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

{"title":"PASSIVE FLOW CONTROL OF SHOCK-WAVE/TURBULENT-BOUNDARY-LAYER-INTERACTIONS USING MICRO VORTEX GENERATORS","authors":"B. Budich, V. Pasquariello, M. Grilli, S. Hickel","doi":"10.1615/tsfp8.1940","DOIUrl":"https://doi.org/10.1615/tsfp8.1940","url":null,"abstract":"We evaluate the suitability of micro vortex generators for the passive flow control of shock-wave/turbulent boundary layer interactions. For this purpose, implicit large eddy simulations using the adaptive local deconvolution method are performed. The flow configuration consists of an oblique shock with deflection angle β = 9.5°, impinging on a turbulent boundary layer at Ma∞ = 2.31 and Re = 67.4 ·103. Analysis focuses on the assessment of the relative displacement between the control devices and the shock system, the complex flow structure behind the devices and the low-frequent motions of the separated region. INTRODUCTION Interactions of shock waves with turbulent boundary layers (SWBLI) can be encountered in virtually every high speed application, including engine intakes, turbomachinery or rocket engines. It is well known that shock induced flow separation is followed by severe energy losses and flow distortion degrading overall system performance (Babinsky et al., 2009; Lin, 2002). Additionally, substantial thermal and pressure loads result from the interaction. In conjunction with their highly unsteady nature, SWBLI are of major concern also for the structural integrity and life time of high speed vehicles. In order to address these issues, control devices can be deployed (Délery, 1985). Here, we focus on passive flow control using vortex generators (VGs), which rank among the most promising approaches to boundary layer control (Lin, 2002). Placed upstream of the interaction, these devices induce a pair of counter-rotating, longitudinal vortices that energize the boundary layer flow within their wake. A valuable modification of conventional-type VGs are micro vortex generators (μVGs) possessing a device height of hV G δ0, with δ0 being the 99%-boundary layer thickness. Due to their smaller height, exposure to lower fluid velocities, and reduced surface as well as cross-sectional areas, μVGs result in substantially lower parasitic losses and flow distortion while still efficiently increasing resistance against flow separation (Lin, 2002). However, relative placement to the separated region is crucial as dissipation and de-correlation of the vortex pair is of concern. The considered flat plate turbulent boundary layer (TBL) is characterized by a free-stream Mach number Ma∞=2.31 and Reynolds number Reδ =67.4·103, based on hV G","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"27 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":"126564286","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":"Validation of a Fractal Dynamic SGS Combustion Model by DNS of Turbulent Premixed Flame in Strong Shear Flow","authors":"K. Hiraoka, I. Yoshikawa, N. Fukushima, M. Shimura, M. Tanahashi, T. Miyauchi","doi":"10.1615/tsfp8.370","DOIUrl":"https://doi.org/10.1615/tsfp8.370","url":null,"abstract":"A fractal dynamic subgrid scale (SGS) combustion model for large eddy simulation (LES) of turbulent premixed combustion which was developed in our previous study (Yoshikawa et al., 2013) is evaluated through static tests on filtered data of direct numerical simulation (DNS) of H2—air turbulent V-shape premixed flame. The model is based on flamelet concept, fractal characteristics of turbulent premixed flames and scale separation in high Reynolds number turbulence and the accuracy has been demonstrated for freely propagating premixed flame in homogeneous isotropic turbulence (HIT). The results of the static tests validate that the present model has high accuracy and is applicable to conditions where strong mean shear exists and the interaction between flame and turbulence is complex. Furthermore, comparison with some conventional SGS combustion models indicates that the present model has superiority to these models in terms of accuracy. INTRODUCTION Large eddy simulation gains more and more attention as a powerful tool for simulating turbulent combustion. Recently, many attempts applying LES to realistic combustion systems have been made (Colin et al., 2000; Pitsch and Duchamp de Lageneste, 2002; Stone and Menon, 2002; Grinstein and Fureby, 2005; Fureby, 2005; Wang and Bai, 2005; Huang and Yang, 2005; Fiorina et al., 2010; Kuenne et al., 2011; Wang et al., 2013). In LES, physical quantities are filtered and divided into the grid scale (GS) and subgrid scale components. Then, large scale unsteady phenomena represented by the GS components are computed, while the contribution of SGS phenomena to those of GS is given by SGS models. Since combustion is intrinsically unsteady, LES is expected to be more accurate than the classical Reynolds Averaged Navier-Stokes (RANS) simulation for numerical simulations of turbulent combustion. In LES of turbulent combustion, tracking of the flame front is one of the difficulties, since the flame thickness is generally quite thin compared to the LES filter width (), where the filter width should be in the inertial sub-range of turbulent spectrum. For tracking the flame front, Gequation (Kerstein et al., 1988) is frequently used. In the approach, flame front is represented as an infinitely thin scalar iso-surface and its propagation is computed. For extending this approach to LES, G-equation is filtered. Then, a closure model (SGS combustion model) for turbulent burning velocity, ST, is introduced to solve the filtered G-equation. Since accuracy of LES strongly depends on the SGS model, highly accurate SGS models are required to acquire trustworthy results. However, almost all SGS combustion models used in this approach are those extended from RANS models (Pitsch and Duchamp de Lageneste, 2002; Stone and Menon, 2002; Wang and Bai, 2005; Huang and Yang, 2005) and their accuracy in LES is not assured. In our previous study (Yoshikawa et al., 2013), a fractal dynamic SGS combustion model based on flamelet concept, fract","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"14 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":"125256039","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":"IMPLEMENTING SCHMIDT NUMBER DEPENDENCE IN A STOCHASTIC LAGRANGIAN MODEL FOR THE SCALAR GRADIENT","authors":"Michel Gonzalez","doi":"10.1615/tsfp8.1380","DOIUrl":"https://doi.org/10.1615/tsfp8.1380","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"53 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":"130786021","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":"EFFECTS OF A FOREST CLEARING: AN EXPERIMENTAL AND NUMERICAL ASSESSMENT","authors":"Tetsuya Nakamura, K. Fukagata, A. Segalini, P. Alfredsson","doi":"10.1615/tsfp8.410","DOIUrl":"https://doi.org/10.1615/tsfp8.410","url":null,"abstract":"There is a renewed interest in the wind estimate over and around forest areas dueto the increasing demand of wind-energy resources. Many researches have been donewith simplied forest models. Howeve ...","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"112 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":"116596525","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 NOVEL DYNAMIC FORCING SCHEME INCORPORATING BACKSCATTER FOR HYBRID RANS/LES","authors":"Qian-Qiu Xun, Bing-Chen Wang","doi":"10.1615/tsfp8.990","DOIUrl":"https://doi.org/10.1615/tsfp8.990","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"148 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":"116635459","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":"STUDY OF BUOYANCY EFFECTS ON A THERMAL MIXING LAYER USING AN X-WIRE PROBE OPERATED SEQUENTIALLY AT DIFFERENT OVERHEATS","authors":"Kodjovi Sodjavi, J. Carlier","doi":"10.1615/tsfp8.510","DOIUrl":"https://doi.org/10.1615/tsfp8.510","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":"122353758","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 VORTEX SHEDDING FROM A DUAL-STEP CYLINDER: INFLUENCE OF DIAMETER RATIO AND ASPECT RATIO","authors":"C. Morton, S. Yarusevych","doi":"10.1615/tsfp8.1800","DOIUrl":"https://doi.org/10.1615/tsfp8.1800","url":null,"abstract":"In the present study, the influence of aspect ratio (L/D) and diameter ratio (D/d) on the flow development past a dual-step cylinder is investigated experimentally for ReD = 2100, 1.33 ≤ D/d ≤ 2.67, and 0.2 ≤ L/D ≤ 3. Experiments are carried out in a water flume facility using Laser Doppler Velocimetry (LDV), Particle Image Velocimetry (PIV), and hydrogen bubble flow visualization. The results show that four distinct vortex shedding regimes can be identified based on changes in large cylinder wake development. Depending on the geometrical parameters of the dual-step cylinder, the wake of the large cylinder may involve (i) vortex shedding at a frequency lower than that expected for a uniform cylinder at the same Reynolds number, (ii) irregular shedding, (iii) vortex shedding at a frequency higher than that for a uniform cylinder, and (iv) suppression of large cylinder vortex shedding. Based on the present results and those from previous studies on relevant geometries, a map of wake regimes for a dual-step cylinder has been constructed. INTRODUCTION The present investigation is focused on the flow development over dual-step cylinders. A dual-step cylinder, shown in Fig. 1, consists of a large diameter cylinder (D) of low aspect ratio (L/D) attached coaxially to the mid-span of a small diameter cylinder (d). It is instructive to consider the dual-step cylinder geometry in limiting cases of D/d and L/D. As D/d approaches unity, the dual-step cylinder approaches the geometry of a uniform circular cylinder. On the other hand, for large D/d, the dual-step cylinder resembles a cylinder with two free ends. Hence, it is expected that, depending on the geometrical parameters of the model, the flow development for a dual-step cylinder may be similar to that found for a low aspect ratio uniform cylinder (e.g., Norberg, 1994), a cylinder with free ends (e.g., Inoue & Sakuragi, 2008), or a coin-like cylinder (e.g., Zdravkovich et al., 1998). For uniform circular cylinders mounted between endplates, the frequency of vortex shedding tends to decrease with decreasing aspect ratio for about L/D < 30 (Norberg, 1994). For L/D < 7, the coherence and strength of the vortex shedding decreases, with regular vortex shedding being replaced by the formation of less coherent wake structures (Norberg, 1994). Zdravkovich et al. (1989, 1998) and Inoue & Sakuragi (2008) investigated the flow development over uniform cylinders with two free ends. In the laminar vortex shedding regime, Inoue & Sakuragi (2008) found that three wake patterns can occur depending on ReD and L/D: (i) spanwise vortex shedding, (ii) a steady wake consisting of two counter-rotating streamwise vortices, and (iii) alternate shedding of streamwise vortex pairs from the flat cylinder ends. Zdravkovich et al. (1989) performed experiments for 6000 ≤ ReD ≤ 26000 and 2 ≤ L/D ≤ 8. For all models investigated, spanwise vortex shedding occurred in the wake, however, it was intermittent, and the shedding frequency va","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth 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":"123022694","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":"ESTIMATING THE FRICTION VELOCITY IN A TURBULENT PLANE WALL JET OVER A TRANSITIONALLY ROUGH SURFACE","authors":"N. Rostamy, D. Bergstrom, D. Sumner, J. Bugg","doi":"10.1615/tsfp8.1010","DOIUrl":"https://doi.org/10.1615/tsfp8.1010","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"11 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":"128647454","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":"OSBORNE REYNOLDS' PIPE FLOW: DIRECT COMPUTATION FROM LAMINAR THROUGH TRANSITION TO FULLY-DEVELOPED TURBULENCE","authors":"Xiaohua Wu, P. Moin, R. Adrian, Jon Baltzer, Jean-Pierre Hickey","doi":"10.1615/tsfp8.2220","DOIUrl":"https://doi.org/10.1615/tsfp8.2220","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"47 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":"128479475","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 MODELING OF FOULING PROCESSES ON STRUCTURED SURFACES","authors":"J. Klunker, J. Turnow, N. Kornev","doi":"10.1615/tsfp8.910","DOIUrl":"https://doi.org/10.1615/tsfp8.910","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth 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":"114795353","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}