Intensity-based and a lifetime-based PSP imaging method with enhanced sensitivity

A pressure-/temperature-sensitive paint (PSP/TSP) has been developed and used as a measurement tool for the two-dimensional distribution of pressure and temperature on aerodynamic surfaces. In recent years, although the concern with measuring a pressure difference of several Pa, such as countermeasures against the noise of small fans, has been growing, the resolution of current PSP measurements is limited to several 10 Pa, even with carefully conducted measurements. For highly accurate measurements, researches on the advanced coating films in PSP/TSP have eagerly been conducted to date. However, measurement resolution and accuracy deteriorate when quantum efficiency or lifetime decrease under high pressure or high temperature conditions.

A Wind Tunnel Experimental Study of Icing on NACA0012 Aircraft Airfoil with Silicon Compounds Modified Polyurethane Coatings

Ice formation on the aerodynamic surfaces of an aircraft is regarded as a major problem in the aerospace industry. Ice accumulation may damage parts, sensors and controllers and alter the aerodynamics of the airplane, leading to a range of undesired consequences, including flight delays, emergency landings, damaged parts and increased energy consumption. There are various approaches to reducing ice accretion, one of them being the application of icephobic coatings. In this work, commercially available polyurethane-based coatings were modified and deposited on NACA 0012 aircraft airfoils. A hybrid modification of polyurethane (PUR) topcoats was adopted by the addition of nanosilica and three-functional spherosilicates (a variety of silsesqioxane compound), which owe their unique properties to the presence of three different groups. The ice accretion on the manufactured nanocomposites was determined in an icing wind tunnel. The tests were performed under three different icing conditions: glaze ice, rime ice and mixed ice. Furthermore, the surface topography and wetting behavior (static contact angle and contact angle hysteresis) were investigated. It was found that the anti-icing properties of polyurethane nanocomposite coatings strongly depend on the icing conditions under which they are tested. Moreover, the addition of nanosilica and spherosilicates enabled the reduction of accreted ice by 65% in comparison to the neat topcoat.

Moving-mass-based station keeping of stratospheric airships

Stratospheric airships are lighter-than-air vehicles that work at an altitude of 20km in the lower calm portion of the stratosphere. They can be used as real-time surveillance platforms for environment monitoring and civil communication. Solar energy is the ideal power choice for long-endurance stratospheric airships. Attitude control is important for airships so that they can point at a target for observation or adjust the attitude to improve the output performance of solar panels. Stratospheric airships have a large volume and semi-flexible structure. The typical actuators used are aerodynamic surfaces, vectored thrust and ballonets. However, not all these actuators can work well under special working conditions, such as low density and low speed. In this study, moving-mass control is introduced to stratospheric airships because its control efficiency is independent of airspeed and atmospheric density. A nonlinear feedback controller based on generalised inverse with a nonlinear mapping module is designed to implement moving-mass control. Such a new station keeping scheme with moving masses is proposed for airships with different working situations.

Progresses in Particle-Laden Flows Simulations in Multistage Turbomachinery With OpenFOAM

Numerical simulations of particle-laden flows have received growing attention in the last decade, due to the broad spectrum of industrial applications in which discrete phases prediction is of interest. Among these, ingestion of particles by turbomachinery is an area that is seeing vivid research and studies. The most common technique to tackle this kind of problem is the Eulerian-Lagrangian method, in which individual particles are tracked inside the domain. At the same time, in multi-stage turbomachinery simulations interfaces are needed to couple the flow solution in adjacent domains in relative motion. In this work, an open-source extension for Lagrangian simulations in multistage rotating machines is presented in the foam-extend environment. Firstly, a thorough discussion of the implementation is presented, with particular emphasis on particle passage through General Grid Interfaces (GGI) and mixing planes. Moreover, a mass-conservative particle redistribution technique is described, as such a property is requested at interfaces between Multiple Reference Frame (MRF). The peculiarities of the algorithm are then shown on a relevant test-case. Eventually, three turbomachinery applications are presented, with growing complexity, to show the capabilities of the numerical code in real-life applications. Simulation results in terms of erosion and impacts on aerodynamic surfaces are also presented as examples of possible parameters of interest in particle-laden flow computations.

Mathematical model of fuselage oscillations at transonic flight speeds

Ensuring the safety of supersonic aircraft flights and aerospace systems in the transonic range of M flight numbers still remains an urgent scientific and applied problem. This is caused by the peculiarities of the aerodynamic surfaces flow by inhomogeneous (transonic) air and is due to the emergence of various aeroelastic phenomena in these flight modes and the current lack of a generally accepted model of transonic flutter, even for aerodynamic control surfaces. Based on a joint analysis of the conditions for the formation of shock waves on the surface of the aerodynamic profile, changes in the parameters of supersonic flow across the Prandtl-Meyer expansion fan, and the hypothesis of "dynamic curvature of the aerodynamic profile", the approximate laws of interaction of elastic bending vibrations of the fuselage with fluctuations in shock waves were obtained. The obtained regularities are used to substantiate a mathematical model for estimating excited forces and excited bending moments of the fuselage. The analysis of the obtained mathematical model confirms the theoretical possibility of the appearance of fuselage forms of transonic flutter in supersonic aircraft, which was observed in the flight experiment and which is due to the interaction of shock waves with the angular velocity of the fuselage elastic bending vibrations. With the accepted in the article input geometrical data of a fuselage aerodynamic surfaces’ profile, the maximum possible values of fuselage bending moments are obtained using the developed mathematical model. The obtained mathematical model can be used for a preliminary approximate assessment of the transonic flutter fuselage forms characteristics in supersonic aircraft and aerospace systems.