Numerical study of secondary mass flow modulation in a Bypass Dual-Throat Nozzle

2020 ◽  
pp. 095441002094792
Author(s):  
MH Hamedi-Estakhrsar ◽  
M Ferlauto ◽  
H Mahdavy-Moghaddam
Keyword(s):  
Mass Flow ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Numerical Data ◽  
Thrust Vectoring ◽  
Flow Modulation ◽  
Contraction Ratio ◽  
Turbulent Airflow ◽  
Thrust Vector ◽  
Set Up

The fluidic thrust-vectoring modulation on a Bypass Dual-Throat Nozzle (BDTN) is studied numerically. The thrust vectoring modulation is obtained by varying the secondary mass flow, introducing different area contraction ratios of the bypass duct. The scope of present study is twofold: (i) to set up a model for the control of the secondary mass flow that is consistent with the resolution of the nozzle main flow and (ii) to derive a simplified representation of a valve system embedded in the bypass channel. The simulations of the turbulent airflow inside the BDTN and its efflux in the external ambient have been simulated by using RANS approach with RNG [Formula: see text] turbulence modeling. The numerical results have been validated with experimental and numerical data available in the open literature. The nozzle performance and thrust vector angle are computed for different values of the bypass area contraction ratio. The effects of different secondary mass flow rates on the system resultant thrust ratio and discharge coefficient of the bypass dual-throat nozzle have been investigated. By using the proposed approach to the secondary mass flow modulation, the thrust pitch angle has been controlled up to 27°.

Numerical Study of Aerodynamic Losses of Effusion Cooling Holes in Aero-Engine Combustor Liners

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
A. Andreini ◽  
A. Bonini ◽  
G. Caciolli ◽  
B. Facchini ◽  
S. Taddei
Keyword(s):  
Mass Flow ◽  
Cooling System ◽  
Numerical Study ◽  
Numerical Data ◽  
Good Reliability ◽  
Data Set ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Depth Analysis ◽  
Aero Engine

Due to the stringent cooling requirements of novel aero-engines combustor liners, a comprehensive understanding of the phenomena concerning the interaction of hot gases with typical coolant jets plays a major role in the design of efficient cooling systems. In this work, an aerodynamic analysis of the effusion cooling system of an aero-engine combustor liner was performed; the aim was the definition of a correlation for the discharge coefficient (CD) of the single effusion hole. The data were taken from a set of CFD RANS (Reynolds-averaged Navier-Stokes) simulations, in which the behavior of the effusion cooling system was investigated over a wide range of thermo/fluid-dynamics conditions. In some of these tests, the influence on the effusion flow of an additional air bleeding port was taken into account, making it possible to analyze its effects on effusion holes CD. An in depth analysis of the numerical data set has pointed out the opportunity of an efficient reduction through the ratio of the annulus and the hole Reynolds numbers: The dependence of the discharge coefficients from this parameter is roughly linear. The correlation was included in an in-house one-dimensional thermo/fluid network solver, and its results were compared with CFD data. An overall good agreement of pressure and mass flow rate distributions was observed. The main source of inaccuracy was observed in the case of relevant air bleed mass flow rates due to the inherent three-dimensional behavior of the flow close to bleed opening. An additional comparison with experimental data was performed in order to improve the confidence in the accuracy of the correlation: Within the validity range of pressure ratios in which the correlation is defined (>1.02), this comparison pointed out a good reliability in the prediction of discharge coefficients. An approach to model air bleeding was then proposed, with the assessment of its impact on liner wall temperature prediction.

scholarly journals Numerical study of airfoil with wavy leading edge at high Reynolds number regime

2020 ◽  
Author(s):  
William Denner Pires Fonseca ◽  
Rafael Rosario Da Silva ◽  
Reinaldo Marcondes Orselli ◽  
Adson Agrico De Paula ◽  
Ricardo Galdino da Silva
Keyword(s):  
Reynolds Number ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Numerical Data ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
High Reynolds

In this work, a numerical study of flow around an airfoil with wavy leading edge is presented at a Reynolds number of 3X106. The flow is resolved by considering the RANS (Reynolds Average Navier-Stokes)equations. The baseline geometry is based on the NACA 0021 profile. The wavy leading edge has an amplitude of 3% and wavelength of 11%, both with respect to the airfoil chord. Cases without and with wavy leadingedges are simulated and compared. Initially, studies of the numerical sensitivity with respect to the obtained results, considering aspects such as turbulence modeling and mesh refinement, are carried out as well as bycomparison with corresponding results in the literature. Numerical data such as pressure distribution, shear stress lines on the wing surface, and aerodynamics coefficients are used to describe and investigate the flowfeatures around the wavy leading airfoil. Comparisons between the straight leading edge and the wavy leading edge cases shows an increase of the maximum lift coefficient as well as stall angle for the wavy leading edge configuration. In addition, at an angle of attack near the stall, the present numerical results shows an increase of the drag coefficient with the wavy leading edge airfoil when compared with the corresponding straight leading edge case.

Experimental and Numerical Investigations of Aerodynamic Aspects of Hot Gas Ingestion in Rotor-Stator Systems With Superimposed Cooling Mass Flow

1995 ◽  
Author(s):  
Dieter Bohn ◽  
Erik Johann ◽  
Uwe Krüger
Keyword(s):  
Mass Flow ◽  
Gas Turbines ◽  
Numerical Data ◽  
Finite Volume Scheme ◽  
Hot Gas ◽  
Mainstream Flow ◽  
Set Up ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Shrouded Rotor

Modern “High Temperature Gas Turbines” need very complex cooling configurations. Not only the turbine vanes and blades, but also the turbine discs, are cooled by air flow extracted from the compressor. Therefore, rotor-stator systems with a superimposed cooling mass flow are found in many constructions of gas turbines. The hot gas ingress into the wheelspace between stator and-rotor, taking place under special conditions, is one of the major problems in these systems. An experimental set-up has been built to get a better knowledge of the aerodynamics of such configurations. The ingress of hot gas into the wheelspace with different sealing configurations has been considered by the measurements of surface pressure and velocities (using the LDA-measurement technique) in the shrouded rotor-stator-system. A variable mainstream flow (Ma-number up to 0.7, Re-number up to 2·106) — with and without nozzle guide vanes — has been realized, to obtain flow situations approximating those in real gas turbines. Parallel to the experiments, the flow structure has been calculated numerically using a modern multiblock finite-volume-scheme with non-orthogonal body-fitted grids. The influence of the mainstream flow has also been taken into account. Two different versions of the k-ε-turbulence model have been used to describe the turbulent effects of the flow. Important features of the experimental results are as follows: hot gas ingress can not only occur on the stator but also on the rotor side of the wheelspace depending on the conditions between the cooling gas and the mainstream flow. In real systems with pressure and velocity gradients in the circumferential direction, hot gas ingestion can not be completely prevented. It was only in the 2-D-axisymmetric case, without guide nozzles in the mainstream, that hot gas ingress could be suppressed completely. The numerical data has been compared to the solution obtained by similitude theory as well as to the measurements. It was found that the data correspond reasonably well. The numerical results confirm the conclusions drawn by experiment about the physical mechanism of hot gas ingress into the wheelspace.

Numerical Performances Study of Curved Photovoltaic Panel Integrated with Phase Change Material

2020 ◽  
Vol 22 (4) ◽  
pp. 1439-1452
Author(s):  
Mohamed L. Benlekkam ◽  
Driss Nehari ◽  
Habib Y. Madani
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Numerical Study ◽  
Numerical Data ◽  
Navier Stokes ◽  
Photovoltaic Panel ◽  
Pv Panel ◽  
Energy Equations ◽  
Solid Liquid ◽  
Change Material

AbstractThe temperature rise of photovoltaic’s cells deteriorates its conversion efficiency. The use of a phase change material (PCM) layer linked to a curved photovoltaic PV panel so-called PV-mirror to control its temperature elevation has been numerically studied. This numerical study was carried out to explore the effect of inner fins length on the thermal and electrical improvement of curved PV panel. So a numerical model of heat transfer with solid-liquid phase change has been developed to solve the Navier–Stokes and energy equations. The predicted results are validated with an available experimental and numerical data. Results shows that the use of fins improve the thermal load distribution presented on the upper front of PV/PCM system and maintained it under 42°C compared with another without fins and enhance the PV cells efficiency by more than 2%.

scholarly journals Fast Two-Stage Computation of an Index Policy for Multi-Armed Bandits with Setup Delays

Mathematics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 52
Author(s):  
José Niño-Mora
Keyword(s):  
Numerical Study ◽  
Arithmetic Operation ◽  
Bandit Problem ◽  
Index Policy ◽  
Two Stage ◽  
Second Stage ◽  
Whittle Index ◽  
Set Up ◽  
Computing Method ◽  
Special Case

We consider the multi-armed bandit problem with penalties for switching that include setup delays and costs, extending the former results of the author for the special case with no switching delays. A priority index for projects with setup delays that characterizes, in part, optimal policies was introduced by Asawa and Teneketzis in 1996, yet without giving a means of computing it. We present a fast two-stage index computing method, which computes the continuation index (which applies when the project has been set up) in a first stage and certain extra quantities with cubic (arithmetic-operation) complexity in the number of project states and then computes the switching index (which applies when the project is not set up), in a second stage, with quadratic complexity. The approach is based on new methodological advances on restless bandit indexation, which are introduced and deployed herein, being motivated by the limitations of previous results, exploiting the fact that the aforementioned index is the Whittle index of the project in its restless reformulation. A numerical study demonstrates substantial runtime speed-ups of the new two-stage index algorithm versus a general one-stage Whittle index algorithm. The study further gives evidence that, in a multi-project setting, the index policy is consistently nearly optimal.

Load Characteristics of Steel and Concrete Tubular Members Under Jet Fire: An Experimental and Numerical Study

2010 ◽  
Author(s):  
Jeong Hyo Park ◽  
Bong Ju Kim ◽  
Jung Kwan Seo ◽  
Jae Sung Jeong ◽  
Byung Keun Oh ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Numerical Study ◽  
Fire Load ◽  
Adiabatic Wall ◽  
Fire Engineering ◽  
Ansys Cfx ◽  
Design Values ◽  
Computational Fluid Dynamics Cfd ◽  
Load Characteristics ◽  
Set Up

The aim of this study was to evaluate the load characteristics of steel and concrete tubular members under jet fire, with the motivation to investigate the jet fire load characteristics in FPSO topsides. This paper is part of Phase II of the joint industry project on explosion and fire engineering of FPSOs (EFEF JIP) [1]. To obtain reliable load values, jet fire tests were carried out in parallel with a numerical study. Computational fluid dynamics (CFD) simulation was used to set up an adiabatic wall boundary condition for the jet fire to model the heat transfer mechanism. A concrete tubular member was tested under the assumption that there is no conduction effect from jet fire. A steel tubular member was tested and considered to transfer heat through conduction, convection, and radiation. The temperature distribution, or heat load, was analyzed at specific locations on each type of member. ANSYS CFX [2] and Kameleon FireEx [3] codes were used to obtain similar fire action in the numerical and experimental methods. The results of this study will provide a useful database to determine design values related to jet fire.

Numerical Study of Methane and Air Combustion Inside Heat-Recirculating Combustors

2013 ◽  
Author(s):  
Yanxia Li ◽  
Zhongliang Liu ◽  
Yan Wang ◽  
Jiaming Liu
Keyword(s):  
Gas Flow ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Central Area ◽  
Small Scale ◽  
Inlet Velocity ◽  
Strong Convection ◽  
Simulation Results ◽  
Lean Fuel ◽  
Set Up

A numerical model on methane/air combustion inside a small Swiss-roll combustor was set up to investigate the flame position of small-scale combustion. The simulation results show that the combustion flame could be maintained in the central area of the combustor only when the speed and equivalence ratio are all within a narrow and specific range. For high inlet velocity, the combustion could be sustained stably even with a very lean fuel and the flame always stayed at the first corner of reactant channel because of the strong convection heat transfer and preheating. For low inlet velocity, small amounts of fuel could combust stably in the central area of the combustor, because heat was appropriately transferred from the gas to the inlet mixture. Whereas, for the low premixed gas flow, only in certain conditions (Φ = 0.8 ～ 1.2 when ν0 = 1.0m/s, Φ = 1.0 when ν0 = 0.5m/s) the small-scale combustion could be maintained.

Historic city, tourism performance and development: The balance of social behaviours in the city of Santiago de Compostela (Spain)

2016 ◽  
Vol 16 (3) ◽  
pp. 282-293 ◽  
Author(s):  
Belén Mª Castro Fernández ◽  
Rubén Camilo Lois González ◽  
Lucrezia Lopez
Keyword(s):  
Numerical Data ◽  
City Centre ◽  
City Development ◽  
Santiago De Compostela ◽  
Final Destination ◽  
City Tourism ◽  
Set Up ◽  
Historic City ◽  
The City ◽  
The Way

Santiago de Compostela is an iconic place. From the 9th century through to the present day the city has acted as the final destination of a major pilgrimage route named after it. In the article we ask ourselves how the contemporary reinvention of the pilgrimage and pilgrimages on the Way of St. James has boosted tourism development in the city. Development has been concentrated in the historic city centre and in the area around the cathedral. The importance of tourism has transformed the significance of the city itself, which acquires a magical component as a place of arrival and encounter for all kinds of visitors. The historic city has been set up in the 20th century as a destination for the Way and for cultural tourism. The buildings, particularly those connected with the pilgrimage route, become highly attractive and symbolic places and tourists carry out a number of rituals in them. They travel and enjoy Santiago as a unique experience. The study of tourism and of the tourist transformation of Santiago de Compostela is undertaken using a qualitative and quantitative method. The article analyses the heritage and symbolic value of the historic centre, together with the growth of its tourism activities. Numerical data are also provided on the perceptions and behaviour of visitors using surveys carried out by the city's Tourism Observatory.

Frequency selective antenna radome based on metal-dielectric gratings and perforated screens

Antennas ◽  
2021 ◽  
Author(s):  
A. O. Kasyanov
Keyword(s):  
Antenna Arrays ◽  
Electromagnetic Compatibility ◽  
Numerical Study ◽  
Numerical Data ◽  
Microwave Antenna ◽  
Frequency Selective Surfaces ◽  
Radio Electronic ◽  
Dielectric Gratings ◽  
Study Results ◽  
Frequency Selective

This article is devoted to the analysis of numerical study results of printed frequency selective surfaces scattering characteristics. It has been shown that these frequency selective surfaces may be used as antenna radomes. Numerical results have been obtained by full-wave simulation of frequency-selective surfaces with dielectric covers. The numerical research results of the scattering characteristics of printed frequency selective surfaces as antenna radomes based on metal-dielectric gratings and thick perforated screens have been presented. A comprehensive numerical study of microwave frequency selective surfaces based on multi-element multilayer printed reflectarrays and thick perforated screens has been carried out. Constructive solutions for metal-dielectric structures in integral design, realizing the functions of frequency selective surfaces, have been found. These solutions are based on performed numerical studies. The problems of constructive implementation of multilayer planar spatially selective as frequency selective surfaces have been considered. These frequency selective surfaces are integrated into radiation systems of modern multi-element printed phased arrays. The problems connected with creation of such arrays have been also considered. The numerical simulation results for frequency selective surfaces based on metal gratings with dielectric covers have been obtained. These results can be used to select the most rational options for the topology of metal-dielectric gratings. Such solutions may be useful for design of multifunctional radomes in microwave antenna systems. Based on the obtained numerical data, the possibilities of using flat gratings as frequency selective surfaces in the composition of antenna radomes have been considered. The spatial frequency-selective structures proposed in this work are performed as multi-planar printed gratings. These gratings are designed to ensure electromagnetic compatibility of closely spaced radio electronic sets. These radio electronic sets operate in close frequency ranges. They contain antenna arrays. These arrays are placed under the antenna radomes.

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