Еstimation of the turbulence scale in flame using the method of IR diagnostics

2015 ◽  
Author(s):  
E. L. Loboda ◽  
O. V. Matvienko ◽  
M. V. Agafontsev ◽  
V. V. Reyno
Keyword(s):  
Turbulence Scale ◽  
Ir Diagnostics

scholarly journals Prediction of Liner Metal Temperature of an Aeroengine Combustor with Multi-Physics Scale-Resolving CFD

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 901
Author(s):  
Davide Bertini ◽  
Lorenzo Mazzei ◽  
Antonio Andreini
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Turbulence Models ◽  
Metal Temperature ◽  
Lean Burn ◽  
Turbulence Scale ◽  
Ansys Fluent ◽  
Multi Scale ◽  
Assessment Tests ◽  
Rans Turbulence Models

Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS turbulence models provide a reasonable prediction, despite some well-known limitations in reproducing the turbulent mixing in highly unsteady flows. Their affordable cost is ideal in the preliminary design steps, whereas, in the detailed phase of the design process, turbulence scale-resolving methods (such as LES or similar approaches) can be preferred to significantly improve the accuracy. Despite that, in dealing with multi-physics and multi-scale problems, as for Conjugate Heat Transfer (CHT) in presence of radiation, transient approaches are not always affordable and appropriate numerical treatments are necessary to properly account for the huge range of characteristics scales in space and time that occur when turbulence is resolved and heat conduction is simulated contextually. The present work describes an innovative methodology to perform CHT simulations accounting for multi-physics and multi-scale problems. Such methodology, named U-THERM3D, is applied for the metal temperature prediction of an annular aeroengine lean burn combustor. The theoretical formulations of the tool are described, together with its numerical implementation in the commercial CFD code ANSYS Fluent. The proposed approach is based on a time de-synchronization of the involved time dependent physics permitting to significantly speed up the calculation with respect to fully coupled strategy, preserving at the same time the effect of unsteady heat transfer on the final time averaged predicted metal temperature. The results of some preliminary assessment tests of its consistency and accuracy are reported before showing its exploitation on the real combustor. The results are compared against steady-state calculations and experimental data obtained by full annular tests at real scale conditions. The work confirms the importance of high-fidelity CFD approaches for the aerothermal prediction of liner metal temperature.

Two months of measurements with an autonomous thermodynamic Raman lidar in Lindenberg

2021 ◽  
Author(s):  
Diego Lange Vega ◽  
Andreas Behrendt ◽  
Volker Wulfmeyer
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Inversion Layer ◽  
Measurement Range ◽  
High Accuracy ◽  
Free Troposphere ◽  
Raman Lidar ◽  
Backscatter Coefficient ◽  
Geophysical Research ◽  
Turbulence Scale

<p>Between 15 July 2020 and 19 September 2021, the Atmospheric Raman Temperature and Humidity Sounder (ARTHUS) collected data at the Lindenberg Observatory of the Deutscher Wetterdienst (DWD), including temperature and water vapor mixing ratio with a high temporal and range resolution.</p> <p>During the operation period, very stable 24/7 operation was achieved, and ARTHUS demonstrated that is capable to observe the atmospheric boundary layer and lower free troposphere during both daytime and nighttime up to the turbulence scale, with high accuracy and precision, and very short latency. During nighttime, the measurement range increases even up to the tropopause and lower stratosphere.</p> <p>ARTHUS measurements resolve the strength of the inversion layer at the planetary boundary layer top, elevated lids in the free troposphere, and turbulent fluctuations in water vapor and temperature, simultaneously (Lange et al., 2019, Wulfmeyer et al., 2015). In addition to thermodynamic variables, ARTHUS provides also independent profiles of the particle backscatter coefficient and the particle extinction coefficient from the rotational Raman signals at 355 nm with much better resolution than a conventional vibrational Raman lidar.</p> <p>At the conference, highlights of the measurements will be presented. Furthermore, the statistics of more than 150 comparisons with local radiosondes will be presented which confirm the high accuracy of the temperature and moisture measurements of ARTHUS.</p> <p><strong><em>Acknowledgements</em></strong></p> <p>The development of ARTHUS was supported by the Helmholtz Association of German Research Centers within the project Modular Observation Solutions for Earth Systems (MOSES). The measurements in Lindenberg were funded by DWD.</p> <p><strong><em>References </em></strong></p> <p>Lange, D., Behrendt, A., and Wulfmeyer, V. (2019). Compact operational tropospheric water vapor and temperature Raman lidar with turbulence resolution. <em>Geophysical Research Letters</em>, 46. https://doi.org/10.1029/2019GL085774</p> <p>Wulfmeyer, V., R. M. Hardesty, D. D. Turner, A. Behrendt, M. P. Cadeddu, P. Di Girolamo, P. Schlüssel, J. Van Baelen, and F. Zus (2015), A review of the remote sensing of lower tropospheric thermodynamic profiles and its indispensable role for the understanding and the simulation of water and energy cycles, <em>Rev. Geophys.</em>, 53,819–895, doi:10.1002/2014RG000476</p>

Nursing Turbulence in Critical Care: Relationships With Nursing Workload and Patient Safety

2020 ◽  
Vol 29 (3) ◽  
pp. 182-191
Author(s):  
Jennifer Browne ◽  
Carrie Jo Braden
Keyword(s):  
Critical Care ◽  
Patient Safety ◽  
Quality Of Care ◽  
Full Range ◽  
Operational Definition ◽  
Nursing Workload ◽  
Turbulence Scale ◽  
Safety Risk ◽  
Care Relationships

Background Increased nursing workload can be associated with decreased patient safety and quality of care. The associations between nursing workload, quality of care, and patient safety are not well understood. Objectives The concept of workload and its associated measures do not capture all nursing work activities, and tools used to assess healthy work environments do not identify these activities. The variable turbulence was created to capture nursing activities not represented by workload. The purpose of this research was to specify a definition and preliminary measure for turbulence. Methods A 2-phase exploratory sequential mixed-methods design was used to translate the proposed construct of turbulence into an operational definition and begin preliminary testing of a turbulence scale. Results A member survey of the American Association of Critical-Care Nurses resulted in the identification of 12 turbulence types. Turbulence was defined, and reliability of the turbulence scale was acceptable (α = .75). Turbulence was most strongly correlated with patient safety risk (r = 0.41, n = 293, P < .001). Workload had the weakest association with patient safety risk (r = 0.16, n = 294, P = .005). Conclusions Acknowledging the concepts of turbulence and workload separately best describes the full range of nursing demands. Improved measurement of nursing work is important to advance the science. A clearer understanding of nurses’ work will enhance our ability to target resources and improve patients’ outcomes.

scholarly journals Hybrid Turbulence Models: Recent Progresses and Further Researches

2019 ◽  
Vol 130 ◽  
pp. 01013
Author(s):  
Hariyo Priambudi Setyo Pratomo ◽  
Fandi Dwiputra Suprianto ◽  
Teng Sutrisno
Keyword(s):  
Turbulent Flows ◽  
Turbulence Modeling ◽  
A Priori ◽  
Computational Cost ◽  
Turbulence Models ◽  
Turbulence Scale ◽  
Research Activities ◽  
Daunting Task ◽  
Active Research ◽  
Inherent Nature

Turbulence simulation remains one of the active research activities in computational engineering. Along with the increase in computing power and the prime motivation of improving the accuracy of statistical turbulence modeling approaches and reducing the expensive computational cost of both direct numerical and large turbulence scale- resolving simulations, various hybrid turbulence models being capable of capturing unsteadiness in the turbulence are now accessible. Nevertheless this introduces the daunting task to select an appropriate method for different cases as one can not know a priori the inherent nature of the turbulence. It is the aim of this paper to address recent progresses and further researches within a branch of the hybrid RANS-LES models examined by the first author as simple test cases but generating complex turbulent flows are available from experimentation. In particular, failure of a seamless hybrid formulation not explicitly dependent on the grid scale is discussed. From the literature, it is practical that at least one can go on with confidence when choosing a potential hybrid model by intuitively distinguishing between strongly and weakly unstable turbulent flows.

Effects of Tumble and Swirl Flows on the Turbulence Scale Near the TDC in a 4-Valve S.I. Engine

2001 ◽  
Author(s):  
Ki Hyung Lee ◽  
Chang Sik Lee ◽  
Hyun Jong Park ◽  
Dae Sik Kim
Keyword(s):  
Flow Field ◽  
Propagation Speed ◽  
Turbulence Scale ◽  
Iccd Camera ◽  
Spark Plug ◽  
Swirl Flows ◽  
Intake Stroke ◽  
Initial Flame ◽  
Cylinder Flow ◽  
Intake Flow

Abstract It has known that the in-cylinder flow field has a significant effect on the engine combustion. Especially, the turbulence scale at the ignition toning plays an important role in enhancing propagation speed of initial flame. Thus, in this study, various flow fields such as tumble and swirl flows were generated by intake flow control valves. The effects of tumble and swirl flows on the turbulence scale were experimentally investigated in a 4-valve S.I. engine. For the investigation of the flow field, the single frame PTV and the two color PIV techniques were developed to clarify in-cylinder flow pattern during intake stroke and turbulence intensity near the spark plug during compression stroke, respectively. The flame propagation was visualized by an ICCD camera and its images were analyzed to compare the flow field.

scholarly journals Observations of Transient Linear Organization and Nonlinear Scale Interactions in Lake-Effect Clouds. Part II: Nonlinear Scale Interactions

2005 ◽  
Vol 133 (3) ◽  
pp. 692-706 ◽  
Author(s):  
Natasha L. Miles ◽  
Johannes Verlinde
Keyword(s):  
Nonlinear Interactions ◽  
Atmospheric Conditions ◽  
Lake Ice ◽  
Turbulence Scale ◽  
Scale Interactions ◽  
Roll Vortices ◽  
Interaction Terms ◽  
Lake Effect ◽  
Nonlinear Scale ◽  
Organized Convection

Abstract Linearly organized convection and associated horizontal roll vortices occasionally occur in atmospheric conditions in which theory predicts only cellular organization. One possible contributor to the occurrence of rolls in such conditions is nonlinear interactions between different scales of motion. In the winter of 1997/98, the Lake-Induced Convection Experiment (Lake-ICE) was conducted in part to investigate scale interactions in linearly organized convection. As discussed in Part I of this series, transient linear organization was observed during a wintertime lake-effect event during Lake-ICE. In Part II two-part nonlinear scale interactions and their possible role in the occurrence of linear organization in an unfavorable environment are investigated. Turbulence-scale vertical velocity variance peaks were consistently observed during roll strengthening and decay, suggesting a link between the scales. Composites of the nonlinear interaction terms in the roll-scale vertical turbulent kinetic energy (TKE) budget revealed that nonlinear interactions between the roll and turbulence scales were large compared to the observed change in roll-scale TKE, but do not coincide in time.

NOAA'S Hurricane Intensity Forecasting Experiment: A Progress Report

2013 ◽  
Vol 94 (6) ◽  
pp. 859-882 ◽  
Author(s):  
Robert Rogers ◽  
Sim Aberson ◽  
Altug Aksoy ◽  
Bachir Annane ◽  
Michael Black ◽  
...  
Keyword(s):  
Life Cycle ◽  
Tropical Cyclone ◽  
Real Time ◽  
Doppler Radar ◽  
Multiple Scales ◽  
Statistical Prediction ◽  
Intensity Change ◽  
Turbulence Scale ◽  
Real Time Analysis ◽  
The Impact

An update of the progress achieved as part of the NOAA Intensity Forecasting Experiment (IFEX) is provided. Included is a brief summary of the noteworthy aircraft missions flown in the years since 2005, the first year IFEX flights occurred, as well as a description of the research and development activities that directly address the three primary IFEX goals: 1) collect observations that span the tropical cyclone (TC) life cycle in a variety of environments for model initialization and evaluation; 2) develop and refine measurement strategies and technologies that provide improved real-time monitoring of TC intensity, structure, and environment; and 3) improve the understanding of physical processes important in intensity change for a TC at all stages of its life cycle. Such activities include the real-time analysis and transmission of Doppler radar measurements; numerical model and data assimilation advancements; characterization of tropical cyclone composite structure across multiple scales, from vortex scale to turbulence scale; improvements in statistical prediction of rapid intensification; and studies specifically targeting tropical cyclogenesis, extratropical transition, and the impact of environmental humidity on TC structure and evolution. While progress in TC intensity forecasting remains challenging, the activities described here provide some hope for improvement.

Sign in / Sign up

Export Citation Format

Share Document