Long-Duration Time-Resolved PIV to Study Unsteady Aerodynamics

2010 ◽  
Vol 59 (12) ◽  
pp. 3262-3269 ◽  
Author(s):  
Zachary J. Taylor ◽  
Roi Gurka ◽  
Gregory A. Kopp ◽  
Alex Liberzon
Keyword(s):  
Unsteady Aerodynamics ◽  
Time Resolved ◽  
Duration Time ◽  
Long Duration

scholarly journals Time-resolved spectral correlations of long-duration γ-ray bursts

2009 ◽  
Vol 393 (4) ◽  
pp. 1209-1218 ◽  
Author(s):  
C. Firmani ◽  
J. I. Cabrera ◽  
V. Avila-Reese ◽  
G. Ghisellini ◽  
G. Ghirlanda ◽  
...  
Keyword(s):  
Time Resolved ◽  
Long Duration ◽  
Γ Ray

Unsteady Aerodynamics of a Low Aspect Ratio Turbine Stage: Modeling Issues and Flow Physics

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
G. Persico ◽  
A. Mora ◽  
P. Gaetani ◽  
M. Savini
Keyword(s):  
Aspect Ratio ◽  
Coming Out ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Fast Response ◽  
Operating Conditions ◽  
Pressure Probe ◽  
Turbine Stage ◽  
Time Resolved ◽  
Low Aspect Ratio

In this paper the three-dimensional unsteady aerodynamics of a low aspect ratio, high pressure turbine stage are studied. In particular, the results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX, are critically evaluated against experimental data. Measurements were carried out with a novel three-dimensional fast-response pressure probe in the closed-loop test rig of the Laboratorio di Fluidodinamica delle Macchine of the Politecnico di Milano. An analysis is first reported about the strategy to limit the CPU and memory requirements while performing three-dimensional simulations of blade row interaction when the rotor and stator blade numbers are prime to each other. What emerges as the best choice is to simulate the unsteady behavior of the rotor alone by applying the stator outlet flow field as a rotating inlet boundary condition (scaled on the rotor blade pitch). Thanks to the reliability of the numerical model, a detailed analysis of the physical mechanisms acting inside the rotor channel is performed. Two operating conditions at different vane incidence are considered, in a configuration where the effects of the vortex-blade interaction are highlighted. Different vane incidence angles lead to different size, position, and strength of secondary vortices coming out from the stator, thus promoting different interaction processes in the subsequent rotor channel. However some general trends can be recognized in the vortex-blade interaction: the sense of rotation and the spanwise position of the incoming vortices play a crucial role on the dynamics of the rotor vortices, determining both the time-mean and the time-resolved characteristics of the secondary field at the exit of the stage.

scholarly journals Some climatological features of thunderstorms at Thiruvananthapuram, Kochi and Kozhikode airports

MAUSAM ◽  
2021 ◽  
Vol 52 (2) ◽  
pp. 357-364
Author(s):  
K. SANTHOSH ◽  
R. SARASA KUMARI ◽  
V. K. GANGADHARAN ◽  
N. V. SASIDHARAN
Keyword(s):  
Thunderstorm Activity ◽  
Post Monsoon ◽  
Duration Time ◽  
Long Duration

The average monthly frequency of thunderstorms, its annual and monthly frequency of duration, time of commencement and frequency of thunderstorms in relation to duration and time of commencement at three aerodrome stations of Thiruvananthapuram, Kochi and Kozhikode have been presented in this paper. It is found that thunderstorm activity is maximum in pre-monsoon months at Thiruvananthapuram and Kochi and in post monsoon months at Kozhikode. Majority of the thunderstorms are of duration less than three hours and have a preference to commence between 9 and 18 UTC in all stations whereas long duration thunderstorms generally commence between 9 and 15 UTC.

Migration enhancement on ZnSe surface in photoassisted molecular beam epitaxy and long duration time of the effects

1994 ◽  
Vol 138 (1-4) ◽  
pp. 14-18 ◽  
Author(s):  
S. Ichikawa ◽  
N. Matsumura ◽  
K. Yamawaki ◽  
K. Senga ◽  
J. Saraie
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Duration Time ◽  
Long Duration

scholarly journals Characterization of the Unsteady Aerodynamics of Optimized Turbine Blade Tips through Modal Decomposition Analysis

2019 ◽  
Vol 4 (2) ◽  
pp. 12
Author(s):  
Bogdan C. Cernat ◽  
Sergio Lavagnoli
Keyword(s):  
High Performance ◽  
Decomposition Analysis ◽  
Unsteady Aerodynamics ◽  
Tip Leakage Flow ◽  
Modal Decomposition ◽  
Time Resolved ◽  
Leakage Flows ◽  
Numerical Predictions ◽  
Blade Tip ◽  
Generation Mechanisms

The present research focused on the analysis of the leakage flows developing from advanced blade tip geometries. The aerodynamic field of a contoured blade tip and of a high-performance rimmed blade were investigated against a baseline squealer rotor. Time-resolved numerical predictions were combined with high-frequency pressure measurements to characterize the tip leakage flow of each tip design. High spatial and temporal resolution measurements provided a detailed representation of the unsteady flow in the near-tip region and at the stage outlet. Numerical computations, based on the nonlinear harmonic method, were employed to assess the unsteady blade row interactions and identify the loss generation mechanisms depending on the tip design. The space- and time-resolved flow field was analysed by modal decomposition to identify the main periodicities of the near-tip and outlet flow and classify the most relevant sources of aerodynamic unsteadiness and entropy generation across the stage.

Aerodynamic Performance Measurement in a Fully Scaled Transient Turbine Test Facility

2007 ◽  
Author(s):  
N. R. Atkins ◽  
R. W. Ainsworth ◽  
N. W. Harvey
Keyword(s):  
Heat Transfer ◽  
Steady Flow ◽  
Large Scale ◽  
Unsteady Aerodynamics ◽  
Aerodynamic Performance ◽  
Test Facility ◽  
Performance Measurements ◽  
Time Resolved ◽  
Simultaneous Study ◽  
Practical Performance

The practical performance, both the efficiency and durability, of a High-Pressure (HP) turbine depends on many interrelated factors, including both the steady and unsteady aerodynamics and the heat transfer characteristics. The aerodynamic performance of new turbine designs has traditionally been tested in large scale steady flow rigs, but the testing is adiabatic, and the measurement of heat transfer is very difficult. This paper presents the results of turbine aerodynamic performance measurements at the Oxford Rotor Facility (ORF). Transient test facilities such as the Oxford Rotor allow the simultaneous study of turbine performance and heat transfer. The transient operation gives engine representative Mach number, Reynolds number and gas-to-wall temperature ratios, which are key to the aerothermodynamics of a highly-loaded, transonic, HP turbine stage. Time resolved experimental results are presented together with numerical CFD predictions over a 3% range of non-dimensional speed. The precision uncertainty of the measurements has been resolved to a level comparable with the state of the art in steady flow testing, in the region of ±0.3%.

scholarly journals Influence of Vane-Blade Spacing on Transonic Turbine Stage Aerodynamics: Part II — Time-Resolved Data and Analysis

1998 ◽  
Author(s):  
Judy A. Busby ◽  
Roger L. Davis ◽  
Daniel J. Dorney ◽  
Michael G. Dunn ◽  
Charles W. Haldeman ◽  
...  
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Numerical Solutions ◽  
Unsteady Aerodynamics ◽  
Total Pressure Loss ◽  
Turbine Stage ◽  
Airfoil Surface ◽  
Time Resolved ◽  
Transonic Turbine ◽  
Inlet Conditions

This paper presents results of a combined experimental/computational investigation into the effects of vane-blade spacing on the unsteady aerodynamics of a transonic turbine stage. Time-resolved data were taken in a shock-tunnel facility in which the flow was generated with a short-duration source of heated and pressurized air. This data is compared with the results obtained from four unsteady Navier-Stokes solvers. The time-resolved flow for three axial spacings is examined. For each vane-blade spacing, the inlet conditions were nearly identical and the vane exit flow was transonic. Surface-mounted high-response pressure transducers at midspan were used to obtain the pressure measurements. The computed two-dimensional unsteady airfoil surface pressure predictions are compared with the Kulite pressure transducer measurements. The unsteady and axial spacing effects on loading and performance are examined. In general the numerical solutions compared very favorably with each other and with the experimental data. The overall predicted stage losses and efficiencies did not vary much with vane/blade axial spacing. The computations indicated that any increases in the blade relative total pressure loss were offset by a decrease in vane loss as the axial spacing was decreased. The decrease in predicted vane total pressure loss with decreased axial spacing was primarily due to a reduction in the wake mixing losses. The increase in predicted blade relative total pressure loss with a decrease in axial spacing was found to be mainly due to increased vane wake/blade interaction.

Influence of Vane-Blade Spacing on Transonic Turbine Stage Aerodynamics: Part II—Time-Resolved Data and Analysis

1999 ◽  
Vol 121 (4) ◽  
pp. 673-682 ◽  
Author(s):  
J. A. Busby ◽  
R. L. Davis ◽  
D. J. Dorney ◽  
M. G. Dunn ◽  
C. W. Haldeman ◽  
...  
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Numerical Solutions ◽  
Unsteady Aerodynamics ◽  
Total Pressure Loss ◽  
Turbine Stage ◽  
Airfoil Surface ◽  
Time Resolved ◽  
Transonic Turbine ◽  
Inlet Conditions

This paper presents results of a combined experimental/computational investigation into the effects of vane–blade spacing on the unsteady aerodynamics of a transonic turbine stage. Time-resolved data were taken in a shock-tunnel facility in which the flow was generated with a short-duration source of heated and pressurized air. This data is compared with the results obtained from four unsteady Navier–Stokes solvers. The time-resolved flow for three axial spacings is examined. For each vane–blade spacing, the inlet conditions were nearly identical and the vane exit flow was transonic. Surface-mounted high-response pressure transducers at midspan were used to obtain the pressure measurements. The computed two-dimensional unsteady airfoil surface pressure predictions are compared with the Kulite pressure transducer measurements. The unsteady and axial spacing effects on loading and performance are examined. In general the numerical solutions compared very favorably with each other and with the experimental data. The overall predicted stage losses and efficiencies did not vary much with vane/blade axial spacing. The computations indicated that any increases in the blade relative total pressure loss were offset by a decrease in vane loss as the axial spacing was decreased. The decrease in predicted vane total pressure loss with decreased axial spacing was primarily due to a reduction in the wake mixing losses. The increase in predicted blade relative total pressure loss with a decrease in axial spacing was found to be mainly due to increased vane wake/blade interaction.

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