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

{"title":"Inner-outer interaction in a rapidly sheared boundary layer","authors":"J. Morrison, Sourabh S. Diwan","doi":"10.1615/tsfp10.670","DOIUrl":"https://doi.org/10.1615/tsfp10.670","url":null,"abstract":"In the present work we study the inner-outer interaction in wall turbulence using a novel experimental arrangement of first generating a shearless boundary layer over a moving ground plane in the presence of grid turbulence, which is then passed over a stationary floor downstream resulting in a rapidly sheared boundary layer. The velocity spectra in such a boundary layer are shown to mimic the spectral features typical of a canonical turbulent boundary layer over a range of Reynolds numbers. This suggests that the rapidly sheared boundary layer consists of coherent structures that are qualitatively similar to the large-scale motions and superstructures observed in a canonical turbulent boundary layer. Static pressure fluctuations measured using a specially-made “needle” probe reveal the variation of the pressure field inside the rapidly sheared boundary layer. The pressure fluctuations in the free stream are seen to be highly correlated with wall pressure, especially when the boundary layer is sufficiently thin, supporting the view that the pressure fluctuations can play an important role in coupling turbulent eddies in the inner and outer regions. Further, we show that the present experimental arrangement is well-suited to studying the relative importance of the “top-down” and “bottom-up” mechanisms in wall turbulence in a systematic manner. The results obtained so far suggest that the top-down mechanism is dominant near the leading edge of the stationary surface with the bottom-up mechanism becoming progressively important as the boundary layer grows downstream.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123620513","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":"DISSIPATIVE RANGE STATISTICS OF TURBULENT FLOWS WITH VARIABLE VISCOSITY","authors":"M. Gauding, L. Danaila, E. Varea","doi":"10.1615/tsfp10.520","DOIUrl":"https://doi.org/10.1615/tsfp10.520","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122504201","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-SIMILARITY OF PASSIVE SCALARS IN A DECELERATING JET","authors":"D. Shin, A. Aspden, E. Richardson","doi":"10.1615/tsfp10.790","DOIUrl":"https://doi.org/10.1615/tsfp10.790","url":null,"abstract":"Scalar mixing is investigated in a decelerating turbulent round jet using direct numerical simulation. The mass fraction of jet fluid and the fluid residence time, measured by the mass-weighted age of the jet fluid, both exhibit self-similar radial profiles in statistically-stationary turbulent jets. Upon stopping the inflow, a deceleration wave passes through the jet, behind which a new self-similar state is observed for the two scalar variables. The self-similar state during the jet deceleration is different from that in the statistically-stationary jet. Opposite to its behaviour in the steady-state jet, the jet fluid mass fraction exhibits a linear increase with downstream distance in the decelerating jet, whereas the centreline mass-weighted age of jet fluid remains proportional to downstream distance. The dynamics of the scalar mixing in the transient self-similar state are discussed through analysis of the scalar transport budgets.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126805500","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":"Suppression of Large Scale Structures in a Turbulent von Karman Flow using Random Forcing","authors":"Hanna Berning, T. Grünberg, T. Rösgen","doi":"10.3929/ethz-b-000220701","DOIUrl":"https://doi.org/10.3929/ethz-b-000220701","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"207 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121800662","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":"Temporal and spatial intermittencies within channel flow turbulence near transition","authors":"A. Kushwaha, J. S. Park, M. Graham","doi":"10.1103/PHYSREVFLUIDS.2.024603","DOIUrl":"https://doi.org/10.1103/PHYSREVFLUIDS.2.024603","url":null,"abstract":"Direct numerical simulations (DNS) of plane Poiseuille flow are performed in an extended domain at friction Reynolds numbers ranging from 70 to 100. In minimal domains, turbulence in this Reynolds number range displays substantial intermittency that is associated with chaotic movement of turbulent trajectories between lower and upper branch invariant solutions known as exact coherent states (ECS). The present work aims to address the relationship between temporal dynamics in minimal channels and spatiotemporal dynamics in extended domains. Both temporal and spatial analyses of the turbulent velocity fields are performed, the latter using image analysis methods. These analyses partition the flow characteristics into low-, intermediateand high-drag classes; we present the differences between flows fields in these classes in terms of simple quantities like mean velocity, wall shear stress, and flow structures. The temporal and spatial analysis methods, although completely independent of one another, yield very similar results for both lowand high-drag regions. In particular, the conditional mean profiles in regions of low drag closely resemble those found in low-drag temporal intervals in the minimal channel. Finally, we address the possibility of similarities between turbulence and exact coherent states in two ways: (1) comparing wall shear stress in localized patches the size of minimal channels in large domains with those in actual minimal channel and (2) comparing conditional mean velocity profiles during low-drag events with mean profiles from lower branch ECS. These analyses show that both the local near-wall flow structure in the low-drag patches of the large domain and the conditional mean profiles in the region y+ 30 resemble those of a lower branch minimal domain ECS. In summary, the results presented here suggest that spatiotemporal intermittency in transitional channel flow turbulence is related to temporal intermittency, and by extension to the state space structure, in the minimal channel.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121220970","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":"REFRACTIVE INDEX MATCHED PIV MEASUREMENTS OF FLOW AROUND INTERACTING BARCHAN DUNES","authors":"N. Bristow, G. Blois, Taehoon Kim, J. Best, K. Christensen","doi":"10.1615/tsfp10.690","DOIUrl":"https://doi.org/10.1615/tsfp10.690","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":"2016-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115174240","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":"MULTI-MEASUREMENT CORRELATIONS IN THE NEAR-FIELD OF A COMPLEX SUPERSONIC JET USING TIME-RESOLVED SCHLIEREN IMAGING","authors":"A. Tenney, T. Coleman, J. Lewalle, M. Glauser, S. Gogineni","doi":"10.2514/6.2017-1887","DOIUrl":"https://doi.org/10.2514/6.2017-1887","url":null,"abstract":"In this study, we aim to characterize the dynamics and visualize the propagation of fluctuations in the near field of a complex multi-stream jet over an aft deck plate. The flow is visualized using time resolved schlieren photography (up to 400,000 frames per second) while pressure on the aft deck plate is simultaneously sampled using Kulite pressure sensors. Time series are constructed using the schlieren photographs and conditioned to reduce the effects of signal drift. The analysis is focused in several regions identified in previous studies as dynamically interesting through their high levels of pressure variance and rich spectral content. Space-Time cross correlations are utilized to visualize propagation of fluctuations from the near field to the far field, and several propagation pathways are identified. This process is repeated for band-pass filtered schlieren signals, and a case is made for the separability of near field dynamics into distinct frequency bands. Introduction Over the last several decades, performance requirements of both commercial and military aircraft have led to increasingly complex propulsion systems, often including rectangular multi-stream nozzle configurations. Only within the last few years has noise become a design parameter for propulsion and airframe engineers [1]. While a complete theoretical understanding of jet noise has remained elusive, there is a wealth of information on which to build our knowledge base. There is a large number of theoretical and experimental studies focused on the flow regimes with which this study deals. In his 1991 chapter in Aeroacoustics of Flight Vehicles [2], Tam gives a thorough description of possible acoustic sources in the near field of supersonic jets. He highlights the importance of large scale motions in noise production where M j (jet Mach number) is greater than 1. Of particular interest are the phenomena of Mach wave radiation and broadband shock associated noise, particularly because they have firm theoretical descriptions [3], [4], and will be prominent sources of noise in our experiment due to our chosen design conditions. In addition to the fundamental theoretical and experimental work outlined in [2], more recent applied work has been performed by Bridges cataloguing the acoustic character of pure retangular jets [5] and those exhausting over flat plates. In the aforementioned study, it was shown that noise increases with deck length and that the deck edge acts like a dipole in its velocity scaling and directivity [6]. The goal of the present study is to utilize time resolved schlieren photography to observe and characterize the nearfield phenomena contributing to far-field noise, as described in the existing literature. With this time resolved view of the near-field, we hope to make more reliable predictions about far-field noise, particularly in the complex flows seen in modern day and next-generation aircraft exhaust. To this end, a multi-stream supersonic jet flo","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116735487","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":"Turbulent boundary layer measurements over permeable surfaces","authors":"C. Efstathiou, M. Luhar","doi":"10.1615/tsfp10.620","DOIUrl":"https://doi.org/10.1615/tsfp10.620","url":null,"abstract":"Laser Doppler Velocimetry (LDV) measurements were made in turbulent boundary layers over a flat plate. Commercially available, open cell foams with pore sizes varying from 0.3-2mm were flush mounted into a cutout in the downstream half of the plate. The friction Reynolds number over the smooth wall upstream of the porous section was Reτ ≈ 1690. Measurements made to within 140μm (3-4 viscous units) of the porous interface revealed a substantial slip velocity at the interface (> 30% of the free stream velocity) that was approximately constant across changing substrate geometry. A mean velocity deficit, increasing with pore size, was observed further from the wall in the region corresponding to the log-layer in smooth wall boundary layers. For all foams, an elevated streamwise turbulence intensity was found further into the boundary layer (until y/δ ≈ 0.2). An outer peak in turbulence intensity was found for the largest pore sizes.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"2118 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":"127466251","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 FREQUENCY WAKE DYNAMICS OF CANTILEVERED CIRCULAR CYLINDERS AT AN ASPECT RATIO OF 4","authors":"C. Morton, M. Saeedi, M. Shahroodi, Matthew G. Kindree, R. Martinuzzi","doi":"10.1615/tsfp10.850","DOIUrl":"https://doi.org/10.1615/tsfp10.850","url":null,"abstract":"Near-wake characteristics of a low aspect ratio (h/d = 4) cantilevered circular cylinder protruding a thin laminar boundary layer have been investigated both experimentally (Re = 10,400) and numerically (Re = 300). Despite the substantial differences in the investigated Re, the unsteady wake topology exhibits similar instability mechanisms: (i) a Kármán-like vortex shedding instability, and (ii) a lowfrequency instability which manifests as a coupling between the flow over the free end and the base flow near the cylinder-wall junction. Attention is drawn to the lowfrequency instability, which comprises a significant portion of the kinetic energy content in the wake, and has not been reported in previous experimental or numerical investigations. It appears to be characteristic of intermediate aspect ratio cantilevered circular geometries. INTRODUCTION The flow across cantilevered bluff bodies is ubiquitous in the natural environment and in industrial applications, e.g.: wind loadings on trees, buildings, cross-flow heat exchangers and chimney stacks. Hence, it is not surprising that such geometries have been the subject of a multitude of experimental and numerical studies over the last century (e.g., Fox & Apelt (1993), Rodi (1997), Okamoto & Yagita (1973), Martinuzzi & Havel (2004), Rostamy et al. (2012)). Previous experimental studies on cantilevered bluff bodies have shown that the flow development and related structural loading characteristics strongly depend on the oncoming boundary layer characteristics, the body aspect ratio and the Reynolds number Re of the flow based on the characteristic length scale of the body (e.g., Okamoto & Yagita (1973) and others). It is widely accepted that above a critical aspect ratio, the oscillatory dynamics due to a vortex shedding instability dominate the wake development. For Reynolds numbers relevant to turbulent vortex shedding conditions, the dominant vortical structures exhibit significant temporal modulations in their strength (amplitude) which are linked to a low-frequency drift in the base flow (Bourgeois et al., 2013). The base flow modulation is resolvable with Proper Orthogonal Decomposition (POD) analysis and is consistent with mean-field theory (Stuart, 1958): an energetic exchange exists between the modes associated with vortex shedding and the low-frequency shift mode (Noack et al., 2003). At low Re, this energetic exchange occurs at the onset of the vortex shedding instability (Noack et al., 2003), until the system reaches a dynamically stable state with a constant shedding amplitude. For higher Re turbulent flows, Bourgeois et al. (2013) showed that the vortex shedding is continuously perturbed from its limitcycle oscillation and this process is modelled well with mean-field theory. Presently, it remains unclear if a lowfrequency shift mode persists for all turbulent bluff body wakes exhibiting quasi-periodic vortex shedding. The focus of the present study is to investigate laminar and turb","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"40 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":"123333696","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":"Measurements of the two-dimensional energy spectra of wall-turbulence at high Reynolds number","authors":"J. Monty, D. Chandran, R. Baidya, I. Marusic","doi":"10.1615/tsfp10.70","DOIUrl":"https://doi.org/10.1615/tsfp10.70","url":null,"abstract":"This paper describes a technique to experimentally measure the two-dimensional energy spectra of the streamwise velocity in wallturbulence. The technique is validated at low Reynolds numbers using Direct Numerical Simulation (DNS) data. It is found that a correction to the high wavenumber range of the energy spectra is required owing to physical limitations on minimum probe separation. The measurement technique and DNS-based correction scheme is employed in the University of Melbourne High Reynolds number (Re) wind-tunnel to measure the 2D spectra at high Re for the first time. The results are compared with attached eddy simulation models, showing that hierarchies of high-aspect ratio eddies are required to accurately capture the large-scale energy behaviour.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"54 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":"115985312","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}