Combined Momentum Theory and Simple Vortex Theory Inflow Model for Multirotor Configurations

2021 ◽  
Author(s):  
Feyyaz Guner ◽  
J. V. R. Prasad
Keyword(s):  
Experimental Data ◽  
Ad Hoc ◽  
Complex Flow ◽  
Momentum Theory ◽  
Vortex Theory ◽  
Performance Predictions ◽  
Flow Interactions ◽  
Overall Performance ◽  
And Performance ◽  
Flight Simulations

For conventional main/tail rotor helicopters, momentum theory-based inflow models are still popular for design trade studies and flight simulations. However, simple momentum theory-based inflow models are not readily applicable in design trade studies of multirotor configuration vehicles where complex flow interactions among rotors can have a significant impact on vehicle overall performance, and hence, can impact vehicle sizing. The use of empirically corrected ad hoc inflow models is not often satisfactory. In this study, momentum theory is combined with a simple vortex theory in the development of a combined momentum theory and simple vortex theory (CMTSVT) based inflow model that is readily applicable to generic multirotor configurations. The developed model is validated against some multirotor inflow models and experimental data from the literature through comparisons of inflow predictions and performance predictions for different dual-rotor configurations. Further, inflow predictions using the proposed inflow model for a partially overlapping quad-rotor configuration are presented to illustrate the significance of rotor-on-rotor flow interactions in multirotor vehicle configurations.

Design and Performance Analysis of Vane Wheel

2015 ◽  
Author(s):  
Woo-Chan Seok ◽  
Hyoungsuk Lee ◽  
Tobias Zorn ◽  
Vladimir Shigunov
Keyword(s):  
Open Water ◽  
Power Reduction ◽  
Model Tests ◽  
Propulsive Efficiency ◽  
Towing Tank ◽  
Momentum Theory ◽  
Computational Fluid Dynamics Cfd ◽  
Overall Performance ◽  
And Performance ◽  
Blade Element

For the analysis, a vane wheel was considered consisting of two portions, namely, a turbine portion and a propeller portion. The turbine portion was designed using Blade Element Momentum Theory (BEMT); the propeller portion, Computational Fluid Dynamics (CFD) under open-water conditions. Model tests were conducted at Hyundai Maritime Research Institute (HMRI) in their towing tank, using a Contra Rotating Propeller (CRP) dynamometer. Model tests as well as full-scale CFD calculations were performed to predict overall performance. The CFD calculations showed better performance compared to the model tests. In general, the analyzed vane wheel improved the propulsive efficiency via power reduction compared to the case without a vane wheel.

scholarly journals Using Aerial and Vehicular NFV Infrastructures to Agilely Create Vertical Services

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1342
Author(s):  
Borja Nogales ◽  
Miguel Silva ◽  
Ivan Vidal ◽  
Miguel Luís ◽  
Francisco Valera ◽  
...  
Keyword(s):  
Ad Hoc Network ◽  
Ad Hoc ◽  
Cost Effective ◽  
Network Services ◽  
Network Function Virtualization ◽  
Mobile Environments ◽  
Network Resources ◽  
The Public ◽  
Network Function ◽  
And Performance

5G communications have become an enabler for the creation of new and more complex networking scenarios, bringing together different vertical ecosystems. Such behavior has been fostered by the network function virtualization (NFV) concept, where the orchestration and virtualization capabilities allow the possibility of dynamically supplying network resources according to its needs. Nevertheless, the integration and performance of heterogeneous network environments, each one supported by a different provider, and with specific characteristics and requirements, in a single NFV framework is not straightforward. In this work we propose an NFV-based framework capable of supporting the flexible, cost-effective deployment of vertical services, through the integration of two distinguished mobile environments and their networks: small sized unmanned aerial vehicles (SUAVs), supporting a flying ad hoc network (FANET) and vehicles, promoting a vehicular ad hoc network (VANET). In this context, a use case involving the public safety vertical will be used as an illustrative example to showcase the potential of this framework. This work also includes the technical implementation details of the framework proposed, allowing to analyse and discuss the delays on the network services deployment process. The results show that the deployment times can be significantly reduced through a distributed VNF configuration function based on the publish–subscribe model.

Advances in coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery

2020 ◽  
pp. 095441002096645
Author(s):  
Jie Gao ◽  
Chunde Tao ◽  
Dongchen Huo ◽  
Guojie Wang
Keyword(s):  
Performance Improvement ◽  
High Efficiency ◽  
Three Dimensional ◽  
Great Influence ◽  
Aerodynamic Characteristics ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Axial Turbine ◽  
Flow Interactions ◽  
And Performance

Marine, industrial, turboprop and turboshaft gas turbine engines use nonaxisymmetric exhaust volutes for flow diffusion and pressure recovery. These processes result in a three-dimensional complex turbulent flow in the exhaust volute. The flows in the axial turbine and nonaxisymmetric exhaust volute are closely coupled and inherently unsteady, and they have a great influence on the turbine and exhaust aerodynamic characteristics. Therefore, it is very necessary to carry out research on coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics, so as to provide reference for the high-efficiency turbine-volute designs. This paper summarizes and analyzes the recent advances in the field of coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery. This review covers the following topics that are important for turbine and volute coupled designs: (1) flow and loss characteristics of nonaxisymmetric exhaust volutes, (2) flow interactions between axial turbine and nonaxisymmetric exhaust volute, (3) improvement of turbine and volute performance within spatial limitations and (4) research methods of coupled turbine and exhaust volute aerodynamics. The emphasis is placed on the turbine-volute interactions and performance improvement. We also present our own insights regarding the current research trends and the prospects for future developments.

scholarly journals Array databases: concepts, standards, implementations

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Peter Baumann ◽  
Dimitar Misev ◽  
Vlad Merticariu ◽  
Bang Pham Huu
Keyword(s):  
Service Quality ◽  
Ad Hoc ◽  
Query Language ◽  
Distributed Processing ◽  
Database Systems ◽  
Database Technology ◽  
Comprehensive Survey ◽  
Spatio Temporal ◽  
And Performance ◽  
Array Databases

AbstractMulti-dimensional arrays (also known as raster data or gridded data) play a key role in many, if not all science and engineering domains where they typically represent spatio-temporal sensor, image, simulation output, or statistics “datacubes”. As classic database technology does not support arrays adequately, such data today are maintained mostly in silo solutions, with architectures that tend to erode and not keep up with the increasing requirements on performance and service quality. Array Database systems attempt to close this gap by providing declarative query support for flexible ad-hoc analytics on large n-D arrays, similar to what SQL offers on set-oriented data, XQuery on hierarchical data, and SPARQL and CIPHER on graph data. Today, Petascale Array Database installations exist, employing massive parallelism and distributed processing. Hence, questions arise about technology and standards available, usability, and overall maturity. Several papers have compared models and formalisms, and benchmarks have been undertaken as well, typically comparing two systems against each other. While each of these represent valuable research to the best of our knowledge there is no comprehensive survey combining model, query language, architecture, and practical usability, and performance aspects. The size of this comparison differentiates our study as well with 19 systems compared, four benchmarked to an extent and depth clearly exceeding previous papers in the field; for example, subsetting tests were designed in a way that systems cannot be tuned to specifically these queries. It is hoped that this gives a representative overview to all who want to immerse into the field as well as a clear guidance to those who need to choose the best suited datacube tool for their application. This article presents results of the Research Data Alliance (RDA) Array Database Assessment Working Group (ADA:WG), a subgroup of the Big Data Interest Group. It has elicited the state of the art in Array Databases, technically supported by IEEE GRSS and CODATA Germany, to answer the question: how can data scientists and engineers benefit from Array Database technology? As it turns out, Array Databases can offer significant advantages in terms of flexibility, functionality, extensibility, as well as performance and scalability—in total, the database approach of offering “datacubes” analysis-ready heralds a new level of service quality. Investigation shows that there is a lively ecosystem of technology with increasing uptake, and proven array analytics standards are in place. Consequently, such approaches have to be considered a serious option for datacube services in science, engineering and beyond. Tools, though, vary greatly in functionality and performance as it turns out.

Initiation and Statistical Evolution of Horizontal Slug Flow With a Two-Fluid Model

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
A. O. Nieckele ◽  
J. N. E. Carneiro ◽  
R. C. Chucuya ◽  
J. H. P. Azevedo
Keyword(s):  
Experimental Data ◽  
Slug Flow ◽  
Fluid Model ◽  
Subsequent Development ◽  
Complex Flow ◽  
Horizontal Pipes ◽  
Dimensional Version ◽  
Two Fluid Model ◽  
Log Normal ◽  
Two Fluid

In the present work, the onset and subsequent development of slug flow in horizontal pipes is investigated by solving the transient one-dimensional version of the two-fluid model in a high resolution mesh using a finite volume technique. The methodology (named slug-capturing) was proposed before in the literature and the present work represents a confirmation of its applicability in predicting this very complex flow regime. Further, different configurations are analyzed here and comparisons are performed against different sets of experimental data. Predictions for mean slug variables were in good agreement with experimental data. Additionally, focus is given to the statistical properties of slug flows such as shapes of probability density functions of slug lengths (which were represented by gamma and log-normal distributions) as well as the evolution of the first statistical moments, which were shown to be well reproduced by the methodology.

scholarly journals Large Temperature Fluctuations due to Cold-Air Pool Displacement along the Lee Slope of a Desert Mountain

2017 ◽  
Vol 56 (4) ◽  
pp. 1083-1098 ◽  
Author(s):  
Matthew E. Jeglum ◽  
Sebastian W. Hoch ◽  
Derek D. Jensen ◽  
Reneta Dimitrova ◽  
Zachariah Silver
Keyword(s):  
Low Frequency ◽  
Temperature Fluctuations ◽  
Atmospheric Modeling ◽  
Large Temperature ◽  
Complex Flow ◽  
Near Surface ◽  
Cold Air ◽  
Flow Interactions ◽  
Initial Drop ◽  
Program Temperature

AbstractLarge temperature fluctuations (LTFs), defined as a drop of the near-surface temperature of at least 3°C in less than 30 min followed by a recovery of at least half of the initial drop, were frequently observed during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program. Temperature time series at over 100 surface stations were examined in an automated fashion to identify and characterize LTFs. LTFs occur almost exclusively at night and at locations elevated 50–100 m above the basin floors, such as the east slope of the isolated Granite Mountain (GM). Temperature drops associated with LTFs were as large as 13°C and were typically greatest at heights of 4–10 m AGL. Observations and numerical simulations suggest that LTFs are the result of complex flow interactions of stably stratified flow with a mountain barrier and a leeside cold-air pool (CAP). An orographic wake forms over GM when stably stratified southwesterly nocturnal flow impinges on GM and is blocked at low levels. Warm crest-level air descends in the lee of the barrier, and the generation of baroclinic vorticity leads to periodic development of a vertically oriented vortex. Changes in the strength or location of the wake and vortex cause a displacement of the horizontal temperature gradient along the slope associated with the CAP edge, resulting in LTFs. This mechanism explains the low frequency of LTFs on the west slope of GM as well as the preference for LTFs to occur at higher elevations later at night, as the CAP depth increases.

scholarly journals Study of a test methodology to assess potential drift generated by air-assisted sprayers

2013 ◽  
Vol 44 (2s) ◽  
Author(s):  
Paolo Balsari ◽  
Paolo Marucco ◽  
Claudio Bozzer ◽  
Mario Tamagnone
Keyword(s):  
Experimental Data ◽  
Ad Hoc ◽  
Sustainable Use ◽  
Spray Drift ◽  
Field Crop ◽  
The European Union ◽  
Pesticide Application ◽  
Buffer Zones ◽  
Iso Standard ◽  
Test Methodology

During pesticide application spray drift may cause diffuse pollution phenomena in the environment. In the last years the European Union, through the Directive on the sustainable use of pesticides (128/2009 EC), has recommended the adoption of measures enabling to prevent spray drift. Among these measures, the adoption of buffer zones beside the sprayed fields requires to consider different widths for these no spray zones according to the amount of spray drift generated by the spraying equipment used for application. It is therefore necessary to classify the different sprayer models according to drift risk. For what concerns the sprayers used on arboreal crops, in order to make this classification in a simple and quick way as it was already proposed for the field crop sprayers (ISO FDIS 22369-3), a study was started aimed at defining a methodology to assess potential drift produced by the different sprayer models in absence of wind, using ad hoc test benches. On the basis of the positive first experimental data obtained, a first proposal for a new ISO standard methodology was prepared.

scholarly journals An improved supervisory protocol for automatic selection of routing protocols in environment-aware vehicular ad hoc networks

2018 ◽  
Vol 14 (11) ◽  
pp. 155014771881505 ◽  
Author(s):  
Ishtiaq Wahid ◽  
Ata Ul Aziz Ikram ◽  
Masood Ahmad ◽  
Fasee Ullah
Keyword(s):  
Routing Protocols ◽  
Vehicular Ad Hoc Networks ◽  
Ad Hoc ◽  
Performance Metrics ◽  
Mobility Model ◽  
Operational Environment ◽  
Trade Offs ◽  
Microscopic Features ◽  
And Performance ◽  
Hoc Networks

With resource constraint’s distributed architecture and dynamic topology, network issues such as congestion, latency, power awareness, mobility, and other quality of service issues need to be addressed by optimizing the routing protocols. As a result, a number of routing protocols have been proposed. Routing protocols have trade-offs in performance parameters and their performance varies with the underlying mobility model. For designing an improved vehicular ad hoc network, three components of the network are to be focused: routing protocols, mobility models, and performance metrics. This article describes the relationship of these components, trade-offs in performance, and proposes a supervisory protocol, which monitors the scenario and detects the realistic mobility model through analysis of the microscopic features of the mobility model. An analytical model is used to determine the best protocol for a particular mobility model. The supervisory protocol then selects the best routing protocol for the mobility model of the current operational environment. For this, EstiNet 8.1 Simulator is used to validate the proposed scheme and compare its performance with existing schemes. Simulation results of the proposed scheme show the consistency in the performance of network throughout its operation.

Behavior and Performance of Refrigerant Mixture HFC125/HC290 in Heat Pumps

2013 ◽  
Author(s):  
Xiaowei Fan ◽  
Fang Wang ◽  
Huifan Zheng ◽  
Xianping Zhang ◽  
Di Xu
Keyword(s):  
Energy Consumption ◽  
Heat Pumps ◽  
Operating Conditions ◽  
Environment Friendly ◽  
Factors Affecting ◽  
Refrigerant Mixture ◽  
Important Direction ◽  
Overall Performance ◽  
And Performance ◽  
Binary Refrigerant

The refrigerant mixtures provide an important direction in selecting new environment-friendly alternative to match the desirable properties with the existing halogenated refrigerants or future use in the new devices, in which, HFCs refrigerants with zero ODP combined with HCs refrigerants with zero ODP and lower GWP are of important value in the fields of application. In the present work, research on HFC125/HC290 (25/75 by mass) binary refrigerant mixture used in heat pumps was carried out, and parameters, factors affecting the performance were investigated, and compared with that of HCFC22 under the same operating conditions. It has been found that the new mixture can improve the actual COP by 2 to 13% and hence it can reduce the energy consumption by 20 to 31.5%. The overall performance has proved that the new refrigerant mixture could be a promising substitute for HCFC22.

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