State-space model identification and feedback control of unsteady aerodynamic forces

Unsteady aerodynamic models are necessary to accurately simulate forces and develop feedback controllers for wings in agile motion; however, these models are often high dimensional or incompatible with modern control techniques. Recently, reduced-order unsteady aerodynamic models have been developed for a pitching and plunging airfoil by linearizing the discretized Navier-Stokes equation with lift-force output. In this work, we extend these reduced-order models to include multiple inputs (pitch, plunge, and surge) and explicit parameterization by the pitch-axis location, inspired by Theodorsen's model. Next, we investigate the na\"{\i}ve application of system identification techniques to input--output data and the resulting pitfalls, such as unstable or inaccurate models. Finally, robust feedback controllers are constructed based on these low-dimensional state-space models for simulations of a rigid flat plate at Reynolds number 100. Various controllers are implemented for models linearized at base angles of attack $\alpha_0=0^\circ, \alpha_0=10^\circ$, and $\alpha_0=20^\circ$. The resulting control laws are able to track an aggressive reference lift trajectory while attenuating sensor noise and compensating for strong nonlinearities.Comment: 20 pages, 13 figure

Sustaining the 3Rs - Rural, Regional and Remote Housing Markets in Western Australia

The housing markets of non-metropolitan Australia are often ignored by both policy makers and academics. The factors influencing housing demand and supply in this diverse sector are not well understood and are often very different to urban markets. This paper explores a selection of rural, regional and remote (3R) housing markets within Western Australia and unpicks some of the issues which drive these markets. For example, the resources boom has had a dramatic affect on 3R towns in Western Australia with the demand for accommodation from mining companies and supporting organisations placing severe pressure on housing markets, both large and small. Resource industry-led demand has increased house prices and rents dramatically in some areas resulting in serious affordability issues for communities. However, even those towns without resource based industries have seen price growth in excess of metropolitan areas creating significant challenges for these communities and their policy makers. Using house price data for Western Australia, the paper explores how different 3R housing markets have been affected by a variety of economic conditions. The paper builds on the quantitative analysis by utilising results from four case study towns within the State. The case studies allow an exploration of the key supply and demand drivers in these towns and offer an insight into the unique circumstances influencing 3R housing markets in Australia. The paper concludes with a discussion of the challenges facing policy makers if they are to deliver thriving and sustainable communities in non-metropolitan Australia

A native-visitor in Western Australia: an account of an insider-outsider

Purpose – This study aims to apply confirmatory personal introspection (CPI) to illuminate the experiences of the authors as partial native-visitors to Western Australia. The native-visitor is the tourist who is able to see beyond Urry’s shallow conception of the Tourist Gaze through their lengthy immersion as “insiders” in the destination’s culture. In this paper, the experiences of two immigrants, the authors, to Western Australia illustrate the different perspectives of the Tourist Gaze 4.0. Design/methodology/approach – The paper uses CPI, as this is a more reliable method of uncovering a traveler’s experiences than subjective personal introspection because CPI uses additional data sources such as written historical records and photographs for confirming the researcher’s accounts. In this study, accounts of both authors alongside photographs are used to both confirm and contrast their individual experiences. Findings – The paper demonstrates the varied forms of the tourist gaze, with an emphasis on that of the native visitor. The findings illustrate how individuals’ both maintain aspects of their original cultural identity and adopt those of the new country after an extended time living in that country. This enables individuals to see attractions and destinations from an insider perspective. Practical implications – This study shows how even after an extended period of time living in a new country, visitors may not have the cultural confidence to behave as local residents at tourist attractions and destinations, which could limit their engagement and enjoyment of these experiences. Marketers should take this into account in designing and promoting tourist experiences to visitors. Originality/value – CPI provides a valuable means for illustrating the range of perspectives within the Tourist Gaze 4.0. The method enables individuals’ rich experiences to be uncovered but at the same time uses multiple data sources to provide additional rigour

The Sedimentary Environment Below Earth’s Polar Ice Cap as a Microbial Habitat

University of Rhode Island faculty participated in drilling of the polar ice cap to study microbial diversity and adaptation to subsurface life under conditions that may mimic extraterrestrial subsurface conditions

Unsteady Aerodynamic Forces on Small-Scale Wings: Experiments, Simulations, and Models

The goal of this work is to develop low order dynamical systems models for the unsteady lift and drag forces on small wings in various modes of flight, and to better understand the physical characteristics of unsteady laminar separation. Velocity field and body force data for a flat plate at static angle of attack and in sinusoidal pitch and plunge maneuvers are generated by 2D direct numerical simulations using an immersed boundary method at Re = 100. The lift of a sinusoidally plunging plate is found to deviate from the quasi-steady approximation at a reduced frequency of k = 0.5 over a range of Strouhal numbers. Lagrangian coherent structures illustrate formation and convection of a leading-edge vortex in sinusoidal pitch and plunge. A phenomenological ODE model with three states is shown to reproduce the lift on a flat plate at a static angle of attack above the stall angle. DNS for a 3D pitch-up maneuver of a rectangular plate at Re = 300 shows the effect of aspect ratio on vortical wake structure and lift. Wind tunnel experiments of a wing in single pitch-up and sinusoidal pitch maneuvers are compared with a dynamic model incorporating time delays and relaxation times to produce hysteresis