High reynolds number tools and techniques for civil aircraft design - an overview of the HiReTT programme

The collaborative research project HiReTT, coordinated by Airbus UK, is focused on understanding the effects of scale on aircraft drag. The project was launched in January 2000 as part of the European Fifth Framework Programme. In this paper an overview of the HiReTT project objectives and work plan is given to together with progress achieved in the first year of the project. The improvement in analysis tools and test techniques delivered by this programme will enable an accurate prediction of aircraft performance to be made with the aircraft design process that can be validated ahead of first flight.     

Aircraft fuels and their effect upon engine emissions

Although pollutant emissions from aircraft are mainly determined by the technology of the engines, fuel composition plays a significant part. This paper describes recent developments in jet fuel technology and possible modifications or substitution of currently available jet fuel by oxygenated hydrocarbons, biofuels and cryofuels.     

Time variations of dynamical processes in the midlatitude upper mesosphere — lower thermosphere

Complex studies with the use of spectrum and harmonic analysis allow determination of wave disturbances in the prevailing and tidal wind, and also mesoscale short period oscillation intensity per unit mass. We particularly find enhanced periods of 4–6, 9–12, 15–20, 25–30 days, which are typical for planetary waves in the lower and middle atmosphere of the Earth. We also reveal the non-linear character of vertical amplitude and phase profiles for wave disturbances with planetary wave scales in the prevailing, tidal and short period oscillation intensity. This non-linearity is interpreted as a consequence of the non-linear interaction of waves such as internal gravity waves, tides and planetary waves among themselves and with background movements.     

Aircraft emission research within ISTC project

This research is aimed at obtaining experimental data on contamination of the atmosphere by emissions from aircraft engines in cruise flight conditions, to establish and improve models of the physical and chemical processes which take place in the aircraft wake and in the general zone of air traffic corridors. An Su-24 ‘sounder’ aircraft equipped with an air sampling and collection system has been established to obtain the necessary atmospheric samples in flight, and procedures have been developed for performing the research flights. Techniques have also been developed for chemical analysis of the samples.     

Safety,environment, ATM: Three key issues!

Demand for air travel increases rapidly - world-wide by about 5% annually. Between 2000 and 2020 more than 14,000 large new airliners will have been delivered to create a world fleet of 20,000 airliners after old types are withdrawn. About 40% of world-wide air travel has a European arrival or departure point. What are consequences of these predictions? This article introduces the section on Air Transport, where these problems will be covered in more depth.     

Variations of the ground-level ultraviolet radiation in East Siberia

Daily measurements of the ground-level ultraviolet radiation (UVR) for the years 1998–2000 were used to investigate the seasonal UVR variation in the East Siberian region. The study revealed the asymmetry of the seasonal UVR variation with respect to the angular altitudes of the Sun, caused by the seasonal variation of the total ozone content (TOC), and possibly by the presence of the snow cover. Characteristics of the occurrence of short-lasting increases in UVR are considered, which are associated with TOC anomalies and with high atmospheric transparency. Fluctuations of the ground-level UVR with periods of 2.8, 6–13 and 26 days are identified. A study is made of the dependence of the ground-level UVR on solar activity. Statistically significant correlation coefficients with solar activity indices are obtained.     

Tethers and debris mitigation

In recent years, the use of tethers has been proposed for reduction of space debris either through momentum transfer or use of electrodynamic effects. Tethers have been shown to at least theoretically allow for quick, elegant and cost-effective deorbit of defunct satellites or spent stages. On the other hand, the large risk that tethers themselves may pose to other satellites in orbit has been recognized as well. The large collision area of tethers, combined with operational hazards and meteoroid risk may result in a large orbital exposure. For example, in 1997, the ESA/Dutch 35-km tether deployment of YES from TEAMSAT was inhibited after an analysis of the collision risk for the case the tether operation would fail. The question rises how these two points of view compare to eachother. This paper intends to highlight a representative selection of the proposed tether applications while taking into account the added risks caused by the tethers themselves.Typical applications from recent literature will be briefly described, such as an Ariane 502 spent stage re-entry from GTO and the concept of deboost of defunct satellites by interaction of a conductive tether with the Earth magnetic field.Mass savings of the tethered sytems versus conventional equivalents will be evaluated.Based on a crude risk analysis, involving elements such as mission complexity, dynamic stability, meteoroid risk and orbital life time, a general outline of limiting factors can be given for the various applications. Special attention is reserved for implementation of mechanisms that help reduce this tether risk, such as the DUtether (Tether Degradable by Ultraviolet), utilization of airdrag and solar pressure, the effect of residual current in bare tethers, tether retrieval etc.It is proposed how a net tether-induced mitigation can be compared to that of conventional alternatives, i.e. deboost by rocket engine or a completely passive approach.This comparison is put in the perspective of an ever-increasing occupation of the space environment.It is concluded that tethers can in fact help mitigate the debris risk and that for each application a useful niche can be defined. It is argued that eliminating pollution directly after use of the precious resource of space is not only good custom, but also an important way to make the risk of debris controllable and independent of future trends. Although tethers may have large exposure in terms of area-time product, they deliver a quick cleaning service that may be appreciated by the future users of space.     

GPS based prediction of the instantaneous impact point for sounding rockets

As part of the range safety operations during a sounding rocket launch, a real-time prediction of the instantaneous impact point (IIP) is performed to monitor the expected touch down point in case of a boost termination. Supplementary to traditional radar tracking, the IIP prediction is nowadays based on GPS navigation data, which offer an inherently higher accuracy and reduced data noise. To comply with the increased tracking performance, a consistent set of equations suitable for real-time computation of the approximate IIP is established. Aside from a consideration of gravitational forces, reference frame rotation and Earth curvature, the model can also account for drag during the ascent trajectory provided that a priori information on the ballistic properties of the launch vehicle is available. The algorithm is tested for a representative set of mission profiles and applied to GPS flight data of an Improved Orion rocket and a Maxus rocket launched at Esrange, Kiruna.     

Modelling ignition probability with pairwise mixing-reaction model for flame particle tracking

Reduced order models for ignition analysis can offer insights into ignition processes and facilitate the combustor optimization. In this study, a Pairwise Mixing-Reaction (PMR) model is formulated to model the interaction between the flame particle and the surrounding cell mixture during Lagrangian flame particle tracking. Specifically, the model accounts for the two-way coupling of mass and energy between the flame particle and the surrounding shell layer by modelling the corresponding turbulent mixing, chemical reaction and evaporation process if present. The state of a flame particle, e.g., burnt, hot gas or extinguished, is determined based on particle temperature. This model can properly describe the ignition process with a spark kernel being initiated in a nonflammable region, which is of practical importance in certain turbine engines and has not been rigorously accounted for by the existing models based on the estimation of local Karlovitz number. The model is integrated into an ignition probability analysis platform and is demonstrated for a methane/air bluff-body flame with the flow and fuel/air mixing characteristics being extracted from a non-reacting simulation. The results show that for the spark location being at the extreme fuel-lean outer shear layer of the recirculation zone, PMR can yield ignition events with a significant number of active flame particles. The mechanisms for the survival of the initial flame particles and the entrainment of the survived flame particles into the recirculation zone are analyzed. The results also show that the ignition probability map from PMR agrees well with the experimental observation: a high ignition probability in the shear layer of the recirculation zone near the mean stoichiometric surface, and low ignition probabilities inside the recirculation zone and the top stagnation region of the recirculation zone. The parametric study shows that the predicted shape of the ignition progress factor and ignition probability is in general insensitive to the model parameters and the model is adequate for quantifying the regions with high ignition probabilities.