A Review of Rapid Distortion Theory

With the depleting non-renewable fuel sources like coal and an ever-increasing demand for energy, we need to start looking into renewable energy sources. These are of paramount importance for a sustainable and green future. Wind Energy is one of the most important sources of renewable energy. But, setting up a wind farm requires considerable land area and land acquisitions are often faced with legal hurdles. This necessitates setting up offshore wind turbines. But, when we talk about offshore wind farms, we need to address the age-old phenomenon: “Turbulence”. Presently, we are trying to develop enhanced controllers for wind farms which will increase the efficiency of the wind farms. The effects of rapidly changing wake aerodynamics i.e. breakdown of strong tip and hub vortices mixed up with low intensity turbulence in the inflow of the rotor and counter-rotation of the wake i.e. determinate velocity component in wake turbulence field will affect the overall performance of the wind farm. This paper provides a brief review on Rapid Distortion Theory (RDT) to model the turbulence.

Measurement Report: Strong Valley Wind Events during the International Collaborative Experiment – PyeongChang 2018 Olympic and Paralympic Winter Games Project

Strong gusty wind events were responsible for some of the poor performances of competitors and resulted in schedule changes during the PyeongChang 2018 Olympic and Paralympic Winter Games. Three events at two venues were investigated to document and articulate the wind forecasting and nowcasting challenges. Upper air analysis showed that the Games were dominated by northwesterly synoptic flow. Froude and Reynolds number analyses indicated that vortex shedding or wake turbulence were the dominant mechanisms in the lee of the mountains where the free-style competitions were conducted. Three types of wind data (10 and 1 min averages plus 1 minute maximums) from automatic weather stations that were reported every minute were analyzed using advanced techniques (Hovmueller, wavelet and eigen analysis frequency estimation). For the two days of Event 1, the conditions were well mixed throughout the day and night. For the other events, diurnal variations were observed with a stable atmosphere at night, well mixed in the afternoon and with 2–4 hour transition periods in the morning and evenings. Turbulence was best portrayed using wavelet analysis and vortex shedding was best portrayed using the eigen analysis frequency estimation method. The latter revealed dominant frequencies, presumably associated with vortex shedding with periodicities of 20 to 90 minutes. Nowcast implications are discussed.

The jet stream and climate change

This article introduces factors contributing significantly to climate change that have been largely neglected in both the scientific and popular press. These factors have immediate implications for public policy directed at slowing, halting and even reversing climate change and its effects. This article argues that in addition to the known contributions made by greenhouse gasses, climate change is also driven by shifts in the patterns of global atmospheric circulation which are influenced by persistent, large-scale vortices caused by the wake turbulence left by commercial air traffic. Because this traffic is highly concentrated along the most frequently traveled routes, the vortices aircraft create have transformed into semi-permanent atmospheric circulation which have widespread effects on how the atmosphere traps and releases heat. It is also possible that these changes alter the loss of water from the atmosphere. This would endanger all life on earth, not just the human population.

Benefits Derived from Arrival Management and Wake Turbulence Re-Categorization in China

Air traffic administration requires evidence when promoting new technology or a new concept of operation. Therefore, when decision support tools are applied, it is necessary to analyze the costs and benefits quantitatively. This paper focuses on the evaluation of Key Performance Indicators (KPIs) correlated with the improvement of arrival operations after the implementation of the Arrival Management (AMAN) system and Wake Turbulence Re-categorization in China (RECAT-CN). Firstly, we give an overview of the implementation of the AMAN system and RECAT in China. Secondly, the KPIs related to the arrival operation are established according to the characteristics of AMAN and RECAT-CN, based on the existing KPI systems in the field of Air Traffic Management (ATM). The proposed KPIs are: airport acceptance rate; final approach interval; flight time within the terminal area (TMA); and taxi-in time. Thirdly, arrival operation within the TMA around Guangzhou International Airport is used as an example to carry out the quantitative analysis. The region and time range were defined for the performance comparison, and external factors were also examined. Finally, using descriptive and inferential statistics, the proposed KPIs’ comparison results are presented and visualized. Such results indicate a significant improvement in arrival operation with the AMAN system and RECAT-CN at Guangzhou International Airport.

Data-Driven Simulation for Evaluating the Impact of Lower Arrival Aircraft Separation on Available Airspace and Runway Capacity at Tokyo International Airport

Although the application of new wake turbulence categories, the so-called “RECAT (wake turbulence category re-categorization)”, will realize lower aircraft separation minima and directly increase runway throughput, the impacts of increasing arrival traffic on the surrounding airspace and arrival traffic flow as a whole have not yet been discussed. This paper proposes a data-driven simulation approach and evaluates the effectiveness of the lower aircraft separation in the arrival traffic at the target airport. The maximum runway capacity was clarified using statistics on aircraft types, stochastic distributions of inter-aircraft time and runway occupancy time, and the levels of the automation systems that supported air traffic controllers’ separation work. Based on the estimated available runway capacity, simulation models were proposed by analyzing actual radar track and flight plan data during the 6 months between September 2019 and February 2020, under actual operational constraints and weather conditions. The simulation results showed that the application of RECAT would reduce vectoring time in the terminal area by 7% to 10% under the current airspace and runway capacity when following a first-come first-served arrival sequence. In addition, increasing airspace capacity by 10% in the terminal area could dramatically reduce en-route and takeoff delay times while keeping vectoring time the same as under the current operation in the terminal area. These findings clarified that applying RECAT would contribute to mitigating air traffic congestion close to the airport, and to reducing delay times in arrival traffic as a whole while increasing runway throughput. The simulation results demonstrated the relevance of the theoretical results given by queue-based approaches in the authors’ past studies.

Optimizing The Utilization of Third Runway in Soekarno Hatta International Airport Using Time Space Analysis

The aim of this research is to optimise the utilization of third runway in Soekarno Hatta International Airport by giving recommendation based on calculation and simulation of runway capacity. The flight schedule data in Soekarno-Hatta International Airport was taken from flightradar24.com for duration of 1- 6 January 2020. The calculation of the runway capacity uses time space analysis method and simulation in BlueSky ATM Simulator. The highest runway capacity of 44 flights per hour is reached when the runway operates as take-off only or landing-only configuration. The simulation is conducted for 3 scenarios: 2 runways configuration, 3 runways configuration and 3 runways configuration with modification. The log data of simulation is analysed using Python programming to know the separation for every pair of flights and ensured that the minima distance due to wake turbulence is fulfilled. The recommendations are runway 07L/25R and 06/24 operates as segregated parallel operation by installing ILS on runway 06/24, extending NP2 and NP3 taxiway for increasing the capacity and reducing the runway incident probability. The results from extending the taxiway are the operation of runway 06/24 will not disturb runway 07L/25R operation, the runway capacity will increase by 60%, and the utilization of third runway will increase by 55%.

High-Resolution Analysis of Wind Flow Behavior on Ship Stacks Configuration: A Portuguese Case Study

Atmospheric emissions related to harbor-related activities can significantly contribute to air pollution of coastal urban areas and so, could have implications to the citizens’ health that live in those areas. Of great concern is the local impact of the emissions that are generated while ships are at berth, since not all types of ships switch off the main engines. This paper intends to investigate the influence of the stack configuration for generic cargo ships on the exhaust smoke dispersion, using the Port of Leixões as a case study and a series of wind tunnel experiments with support of Particle Image Velocimetry (PIV) technique. For that, different configurations of the stack of a cargo ship (in terms of height, geometry and diameter) were simulated under the typical wind conditions of the study area. The PIV results indicate negligible differences between the medium and long stack height, with the short stack height presenting a strong impact on the flow field around the stack. For the short stack height, the flow field is not only disturbed by the stack, but also by the cargo ship bridge, with both obstacles promoting disturbances on the flow field and creating a large wake turbulence effect, which is important for the downwash phenomena. Regarding the effects linked with two distinct geometries (straight or curved), the results show that the straight chimney led to higher perturbation of wind field when compared with the curved geometry. The curved stack presents an increase of vorticity, indicating the generation of more turbulent structures. The PIV results also confirmed that higher wind velocity at the inlet conducts to higher vorticity levels, as well as a higher number of Kelvin–Helmholtz structures. For distinct wind conditions the PIV measurements point out different patterns, indicating the northern wind direction as the most favorable condition for the exposure of dock workers to pollutants. Overall, the results showed that a ship stack with a curved end, medium length and smaller diameter has the capability to promote the behaviors in the flow that are coherent with increased pollutant dispersion.