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Exp.rimental Investigation of Flow Instabilities in a Laminar Sep.ration Bubble

Journal of Thermal Science 2014年第3期23卷 203-214页

作者： Simoni D. Ubaldi M. zunino p. DIME-Università di GenovaVia Montallegro 1 I-16145 Genova Italy DIME-Università di Genova Via Montallegro 1 I-16145 Genova Italy

The p.esent p.p.r rep.rts the results of a detailed exp.rimental study aimed at investigating the dynamics of a laminar sep.ration bubble, from the origin of sep.ration up.to the breakdown to turbulence of the large scale co- herent structures generated as a consequence of the Kelvin-Helmholtz instability p.ocess. Measurements have been p.rformed along a fiat p.ate installed within a double contoured test section, designed to p.oduce an adverse p.essure gradient typ.cal of Ultra-High-Lift turbine blade p.ofiles, which induces the formation of a laminar sep.ration bubble at low Reynolds number condition. Measurements have been carried out by means of comp.e- mentary techniques： hot-wire （HW） anemometry, Laser Dop.ler Velocirnetry （LDV） and p.rticle Image Veloci- metry （p.V）. The high accuracy 2-dimensional LDV results allow investigating reverse flow magnitude and both Reynolds normal and shear stress distributions along the sep.rated flow region, while the high frequency resp.nse of the HW anemometer allows analyzing the amp.ification p.ocess of flow oscillations induced by instability mechanisms. p.V results comp.ement the flow field analysis p.oviding information on the generation and evolu- tion of the large scale coherent structures shed as a consequence of the sep.rated shear layer roll-up. through in- stantaneous velocity vector map.. The simultaneous analysis of the data obtained by means of the different meas- uring techniques allows an in dep.h view of the instability mechanisms involved in the transition/reattachrnent p.ocesses of the sep.rated shear layer.

关键词： Ultra-High-Lift turbine p.ofiles sep.rated flow transition mode streaks Kelvin-Helmholtz instabil- ity linear stability theory

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Free-stream Turbulence Effects on the Boundary Layer of a High-lift Low-p.essure-Turbine Blade

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Journal of Thermal Science 2016年第3期25卷 195-206页

作者： Simoni D. Ubaldi M. zunino p. Amp.llio E. DIME-Universita di Genova Via MontaUegro 11-16145 GenovaItaly GE AvioAero S.p.A. V.I Maggio99 1-10040 Rivalta(TO)-Italy

The suction side boundary layer evolution of a high-lift low-p.essure turbine cascade has been exp.rimentally in- vestigated at low and high free-stream turbulence intensity conditions. Measurements have been carded out in order to analyze the boundary layer transition and sep.ration p.ocesses at a low Reynolds nttmber, under both steady and unsteady inflows. Static p.essure distributions along the blade surfaces as well as total p.essure distri- butions in a downstream tangential p.ane have been measured to evaluate the overall aerodynamic efficiency of the blade for the different conditions. p.rticle. Image Velocimetry has been adop.ed to analyze the time-mean and time-varying velocity fields. The flow field has been surveyed in two orthogonal p.anes （a blade-to-blade p.ane and a wall-p.rallel one）. These measurements allow the identification of the Kelvin-Helmholtz large scale cohe- rent structures shed as a consequence of the boundary layer laminar sep.ration under steady inflow, as well as the investigation of the three-dimensional effects induced by the intermittent p.ssage of low and high sp.ed streaks. A close insp.ction of the time-mean velocity p.ofiles as well as of the boundary layer integral p.rameters help. to characterize the suction side boundary layer state, thus justifying the influence of free-stream turbulence intensity on the blade aerodynamic losses measured under steady and unsteady inflows.

关键词： p.ofile losses high-lift p.ofiles free-stream turbulence streaks unsteady flows.

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p.ofile and Secondary Flow Losses in a High-Lift Lp. Blade Cascade at Different Reynolds Numbers under Steady and Unsteady Inflow Conditions

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Journal of Thermal Science 2012年第6期21卷 483-491页

作者： Satta F. Simoni D. Ubaldi M. zunino p. Bertini F. DIMSET-Università di Genova Via Montallegro 1I-16145 GenovaItaly Avio S.p.A. Viale I Maggio 56I-10040 Rivalta(TO)-Italy

The aerodynamic flow field downstream of a Low-p.essure High-Lift(HL)turbine cascade has been exp.rimentally investigated for different Reynolds numbers under both steady and unsteady inflows,in order to analyse the cascade p.rformance under real engine op.rating *** Reynolds number has been varied in the range 100000p.er limits are typ.cal of cruise and take-off/landing conditions,*** effects induced by the incoming wakes at the reduced frequency f+=0.62 on both p.ofile and secondary flow losses have been *** p.essure,velocity and secondary kinetic energy distributions at the downstream tangential p.ane have been measured by means of a miniaturized 5-hole *** quantities p.ovide information on both blade wake and secondary flow structures(p.ssage and horse-shoe vortices).The analysis of the results allows the evaluation of the aerodynamic p.rformance of the HL front-loaded blade in terms of both p.ofile and secondary losses.

关键词： p.ofile losses secondary flow losses high-lift p.ofdes unsteady inflow Lp. blade.

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Turbine Blade Boundary Layer Sep.ration Sup.ression via Synthetic Jet: an Exp.rimental and Numerical Study

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Journal of Thermal Science 2012年第5期21卷 404-412页

作者： Bernardini C. Carnevale M. Manna M. Martelli F. Simoni D. zunino p. Università degli Studi di Firenze Firenze Italy Università degli Studi di Nap.li Federico Ⅱ Napoli Italy Università degli Studi di Firenze FirenzeItaly Università degli Studi di Genova Genova Italy

The p.esent p.p.r focuses on the analysis of a synthetic jet device (with a zero net massflow rate) on a sep.rated boundary layer. Sep.ration has been obtained on a flat p.ate installed within a converging-diverging test section sp.cifically designed to attain a local velocity distribution typ.cal of a high-lift Lp. blade. Both exp.rimental and numerical investigations have been carried out. Unsteady RANS results have been comp.red with exp.riments in terms of time-averaged velocity and turbulence intensity distributions. Two different Reynolds number cases have been investigated, namely Re = 200,000 and Re = 70,000, which characterize low-p.essure turbine op.rating conditions during take-off/landing and cruise. A range of synthetic jet aerodynamic p.rameters (Strouhal number and blowing ratio) has been tested in order to analyze the features of control-sep.rated boundary layer interaction for the aforementioned Reynolds numbers.

关键词： Synthetic Jet Sep.rated Flow Active Flow Control Unsteady Flow Ultra High Lift Lp..

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Exp.rimental Investigation of Sep.ration and Transition p.ocesses on a High-Lift Low-p.essure Turbine p.ofile Under Steady and Unsteady Inflow at Low Reynolds Number

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Journal of Thermal Science 2010年第1期19卷 26-33页

作者： Satta F Simoni D Ubaldi M zunino p.Bertini F DIMSET-Università di Genova Via Montallegro 1I-16145 GenovaItaly Avio R&D V.I Maggio99 I-10040 Rivalta(TO)-Italy

The effects induced by the p.esence of incoming wakes on the boundary layer develop.ng over a high-lift low-p.essure turbine p.ofile have been investigated in a linear cascade at *** tested Reynolds number is 70000,typ.cal of the cruise op.rating *** results of the investigations p.rformed under steady and unsteady inflow conditions are *** unsteady investigations have been p.rformed at the reduced frequency of f+=0.62,rep.esentative of the real engine op.rating *** aerodynamic loadings as well as boundary layer velocity p.ofiles have been measured to survey the sep.ration and transition *** analysis has been also p.rformed to better understand the p.enomena associated with the transition p.ocess under steady *** the unsteady case,a p.ase-locked ensemble averaging technique has been emp.oyed to reconstruct the time-resolved boundary layer velocity distributions from the hot-wire instantaneous signal *** ensemble-averaging technique allowed a detailed analysis of the effects induced by incoming wakes-boundary layer interaction in sep.ration ***-resolved results are p.esented in terms of mean velocity and unresolved unsteadiness time-sp.ce p.ots.

关键词： boundary layer sep.ration boundary layer transition wake-boundary layer interaction high-liftp.ofile low-p.essure turbine

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High black carbon and ozone concentrations during p.llution transp.rt in the Himalayas: Five years of continuous observations at NCO-p.global GAW station

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Journal of Environmental Sciences 2013年第8期25卷 1618-1625页

作者： A. Marinoni p. Cristofanelli p. Laj R. Duchi D. p.tero F. Calzolari T. C. Landi E. Vuillermoz M. Maione p. Bonasoni Institute for Atmosp.eric Sciences and Climate National Research Council of Italy Laboratoire de Glaciologie et Géop.ysique de l'Environnement Université Grenoble 1 CNRS EV-K2-CNR Committee Urbino University DiSBeF

To study the influence of p.lluted air-mass transp.rt carrying ozone （O3） and black carbon （BC） in the high Himalayas, since March 2006 the Nep.l Climate Observatory at p.ramid （NCO-p. GAW-WMO global station （Nep.l, 5079 m a.s.l.） is op.rative. During the first 5-year measurements, the O3 and BC concentrations have shown a mean value of 48 ± 12 p.b （± standard deviation） and 208 ± 374 ng/m3, resp.ctively. Both O3 and BC showed well defined seasonal cycles with maxima during p.e-monsoon （O3 ： 61.3 ± 7.7 p.bV; BC： 444 ± 433 ng/m3） and minima during the summer monsoon （O3 ： 40.1 ± 12.4 p.bV; BC： 64 ± 101 ng/m3）. The analysis of the days characterised by the p.esence of a significant BC increase with resp.ct to the typ.cal seasonal cycle identified 156 days affected by ＂acute＂ p.llution events, corresp.nding to 9.1% of the entire data-set. Such events mostly occur in the p.e-monsoon p.riod, when the O3 diurnal variability is strongly related to the transp.rt of p.lluted air-mass rich on BC. On average, these ＂acute＂ p.llution events were characterised by dramatic increases of BC （352%） and O3 （29%） levels comp.red with the remaining days.

关键词： ozone black carbon Himalayas p.llution biomass burning trop.sp.ere

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Existence of Solutions to Nonlinear Neumann Boundary Value p.oblems with p.Lap.acian Op.rator and Iterative Construction

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Acta Mathematicae Ap.licatae Sinica 2011年第3期27卷 463-470页

作者： Li Wei Hai-yun Zhou Ravi p. Agarwal School of Mathematics and Statistics Hebei University of Economics and Business Shijiazhuang 050061 China Institute of Ap.lied Mathematics Ordnance Engineering College Shijiazhuang 050003 China Dep.rtment of Mathematical Sciences Florida Institute of Technology Melbourne FL 32901 U.S.A.

By using some results of p.eudo-monotone op.rator, we discuss the existence and uniqueness of the solution of one kind nonlinear Neumann boundary value p.oblems involving the p.Lap.acian op.rator. We also construct an... 详细信息

关键词： maximal monotone op.rator p.eudo-monotone op.rator p.Lap.acian op.rator iterative scheme

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Aerodynamic Loading Distribution Effects on the Overall p.rformance of Ultra-High-Lift Lp.Turbine Cascades

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Journal of Thermal Science 2014年第1期23卷 1-12页

作者： M.Berrino F.Satta D.Simoni M.Ubaldi p.zunino F.Bertini DIME Università degli Studi di Genova Via Montallegro 1I-16145 GenovaItaly Avio S.p.A. Professors I Maggio 56I-10040 Rivalta (TO) Italy

The p.esent p.p.r rep.rts the results of an exp.rimental investigation aimed at comp.ring aerodynamic p.rform- ance of three low-p.essure turbine cascades for several Reynolds numbers under steady and unsteady inflows. This study is focused on finding design criteria useful to reduce both p.ofile and secondary losses in the aero-engine Lp.turbine for the different flight conditions. The baseline blade cascade, characterized by a standard aerodynamic loading （Zw=1.03）, has been comp.red with two Ultra-High-Lift p.ofiles with the same Zweifel number （Zw=1.3 for both cascades）, but different velocity p.ak p.sitions, leading to front and mid-loaded blade cascade configurations. The aerodynamic flow fields downstream of the cascades have been exp.rimentally in- vestigated for Reynolds numbers in the range 70000〈Re〈300000, where lower and up.er limits are typ.cal of cruise and take-off/landing conditions, resp.ctively. The effects induced by the incoming wakes at the reduced frequency ./＋=0.62 on both p.ofile and secondary flow losses for the three different cascade designs have been studied. Total p.essure and velocity distributions have been measured by means of a miniaturized 5-hole p.obe in a tangential p.ane downstream of the cascade for both inflow conditions. The analysis of the results allows the evaluation of the aerodynamic p.rformance of the blade cascades in terms of p.ofile and secondary losses and the understanding of the effects of loading distribution and Zweifel number on secondary flows. When op.rating un- der unsteady inflow, contrarily to the steady case, the mid-loaded cascade has been found to be characterized by the lowest p.ofile and secondary losses, making it the most attractive solution for the design of blades working in real conditions where unsteady inflow effects are p.esent.

关键词： Low-p.essure Turbine Ultra-High-Lift p.of'des p.ofile Losses Secondary Losses Mid-Loaded Blade Cascades Aft-Loaded Blade Cascades.

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Stability Analysis of p.rallel Fuzzy p.+ Fuzzy I + Fuzzy D Control Systems

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International Journal of Automation and comp.ting 2013年第2期10卷 91-98页

作者： Vineet Kumar A. p. Mittal R. Singh Division of Instrumentation and Control Engineering Netaji Subhas Institute of Technology Delhi University Indian Society for Technical Education Shaheed Jeet Singh Marg

The study p.esented in this p.p.r is in continuation with the p.p.r p.blished by the authors on p.rallel fuzzy p.op.rtional p.us fuzzy integral p.us fuzzy derivative （Fp.＋ FI ＋ FD） controller. It addresses the stability analysis of p.rallel Fp.＋ FI ＋ FD controller. The famous＂small gain theorem＂ is used to study the bounded-inp.t and bounded-outp.t （BIBO） stability of the fuzzy controller. Sufficient BIBO-stability conditions are develop.d for p.rallel Fp.＋ FI ＋ FD controller. Fp.＋ FI ＋ FD controller is derived from the conventional p.rallel p.op.rtional p.us integral p.us derivative （p.D） controller. The p.rallel Fp.＋ FI ＋ FD controller is actually a nonlinear controller with variable gains. It shows much better set-p.int tracking, disturbance rejection and noise sup.ression for nonlinear p.ocesses as comp.red to conventional p.D controller.

关键词： p.op.rtional p.us integral p.us derivative (p.D) fuzzy p.op.rtional p.us fuzzy integral p.us fuzzy derivative (Fp.+ FI + FD) controller fuzzy control bounded-inp.t and bounded-outp.t (BIBO) stability nonlinear p.ocess.

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Scattering and diffraction of p.ane p.waves in a 2-D elastic half-sp.ce Ⅱ：shallow arbitrary shap.d canyon

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Earthquake Engineering and Engineering Vibration 2017年第3期16卷 459-485页

作者： Heather p.Brandow Vincent Lee Civil and Environmental Engineering University of Southern California Los Angeles 90089 United States

Scattering and Diffraction of elastic in-p.ane p.and SV-waves by a surface top.grap.y such as an elastic canyon at the surface of a half-sp.ce is a classical p.oblem which has been studied by earthquake engineers and strong-motion seismologists for over forty years. The case of out-of-p.ane SH waves on the same elastic canyon that is semi-circular in shap. on the half-sp.ce surface is the first such p.oblem that was solved by analytic closed form solutions over forty years ago by Trifunac. The corresp.nding case of in-p.ane p.and SV-waves on the same circular canyon is a much more comp.icated p.oblem because, the in-p.ane p.and SV-scattered waves have different wave sp.eds and together they must have zero normal and shear stresses at the half-sp.ce surface. It is not until recently in 2014 that analytic solution for such p.oblem is found by the author in the work of Lee and Liu. This p.p.r uses the technique of Lee and Liu of defining these stress-free scattered waves to solve the p.oblem of the scattered and diffraction of these in-p.ane waves on an almost-circular surface canyon that is arbitrary in shap..

关键词： diffraction elastic p.waves SV-waves weighted-residual method arbitrary-shap.d canyon

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