Influence of Kite Characteristics on Propulsive Power Applied to Ship Auxiliary Propulsion

A Design of Experiment method was applied combined with a performance prediction program to assess the influence of four design parameters on the propulsive capacity of kites used as auxiliary propulsion for merchant vessels. Those parameters are the lift coefficient, the lift to drag ratio or drag angle, the maximal load bearable by the kite and the ratio of the tether length on the square root of the kite area. These parameters are independent from the kite area and, therefore, they could be used with various kite ranges and types. The maximum wing load parameter is the one that shows the most influence on the propulsive force. Over 50% of the gains obtained through this study are directly attributable to it. Then the ratio of the tether length on the square root of the kite area comes as the second greatest influence factor for true wind angles above 70°. While the drag angle is more influential for the narrower angles. In fact, the most substantial gains are made upwind.

Evolution of Piston-Engine Fighter Aircrafts: Cluster Analysis to Study the History of Technology. Part 2

The article carries out cluster analysis of serial piston-engine fighters. 672 modifications built in 26 countries from 1913 to 1951 are taken into account. Maximum speed, wing load, power load and weight ratio are chosen as coordinates. Clustering reveals pioneering design: the earliest models in each cluster. One can also measure the dynamics of ideas lifetime that is the period when similar aircrafts (those within one cluster) were manufactured following the same methodology. The frequency new clusters emerged demonstrates the speed of technological progress. The author has found the turning points of development. These are 1930 and 1935. Until 1930 flight characteristics were increasing both due to an increase in thrust-to-weight ratio and an increase of wing load. Later the thrust-to-weight ratio remains practically unchanged. In 1935 the first aircraft appeared from three of the 19 clusters at once. Among them are the little-known Yugoslav fighter Ikarus IK-2 and the Soviet I-16 Type 5. The change of leading countries and the lifetime of ideas have been studied as well. The interval between the manufacture of the first and the last model, related to the cluster, corresponds to the time period when designers followed the same approach when designing an aircraft. Between wars, this interval exceeded 10 years whereas during rapid development periods it was 5-6 years shorter.

Evolution of Fighter Aircrafts in the interwar Years: Cluster Analysis in History of Engineering

The article carries out cluster analysis of piston-engine fighters designed between 1920 and 1944 and takes into account more than 500 modifications of aircrafts that were serially manufactured in 18 countries. The author divides the period understudy into five-year segments and studies designs as far as such parameters as maximum speed, wing load and power load are concerned. Correlations of these variables are considered as well and special attention is paid to the correct distance determination. The article demonstrates dynamics of the main fighter characteristics between the world wars. It was found out that the main factor in the growth of fighter speed in 1920-1944 was the wing load related to modernization of profiles, quality and mechanization of the wing rather than growth of engine power of aircrafts. One can see repeating models of development in each period. These are a “power” approach that used new technologies “straightforwardly”, for instance, by totally increasing power loading, and a complex approach that provided for much better results. The author has revealed the leadership of the British aerodynamic school in 1920-1940 and has numerically demonstrated the change in the focus of the US design school from a "powerful engine - light aircraft" method to a "perfect aerodynamics - long flight range" method. He has shown the place of the Soviet design school as well. It has been found out that the last (during this period) sharp increase of wing load was not performed in the USSR and Japan. This led to rather low speed of fighters in these countries during the Second World War. The author discusses the reasons for this as well.

Variation in Wing Load of Female Spruce Budworms (Lepidoptera: Tortricidae) During the Course of an Outbreak: Evidence for Phenotypic Response to Habitat Deterioration in Collapsing Populations

Reproduction in female spruce budworms, Choristoneura fumiferana, entails sedentary oviposition early in life (gravid females with their heavy abdomen full of eggs are unable to sustain flight), followed by short- and long-range dispersal by females that have laid a portion of their eggs. Body size measurements (wing surface area and dry weight) of gravid females, spent females at death (after all eggs are laid), and inflight females captured at light traps were collected at one location (forest stands near Fredericton in New Brunswick) over multiple years, from the outbreak stage (1976–1979: peak budworm abundance) to late declining phase with collapsing populations (1988–1989, following near two-fold magnitude of decline in adult density after 1987). For both demographic phases, females rarely flew until having laid at least 40% of their eggs, in contradiction to the hypothesis that females in defoliated forest stands can fly upon emergence due to their light-weight abdomen. As expected, the weight and fecundity of females in 1988–1989 was significantly lower than early on; in terms of body size (wing surface area), however, females were larger in late outbreak phase. These trends suggest that females have evolved morphological adaptation to further dispersal from deteriorated habitats.

Wing Load and Angle of Attack Identification by Integrating Optical Fiber Sensing and Neural Network Approach in Wind Tunnel Test

The load and angle of attack (AoA) for wing structures are critical parameters to be monitored for efficient operation of an aircraft. This study presents wing load and AoA identification techniques by integrating an optical fiber sensing technique and a neural network approach. We developed a 3.6-m semi-spanned wing model with eight flaps and bonded two optical fibers with 30 fiber Bragg gratings (FBGs) each along the main and aft spars. Using this model in a wind tunnel test, we demonstrate load and AoA identification through a neural network approach. We input the FBG data and the eight flap angles to a neural network and output estimated load distributions on the eight wing segments. Thereafter, we identify the AoA by using the estimated load distributions and the flap angles through another neural network. This multi-neural-network process requires only the FBG and flap angle data to be measured. We successfully identified the load distributions with an error range of −1.5–1.4 N and a standard deviation of 0.57 N. The AoA was also successfully identified with error ranges of −1.03–0.46° and a standard deviation of 0.38°.