scholarly journals Time-Volume Estimation of Velocity Fields From Nonsynchronous Planar Measurements Using Linear Stochastic Estimation

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Daniel Butcher ◽  
Adrian Spencer
Keyword(s):  
Three Dimensional ◽  
Velocity Estimation ◽  
Volume Estimation ◽  
Stochastic Estimation ◽  
Time Resolved ◽  
Linear Stochastic Estimation ◽  
Planar Velocity ◽  
Input Field ◽  
Flow Information ◽  
Input Plane

The work presented in this paper combines multiple nonsynchronous planar measurements to reconstruct an estimate of a synchronous, instantaneous flow field of the whole measurement set. Temporal information is retained through the linear stochastic estimation (LSE) technique. The technique is described, applied, and validated with a simplified combustor and fuel swirl nozzles (FSN) geometry flow for which three-component, three-dimensional (3C3D) flow information is available. Using the 3C3D dataset, multiple virtual “planes” may be extracted to emulate single planar particle image velocimetry (PIV) measurements and produce the correlations required for LSE. In this example, multiple parallel planes are synchronized with a single perpendicular plane that intersects each of them. As the underlying dataset is known, it therefore can be directly compared to the estimated velocity field for validation purposes. The work shows that when the input time-resolved planar velocity measurements are first proper orthogonal decomposition (POD) filtered, high correlation between the estimations and the validation velocity volumes are possible. This results in estimated full volume velocity distributions, which are available at the same time instance as the input field—i.e., a time-resolved velocity estimation at the frequency of the single input plane. While 3C3D information is used in the presented work, this is necessary only for validation; in true application, planar technique would be used. The study concludes that provided the number of sensors used for input LSE exceeds the number of POD modes used for prefiltering, it is possible to achieve correlation greater than 99%.

scholarly journals Time-Volume Estimation of Velocity Fields From Non-Synchronous Planar Measurements Using Linear Stochastic Estimation

2019 ◽  
Author(s):  
Daniel Butcher ◽  
Adrian Spencer
Keyword(s):  
A Priori ◽  
Velocity Estimation ◽  
Volume Estimation ◽  
Stochastic Estimation ◽  
Data Set ◽  
Time Resolved ◽  
Measured Velocity ◽  
Tomographic Piv ◽  
Linear Stochastic Estimation ◽  
Full Volume

Abstract With increasing complexity of aerodynamic devices such as gas turbine fuel swirl nozzles (FSN) and combustors, the need for time-resolved full volume flow characterisation is becoming greater. Even with modern advancements in both numerical and experimental methods, this remains a challenging area. The work presented in this paper combines multiple non-synchronous planar measurements to reconstruct an estimate of a synchronous, instantaneous flow field of the whole measurement set. Temporal information is retained through the linear stochastic estimation (LSE) technique. The technique is described, applied and validated with a simplified combustor and FSN geometry flow for which 3-component, 3-dimensional (3C3D) flow information is known from published tomographic PIV[1]. Using the tomographic PIV data set, multiple virtual ‘planes’ may be extracted to emulate single planar PIV measurements and produce the correlations required for LSE. In this example, multiple parallel planes are synchronised with a single perpendicular plane that intersects each of them. As the underlying data set is volumetric, the measured velocity is known a priori and therefore can be directly compared to the estimated velocity field for validation purposes. The work shows that when the input time-resolved planar velocity measurements are first POD (proper orthogonal decomposition) filtered, high correlation between the estimations and the validation velocity volumes are possible. This results in estimated full volume velocity distributions which are available at the same time instance as the input field — i.e. a time resolved velocity estimation at the frequency of the single input plane. While 3C3D information is used in the presented work, this is necessary only for validation; in true application planar technique would be used. The study concludes that provided the number of sensors used for input LSE exceeds the number of POD modes used for pre-filtering, it is possible to achieve correlation greater than 99%.

Spectral Linear Stochastic Estimation of the Turbulent Velocity in a Square Three-Dimensional Wall Jet

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Joseph W. Hall ◽  
Daniel Ewing
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Turbulent Velocity ◽  
Stochastic Estimation ◽  
Wall Jet ◽  
Large Scale Structures ◽  
Square Channel ◽  
Linear Stochastic Estimation ◽  
Rapid Changes ◽  
Turbulent Velocity Field

The instantaneous turbulent velocity field in a three-dimensional wall jet was estimated from the fluctuating wall pressure using a spectral linear stochastic estimation technique. The wall jet investigated issued from a long square channel with Reynolds number of 90,000. Two downstream positions in the intermediate field were examined, x/h=10 and x/h=20, owing to the rapid changes in wall jet development over this region. The results indicate that the passage of the large-scale structures cause large, coherent lateral sweeps of fluid across the entire span of the wall jet. These sweeps are caused by the passage of half horseshoe-like structures and appear to be responsible for the larger lateral development of this flow.

Spectral Linear Stochastic Estimation of the Turbulent Velocity in a Square Three-Dimensional Wall Jet

2007 ◽  
Author(s):  
Joseph W. Hall ◽  
Daniel Ewing
Keyword(s):  
Large Scale ◽  
Rapid Change ◽  
Three Dimensional ◽  
Turbulent Velocity ◽  
Stochastic Estimation ◽  
Wall Jet ◽  
Large Scale Structures ◽  
Square Channel ◽  
Linear Stochastic Estimation ◽  
Turbulent Velocity Field

The instantaneous turbulent velocity field in a three-dimensional wall jet was estimated from the fluctuating wall pressure using a spectral Linear Stochastic Estimation (LSE) technique. The jet issued from a long square channel with Reynolds number of 90,000. Two downstream positions in the intermediate field were examined, x/h = 10 and x/h = 20, owing to the rapid change in wall jet development over this region. The results indicate that the passage of the large-scale structures causes large, coherent lateral sweeps of fluid across the entire span of the wall jet. The sweeps appear to be caused by the passage of half horseshoe-like structures. As the structures evolve downstream they develop a longer outer leg, and become more offset, traits that both contribute to the large lateral growth of this flow.

scholarly journals Picosecond time-resolved photon antibunching measures nanoscale exciton motion and the true number of chromophores

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gordon J. Hedley ◽  
Tim Schröder ◽  
Florian Steiner ◽  
Theresa Eder ◽  
Felix J. Hofmann ◽  
...  
Keyword(s):  
Rational Design ◽  
Three Dimensional ◽  
Dna Origami ◽  
Fluorescent Nanoparticles ◽  
Time Resolved ◽  
Exciton Diffusion ◽  
Polymer Aggregates ◽  
True Number ◽  
Particle Level ◽  
Photon Antibunching

AbstractThe particle-like nature of light becomes evident in the photon statistics of fluorescence from single quantum systems as photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here we develop picosecond time-resolved antibunching to identify and decode such processes. We use this method to measure the true number of chromophores on well-defined multichromophoric DNA-origami structures, and precisely determine the distance-dependent rates of annihilation between excitons. Further, this allows us to measure exciton diffusion in mesoscopic H- and J-type conjugated-polymer aggregates. We distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Our method provides a powerful lens through which excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles and materials for optoelectronic devices.

Impact of an Aortic Nitinol Stent Graft on Flow Measurements by Time-resolved Three-dimensional Velocity-encoded MRI

2012 ◽  
Vol 19 (3) ◽  
pp. 274-280 ◽  
Author(s):  
Fabian Rengier ◽  
Michael Delles ◽  
Roland Unterhinninghofen ◽  
Sebastian Ley ◽  
Sasan Partovi ◽  
...  
Keyword(s):  
Stent Graft ◽  
Three Dimensional ◽  
Flow Measurements ◽  
Time Resolved ◽  
Nitinol Stent

Effects of Downstream Vane Bowing and Asymmetry on Unsteadiness in a Transonic Turbine

2018 ◽  
Author(s):  
John P. Clark ◽  
Richard J. Anthony ◽  
Michael K. Ooten ◽  
John M. Finnegan ◽  
P. Dean Johnson ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Time Resolved ◽  
Turbine Engine ◽  
Shock Interactions ◽  
Design Changes ◽  
Post Test ◽  
Measured Time ◽  
Transonic Turbine

Accurate predictions of unsteady forcing on turbine blades are essential for the avoidance of high-cycle-fatigue issues during turbine engine development. Further, if one can demonstrate that predictions of unsteady interaction in a turbine are accurate, then it becomes possible to anticipate resonant-stress problems and mitigate them through aerodynamic design changes during the development cycle. A successful reduction in unsteady forcing for a transonic turbine with significant shock interactions due to downstream components is presented here. A pair of methods to reduce the unsteadiness was considered and rigorously analyzed using a three-dimensional, time resolved Reynolds-Averaged Navier Stokes (RANS) solver. The first method relied on the physics of shock reflections itself and involved altering the stacking of downstream components to achieve a bowed airfoil. The second method considered was circumferentially-asymmetric vane spacing which is well known to spread the unsteadiness due to vane-blade interaction over a range of frequencies. Both methods of forcing reduction were analyzed separately and predicted to reduce unsteady pressures on the blade as intended. Then, both design changes were implemented together in a transonic turbine experiment and successfully shown to manipulate the blade unsteadiness in keeping with the design-level predictions. This demonstration was accomplished through comparisons of measured time-resolved pressures on the turbine blade to others obtained in a baseline experiment that included neither asymmetric spacing nor bowing of the downstream vane. The measured data were further compared to rigorous post-test simulations of the complete turbine annulus including a bowed downstream vane of non-uniform pitch.

Blade-Row Interactions in an LP Turbine at Design and Strong Off-Design Operation

2014 ◽  
Author(s):  
Martin Lipfert ◽  
Jan Habermann ◽  
Martin G. Rose ◽  
Stephan Staudacher ◽  
Yavuz Guendogdu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Three Dimensional ◽  
Suction Side ◽  
Test Facility ◽  
Time Resolved ◽  
Joint Project ◽  
Multi Stage ◽  
Blade Row ◽  
Wake Interactions

In a joint project between the Institute of Aircraft Propulsion Systems (ILA) and MTU Aero Engines a two-stage low pressure turbine is tested at design and strong off-design conditions. The experimental data taken in the altitude test-facility aims to study the effect of positive and negative incidence of the second stator vane. A detailed insight and understanding of the blade row interactions at these regimes is sought. Steady and time-resolved pressure measurements on the airfoil as well as inlet and outlet hot-film traverses at identical Reynolds number are performed for the midspan streamline. The results are compared with unsteady multi-stage CFD predictions. Simulations agree well with the experimental data and allow detailed insights in the time-resolved flow-field. Airfoil pressure field responses are found to increase with positve incidence whereas at negative incidence the magnitude remains unchanged. Different pressure to suction side phasing is observed for the studied regimes. The assessment of unsteady blade forces reveals that changes in unsteady lift are minor compared to changes in axial force components. These increase with increasing positive incidence. The wake-interactions are predominating the blade responses in all regimes. For the positive incidence conditions vane 1 passage vortex fluid is involved in the midspan passage interaction leading to a more distorted three-dimensional flow field.

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