scholarly journals Swirl Distortion Using Stream Vanes for Boundary Layer Ingestion Research

2019 ◽  
Author(s):  
Julia E. Stephens ◽  
Mark Celestina ◽  
Christopher Hughes
Keyword(s):  
Boundary Layer ◽  
Test Facility ◽  
Interface Plane ◽  
Type I ◽  
Cfd Simulations ◽  
Measurement Plane ◽  
Dense Grid ◽  
The Impact ◽  
Probe Measurements ◽  
Good Agreement

Abstract The swirl distortion of a StreamVane™ was investigated in the NASA Glenn Research Center W8 test facility. The StreamVane™ was designed and generated by Virginia Tech based on CFD simulations and included a center body at the aerodynamic interface plane. The swirl pattern generated by the distortion was evaluated using a dense grid of 5-hole Pitot probe measurements captured using a rotating array of probes. Good agreement was found between the design intent and the results at 38.5 kg/s mass flow. The StreamVane™ swirl results were compared to clean facility flow at 5 inlet mass flows and found to be consistent. Additionally, the axial location of the StreamVane™ relative to the measurement plane was investigated to determine the impact on downstream total pressure loss generated by the vanes. The intent of this work was to assess the viability of using a StreamVane™ to generate a Type I or Type II distortion into a Boundary Layer Ingesting propulsor to assess its aerodynamic performance and aeromechanic response.

A Methodology for a Detailed Loss Prediction in Low Pressure Steam Turbines

2017 ◽  
Author(s):  
Marius Grübel ◽  
Robin M. Dovik ◽  
Markus Schatz ◽  
Damian M. Vogt
Keyword(s):  
Boundary Layer ◽  
Evaluation Method ◽  
Three Dimensional ◽  
Low Pressure ◽  
Steam Turbines ◽  
Cfd Simulations ◽  
Depth Analysis ◽  
Pressure Steam ◽  
The Impact ◽  
Loss Mechanisms

An evaluation method for CFD simulations is presented, which allows an in-depth analysis of different loss mechanisms applying the approach of entropy creation proposed by Denton. The entropy creation within each single mesh element is determined based on the entropy flux through the cell faces and therefore the locations, where losses occur, can be identified clearly. By using unique features of the different loss mechanisms present in low pressure steam turbines, the losses are categorized into boundary layer, wake mixing and shock losses as well as thermodynamic wetness losses. The suitability of the evaluation method is demonstrated by means of steady state CFD simulations of the flow through a generic last stage of a low pressure steam turbine. The simulations have been performed on streamtubes extracted from three-dimensional simulations representing the flow at 10 % span. The impact of non-equilibrium steam effects on the overall loss composition of the stator passage is investigated by comparing the results to an equilibrium steam simulation. It is shown, that the boundary layer losses for the investigated case are of similar magnitude, but the shock and wake losses exhibit significant differences.

Thermal Cavitation Experiments on a NACA 0015 Hydrofoil

2003 ◽  
Author(s):  
Emilio Rapposelli ◽  
Angelo Cervone ◽  
Cristina Bramanti ◽  
Luca d’Agostino
Keyword(s):  
Surface Pressure ◽  
Strong Correlation ◽  
Cavity Length ◽  
Test Facility ◽  
Pressure Coefficients ◽  
Experimental Campaign ◽  
Cavitation Tunnel ◽  
Naca 0015 ◽  
The Impact ◽  
Good Agreement

The present paper illustrates the main results of an experimental campaign conducted in the Thermal Cavitation Tunnel of the CPRTF (Cavitating Pump Rotordynamic Test Facility) at Centrospazio. Experiments were carried out on a NACA 0015 hydrofoil at various incidence angles, cavitation numbers and freestream temperatures, in order to investigate the characteristics of cavitation instabilities and the impact of thermal cavitation effects. Measured cavity length, surface pressure coefficients and unsteady pressure spectra are in good agreement with the data available in the open literature and suggest the existence of a strong correlation between the onset of the various forms of cavitation and instabilities, the thermal cavitation effects, and the effects induced by the presence of the walls of the tunnel. Further analytical investigations will be carried out in order to provide a better interpretation of the above results.

Thermal Cavitation Experiments on a NACA 0015 Hydrofoil

2005 ◽  
Vol 128 (2) ◽  
pp. 326-331 ◽  
Author(s):  
Angelo Cervone ◽  
Cristina Bramanti ◽  
Emilio Rapposelli ◽  
Luca d’Agostino
Keyword(s):  
Surface Pressure ◽  
Strong Correlation ◽  
Cavity Length ◽  
Test Facility ◽  
Pressure Coefficients ◽  
Experimental Campaign ◽  
Cavitation Tunnel ◽  
Naca 0015 ◽  
The Impact ◽  
Good Agreement

The present paper illustrates the main results of an experimental campaign conducted in the Thermal Cavitation Tunnel of the Cavitating Pump Rotordynamic Test Facility (CPRTF) at Centrospazio/Alta S.p.A. Experiments were carried out on a NACA 0015 hydrofoil at various incidence angles, cavitation numbers, and freestream temperatures, in order to investigate the characteristics of cavitation instabilities and the impact of thermal cavitation effects. Measured cavity length, surface pressure coefficients, and unsteady pressure spectra are in good agreement with the data available in the open literature and suggest the existence of a strong correlation between the onset of the various forms of cavitation and instabilities, the thermal cavitation effects, and the effects induced by the presence of the walls of the tunnel. Further analytical investigations are planned in order to provide a better interpretation of the above results.

scholarly journals HO<sub>x</sub> observations over West Africa during AMMA: impact of isoprene and NO<sub>x</sub>

2010 ◽  
Vol 10 (7) ◽  
pp. 17029-17072 ◽  
Author(s):  
D. Stone ◽  
M. J. Evans ◽  
R. Commane ◽  
T. Ingham ◽  
C. F. A. Floquet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
West Africa ◽  
Water Vapour ◽  
Field Studies ◽  
Atmospheric Composition ◽  
Physical Parameters ◽  
Aircraft Measurements ◽  
Field Campaign ◽  
The Impact ◽  
Good Agreement

Abstract. OH and HO2 aircraft measurements made over West Africa during the AMMA field campaign in summer 2006 have been investigated using a box model constrained to observations of long-lived species and physical parameters. "Good" agreement was found for HO2 (modelled to observed gradient of 1.23±0.11). However, the model significantly overpredicts OH concentrations. The reasons for this are not clear, but may reflect instrumental instabilities affecting the OH measurements. Within the model HOx concentrations in West Africa are controlled by relatively simple photochemistry, with production dominated by ozone photolysis and reaction of O(1D) with water vapour, and loss processes dominated by HO2+HO2 and HO2+RO2. Isoprene chemistry was found to influence forested regions. In contrast to several recent field studies in very low NOx and high isoprene environments we do not observe any dependence of model success for HO2 on isoprene and attribute this to efficient recycling of HOx through RO2+NO reactions under the moderate NOx concentrations (5–300 ppt NO in the boundary layer) encountered during AMMA. This suggests that some of the problems with understanding the impact of isoprene on atmospheric composition may be limited to the extreme low range of NOx concentrations.

scholarly journals HO<sub>x</sub> observations over West Africa during AMMA: impact of isoprene and NO<sub>x</sub>

2010 ◽  
Vol 10 (19) ◽  
pp. 9415-9429 ◽  
Author(s):  
D. Stone ◽  
M. J. Evans ◽  
R. Commane ◽  
T. Ingham ◽  
C. F. A. Floquet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
West Africa ◽  
Water Vapour ◽  
Field Studies ◽  
Box Model ◽  
Atmospheric Composition ◽  
Physical Parameters ◽  
Field Campaign ◽  
The Impact ◽  
Good Agreement

Abstract. Aircraft OH and HO2 measurements made over West Africa during the AMMA field campaign in summer 2006 have been investigated using a box model constrained to observations of long-lived species and physical parameters. "Good" agreement was found for HO2 (modelled to observed gradient of 1.23 ± 0.11). However, the model significantly overpredicts OH concentrations. The reasons for this are not clear, but may reflect instrumental instabilities affecting the OH measurements. Within the model, HOx concentrations in West Africa are controlled by relatively simple photochemistry, with production dominated by ozone photolysis and reaction of O(1D) with water vapour, and loss processes dominated by HO2 + HO2 and HO2 + RO2. Isoprene chemistry was found to influence forested regions. In contrast to several recent field studies in very low NOx and high isoprene environments, we do not observe any dependence of model success for HO2 on isoprene and attribute this to efficient recycling of HOx through RO2 + NO reactions under the moderate NOx concentrations (5–300 ppt NO in the boundary layer, median 76 ppt) encountered during AMMA. This suggests that some of the problems with understanding the impact of isoprene on atmospheric composition may be limited to the extreme low range of NOx concentrations.

scholarly journals Numerical and experimental characterization of splitter blade impact on pump as turbine performance

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042199324
Author(s):  
Daniel Adu ◽  
Jianguo Du ◽  
Ransford O Darko ◽  
Eric Ofosu Antwi ◽  
Muhammad Aamir Shafique Khan
Keyword(s):  
Rotational Speed ◽  
Simulated Data ◽  
Maximum Deviation ◽  
Cfd Simulations ◽  
Flow Rates ◽  
Turbine Performance ◽  
Hydropower Dams ◽  
The Impact ◽  
Good Agreement

Several rivers and streams are available in Africa and Asian regions with great potentials not applicable for constructing large hydropower dams but feasible for small and mini hydro generation. This study strive for investigating the impact of splitter blade on pump as turbine performance considering different speed and flow rates. Two specific centrifugal pump models one with six blades without splitter and another with four blades and four splitters were used for the study. The inlet diameter and outlet diameters of both impellers were 104 mm/116 mm, and 160 mm respectively at a designed flow rate Q = 12.5 m3/h, head H = 16 m, rotational speed n = 1450 rpm and efficiency of 56%, outlet impeller width of 0.006 m, a blade outlet angle of 30° was used for the study. CFD simulations were conducted with the use of k-ε turbulence model. The influence of splitter blade position on the performance of pump as turbine in the selected specific pumps with and without splitter blades has been investigated both experimentally and numerically at three different flow rates and rotational speed. The simulated data were in good agreement with the experimental results, the maximum deviation error between the CFD and test for each model are 5.6%, 2.6%, for the head and efficiency; 7.5% and 3.6% at different flow conditions.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

scholarly journals Measuring Hydrometeors Using a Precipitation Microphysical Characteristics Sensor: Sampling Effect of Different Bin Sizes on Drop Size Distribution Parameters

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xichuan Liu ◽  
Taichang Gao ◽  
Yuntao Hu ◽  
Xiaojian Shu
Keyword(s):  
Drop Size ◽  
Rain Rate ◽  
Monte Carlo Model ◽  
Rain Gauge ◽  
Sampling Schemes ◽  
Distribution Parameters ◽  
Optimum Sampling ◽  
Simulation Results ◽  
The Impact ◽  
Good Agreement

In order to improve the measurement of precipitation microphysical characteristics sensor (PMCS), the sampling process of raindrops by PMCS based on a particle-by-particle Monte-Carlo model was simulated to discuss the effect of different bin sizes on DSD measurement, and the optimum sampling bin sizes for PMCS were proposed based on the simulation results. The simulation results of five sampling schemes of bin sizes in four rain-rate categories show that the raw capture DSD has a significant fluctuation variation influenced by the capture probability, whereas the appropriate sampling bin size and width can reduce the impact of variation of raindrop number on DSD shape. A field measurement of a PMCS, an OTT PARSIVEL disdrometer, and a tipping bucket rain Gauge shows that the rain-rate and rainfall accumulations have good consistencies between PMCS, OTT, and Gauge; the DSD obtained by PMCS and OTT has a good agreement; the probability of N0, μ, and Λ shows that there is a good agreement between the Gamma parameters of PMCS and OTT; the fitted μ-Λ and Z-R relationship measured by PMCS is close to that measured by OTT, which validates the performance of PMCS on rain-rate, rainfall accumulation, and DSD related parameters.

scholarly journals The impact of a foehn wind on PM10 concentrations and the urban boundary layer in complex terrain: a case study from Kraków, Poland

Tellus B ◽  
2021 ◽  
Vol 73 (1) ◽  
pp. 1-26
Author(s):  
Piotr Sekuła ◽  
Anita Bokwa ◽  
Zbigniew Ustrnul ◽  
Mirosław Zimnoch ◽  
Bogdan Bochenek
Keyword(s):  
Boundary Layer ◽  
Complex Terrain ◽  
Urban Boundary Layer ◽  
The Impact
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