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

{"title":"SCALING LAWS FOR THE PERFORMANCE OF RIGID PROPULSORS INTENDED FOR UNDERWATER LOCOMOTION","authors":"D. Floryan, T. Buren, C. Rowley, A. Smits","doi":"10.1615/tsfp10.580","DOIUrl":"https://doi.org/10.1615/tsfp10.580","url":null,"abstract":"Scaling laws are presented for the propulsive performance of rigid foils undergoing oscillatory motion in water. Water tunnel experiments on a nominally two-dimensional foil show that the scaling laws provide an excellent description of the data for thrust, power, and efficiency. The scaling laws are then extended to account for the effects of non-sinusoidal motions by using a parameter based on the maximum velocity of the trailing edge, which describes the experiments on non-sinusoidal gaits described by Jacobi elliptic functions reasonably well. Lastly, intermittent motions are considered. The thrust and power is shown to scale linearly with the duty cycle, and scaling laws for the energetics are presented. Intermittent motions are generally energetically advantageous over continuous motions, unless metabolic energy losses are sufficiently high.","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":"127056585","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":"EXPERIMENTAL STUDY OF TURBULENT STRUCTURE OVER PERMEABLE WALLS WITH A REFRACTIVE-INDEX-MATCHING TECHNIQUE","authors":"Taehoon Kim, G. Blois, J. Best, K. Christensen","doi":"10.1615/tsfp10.30","DOIUrl":"https://doi.org/10.1615/tsfp10.30","url":null,"abstract":"","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":"126414694","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":"DEVELOPMENT AND CHARACTERIZATION OF A PULSED JET ACTUATOR BASED ON SONIC FLOW CONTROLLED BY PLASMA","authors":"J. Bonnet, Gwenael Acher, P. Audier, A. Robert, A. Lebedev, N. Benard, E. Moreau","doi":"10.1615/tsfp10.430","DOIUrl":"https://doi.org/10.1615/tsfp10.430","url":null,"abstract":"The modulation of a sonic flow in view of high authority actuator design is based on the increase of the temperature at a sonic throat with the help of a plasma discharge. Indeed, for a perfect gas, the flow rate being proportional to the inverse of the square root of the temperature at a constant settling chamber pressure, the jet flow rate should be able to be varied. In view of flow control actuator design, the frequency is then no limited by any mechanical constraint. The discharge can be either continuous or pulsed at high frequencies. The influence of the settling chamber pressure and electrode gap distance have been investigated. For an aerodynamically steady actuation, the jet flow rate can be reduced down to 70% of its nominal value (30% of flow rate reduction), the best effectiveness being obtained with a DC discharge. The temperature increases from 290K to up to 650K for sonic regime. The speed of sound (and then the jet velocity for sonic conditions) is increased by a factor of 1.5 when the plasma is operated Transient phenomena are evidenced by high speed Schlieren. A low velocity version is obtained with a channel added downstream In this case, a modulation of the subsonic (37m/s) jet velocity is observed, with a max velocity of 60 m/s with a large increase of the velocity fluctuations when the plasma is activated. This actuator has several interests when compared to conventional pulsed jets: no mechanical device, high frequency response. The pulsed jet contains high velocity (by a factor of 1.5), high temperature (by a factor of 2) impulses with lower flow rate and high turbulence levels. INTRODUCTION AND EXPERIMENTAL DESIGN In most cases, active flow control requires high frequency actuators. Particularly for high velocity (eventually supersonic) flow control configurations, high frequency and high authority (in terms of flow rate) are required Cattafesta and Sheplak (2011), Gatski and Bonnet (2014). Some recent developments for supersonic flow control can be found in Emerik et al. (2014), Hupadhyay et al. (2016). Usual pressurized flowing jets monitoring through mechanical valves have a high potential but they are limited in terms of frequency (up to typically a few hundred of Hz). In this project, we developed a new flowing jet driven by a plasma discharge. The principle is to increase the temperature at a sonic throat located upstream of the jet exit with the help of a plasma discharge located at the throat (Fig. 1). For a perfect gas, the flow rate being proportional to the inverse of the square root of the temperature at a constant settling chamber pressure, the jet flow rate can be varied. Although using a plasma discharge, the present method is then quite different from the Spark Jet described by Emerik et al. (2014) in which a continuous flow of fresh air is introduced. Indeed, in this operation, the Spark Jet is associated to an extra air for cooling the cavity that is otherwise heated by the spark. Fig.1. Schematic of th","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"25 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":"127452095","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":"Modulated roll cells in rotating plane Couette flow of viscoelastic fluid","authors":"Tomohiro Nimura, T. Ishida, T. Kawata, T. Tsukahara","doi":"10.1615/tsfp10.300","DOIUrl":"https://doi.org/10.1615/tsfp10.300","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"18 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":"134002283","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":"HIGH-FIDELITY SIMULATIONS OF THE FLOW AROUND WINGS AT HIGH REYNOLDS NUMBERS","authors":"R. Vinuesa, P. Negi, A. Hanifi, D. Henningson, P. Schlatter","doi":"10.1615/tsfp10.1050","DOIUrl":"https://doi.org/10.1615/tsfp10.1050","url":null,"abstract":"Reynolds-number effects in the adverse-pressure-gradient (APG) turbulent boundary layer (TBL) developing on the suction side of a NACA4412 wing section are assessed in the present work. To this end ...","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":"130629259","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":"INVARIANTS OF VELOCITY GRADIENT TENSOR IN COMPRESSIBLE PIPE, NOZZLE AND DIFFUSER FLOWS","authors":"K. Kumari, Somnath Ghosh, J. Mathew","doi":"10.1615/tsfp10.1010","DOIUrl":"https://doi.org/10.1615/tsfp10.1010","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":"130830030","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 persistence of trip-induced spanwise periodicity in developing turbulent boundary layers","authors":"R. Baidya, C. M. Silva, L. Castillo, I. Marusic, N. Hutchins","doi":"10.1615/tsfp10.230","DOIUrl":"https://doi.org/10.1615/tsfp10.230","url":null,"abstract":"The present work investigates spanwise periodic modes introduced at the inception point (trip) of a developing turbulent boundary layer. Empirical evidence suggests that these modes can be persistent, and the idea here is to exploit this apparent persistence/amplification of weak lateral variations in turbulent boundary layers, to explore whether the downstream evolution can be substantially modified. Preliminary results, where micro vortex generators are used to introduce the spanwise modes at the trip, indicate the presence of spanwise alternating modes. These modes appear to strengthen after some distance downstream of their introduction for certain configurations (this strengthening can occur almost 350 blade heights downstream of the trip). Further, the spanwise wavelength of the trip seems to play a critical role in determining the downstream development and subsequent evolution of the turbulent boundary layer towards a canonical state. Collectively, these findings suggest that three-dimensionality introduced at the trip may be a viable approach to perturb the evolution of developing turbulent boundary layers over a large streamwise development length. Introduction A turbulent boundary layer forming on a flat plate appears to exhibit a lateral instability during its development that can sustain and amplify initially weak spanwise perturbations. For example, persistent lateral variations have been observed within developing turbulent boundary layers, even in carefully fabricated, well-controlled wind tunnel facilities with nominally uniform freestream conditions (Klebano ff & Tidstrom, 1959; Watmu ff, 1998). These modes are thought to arise due to subtle imperfections in the upstream screens used for flow conditioning (Bradshaw, 1965; Furuyaet al., 1979; Pooket al., 2016). Townsend (1976, pp. 328-331) demonstrated analytically that small lateral variations in turbulent boundary layers tend to be selectively amplified up to a critical amplitude as the boundary layer develops, with the most amplified or dominant wavelengths tending to be those that are on the order of the boundary layer thickness ( δ). In the case of the studies mentioned above, it is thought that these lateral variations may be introduced from weak flow imperfections in the free-stream. However, these spanwise variations could also be introduced or exacerbated by surface roughness (Gong et al., 1996; Mejia-Alvarez & Christensen, 2013; Reynolds et al., 2007). To investigate this phenomenon, the present work examines the downstream persistence of lateral variations introduced at the inception point (or trip) in a developing zero pressure gradient turbulent boundary layer. In doing so we hope to shed light on the ability of the developing turbulent boundary layer to selectively amplify approximatelyδ-scaled spanwise variations—as proposed by Townsend (1976)—out of pre-existing heterogeneity (this could be heterogeneity in the free-stream, in the trip, or in the surface stress co","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"28 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":"132698596","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":"FARM EFFICIENCY OF LARGE WIND FARMS: EVALUATION USING LARGE EDDY SIMULATION","authors":"N. Ghaisas, A. Ghate, S. Lele","doi":"10.1615/tsfp10.1170","DOIUrl":"https://doi.org/10.1615/tsfp10.1170","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"52 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":"134240362","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 Transition Behind a Discrete Roughness Element Using a Downstream Element","authors":"Alexandre R. Berger, M. McMillan, E. B. White, S. Suryanarayanan, D. Goldstein","doi":"10.1615/tsfp10.910","DOIUrl":"https://doi.org/10.1615/tsfp10.910","url":null,"abstract":"Maintaining laminar flow in boundary layers provides better aerodynamic efficiency than turbulent flow by virtue of the lower wall shear stress of a laminar boundary layers. In practice, maintaining laminar flow at the Reynolds numbers of operating aircraft is extremely difficult. High Re values produce strong instability growth that leads to turbulence and thin boundary layers enable even small surface imperfections to generate significant boundary-layer disturbances.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"9 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":"128005590","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":"Time-resolved PIV investigation of the secondary instability of cross-flow vortices","authors":"J. Serpieri, M. Kotsonis","doi":"10.1615/tsfp10.1250","DOIUrl":"https://doi.org/10.1615/tsfp10.1250","url":null,"abstract":"Time-resolved PIV measurements of the secondary instability modes of cross-flow vortices are presented. Measurements are performed on a large scale 45o swept wing at chord Reynolds number of 2.17 million in a low turbulence wind-tunnel facility. Using acquisition frequencies of 20 kHz, the present study is the first experimental demonstration of spatio-temporally resolved measurements of these structures. Statistical and spectral analysis reveals a fluctuating velocity field, strongly conditioned in space by the primary stationary cross-flow vortex. The flow structures related to the type-I high-frequency instability and type-III are captured by Proper Orthogonal Decomposition of the instantaneous flow-fields. Their temporal evolution is analysed showing good agreement with previous studies thus confirming that POD is correctly representing the flow structures of the relevant instability modes. The low frequency meandering oscillation of the stationary vortices, first reported by Serpieri &Kotsonis (2016b), is observed and characterised.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"19 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":"121395473","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}