":"10.1615/tsfp8.1000","DOIUrl":"https://doi.org/10.1615/tsfp8.1000","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"126 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":"128565194","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":"LES-VMS SIMULATIONS OF THERMALLY STRATIFIED TURBULENT WAKES BEHIND TOWED AND AUTO-PROPELLED AXISYMMETRICAL BODY","authors":"B. Sainte-Rose, X. Lenhardt, O. Allain, M. Berton, A. Dervieux","doi":"10.1615/tsfp8.1970","DOIUrl":"https://doi.org/10.1615/tsfp8.1970","url":null,"abstract":"Numerical simulations of close and far wakes behind an axisymmetrical body in a stratified medium are carried out using a Large Eddy Simulation Variational Multi Scale approach to model turbulence. Towed and auto-propelled flow regimes are scrutinized and compared. The characteristic parameters of the flow are Pr = 7, Re = 10000 based on the diameter of the cylinder and F = 25. Realistic results are obtained for the towed case where the so-called three-dimensional (3D), non-equilibrium (NEQ) and quasi two-dimensional (Q2D) regimes are exhibited with very good agreement with experimental and theoretical findings of the litterature. In addition, the effect of auto-propulsion on the flow dynamics is reproduced in a satisfying manner. INTRODUCTION Context The understanding of far turbulent wakes in thermally stratified water is of prime interest for submarine engineers concerned with both hydrodynamic and acoustic stealths. Indeed, the massive separation and the resulting turbulent flow downstream of the device generate both velocity and temperature fluctuations which to turbulent kinetic energy / dissipation and thermal dissipation. Such characteristics of ∗Address all correspondence to this author. the flowfield can be measured by detection devices. In addition, the variations of the fluid’s density can be identified in the reflected signal captured by a sonar. Hence, the objective of submarine engineers is to understand the time-evolution of such quantities in order to establish the influence of parameters such as Reynolds and Prandtl numbers, angle of attack, propulsion, asymmetry, appendages... Their goal is to find a relation between the variations of the measured quantities and the properties of the device (nature of the object, distance, cruising regime, size...) in order to qualify the signals obtained for detection purposes. However, such flows are tedious to accurately analyse on simple theoretical grounds because of non linear phenomena such as turbulence and also because of the complexity of the geometries considered. Moreover, reproducing such wakes at a reasonable scale is very demanding experimentally and the subsequent measurements only give access to a limited number of data too scarce to allow an accurate description of the flow. On the other hand, thanks to the increasing reliability of Computational Fluid Dynamic approaches and the growth of High Performance Computing, numerical simulations of such phenomena are now utilized to tackle such stringent issues. These methods give the engineers an affordable and trustworthy alternative to costly and time-consuming experimental campaigns. Thus, the understanding of turbulent far wakes is made possible thanks to a joint effort between experimental, theoretical and numerical approaches.","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"116 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":"124773377","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}