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

{"title":"The contribution of large scale structures in the power generation of finite scale wind farms using large eddy simulation","authors":"Y. Peet, Tanmoy Chatterjee","doi":"10.1615/tsfp10.500","DOIUrl":"https://doi.org/10.1615/tsfp10.500","url":null,"abstract":"The large scale organizations in the flow around the finite scale wind farms that contribute to the turbine power, have been studied in the current paper. The study has been carried out using Large Eddy Simulation (LES) with near wall modelling, and the turbine forces are modelled using the actuator line model. Proper orthogonal decomposition (POD) has been used as a tool of analysis to understand the large scale features contributing to the power generation by wind turbines in different rows of a wind farm. The POD modes reveal the existence of energetic flow features significantly larger than the turbine rotor diameter contributing to the flux of the mean kinetic energy (MKE). Thes fluxes play an instrumental role in power generation as also observed in the previous literature. New insights on the flow structures around the wind farm have been obtained which opens up further research directions to understand the localized transfer of the MKE flux. INTRODUCTION Large wind farms in atmospheric boundary layer (ABL) are often studied in the asymptotic limit of infinite number of wind turbine rows, where the flow past the wind turbines is fully developed given by periodic boundary conditions in the streamwis and spanwise directions as seen in Frandsen et al. (2006), Calaf et al. (2010), and describable through simple equilibrium laws. This assumption essentially neglects many complex flow features like the growth of the inner layer due to the turbulent dispersion of the wakes, impingement of the wakes from one row of wind turbines to the next row and beyond, which typically results in a decreased power and an increased structural loading of the downstream turbines. More importantly, these flow features which arise due to the spatial variability of the convection of kinetic energy, cannot be neglected for wind farms where the streamwise and spanwise extent of the layout are comparable to the atmospheric boundary layer thickness. The previous literature has shown the contribution of large scale structures responsible for the power generation in infinite wind farms, e.g., using Fourier analysis by Chatterjee & Peet (2016b) and proper orthogonal decomposition (POD) by VerHulst & Meneveau (2014). Hamilton et al. (2016) looked at proper orthogonal decomposition of an experimental database, but they also focused on a homogeneous part of the wind farm beyond the fourth row, that can be approximated by the fully developed condition and row-to-row periodicity. To the authors knowledge, no such study has been performed to understand the behaviour of large scale features in the power generation of aperiodic, finite scale wind farms. Understanding the multi scale dynamics involved in the interaction of large scale atmospheric flows with the wind turbine rotors in the first and subsequent rows is important, as this will improve our interpretation of power generation in wind turbine arrays required for an efficient optimization of the wind farm layout. For infinit","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"70 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":"134577682","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":"Investigation of a turbulent boundary layer flow at high Reynolds number using particle-imaging and implications for RANS modeling","authors":"T. Knopp, N. Reuther, M. Novara, E. Schülein, D. Schanz, A. Schröder, J. Kähler","doi":"10.1615/tsfp10.640","DOIUrl":"https://doi.org/10.1615/tsfp10.640","url":null,"abstract":"The prediction of pressure induced separation of a turbulent boundary layer (TBL) subjected to an adverse pressure gradient (APG) in the subsonic regime using RANS-based CFD is still associated with significant uncertainties. Recently there was new work on TBL at APG both experimentally, e.g., within the EU project EuHIT (see https://www.euhit.org/), and numerically, e.g. in Gungor et al. (2016) and Kitsios et al. (2016). In this work we present a new experiment described in Knopp & Reuther (2015) and Reuther (2015) whose design includes lessons learned from a precursor experiment, see Knopp et al. (2015). We focus on the inner 15% of the boundary layer. Then we attempt to draw conclusions for RANS turbulence modeling with focus on the length scale equation.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"121 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":"132986490","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":"THE TURBULENT BOUNDARY LAYER STRUCTURE OVER DIATOMACEOUS SLIME FOULING","authors":"E. Murphy, J. Barros, M. Schultz, K. Flack, C. Steppe, M. Reidenbach","doi":"10.1615/tsfp10.610","DOIUrl":"https://doi.org/10.1615/tsfp10.610","url":null,"abstract":"Biofilm fouling has a significant effect on ship performance. Here, the impact of biofilm fouling on boundary layer structure is investigated. Turbulent boundary layer measurements were performed over diatomaceous-slime-fouled plates using high resolution PIV. The mean velocity profile over biofilm shows the expected downward shift (∆U), producing higher drag, and hence higher friction velocity. This increase in drag is seen in enhanced turbulent kinetic energy and Reynolds shear stress. Due to the complex nature of the biofilm’s topography, the flow is heterogeneous in the streamwise direction when compared with smooth-wall flows. INTRODUCTION Many biological surfaces are rough, and man-made surfaces, such as ship hulls, tidal turbine blades, and canals often become rough due to biological activity, such as the attachment and growth of organisms, also known as biofouling. This roughness impacts the performance of these engineered systems (Townsin 2003; Walker et al. 2013a; Walker et al. 2013b). Surface roughness due to biofouling on ship hulls has major economic consequences for shipping and Naval activities. For example, for mid-sized vessels alone, biofouling costs the U.S. Navy an estimated $56 million per year due to increased fuel consumption and the costs of cleaning and painting the hull (Schultz et al. 2011). The primary biofouling community seen on Navy vessels is a biofilm, which is composed of bacterial or algal cells embedded in a viscoelastic extracellular polymeric substance (EPS) (Stoodley et al. 1999). The hydrodynamic regime a biofilm grows in, as well as the organismal makeup of a biofilm determines its physical structure. Different species have different cell surface properties (i.e. hydrophobicity or hydrophilicity), that may influence how the structures interact with the flow within the viscous and turbulent boundary layer above the film (de Beer and Kühl 2001). Biofilm thicknesses range from micrometers to centimeters, and the structure of biofilms is highly heterogeneous, often composed of bulbous cell clusters between which are voids that permit fluid flow (de Beer at al. 1996). When grown under shear, biofilms form thin, flexible streamers that protrude from the surface (Taherzadeh et al. 2009). Eddies are shed off of the cell clusters, causing three-dimensional flapping of the streamers (Stoodley et al. 1998). Biofilms found on ship hulls are often primarily composed of diatoms, and are referred to as diatomaceous slimes (Schultz et al. 2015). Fouling-release and antifouling hull coatings can be ineffective at preventing diatomaceous slime fouling (Molino and Wetherbee 2008). These slimes are also common on marine sediments, where they stabilize the sediment and may alter transport between porewater and the water column (Tolhurst et al. 2008). Though biofilms typically have low vertical relief and the roughness elements are compliant, biofilm fouling induces a steep drag penalty on fouled surfaces, increasing the skin f","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"221 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":"133136999","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":"VORTICITY TRANSPORT IN HUMAN AIRWAY MODEL","authors":"A. Nemes, S. Jalal, Tristan Van de Moortele, F. Coletti","doi":"10.1615/tsfp10.380","DOIUrl":"https://doi.org/10.1615/tsfp10.380","url":null,"abstract":"Many previous studies concerned with respiratory fluid mechanics have simplistically assumed steady and laminar flow. Above a certain ventilation frequency, the unsteady nature of the respiratory flow becomes apparent, and inhalation and exhalation cannot be approximated as quasi-stationary processes. Moreover, due to the geometrical structure of the bronchial tree, flow unsteadiness and transition to turbulence can incept even at Reynolds numbers usually considered laminar in parallel flows. Here we investigate the primary features of the oscillatory flow through a 3D printed double bifurcation model that reproduces, in an idealized manner, the self-similar branching of the human bronchial tree. We consider Reynolds and Womersley numbers relevant to physiological conditions between the trachea and the lobar bronchi. Three-component, three-dimensional velocity fields are acquired at multiple phases of the ventilation cycle using Magnetic Resonance Velocimetry (MRV). The phase-averaged volumetric data provide a detailed description of the flow topology, characterizing the main secondary flow structures and their spatio-temporal evolution. We also perform twodimensional by Particle Image Velocimetry (PIV) for the steady inhalation case at a Reynolds number Re = 2000. PIV is carried out by matching the refractive index of the 3D printing resin with a novel combination of anise oil and mineral oil. The instantaneous measurements reveal unsteadiness of the separating unsteady flow in the bifurcation, and the ensemble averages show a clear Reynolds stress pattern indicating that the flow is turbulent at the first bronchial bifurcation already at this relatively low Reynolds number. INTRODUCTION The human respiratory system is structured as a network of branching airways. The trachea splits in the two main bronchioles, which successively bifurcate about sixteen more times down to the terminal bronchi, followed by roughly six generations of alveolar ducts involved in the gas exchange (Kleinstreuer & Zhang 2010). While the actual anatomy is fairly complex and varies between different subjects, general features have been long identified which are remarkably consistent: at the i bronchial generation, the daughter-tomother branch diameter ratio is h = Di+1/Di ≈ 0.8, the length-todiameter ratio of each branch is Li/Di ≈ 3.5, and the bifurcation angle is θ ≈ 60-70° (Weibel 1997). Such proportions minimize the through-flow time during the respiration process and the energy expenditure in bifurcating flow systems, and therefore canonical airway models with such characteristics have been extensively studied. The most classic case is the planar version of the Weibel A model (Weibel 1963), in which the branches consist of circular tubes that bifurcate symmetrically and lay on the same plane. Despite the simplicity of such representation, this has been shown to capture many key aspects of the respiratory airflow both in inspiratory and expiratory mode. Above a certa","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"3 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":"133141535","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":"Self-preservation and the Kolmogorov 1st similarity law","authors":"L. Djenidi, R. Antonia, L. Danaila","doi":"10.1615/tsfp10.1130","DOIUrl":"https://doi.org/10.1615/tsfp10.1130","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"66 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":"125874401","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 REPRESENTATIVE VORTEX SURFACES IN K-TYPE TRANSITIONAL BOUNDARY LAYER","authors":"Yaomin Zhao, Yue Yang, S. Xiong, Shiyi Chen","doi":"10.1615/tsfp10.160","DOIUrl":"https://doi.org/10.1615/tsfp10.160","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"37 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":"124073959","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":"FLOW AROUND NONPARALLEL TANDEM CYLINDERS","authors":"Md Yamin Younis, M. Alam, Yu Zhou","doi":"10.1615/tsfp10.340","DOIUrl":"https://doi.org/10.1615/tsfp10.340","url":null,"abstract":"Flow around two nonparallel tandem cylinders is investigated experimentally to understand the associated fluid dynamics at a Reynolds number Re = 5.6 × 10. Two cylinders of identical diameter D are oppositely inclined by 7.5° measured from the normal to the free stream direction, which leads to an included angle of 15° between the cylinders. Strouhal number (St) and time-mean and instantaneous flow field measurements for L (= L/D = 1 4.05, where L is the cylinder center-to-center spacing) leads to identification of three distinct flows: alternating reattachment flow (regime I, 1 ≤ L < 2.15), bi-stable flow (regime II, 2.15 ≤ L ≤ 3.1), and coshedding flow (regime III, 3.1 < L ≤ 4.05). Regime I is further subdivided into regimes IA and IB contingent on shear layer reattachment and its influence on quasi-steady vortex in the gap and wake. The three flow regimes are totally different from those for parallel cylinders. A spiral vortex forming in the gap that varies along the cylinder span is responsible for making the difference. The sporadic presence of reattachment and coshedding flows results in a jump in St at regime II. In contrast to parallel cylinders, nonparallel cylinders experience another jump in St associated with the coshedding flow at L = 2.5 in regime II. A wake-flow bifurcation at L = 2.5 is responsible for the jump, separating the wake flow turning towards the small L and towards the large L.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"26 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":"130093995","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":"Low-Order Models for Turbulent Flows over Complex Walls","authors":"M. Luhar","doi":"10.1615/tsfp10.450","DOIUrl":"https://doi.org/10.1615/tsfp10.450","url":null,"abstract":"","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":"130015470","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":"NUMERICAL INVESTIGATION OF STRUCTURAL AND STATISTICAL FEATURES OF PREMIXED FLAME UNDER INTENSE TURBULENCE","authors":"R. Ranjan, S. Menon","doi":"10.1615/tsfp10.950","DOIUrl":"https://doi.org/10.1615/tsfp10.950","url":null,"abstract":"In this study results from large-eddy simulation (LES) employing the linear eddy mixing (LEM) model of a freely propagating methane/air turbulent premixed flame interacting with a decaying background turbulence field are analyzed to characterize the effects of Karlovitz number (Ka) ranging from 30 to 120 on the flame-turbulence interaction. The analysis is performed in terms of the resolved and the subgrid-scale (SGS) flame structure, by examining the instantaneous snapshots, spatially averaged profiles, propagation characteristics, and statistical features of the flame. The LES predicts the turbulence-chemistry interaction at high Ka, as in direct numerical simulation (DNS) and experimental studies. In particular, the effects of increased Ka, which results in enhanced mixing and homogenization within the flame region are captured in the simulations, thus providing confidence that LEM model has the potential to capture a wide range of operating conditions encompassing thin reaction zone to broken/distributed reaction zone regimes without requiring any model adjustment.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"136 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":"117030309","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":"Transitional separation bubbles over swept wings","authors":"N. De Tullio, N. Sandham","doi":"10.1615/tsfp10.330","DOIUrl":"https://doi.org/10.1615/tsfp10.330","url":null,"abstract":"Direct numerical simulations and global linear stability analysis have been performed to investigate the effect of sweep on the behaviour of transitional separation bubbles developing over a NACA0012 airfoil at moderate Reynolds numbers. The results indicate that the laminar-turbulent transition inside the bubble is greatly affected by the sweep angle, with the onset of two-dimensional vortex shedding being favoured over three-dimensional vortex shedding as sweep is increased. Both the DNS and global stability results show that the laminar-turbulent transition of the separation bubble is dominated by instability modes developing in the detached shear layer induced by the bubble and sustained by an acoustic feedback loop. An additional set of modes with relatively low frequencies and concentrated inside the separation bubble were also uncovered by a Dynamic Mode Decomposition of the DNS data. These modes are globally unstable and lead to three-dimensional oscillation of the separations bubble.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"2011 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":"121544554","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}