Numerical simulations of commercial aircraft wakes subjected to airport surface weather conditions

1996 ◽  
Author(s):  
Robert Ash ◽  
Z. Zheng
Keyword(s):  
Numerical Simulations ◽  
Weather Conditions ◽  
Commercial Aircraft ◽  
Surface Weather

scholarly journals Fast-Scale Instability and Stabilization by Adaptive Slope Compensation of a PV-Fed Differential Boost Inverter

2021 ◽  
Vol 11 (5) ◽  
pp. 2106
Author(s):  
Abdelali El Aroudi ◽  
Mohamed Debbat ◽  
Mohammed Al-Numay ◽  
Abdelmajid Abouloiafa
Keyword(s):  
Numerical Simulations ◽  
Full Range ◽  
Weather Conditions ◽  
Current Loop ◽  
Point Tracking ◽  
Bifurcation Phenomena ◽  
Slope Compensation ◽  
Power Point ◽  
The Stability ◽  
Detailed Circuit

Numerical simulations reveal that a single-stage differential boost AC module supplied from a PV module under an Maximum Power Point Tracking (MPPT) control at the input DC port and with current synchronization at the AC grid port might exhibit bifurcation phenomena under some weather conditions leading to subharmonic oscillation at the fast-switching scale. This paper will use discrete-time approach to characterize such behavior and to identify the onset of fast-scale instability. Slope compensation is used in the inner current loop to improve the stability of the system. The compensation slope values needed to guarantee stability for the full range of operating duty cycle and leading to an optimal deadbeat response are determined. The validity of the followed procedures is finally validated by a numerical simulations performed on a detailed circuit-level switched model of the AC module.

An Investigation into the Motion Behaviour of a Wind Farm Mothership

2015 ◽  
Author(s):  
Blanca Peña ◽  
Erik P. ter Brake ◽  
Kyriakos Moschonas
Keyword(s):  
Numerical Simulations ◽  
Wind Farm ◽  
Wind Farms ◽  
Weather Conditions ◽  
Offshore Wind ◽  
Financial Benefit ◽  
Offshore Wind Farms ◽  
Motion Characteristics ◽  
Vessel Motion ◽  
Motion Behavior

A number of UK Round Three offshore wind farms are located relatively far from the coast making crew transfer to the sites time consuming, more prone to interruption by weather conditions and increasingly costly. In order to optimize the functionality of a permanent accommodation vessel, Houlder has developed a dedicated Accommodation and Maintenance Wind Farm vessel based on an oil & gas work-over vessel that has been successfully deployed for many years. The Accommodation and Maintenance (A&M) Wind Farm vessel is designed to provide an infield base for Marine Wind Farm operation. The A&M vessel is designed for high operability when it comes to crew access and performance of maintenance and repair of wind turbine components in its workshops. Also general comfort on board is of high regard. As such, the seakeeping behavior of the unit is of great importance. In this publication, the seakeeping behavior is presented on the basis of numerical simulations using 3D diffraction software. The first design iteration is driven by achieving high maneuverability and good motion characteristics for operational up-time and personnel comfort on board the vessel. Model test data of the original work-over vessel has been used to validate and calibrate the numerical simulations. On this basis, parametric studies can be performed to fine-tune a potential new hull form. In turn, this could reduce the number of required physical model tests providing a potential financial benefit and optimized delivery schedule. The vessel motion behavior was tested against the acceptability criteria and crew comfort guidelines of motion behavior for a North Sea environment.

Weather Maps, Forecasts, and Data

2000 ◽  
Author(s):  
C. David Whiteman
Keyword(s):  
Weather Forecast ◽  
Ground Level ◽  
Weather Conditions ◽  
Low Pressure ◽  
Weather Data ◽  
Dimensional Structure ◽  
Synoptic Scale ◽  
Pressure System ◽  
Surface Weather ◽  
Comprehensive Picture

Weather maps prepared by the National Weather Service summarize and synthesize weather data to provide a comprehensive picture of weather conditions at a given time. They are the basis of weather maps used on television to show precipitation, high and low pressure centers, and fronts. Weather maps are produced using both surface data and data from specified pressure levels. Data are plotted and contoured by computer, and analysts use satellite photos, satellite video loops, weather forecast models, and extrapolations from previous frontal and pressure system analyses to locate fronts and pressure centers. An example of a surface weather chart is presented in figure 9.1. A 500-mb chart for the same date and time was presented in figure 5.1. Symbols are used on weather maps to indicate synoptic-scale features. High and low pressure weather systems (highs and lows) are indicated by the letters H and L, with isobars labeled in millibars. Lines indicating frontal positions (section 6.2) represent the position on the ground of boundaries between air masses. Additional meteorological variables, such as temperature, are often analyzed on the same map using dashed or colored lines. Pressure, temperature, and other data from the reporting stations are plotted in coded form at the station locations. A station model specifies the positions in which different types of data are plotted relative to the station location. Figure 9.1 used an abbreviated station model. A complete station model is shown in figure 9.2. Figures 9.3 — 9.7 show additional symbols used in station models to indicate total sky cover, winds, pressure tendency, cloud types, and present weather types, respectively. A surface weather chart, with the symbols indicating fronts and high and low pressure centers and the information included in the station model, provides a snapshot of synoptic-scale conditions at ground level. By overlaying charts for several pressure levels (section 5.1.3), changes with altitude can be identified and the three-dimensional structure of the atmosphere at a given point in time can be visualized. By comparing consecutive charts, the rate of movement of fronts and the rates of development of high and low pressure centers can be determined.

The Problem of Landing Commercial Aircraft in Fog

1934 ◽  
Vol 38 (286) ◽  
pp. 807-836
Author(s):  
R. Stussel
Keyword(s):  
Weather Conditions ◽  
Air Transport ◽  
List Type ◽  
Type Number ◽  
Transport Service ◽  
Commercial Aircraft ◽  
Great Problem ◽  
Short Survey ◽  
Technical Aids ◽  
Bad Weather

Summary(1)Survey of the present methods of carrying out air transport service when visibility is bad.(2)What is essentially required of technical aids for landing under bad weather conditions.(3)Short survey of current German methods for solving the problem of landing in fog.The necessity for being able to carry out air transport unhindered by weather conditions is inseparably associated with the idea of commercial air service. This great problem of “ flight in any weather ” has confronted us since the inception of regular services between places having corresponding traffic needs, that is to say, since the very birth of air transport.

scholarly journals Numerical Simulations of a PV Module with Phase Change Material (PV-PCM) under Variable Weather Conditions

2021 ◽  
Vol 39 (2) ◽  
pp. 643-652
Author(s):  
Stefano Aneli ◽  
Roberta Arena ◽  
Antonio Gagliano
Keyword(s):  
Phase Change ◽  
Numerical Simulations ◽  
Phase Change Materials ◽  
Weather Conditions ◽  
Ansys Fluent ◽  
Pv Panel ◽  
Pv Module ◽  
Pv Modules ◽  
Fluent Software ◽  
Variable Weather

The electrical efficiency of photovoltaic (PV) modules can be improved through the cooling of the PV. Among the passive cooling strategy, one of the most promising concerns the use of phase change materials (PCMs) to decrease the operative temperature of a PV panel. This paper investigates the performances of a conventional PV panel in which two organic PCMs are added (PV-PCM) to reduce the temperature rise of PV cells and consequently to increase the electrical performances. With this aim, unsteady numerical simulations have been carried with Ansys Fluent software using a two-dimensional simplified geometry for the PV modules with the PCM is incorporated (PV-PCM), as well as for the benchmark PV module. The numerical simulations have allowed evaluating the PV cell temperatures, the power production, as well the PCM thermal behavior. As regards this latter aspect the dynamic analysis has evidenced the need to extend the time of simulation at least for two days in such way to take into account of the degree of solidification achieved during the night by the PCM materials. PCM with low melting temperature cannot complete solidifying during the night and so the heat stored during the day will be lesser than the theoretical one. The results of this study pointed out that the PV-PCM units allow achieving higher performances in comparison with a conventional PV module, especially during the hottest months. An increase in the peak power of 10% and of 3.5% of the energy produced all year round is attained.

Estimation of apparent survival probability of the harvestman Paranemastoma sillii sillii (Herman, 1871) from two caves

2017 ◽  
Vol 67 (2) ◽  
pp. 165-176 ◽  
Author(s):  
Rodica Plăiaşu ◽  
Arpat Ozgul ◽  
Benedikt R. Schmidt ◽  
Raluca I. Băncilă
Keyword(s):  
Sex Differences ◽  
Weather Conditions ◽  
Monthly Variation ◽  
Population Parameters ◽  
Apparent Survival ◽  
Sex Effect ◽  
Survival Difference ◽  
Surface Weather ◽  
Capture Recapture ◽  
Western Romania

Reliable estimates of population parameters are lacking for most cave-dwelling species. This lack of knowledge may hinder the appropriate management of caves and populations of cave-dwelling species. Using monthly capture-recapture data and Cormack-Jolly-Seber models, we (i) estimated the apparent survival of individuals in two cave populations of the harvestman Paranemastoma sillii sillii (Herman, 1871) from the Mehedinti Mountains in south-western Romania; (ii) investigated temporal variation in apparent survival; (iii) tested if surface weather conditions affect apparent survival of cave-dwelling harvestmen through their influence upon cave environmental conditions and (iv) tested for sex differences in apparent survival. Our results show that the apparent monthly survival estimates were high for both studied cave populations and there was a significant sex effect on survival. Males had lower survival than females, and the survival difference between caves was larger in males than in females. Temporal (i.e., monthly) variation in apparent survival was low and the weather conditions at the surface had little influence on apparent survival as the environment inside the caves is well buffered against weather fluctuations outside the caves. Our results indicate that caves stabilize survival of facultative cave-dwelling species and may serve as microrefugia for epigean species. We suggest that caves should be considered for conservation because they may serve as a refuge for some epigean species during harsh weather conditions.

Numerical Study for a Catamaran Gripper-Monopile Mechanism of a Novel Offshore Wind Turbine Assembly Installation Procedure

2017 ◽  
Author(s):  
Lars Ivar Hatledal ◽  
Houxiang Zhang ◽  
Karl Henning Halse ◽  
Hans Petter Hildre
Keyword(s):  
Numerical Simulations ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Numerical Study ◽  
Weather Conditions ◽  
Rolling Contact ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Contact Points ◽  
Turbine Installation

Current methods for installation of offshore wind turbines are all sensitive to the weather conditions and the present cost level of offshore wind power is more than twice the cost of land-based units, increasing with water depth. This paper presents numerical simulations of a novel experimental gripper design to reduce the environmental effects applied to a catamaran type of vessel during wind turbine installation. In SFI MOVE project in NTNU Aalesund, our team proposed a novel wind turbine installation process. A new catamaran vessel will carry pre-assembled wind turbines to the installation location. Two new designed grippers on the deck will make a lifting operation to install the wind turbine onto the turbine foundation. Three prismatic grippers with several rolling contact points at the end are attached in an arc at the catamaran’s aft, designed to grasp the turbine foundation in order to make a connection between the two in the horizontal plane. This paper will only emphasize the contact responses between the turbine foundation and the three grippers during the wind turbine installation process. Numerical simulations are carried out using the virtual prototyping framework Vicosim which is developed by NTNU Aalesund. The simulation results show validation of a key part of the proposed new wind turbine installation idea.

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