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

{"title":"ACTIVE FLOW CONTROL FOR DRAG REDUCTION OF VEHICLES USING LARGE EDDY SIMULATION, EXPERIMENTAL INVESTIGATIONS AND REDUCED ORDER MODELING","authors":"John Östh, S. Krajnović, D. Barros, L. Cordier, B. R. Noack, J. Borée, Tony Ruiz","doi":"10.1615/tsfp8.1140","DOIUrl":"https://doi.org/10.1615/tsfp8.1140","url":null,"abstract":"The purpose of this short paper is to introduce first results obtained in a collaborative research between the partners. This research is dedicated to drag reduction of vehicles using LES, experimental investigation and ultimately reduced order modeling. First numerical and experimental results are presented. Experiments show that periodic forcing at high frequencies and amplitudes of the order of the upstream velocities can be viewed as a promising strategy for drag reduction targeted control of three-dimensional bluff-bodies.","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":"114448629","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 OF SEPARATED FLOWS AT MODERATE REYNOLDS NUMBERS APPROPRIATE FOR TURBINE BLADES AND UNMANNED AERO VEHICLES","authors":"F. Cadiuex, G. Castiglioni, J. Domaradzki, T. Sayadi, S. Bose, M. Grilli, S. Hickel","doi":"10.1615/tsfp8.1450","DOIUrl":"https://doi.org/10.1615/tsfp8.1450","url":null,"abstract":"Flows over airfoils and blades in rotating machinery, for unmanned and micro-aerial vehicles, wind turbines, and propellers consist of a laminar boundary layer near the leading edge that is often followed by a laminar separation bubble and transition to turbulence further downstream. Typical RANS turbulence models are inadequate for such flows. Direct numerical simulation (DNS) is the most reliable but is also the most computationally expensive alternative. This work assesses the capability of LES to significantly reduce the resolution requirements for such flows and still provide results of DNS quality. Two flows are considered. A flow over a flat plate with suitable velocity boundary conditions away from the plate to produce a separation bubble and a 2-D flow on a NACA-0012 airfoil. By employing several different codes we conclude that accurate LES are possible using O(1%) of the DNS resolution and that the numerical dissipation plays a significant role in LES of such flows.","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"140 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":"115885499","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 AND SOUND FIELDS OF HEATED SUBSONIC TURBULENTJETS","authors":"C. Bogey, O. Marsden","doi":"10.1615/tsfp8.1420","DOIUrl":"https://doi.org/10.1615/tsfp8.1420","url":null,"abstract":"","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"13 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":"122584316","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 TRANSITION PROCESS FROM REGULAR TO IRREGULAR SHOCK-WAVE/BOUNDARY-LAYER INTERACTION","authors":"J. Matheis, B. Budich, S. Hickel","doi":"10.1615/tsfp8.110","DOIUrl":"https://doi.org/10.1615/tsfp8.110","url":null,"abstract":"The transition process from regular to irregular shockwave/boundary-layer interaction (SWBLI) at M∞ = 2 is studied both numerically and theoretically. The classical twoand three-shock theory is applied for carefully analyzing a data base of well resolved large-eddy simulations (LES). Inviscid theory appears to be a descriptive tool for the interpretation of the highly transient flow field of the SWBLI. Disturbances related to the incoming turbulent boundary layer can be identified as a source of bidirectional transition processes between regular and irregular SWBLI at a critical deflection angle across the incident shock wave. INTRODUCTION A shock wave represents a highly nonlinear phenomenon. The state of the medium that passes the wave changes instantaneously and irreversibly. The complexity of this process increases when more than one shock occurs, for example, in the case of the interaction of a shock with a symmetry plane, a solid surface or the asymmetric intersection of shock waves. The reflection phenomenon was first described by Ernst Mach in 1887, who experimentally observed two different wave configurations, namely the regular reflection (RR) and the irregular reflection / Mach reflection (MR). The symmetric reflection of shock waves in an inviscid framework can be briefly summarized as follows: Characteristic wave pattern of shock reflections (RR and MR) are restricted to certain domains depending on the free stream Mach number M∞ and the deflection angle θ01 across the incident shock. Criteria beyond which RR and MR are theoretically impossible are given by the detachment and the von Neumann condition, respectively; see Ben-Dor (2010) for a comprehensive review. Both RR and MR wave configurations are possible within the parameter space spanned by these two conditions. The existence of such a domain led Hornung et al. (1979) to hypothesize that a hysteresis process could exist in the transition process between both wave patterns. As the deflection across the incident shock increases, transition from RR to MR occurs near the detachment criterion, while in the opposite case transition from MR to RR occurs at the von Neumann condition. Recently, asymmetric intersections of shock waves got into the focus of classical gas-dynamic research, such as shown in Fig. 1a, see Li et al. (1999) and Hu et al. (2009), e.g.. Li et al. (1999) proposed transition criteria for the reflection of asymmetric shock waves corresponding to the (b) (a) Figure 1: (a) Experimental schlieren image of the quasiinviscid MR at M∞ = 4.96, θ01 = 28○ and θ02 = 24○, courtesy of Li et al. (1999). (b) Experimental schlieren image of the ISWBLI at M∞ = 1.965 and θ01 = 15.2○, courtesy of Bardsley & Mair (1950). detachment and von Neumann criteria. In the following, it will become apparent that methods (e.g. shock polars) and transition criteria (θN , θD) developed for inviscid flow in the recent decades also constitute a descriptive tool for analyzing the interaction of shoc","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"34 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":"126381533","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":"COEXISTENCE OF REGIONS OF EQUILIBRIUM AND NON-EQUILIBRIUM TWO-POINT TURBULENCE DYNAMICS IN GRID-GENERATED TURBULENCE BOTH WITH -5/3 SPECTRA BUT DIFFERENT UNDERLYING PHYSICS","authors":"J. Vassilicos, S. Laizet","doi":"10.1615/tsfp8.2080","DOIUrl":"https://doi.org/10.1615/tsfp8.2080","url":null,"abstract":"In this paper we present results concerning the spatial development of energy spectra E11( f ) and their associated integral and Taylor scales in conjunction with the spatial developments of vorticity, strain and production rates of vorticity and strain obtained from Direct Numerical Simulations of spatially developing grid-generated turbulence. We use a fractal square grid and a single mesh grid where the mesh is similar to the largest square on the fractal square grid. We find two adjacent but physically different regions in these flows relatively close to the grid: one where the Q-R diagram has not yet formed its well-known, presumed universal, tear-drop shape (Tsinober (2009)) but E11( f ) ∼ f−5/3 over more than a decade of a frequency range which is set by inlet conditions rather than Kolmogorov scalings: and one where theQ-R diagram immediately adopts the well-known tear-drop shape and E11( f ) ∼ f−5/3 over a Kolmogorov range of frequencies which increases as the local Reynolds number increases. In the one case with the higher local Reynolds numbers, the first region gives rise, as one moves downstream, to the non-equilibrium behaviour Cε ∼ 1/Reλ whilst the second region leads to Cε =Const.","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":"129574685","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":"SMALL SCALE UNIVERSALITY AND SPECTRAL CHARACTERISTICS IN TURBULENT FLOWS","authors":"Y. Kaneda, K. Morishita, T. Ishihara","doi":"10.1615/tsfp8.20","DOIUrl":"https://doi.org/10.1615/tsfp8.20","url":null,"abstract":"A review is given on studies of statistics at small scales in turbulent flows from a view point of universality. It is assumed in the view that the statistics at sufficiently small scales in the absence of mean flow are at a certain kind of local equilibrium state, and the influence of the mean flow may be regarded as a perturbation added to the equilibrium state. This idea has been examined by comparison of spectral characteristics derived by the idea with those in turbulent boundary layers, mixing layers and direct numerical simulations (DNS) of homogeneous turbulent shear flow. The applicability of this idea to turbulent channel flows is discussed in the light of the data of the log-law region in DNS of turbulent channel flows with the friction Reynolds numberReτ up to 5120. INTRODUCTION Turbulence is a phenomenon involving a huge number of degrees of dynamical freedom. A paradigm of study dealing with systems consisting of such a huge number of degrees of freedom is the statistical mechanics of systems at or near thermal equilibrium state. In the statistical mechanics, it is known that although it is difficult to trace the trajectory of each of the molecules or atoms in the physical or phase space, there are certain kinds of simple relations between a few variables, the socalled macroscopic variables, such as the pressure, density and temperature characterizing the equilibrium state. The relations are universal in the sense that they are independent of the detail of the difference in the trajectories of the molecules or atoms. It is also known that there are another kind of universal relations characterizing the response of the thermal equilibrium system to the disturbance added to the system. It is attractive to assume that the similar idea is applicable to turbulence. In fact, underlying the celebrated Kolmogorov theory (Kolmogorov,1941), referred here as K41, is the idea of existence of universal local equilibriums state, the statistics of which can be characterized by a few variables. In this paper, a review is given on studies along this idea with an emphasis on the spectral characteristics. Discussions are also made on the applicability of this idea to turbulent channel flows in the light of the log-law region in recent DNS of turbulent channel flows with the friction Reynolds number Reτ up to 5120. UNIVERSALITY AT LOCAL EQUILIBRIUM STATE We consider here the motion of incompressible fluid obeying the Navier-Stokes (NS) equation. Although it has not been rigorously proved, nor neither is it trivial that there is universality in the statistics of small scales in high Reynolds number turbulence, evidences supporting the existence have been accumulated. Among them is the so-called 4/5 law. The NS equation is compatible with the statistical homogeneity and isotropy of turbulent flows. Under the assumption of the homogeneity and isotropy of the turbulence statistics, the NS equation with the incompressibility condition yields a rigorous rela","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"4 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":"123758838","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":"CHARACTERISTICS OF FLOW OVER A CIRCULAR CYLINDER AT Red=140,000","authors":"Hyun Sik Kim, Jungil Lee, Jooha Kim, Haecheon Choi","doi":"10.1615/tsfp8.1770","DOIUrl":"https://doi.org/10.1615/tsfp8.1770","url":null,"abstract":"In the present study, we conduct both numerical and experimental studies to investigate the characteristics of flow over a circular cylinder at Red = 140,000, where Red is the Reynolds number based on the cylinder diameter d and free-stream velocity. Large eddy simulation (LES) is conducted for numerical investigation, and direct force and particle image velocimetry (PIV) measurements are conducted for experimental investigation. The drag and base pressure coefficients from present numerical and experimental studies agree well with each other. The instantaneous flow over a circular cylinder exhibits various flow structures such as laminar separation at the cylinder surface, shear-layer after the separation, vivid small-scale vortices and vortex shedding in the wake. In the near wake of circular cylinder, it is observed that a vortical structure distorted in spanwise direction and weak vortex shedding intermittently occurs, inducing relatively low drag and lift fluctuations. INTRODUCTION A circular cylinder is a representative bluff body, found in the structures such as wind generator, lamp post, etc. The flow over a circular cylinder at subcritical Reynolds number exhibits various flow phenomena including boundary layer, separation, shear layer evolution and vortex shedding in the wake. Therefore, there have been numerous studies to understand the flow over a circular cylinder experimentally and numerically. However, the experimental results from several researchers show non-negligible variations among themselves (Bearman, 1969; Achenbach and Heinecke, 1981; West and Apelt, 1982; Farell and Blessmann, 1983; Cantwell & Coles, 1983; Szepessy and Bearman, 1992). Furthermore, some attempts were also made to predict the flow around a circular cylinder using large eddy simulation (LES; Fröhlich et al., 1998; Breuer, 2000), but those studies only dealt with the effects of numerics such as grid system, resolution and subgrid-scale models and could not evaluate the prediction performance from numerical simulation due to the scatter in the experimental results. Therefore, in the present study, we investigate the flow over a circular cylinder at a subcritical Reynolds number (Red = 140,000) from both the experimental and numerical approaches. EXPERIMENTAL & COMPUTATIONAL DETAILS August 28 30, 2013 Poitiers, France WAK1A 2 Figure 1. Experimental set-up for (a) force and surface pressure measurements; (b) PIV measurement. Experimental setup The present experiment is conducted in a closed-type wind tunnel whose size of test section is 900 mm × 900 mm. The turbulence intensity is lower than 0.3% at the free-stream velocity of 20 m/s. Figure 1a shows the schematic diagram of the present experimental set-up for force and surface pressure measurements, consisting of a circular cylinder, end plate, load cell, pressure holes, scannivalve, and manometer. The cylinder is made of ABS resin with the diameter d = 70 mm. The aspect ratio of the cylinder is 11.4. Boundary-","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"13 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":"121841033","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":"APPLICATION OF KALMAN FILTERING AND PARTIAL LEAST SQUARE REGRESSION TO LOW ORDER MODELING OF UNSTEADY FLOWS","authors":"R. Leroux, L. Chatellier, L. David","doi":"10.1615/tsfp8.860","DOIUrl":"https://doi.org/10.1615/tsfp8.860","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":"122530921","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":"GRADIENT TRAJECTORY ANALYSIS OF THE TURBULENT/NON-TURBULENT INTERFACE IN A JET FLOW","authors":"M. Gampert, P. Schaefer, J. Boschung, N. Peters","doi":"10.1615/tsfp8.2180","DOIUrl":"https://doi.org/10.1615/tsfp8.2180","url":null,"abstract":"Based on planar high-speed Rayleigh scattering measurements of the mixture fraction Z of propane discharging from a turbulent round jet into co-flowing carbon dioxide at nozzle based Reynolds numbers Re0=3,000-8,600, we use scalar gradient trajectories to investigate the local structure of the turbulent scalar field with a focus on the scalar turbulent/non-turbulent interface. The latter is located between the fully turbulent part of the jet and the outer flow. Using scalar gradient trajectories, we partition the turbulent scalar field into these three regions according to an approach developed by Mellado et al. (2009). Based on these different regions, we investigate in a next step zonal statistics of the scalar pdf P(Z) as well as the scalar difference along the trajectory ∆Z and its mean scalar value Zm, where the latter two quantites are used to parameterize the scalar profile along gradient trajectories. We show that the scalar probability density function P(Z) can be reconstructed from zonal gradient trajectory statistics of the joint probability density function P(Zm,∆Z). Furthermore, we relate our results for the scalar turbulent/non-turbulent interface on the one hand to the findings made in other experimental and numerical studies of the turbulent/non-turbulent interface and discuss them on the other hand in the context of the flamelet approach and the modelling of probability density functions in turbulent non-premixed combustion.","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"98 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":"122594420","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":"EDUCTION SCHEME FOR CONVECTIVE STRUCTURES IN TURBULENT COMPRESSIBLE SEPARATED FLOW","authors":"Tetyana Jiang, L. Larchevêque, P. Dupont","doi":"10.1615/tsfp8.550","DOIUrl":"https://doi.org/10.1615/tsfp8.550","url":null,"abstract":"Evidence of coherent convective vortical structures in a statistical sense is obtained for a turbulent compressible separated flow. Structures are detected and tracked in unsteady data from a Large Eddy Simulations of shock waveboundary layer interaction by means of a new algorithm. This one is based on the detection of the modulations of the instantaneous zero mass flux lines induced by the travelling structures. The educed structures are spatially characterized and their frequencies, convection velocities and dimensions are given. Their effect on the wall pressure and the skin friction coefficients are also described. INTRODUCTION Shock-wave/boundary-layer interaction (SWBLI) has been largely studied for several decades due to their practical interest in aeronautical applications. One critical feature of such flows is the occurrence of low-frequency unsteadiness if the shock-induced adverse pressure gradient is strong enough to induce a separation of the incoming boundary layer. The physics resulting in these lowfrequency unsteadiness, also encountered in many subsonic separated flow (Cherry et al., 1984; Kiya & Sasaki, 1983) is not yet fully understood, see Babinsky & Harvey (2011). However, possible links between the low-frequency unsteadiness and the coherent structures of the mixing layer developing downstream the separation point have been highlighted in recent works, both in subonic (Ehrenstein & Gallaire, 2008) and supersonic regime (Piponniau et al., 2009). It is therefore of importance to obtain a comprehensive description of the characteristics of these structures. Difficulty arise in turbulent flows from the energy preeminence of the structures issued from the incoming boundary layer over the mixing layer ones. Some information where nonetheless obtained in SWBLI from two-point statistics and instantaneous PIV measurements of Dupont et al. (2006); Piponniau et al. (2009). The purpose of the present work is to complete these data by providing a statistical description of the dynamics associated with these Figure 1. Spark Schlieren visualization of the interaction. structures. A conditional averaging method relying on a new eduction scheme of the coherent structures is proposed to this end. As an illustration, it is applied to data obtained from a Large-Eddy Simulation of a Mach 2.3 shock reflection for flow deflection angle of 9.5◦ including a large separation, as described in Agostini et al. (2012). The unsteady properties have been widely validated against the experimental results obtained for the same interaction geometry Agostini et al. (2012). The spatial organization of the flow is illustrated with a short time exposure Schlieren of the interaction in figure 1. The origin of the longitudinal coordinate x was fixed at the mean position (X0) of the unsteady reflected shock. This position was derived from unsteady wall pressure. It was normalized by the length of interaction L defined as the distance between X0 and the extrapolatio","PeriodicalId":206337,"journal":{"name":"Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena","volume":"42 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":"121262387","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}