scholarly journals ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction—Part I—Influence of the RANS Simulation

Acoustics ◽  
2020 ◽  
Vol 2 (3) ◽  
pp. 539-578
Author(s):  
Carolin Kissner ◽  
Sébastien Guérin ◽  
Pascal Seeler ◽  
Mattias Billson ◽  
Paruchuri Chaitanya ◽  
...  
Keyword(s):  
Turbulence Model ◽  
Analytical Methods ◽  
Companion Paper ◽  
Broadband Noise ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Data Set ◽  
The Past ◽  
Flow Turbulence ◽  
Diverse Data

A benchmark of Reynolds-Averaged Navier-Stokes (RANS)-informed analytical methods, which are attractive for predicting fan broadband noise, was conducted within the framework of the European project TurboNoiseBB. This paper discusses the first part of the benchmark, which investigates the influence of the RANS inputs. Its companion paper focuses on the influence of the applied acoustic models on predicted fan broadband noise levels. While similar benchmarking activities were conducted in the past, this benchmark is unique due to its large and diverse data set involving members from more than ten institutions. In this work, the authors analyze RANS solutions performed at approach conditions for the ACAT1 fan. The RANS solutions were obtained using different CFD codes, mesh resolutions, and computational settings. The flow, turbulence, and resulting fan broadband noise predictions are analyzed to pinpoint critical influencing parameters related to the RANS inputs. Experimental data are used for comparison. It is shown that when turbomachinery experts perform RANS simulations using the same geometry and the same operating conditions, the most crucial choices in terms of predicted fan broadband noise are the type of turbulence model and applied turbulence model extensions. Chosen mesh resolutions, CFD solvers, and other computational settings are less critical.

Unsteady Heat Transfer in Stator–Rotor Interaction by Two-Equation Turbulence Model

1999 ◽  
Vol 121 (3) ◽  
pp. 436-447 ◽  
Author(s):  
V. Michelassi ◽  
F. Martelli ◽  
R. De´nos ◽  
T. Arts ◽  
C. H. Sieverding
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Rotor Blade ◽  
Two Dimensions ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Turbine Stage ◽  
Pressure Losses ◽  
Transonic Turbine ◽  
Variable Operating Conditions

A transonic turbine stage is computed by means of an unsteady Navier–Stokes solver. A two-equation turbulence model is coupled to a transition model based on integral parameters and an extra transport equation. The transonic stage is modeled in two dimensions with a variable span height for the rotor row. The analysis of the transonic turbine stage with stator trailing edge coolant ejection is carried out to compute the unsteady pressure and heat transfer distribution on the rotor blade under variable operating conditions. The stator coolant ejection allows the total pressure losses to be reduced, although no significant effects on the rotor heat transfer are found both in the computer simulation and the measurements. The results compare favorably with experiments in terms of both pressure distribution and heat transfer around the rotor blade.

scholarly journals Turbulence Modeling in the Age of Data

2019 ◽  
Vol 51 (1) ◽  
pp. 357-377 ◽  
Author(s):  
Karthik Duraisamy ◽  
Gianluca Iaccarino ◽  
Heng Xiao
Keyword(s):  
Turbulence Modeling ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Data Sets ◽  
Physical Constraints ◽  
The Past ◽  
Recent Developments ◽  
Rans Models ◽  
Engineering Models ◽  
Diverse Data

Data from experiments and direct simulations of turbulence have historically been used to calibrate simple engineering models such as those based on the Reynolds-averaged Navier–Stokes (RANS) equations. In the past few years, with the availability of large and diverse data sets, researchers have begun to explore methods to systematically inform turbulence models with data, with the goal of quantifying and reducing model uncertainties. This review surveys recent developments in bounding uncertainties in RANS models via physical constraints, in adopting statistical inference to characterize model coefficients and estimate discrepancy, and in using machine learning to improve turbulence models. Key principles, achievements, and challenges are discussed. A central perspective advocated in this review is that by exploiting foundational knowledge in turbulence modeling and physical constraints, researchers can use data-driven approaches to yield useful predictive models.

Three-Dimensional Numerical Simulations of Flows Past Smooth and Rough/Bare and Helically Straked Circular Cylinders Allowed to Undergo Two Degree-of-Freedom Motions

2007 ◽  
Author(s):  
Juan P. Pontaza ◽  
Raghu G. Menon ◽  
H. C. Chen
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Cross Flow ◽  
Operating Conditions ◽  
Degree Of Freedom ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Wall Region ◽  
Roughness Effects ◽  
Two Degree Of Freedom

We simulate the flow past smooth and rough rigid circular cylinders that are either bare or outfitted with helical stakes. We consider operating conditions that correspond to high Reynolds numbers of 105 and 106, and allow for two degree-of-freedom motions when the structure is allowed to respond to vortex-induced cross flow and in-line forces. The computations are performed using a parallelized Navier-Stokes in-house solver using overset grids. For smooth surface simulations at a Reynolds number of 105, we use a Smagorinsky Large Eddy Simulation (LES) turbulence model and for the Reynolds number cases of 106 we make use of the unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with a two-layer k-epsilon turbulence model. The rough surface modifications of the two-layer k-epsilon turbulence model due to Durbin et al. (ASME J. Fluids Eng., 2001) are implemented to account for surface roughness effects. In all our computations we aim to resolve the boundary layer directly by using adequate grid spacing in the near-wall region. The predicted global flow parameters under different surface conditions are in good agreement with experimental data and significant VIV suppression is observed when using helically straked cylinders.

scholarly journals Turbine Broadband Noise Predictions Using Linearised Frequency Domain Navier-Stokes Solvers

2021 ◽  
Vol 6 (4) ◽  
pp. 42
Author(s):  
Ricardo Blázquez-Navarro ◽  
Roque Corral
Keyword(s):  
Frequency Domain ◽  
Sound Pressure ◽  
State Of The Art ◽  
Broadband Noise ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Frequency Range ◽  
Low Pressure Turbine ◽  
The Third ◽  
Blade Thickness

A linear frequency domain Navier-Stokes solver is used to retain the influence of turning, thickness, and main geometric parameters on turbine broadband noise. The methodology has been applied to predict the broadband interaction noise produced by a representative low-speed low-pressure turbine section. The differences in the spectra with respect to those yielded by state-of-the-art flat plate based methodologies are up to 6 dB. The differences are caused by multiple effects that semi-analytical methodologies do not account for. The most important are blade thickness and turning, which have been studied separately to quantify their impact on the broadband noise footprint. The influence of changing the turbine operating conditions has been discussed as well. The outlet sound pressure level scales with the third and second power of the inlet and outlet Mach number, respectively, for constant turbulence intensity, within most of the frequency range considered.

Three-Dimensional Numerical Simulations of Flows Past Smooth and Rough/Bare and Helically Straked Circular Cylinders Allowed to Undergo Two Degree-of-Freedom Motions

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Juan P. Pontaza ◽  
Raghu G. Menon ◽  
Hamn-Ching Chen
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Operating Conditions ◽  
Degree Of Freedom ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Wall Region ◽  
Roughness Effects ◽  
Two Degree Of Freedom

We simulate the flow past smooth and rough rigid circular cylinders that are either bare or outfitted with helical strakes. We consider operating conditions that correspond to high Reynolds numbers of 105 and 106, and allow for two degree-of-freedom motions such that the structure is allowed to respond to flow-induced cross-flow and in-line forces. The computations are performed using a parallelized Navier–Stokes in-house solver using overset grids. For smooth surface simulations at a Reynolds number of 105, we use a Smagorinsky large eddy simulation turbulence model and for the Reynolds number cases of 106 we make use of the unsteady Reynolds-averaged Navier–Stokes equations with a two-layer k-epsilon turbulence model. The rough surface modifications of the two-layer k-epsilon turbulence model due to Durbin et al. (2001, “Rough Wall Modification of Two-Layer k-Epsilon,” ASME J. Fluids Eng., 123, pp. 16–21) are implemented to account for surface roughness effects. In all our computations we aim to resolve the boundary layer directly by using adequate grid spacing in the near-wall region. The predicted global flow parameters under different surface conditions are in good agreement with experimental data, and significant vortex-induced vibration suppression is observed when using helically straked cylinders.

scholarly journals Unsteady Heat Transfer in Stator-Rotor Interaction by Two Equation Turbulence Model

1998 ◽  
Author(s):  
V. Michelassi ◽  
F. Martelli ◽  
R. Dénos ◽  
T. Arts ◽  
C. H. Sieverding
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Rotor Blade ◽  
Two Dimensions ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Turbine Stage ◽  
Pressure Losses ◽  
Transonic Turbine ◽  
Variable Operating Conditions

A transonic turbine stage is computed by means of an unsteady Navier-Stokes solver. A two equation turbulence model is coupled to a transition model based on integral parameters and an extra transport equation. The transonic stage is modeled in two-dimensions with a variable span height for the rotor row. The analysis of the transonic turbine stage with stator trailing edge coolant ejection is carried out to compute the unsteady pressure and heat transfer distribution on the rotor blade under variable operating conditions. The stator coolant ejection allows the total pressure losses to be reduced although no significant effects on the rotor heat transfer are found in both the computer simulation and measurements. The results compare favorably with experiments both in terms of pressure distribution and heat transfer around the rotor blade.

Steady Three-Dimensional Simulation of a Transonic Axial Turbine Stage

2001 ◽  
Author(s):  
V. Michelassi ◽  
P. Giangiacomo ◽  
F. Martelli ◽  
R. Dénos ◽  
G. Paniagua
Keyword(s):  
Computational Model ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Turbine Stage ◽  
Data Set ◽  
Axial Turbine ◽  
Stator Blade ◽  
Dimensional Simulation

The performance of a transonic axial turbine stage, representative of a wide class of aeroengines, is computed by a Navier-Stokes solver with a three-equation turbulence model. The stator blade has a coolant ejection slot on the pressure side close to the trailing edge. The stator-rotor interaction is modelled by a mixing plane approach. The tangential mixing strategy is discussed and analysed in terms of area or mass averaging. The computational results are compared with an experimental data set, which includes all the relevant quantities necessary to describe the stage. Both computations and experiments are carried out in four different operating conditions to allow first the effects of changes in Reynolds number and pressure ratio to be assessed and second the sensitivity of the computational model to these changes to be tested. The effect of tip leakage is investigated and CFD is used to help understand the experiments. The predictions compare favourably with experiments for most of the relevant parameters and prove the validity of the simple and fast computational model.

Measuring Congestion and Reliability Impacts of Safety Projects

2021 ◽  
pp. 036119812110067
Author(s):  
Simona Babiceanu ◽  
Sanhita Lahiri ◽  
Mena Lockwood
Keyword(s):  
Performance Measures ◽  
Positive Impact ◽  
Operating Conditions ◽  
Vehicle Miles Traveled ◽  
Data Set ◽  
Data Points ◽  
Practical Recommendations

This study uses a suite of performance measures that was developed by taking into consideration various aspects of congestion and reliability, to assess impacts of safety projects on congestion. Safety projects are necessary to help move Virginia’s roadways toward safer operation, but can contribute to congestion and unreliability during execution, and can affect operations after execution. However, safety projects are assessed primarily for safety improvements, not for congestion. This study identifies an appropriate suite of measures, and quantifies and compares the congestion and reliability impacts of safety projects on roadways for the periods before, during, and after project execution. The paper presents the performance measures, examines their sensitivity based on operating conditions, defines thresholds for congestion and reliability, and demonstrates the measures using a set of Virginia safety projects. The data set consists of 10 projects totalling 92 mi and more than 1M data points. The study found that, overall, safety projects tended to have a positive impact on congestion and reliability after completion, and the congestion variability measures were sensitive to the threshold of reliability. The study concludes with practical recommendations for primary measures that may be used to measure overall impacts of safety projects: percent vehicle miles traveled (VMT) reliable with a customized threshold for Virginia; percent VMT delayed; and time to travel 10 mi. However, caution should be used when applying the results directly to other situations, because of the limited number of projects used in the study.

scholarly journals Change in mean and extreme temperature at Yingkou station in Northeast China from 1904 to 2017

2021 ◽  
Vol 164 (3-4) ◽  
Author(s):  
Xiaoying Xue ◽  
Guoyu Ren ◽  
Xiubao Sun ◽  
Panfeng Zhang ◽  
Yuyu Ren ◽  
...  
Keyword(s):  
Northeast China ◽  
Extreme Temperature ◽  
Maximum Temperature ◽  
Data Set ◽  
The Past ◽  
Significant Downward Trend ◽  
Cold Events ◽  
Temperature Indices ◽  
Increasing Trends ◽  
Change In Mean

AbstractThe understanding of centennial trends of extreme temperature has been impeded due to the lack of early-year observations. In this paper, we collect and digitize the daily temperature data set of Northeast China Yingkou meteorological station since 1904. After quality control and homogenization, we analyze the changes of mean and extreme temperature in the past 114 years. The results show that mean temperature (Tmean), maximum temperature (Tmax), and minimum temperature (Tmin) all have increasing trends during 1904–2017. The increase of Tmin is the most obvious with the rate of 0.34 °C/decade. The most significant warming occurs in spring and winter with the rate of Tmean reaching 0.32 °C/decade and 0.31 °C/decade, respectively. Most of the extreme temperature indices as defined using absolute and relative thresholds of Tmax and Tmin also show significant changes, with cold events witnessing a more significant downward trend. The change is similar to that reported for global land and China for the past six decades. It is also found that the extreme highest temperature (1958) and lowest temperature (1920) records all occurred in the first half of the whole period, and the change of extreme temperature indices before 1950 is different from that of the recent decades, in particular for diurnal temperature range (DTR), which shows an opposite trend in the two time periods.

Computed Effects of Rotor-Induced Swirl on Brush Seal Performance—Part 2: Bristle Force Analysis

1996 ◽  
Vol 118 (4) ◽  
pp. 920-926 ◽  
Author(s):  
M. C. Sharatchandra ◽  
D. L. Rhode
Keyword(s):  
Inclination Angle ◽  
Flow Direction ◽  
Flow Simulation ◽  
Companion Paper ◽  
Navier Stokes ◽  
Brush Seal ◽  
Swirl Flows ◽  
Lift Off ◽  
Square Configuration ◽  
Periodic Module

This paper analytically investigates the aerodynamic bristle force distributions in brush seals used in aircraft gas turbine engines. These forces are responsible for the onset of bristle tip lift-off from the rotor surface which significantly affects brush seal performance. In order to provide an enhanced understanding of the mechanisms governing the bristle force distributions, a full Navier-Stokes flow simulation is performed in a streamwise periodic module of bristles corresponding to the staggered square configuration. As is the case with a companion paper (Sharatchandra and Rhode, 1996), this study has the novel feature of considering the combined effects of axial (leakage) and tangential (swirl) flows. Specifically, the effects of intra-bristle spacing and bristle inclination angle are explored. The results indicate that the lifting bristle force increases with reduced intra-bristle spacing and increased inclination angle. It was also observed that increases in the axial or tangential flow rates increased the force component in the normal as well as the flow direction.

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