A summary of the ways in which aviation impacts the environment is presented and the ratio of the energy liberated during a flight to the revenue work done (ETRW) is identified as a key indicator in the assessment of environmental impact. Using the ‘Breguet’ range equation, a number of theorems relating to ETRW are derived and discussed. This is followed by an approximate analysis to produce estimates for the ETRW of aircraft currently in service. It is found that the global fleet average value for ETRW is much higher than those estimated for existing individual aircraft. An explanation of the difference is presented, with the contributions from airline operations and air traffic management identified and quantified. Consideration is then given to the potential for future reduction in ETRW through advances in materials, alternative fuels, structures, aerodynamics and propulsion technologies and the likely benefits are quantified. The improvement in ETRW that could be achieved if this parameter was minimised in the design process with the current level of technology is also considered. Finally, the likelihood of performance improvements being introduced in the short, medium and long term is briefly discussed.

According to multi-node model, the dynamics equations of conical parachute system for simulating shape deformation process of the flexible canopy in the opening process were established. With the combination of dynamics equations code and computational fluid dynamics (CFD) software, the fluid-structure interaction investigation of the conical parachute was carried out. Also the change of parachute shape and flow field, inflation time, the rate of descent, the distance of descent, and other relevant data were achieved. This paper has focused on analysing vortex structure of the flow field in the opening process of conical parachute, and laid the foundation for studying mechanics mechanism of flow field variation of conical parachute in future.

The effect of tip geometry on discharge coefficient and heat transfer is investigated both experimentally and numerically using idealised models of an unshrouded rotor blade. A flat tip was compared with two squealer-type geometries (a cavity and suction-side squealer) under the transonic conditions expected in the gas turbine engine. Heat transfer measurements were performed using a transient liquid crystal technique while a duplicate test section was used for measuring the pressure field. Computations were carried out using an unstructured, fully compressible, three-dimensional RANS (Reynolds averaged Navier Stokes) solver. Initial computations performed using a low Reynolds number k-ε model demonstrated the inability of the model to predict the Nusselt number with reasonable accuracy. Further computations performed using a low Reynolds number k-ω model improved the predictions dramatically. The computed discharge coefficient and the average Nusselt number over the blade tip agreed well with the experiments. Three upstream-total to exit-static pressure ratios were used to create a range of engine-representative Mach numbers. Both experimental and numerical studies at the lower pressure ratio of 1·3 (exit Mach number ~ 0·65) established the cavity geometry as the best performer from an aerodynamic perspective by reducing the discharge through the tip. However, from the heat transfer perspective, both the peak Nusselt number and the average heat transfer to the tip were higher than the flat tip. At the higher pressure ratios of 1·85 and 2·27 (corresponding to exit Mach numbers ~ 0·98 and 1·12) the discharge coefficient and heat transfer to the tip increases. This paper explores the fluid dynamics associated with these flows and shows that the highest heat transfer is caused by reattachment and flow impingement. The fluid dynamic computations provide insight into the experimental measurements and were successfully compared with simple analytical models.

Subsonic wind tunnel experiments were conducted to study the effect of forced transition on the pressure distribution in the concave portion of contraction. Further more, the effect of early transition on the turbulence level in the test section of the wind tunnel is studied. Measurements were performed by installing several trip strips at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence intensity and on the pressure distribution. The reduction in the free stream turbulence as well as the wall static pressure distribution varied significantly with the location of the trip strip. The results confirm the significant impact of the tripped boundary layer on the control of adverse pressure gradient. The trip strip at X/L = 0.115 improves pressure distribution in contraction and reduces turbulence intensity in the test section, considerably.

The aim of this paper is to determine the mathematical relationship (model) between control deflections and structural deflections of the F/A-18 modified aircraft in the active aeroelastic wing technology program. Five sets of signals from flight flutter tests corresponding to the excited sources were measured by NASA Dryden Flight Research Center. These excitation inputs are: differential ailerons, collective ailerons, collective stabilisers, differential stabilisers, and rudders. The signals to be used by the model are of two types: control deflection time histories and corresponding structural deflections on the wing and trailing-edge flaps. We choose to use the subspace identification method based on reconstructing the observability matrix in order to identify the nonlinear multi-input, linear-in-the-states, multi-output system. We identify models (input/output characteristics) by applying this method for a number of sixteen flight conditions for which the Mach number varies from 0·85 to 1·30 and the altitudes vary from 5,000ft to 25,000ft. Very good results are obtained with a fit between the estimated and the measured signals and a correlation coefficient higher than 90%.

According to multi-node model, the dynamics equations of conical parachute system for simulating shape deformation process of the flexible canopy in the opening process were established. With the combination of dynamics equations code and computational fluid dynamics (CFD) software, the fluid-structure interaction investigation of the conical parachute was carried out. Also the change of parachute shape and flow field, inflation time, the rate of descent, the distance of descent, and other relevant data were achieved. This paper has focused on analysing vortex structure of the flow field in the opening process of conical parachute, and laid the foundation for studying mechanics mechanism of flow field variation of conical parachute in future.