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

{"title":"THE FLOW FIELD INSIDE A RANQUE-HILSCH VORTEX TUBE PART I: EXPERIMENTAL ANALYSIS USING PLANAR FILTERED RAYLEIGH SCATTERING","authors":"U. Doll, Eike Burow, M. Beversdorff, G. Stockhausen, C. Willert, C. Morsbach, Daniel Schlüß, M. Franke","doi":"10.1615/tsfp9.800","DOIUrl":"https://doi.org/10.1615/tsfp9.800","url":null,"abstract":"The flow field of a Ranque-Hilsch vortex tube is characterized experimentally. Firstly conventional probe based technology is used in order to measure inlet and outlet temperatures as well as to acquire temporally resolved wall pressure data over a wide range of operating conditions. Secondly the filtered Rayleigh scattering technique is employed in order to gather detailed temporally averaged planar information on the vortex tube’s flow topology. These measurements form the basis of a detailed numerical study in part II of this contribution.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"10 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":"121308795","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":"DIRECT NUMERICAL SIMULATION OF THE WAKE OF A NORMAL THIN FLAT PLATE: INFINITE VS. FINITE WIDTH","authors":"A. Hemmati, D. Wood, R. Martinuzzi","doi":"10.1615/tsfp9.200","DOIUrl":"https://doi.org/10.1615/tsfp9.200","url":null,"abstract":"","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth 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":"114318985","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":"OPEN LOOP CONTROL OF A TURBULENT BACKWARD FACING STEP BY DBD PLASMA ACTUATORS","authors":"N. Benard, P. Sujar-Garrido, J. Bonnet, E. Moreau","doi":"10.1615/tsfp9.920","DOIUrl":"https://doi.org/10.1615/tsfp9.920","url":null,"abstract":"A non-thermal surface plasma discharge (dielectric barrier discharge) is installed at the step corner of a backwardfacing step (U0=15 m/s, Reh=30000, Reθ=1650). Wall pressure sensors are used to estimate the reattaching location downstream of the step and also to measure the global wall pressure fluctuation coefficients. A parametric study is performed where the voltage amplitude, the burst frequency and the duty-cycle of the input high voltage are investigated separately regarding their performance. PIV is used to analyse the impact on the dynamic of the flow. The minimum reattaching position is achieved by forcing the flow at the shear layer mode through 2D periodic perturbations in the initial region at Sth=0.25 (Stθ=0.013), where a large spreading rate is obtained by increasing the periodicity of the vortex street and by enhancing the vortex pairing process. A recirculation reduction by 22% is observed. Pressure fluctuations are maximized for an actuation at half the shear layer mode (Sth=0.125 or Stθ=0.006). In this case, the vortex pairing goes along with sequences of single vortex growing by fluid entrainment during their convection.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"15 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":"116208126","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 Flame Flashback by Combustion Induced Vortex Breakdown","authors":"E. Tangermann, M. Klein, M. Pfitzner","doi":"10.1615/tsfp9.170","DOIUrl":"https://doi.org/10.1615/tsfp9.170","url":null,"abstract":"Flame flashback is a major concern during the design of lean premixed gas turbine combustors. One particular mechanism of flame flashback in swirl stabilized combustors is the combustion induced vortex breakdown (CIVB), where the flame can propagate upstream against flow velocities far higher than the local turbulent flame speed. In the present work flame flashback by CIVB has been investigated for two combustors of different scale using large eddy simulation. The LES offers full access to a well resolved flow field and allows a detailed analysis of the fluid mechanical processes happening around the flame tip. The method is shown being able to reproduce the operating points limiting stable operation. The analysis of each flashback process then reveals, that the driving mechanism is different for both combustors depending on their size and the swirl velocity field. Either a baroclinic push or a flame propagation by stretching of the flow can be observed. INTRODUCTION Lean premixed combustion in gas turbine burners is an effective way to reduce NOx emissions. However, a major concern is the stability of the combustion process, since ignitable gas is present upstream of the combustion zone bringing the risk of flame flashback, and since the lean flame needs to be prevented from extinction by sophisticated stabilization mechanisms. Several ways of flame stabilization are common, usually they feature the recirculation of burnt, hot gas to provide activation energy for the ignition of fresh gas. The recirculation can be realized in the wake of a body or by fluid mechanical instabilities like a vortex breakdown, the latter of which has been used in the presently investigated configurations. The premixed flow enters the burner from a plenum through a swirl generator into a mixing tub, where a perfect mixture of the reactants is achieved in the swirling flow. A vortex breakdown is forced at the entry of the combustion chamber caused by the sudden change in diameter of the confining walls. The thus created recirculation zone transports hot burnt gas upstream igniting the arriving fresh gas. The vortex breakdown can also be caused by an obstacle located on the centreline. Inside a recirculation zone the flame front can act as such an obstacle and influence the vortex breakdown. The so called combustion induced vortex breakdown (CIVB) has been described by Fritz et al. (2004). If the flame front is located far enough upstream within the swirl tube it can push the vortex breakdown further upstream, which itself pulls the flame even further upstream. The recirculation zone propagates against the flow at a higher velocity than the local turbulent flame speed. Due to the confinement the experimental access to the propagating flame is very limited. Most of the process takes place inside the mixing tube. By using a silica glass mixing tube optical measurement can be used with some restrictions (Fritz 2004, Konle 2008). The curved surface leads to bending effects ","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth 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":"127666588","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":"EFFECTIVENESS OF FLOW-EXCITED HELMHOLTZ RESONATOR ON TURBULENCE STRUCTURES IN STREAMWISE AND SPANWISE DIRECTIONS","authors":"F. Ghanadi, M. Arjomandi, B. Cazzolato, A. Zander","doi":"10.1615/tsfp9.410","DOIUrl":"https://doi.org/10.1615/tsfp9.410","url":null,"abstract":"","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth 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":"127709427","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":"CONSEQUENCES OF SELF-PRESERVATION IN A TURBULENT FAR-WAKE","authors":"S. Tang, R. Antonia, L. Djenidi, Y. Zhou","doi":"10.1615/tsfp9.210","DOIUrl":"https://doi.org/10.1615/tsfp9.210","url":null,"abstract":"","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"43 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131789723","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":"FULLY TURBULENT FLOW IN A PHYSIOLOGICALLY REALISTIC HUMAN AIRWAY BIFURCATION","authors":"F. Stylianou, S. Kassinos","doi":"10.1615/tsfp9.1200","DOIUrl":"https://doi.org/10.1615/tsfp9.1200","url":null,"abstract":"Recent computational studies have shown that the airflow in the upper human airways is turbulent during much of the respiratory cycle. A feature of respiratory airflow that poses a challenge to computations based on ReynoldsAveraged Navier-Stokes (RANS) closures is the laminarturbulent-laminar transition as the flow moves from the mouth through the glottis and down to the lower conducting airways. Turbulence and unsteadiness are expected at least through the first few bifurcations of the airways. In the case of inhaled medicines, and depending on the size of the particles in the formulation, airway bifurcations are areas of preferential deposition. In this study we perform for the first time, Large Eddy Simulations (LES) and Direct Numerical Simulations (DNS) of fully developed turbulent flow through a single human airway bifurcation, emulating steady prolonged inspiration and expiration conditions. We also perform RANS simulations via the v2− f closure model and compare with our DNS and LES results. We examine the mean flow characteristics and the turbulent vortical structures as well as their effect on the deposition of particles of different sizes.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"172 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":"115794498","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":"COMPUTATIONAL FLUID DYNAMICS (CFD) SIMULATIONS OF AEROSOL DEPOSITION IN THE LUNGS","authors":"P. Koullapis, S. Kassinos, Ching-Long Lin","doi":"10.1615/tsfp9.1190","DOIUrl":"https://doi.org/10.1615/tsfp9.1190","url":null,"abstract":"In the current study, Large Eddy Simulations (LES) are used to investigate the transport and deposition of inhaled aerosol particles (dp = 0.1, 0.5, 1, 2.5, 5, 10 μm) in a realistic geometry of the human airways under steady inhalation. The effects of electrostatic charge and lower generation airway narrowing caused by Chronic Obstructive Pulmonary Disease (COPD) on particle transport and deposition are examined for various flowrates (sedentary 15.2 lt/min, light 30 lt/min and heavy activity 60 lt/min). Results show that the mean flow structures at the three flowrates are qualitatively similar regardless of Reynolds number. Similar swirling motions are generated from the impingement of the laryngeal jet on the tracheal front wall. However, higher turbulent intensities that persist further downstream in the trachea and the main bronchi are observed as the flowrate is increased. The Deposition Efficiency (DE) of particles is increased with the flowrate due to greater inertial impaction. The majority of the larger particles are filtered in the mouththroat region, while 0.1, 0.5 and 1μm diameter particles have similar DE at a given flowrate. The effect of charge on DE of particles is more pronounced for smaller particles; 1000 elementary charge units on 0.1, 0.5, 1 and 2.5 μm diameter particles results in approximately 7, 3, 2.5 and 1.5 times greater overall DE than that with no charge, respectively. Obstructed lower generation airways result in enhanced deposition due to impaction caused by higher velocities in these airways. INTRODUCTION Computational Fluid Dynamics (CFD) techniques are being increasingly used to simulate flow behavior in the human respiratory system. Recent works include Reynolds Averaged Navier-Stokes (RANS) simulations (Luo & Liu, 2008), Large Eddy Simulations (LES) (Choi et al. (2009), Radhakrishnan & Kassinos (2009)) and Direct Numerical Simulations (DNS) (Lin et al., 2007). Both idealized model geometries and geometries obtained from medical imaging have been used. The deposition of therapeutic or pollutant xenobiotic particles is dependent on the characteristics of the respiratory flow by which they are transported (Xi & Longest, 2007). The ultimate goal of the application of CFD techniques is an in-depth understanding of the fate of inhaled pollutants, including deposition and possible mucus clearance, as well as the efficient pulmonary delivery of drugs targeting respiratory or systemic diseases. An important parameter affecting both the characteristics of the airflow and particle transport is the inhalation rate. A higher flowrate causes an earlier transition to turbulence and higher overall turbulence levels. Johnstone et al. (2004) studied experimentally the velocity fields in an idealized model of the human extrathoracic airway during steady inspiration and found that Reynolds stress profiles were highly dependent on inhalation flowrate, especially in the separated shear layer regions. Flow rates of 15, 30 and 60 lt/mi","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"299 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":"124271449","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 ROTATING FLOWS WITH SEPARATION USING THE ELLIPTIC-BLENDING REYNOLDS-STRESS MODEL","authors":"R. Manceau","doi":"10.1615/tsfp9.790","DOIUrl":"https://doi.org/10.1615/tsfp9.790","url":null,"abstract":"The present paper addresses the issue of the reproduction of rotating flows with separation of the boundary layer that are relevant to many turbomachinery applications. In order to account for both the wall/turbulence and the Coriolis force/turbulence interactions at the RANS level, a second-moment closure valid in the near-wall region is necessary. The Elliptic Blending Reynolds Stress Model (EB-RSM), originally proposed by Manceau & Hanjali c (2002) is such a closure model. Various modifications to this model by several authors during the last decade are revisited from the theoretical standpoint and investigated in detail in comparison with recent DNS databases for high-Reynolds number channel flows, spanwise rotating channel flows with strong rotation rates, up to complete laminarization, and the separated flow after a sudden expansion without and with system rotation.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"5 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":"116949313","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":"Energy balance in turbulent gas-solid channel flow","authors":"Lihao Zhao, Qingqing Pan, H. Andersson","doi":"10.1615/tsfp9.1170","DOIUrl":"https://doi.org/10.1615/tsfp9.1170","url":null,"abstract":"The aim of the present study is to examine the implications of particle additives on the transfer, conversion and dissipation of mechanical energy in a turbulent gas-solid channel flow. To achieve this goal we have performed two-way coupled direct numerical simulations (DNSs) of gas-solid channel flow. Equations for fluid mean flow kinetic energy (KE) and fluid turbulent kinetic energy (TKE) are used in the results analysis. To highlight the influence of particles, the KE budgets were compared with the results of un-laden channel flow, i.e. without any additives. It was found that in the un-laden flow, 57.2% of the energy input was directly dissipated in the mean flow, whereas 40.2% was converted to turbulence through mean shear production before being dissipated by viscous action at small scales. By contrast, in the particle-laden flow, the interaction of the particles and fluid appears in the energy budgets. In the mean-flow energy balance, the mean dissipation accounted for 59.1% of the energy supply. This is comparable with the un-laden flow. However, the energy loss from the mean flow reduced from 40.2% to 13.7%, but was partly compensated by the new sink term (24.7%) which represents negative work done by the particles. The results also suggested that the mean flow loses kinetic energy to particles in the centre region of the channel, whereas it gains energy from the particles in the near-wall region. In the TKE budget, the particles released kinetic energy to the turbulence and this energy is likely obtained from the mean flow. This extra energy supply compensates partially for the substantial reduction of the mean shear production to about 2/3 of the production in the un-laden channel. Ultimately TKE is dissipated by deformation work due to the fluctuating viscous stresses. We concluded that the particles play an intermediary role in the energy transfer and conversion from the mean flow to the turbulence. INTRODUCTION Particle-laden flow is one of the most common twophase flows, which is found both in nature and industry, such as air transport of pollutants, fluidized bed in chemical processes, and dispersion of volcanic ash in the atmosphere. The complexity of the turbulent fluid motion leads to fascinating dynamics of particle suspensions as well as complicated particle-fluid interactions, such as kinetic energy transfer between the solid and gas phases (see Zhao et al. 2013). It is known that the addition of tiny particles can modulate the fluid motion and either augmentation or attenuation of the turbulence has been observed (Balachandar & Eaton 2010, Squires & Eaton 1990). Such phenomena have been widely explored by means of experiments and numerical simulations, such as Squires & Eaton (1990), Pan & Banerjee (1996), Dritselis and Vlachos (2008), Zhao et al. (2010). Kinetic energy budgets are one of the primary tools to examine the turbulent flow. Andersson & Barri (2008) investigated KE transport and conversion in an unladen turbule","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth 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":"129772574","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}