Amberyn Thomas

Velocimetry and Thermometry of Supersonic Flow Around a Cylindrical Body

The supersonic flow around a cylindrical body has been studied using two optical techniques. For both sets of measurements, the cylinder was mounted from the side of the tunnel, allowing investigation of the bow shock region as well as in the wake. A new technique, laser-enhanced ionization flow tagging, was used for streamwise velocity determinations behind the body. From these measurements, it was found that the downstream velocity outside the wake was (1.90 +/- 0.06) km/s, whereas inside the wake the velocity was about 0-500 m/s in the upstream direction. Planar laser induced fluorescence of nitric oxide was employed for temperature determinations. It was established that the freestream temperature was (2120 +/- 100) K, decreasing to around (1550 +/- 400) K in the wake.

Velocity measurements by flow tagging employing laser enhanced ionisation and laser induced fluorescence

A new flow tagging technique for measurements of gas velocities over a wide range of flow conditions is proposed. This method employs the laser-based spectroscopic techniques of laser-enhanced ionisation (LEI) and laser induced fluorescence (LIF). Initially the flow to be studied is seeded with a small amount of sodium. The flow is then tagged by utilising LEI to deplete a substantial fraction (80%) of the neutral sodium species in a well defined region upstream of the flow. Finally, single laser pulse planar LIF is used to create a two-dimensional (2D) inverse image of the depleted tagged region downstream of the flow at a specific time delay. The feasibility of this method was demonstrated in two different types of air-acetylene flame by measuring instantaneous 2D flow structures. Flame velocities were determined with an accuracy of better than 10%.

Emission and holographic interferometry measurements in a superorbital expansion tube

Free-piston-driven expansion tubes are capable of generating flaw conditions over a wide range of enthalpies ranging from orbital up to superorbital velocities. Initial optical measurements aimed at investigating the flow in such a facility are presented. Emission studies were used to identify impurities in the how and to investigate spectral regions that are accessible by optical techniques. At moderate enthalpies, it was found that significant radiation resulted from metallic contaminants. At high enthalpies, the spectrum consisted of a number of atomic lines together with a broadband background component indicative of the presence of electrons. The presence of this radiation may limit the applicability of optical techniques that require spectral regions free from the influence of atomic transitions or background radiation. Emission spectroscopy (through Stark broadened hydrogen lines) and two-wavelength holographic interferometry were used to measure the electron number density behind a bow shock on a blunt body at conditions where significant ionization was observed. They yielded average concentrations of (3 +/- 1) x 10(17) cm(-3) from the emission measurements and (3.8 +/- 0.6) x 10(17) cm(-3) from the interferometry.

Ionizing nitrogen and air flows in a superorbital expansion tube

Vehicles on interplanetary missions enter atmospheres at very high (superorbital) velocities. The kinetic energy of the craft causes dissociation of molecules and ionization of all of the species present in the gas. Ground-based testing of such conditions in nitrogen has been performed in a new superorbital expansion tube, X2, using two optical techniques. Emission measurements identified sources of visible radiation that may influence optical measurements and can also contribute to radiative heat transfer. As well, the emission spectra from Stark-broadened hydrogen lines were used to measure electron concentrations between the bow shock and the body. Two-wavelength holographic interferometry was used to provide two-dimensional density and electron concentration profiles of the flow. Peak electron levels of around (4.0 +/- 0.6) x 10(16) cm(-3) were observed that agreed well with equilibrium estimates, A gradual increase in electron population after the shock was observed, reaching a maximum of about one-quarter of the distance from the body to the shock along the stagnation streamline. Thereafter the concentration decreased because of the influence of the body. Comparisons were also made between Rows over different sized cylinders and between air and nitrogen Rows.

Resonant degenerate four-wave mixing in I 2 : Effect of buffer gas pressure

The influence of molecular collisions on the production of the degenerate four-wave mixing signal in I(2) is presented. Measurements were performed on gaseous molecular iodine, I(2), contained in a glass cell in which pressure, temperature, and species concentration are easily and independently varied. Frequencydoubled outputs from a seeded Nd:YAG laser and an excimer-pumped dye laser were used as excitation sources. We have studied the dependence of signal strength versus buffer gas pressure, with pump intensity as a third parameter. It is evident from our results that, for pump intensities of less than 1 MW/cm(2), the pressure dependence of the signal follows that given by a simple two-level model in the homogeneously broadened regime. In this regime collisional deexcitation becomes significant, leading to changes in saturation intensity. This is evidenced by a reduction in the signal with an increase in buffer gas pressure. This behavior is similar to that seen in laser-induced fluorescence. At higher pump intensities, the signal is seen to increase with pressure; this behavior cannot be described by the simple two-level model.

LEI velocimetry and PLIF thermometry of supersonic flow around a cylindrical body

Two laser-based optical techniques have been applied to the supersonic flow produced in a small shock tube for velocity and temperature determinations. Laser enhanced ionisation flow tagging was used for velocity determinations in the wake of a cylinder, and planar laser induced fluorescence of nitric oxide was employed for temperature determinations.

Evolution of Research Support Services at an Academic Library: Specialist Knowledge Linked by Core Infrastructure

ABSTRACT Research support services at The University of Queensland Library (UQ Library) have evolved in response to the global and national drivers, which have impacted on broader University strategy. UQ Librarys success in responding to these drivers has involved leveraging the information within, and capacity of, the institutional repository, the core of our research support services. UQ Library is a critical enabler of the Universitys research mission, actively partnering with researchers throughout the research lifecycle. The evolution of these services has required a shifting staffing framework, combining a traditional liaison library model with functional teams to deliver agile services, which add strategic value to the University. This article explores how functional teams, collaborating with traditional liaison librarian roles, deliver innovative services, how these services are linked by the institutional repository, and how we address key challenges of this service model.

Creating a Connected Future Through Information and Digital Literacy: Strategic Directions at The University of Queensland Library

Abstract As knowledge-intensive institutions, universities face many challenges resulting from today’s highly dynamic technological environment. While the ways in which learners and researchers engage with digital information resources are complex and diverse, there is a keen awareness of the varying levels of information and digital literacy skills amongst students and academic staff. A university-wide approach to skills development, involving all stakeholders, has been recommended as a valid approach to addressing some of the issues. At the University of Queensland, the Library has led the way with the development of a future-focused strategic framework for information and digital literacy to help shape the University’s academic policies and practices. After reviewing the principles that underpin the strategic framework (collaboration, alignment, innovation, sustainability and evaluation), the paper presents some of the key strategies which have been introduced to encourage the development of digital skills in the contexts of undergraduate teaching and learning, digital scholarship and eResearch. It is argued that there is great potential for library staff to extend their reach and serve as digital facilitators, connectors and collaborators, making a significant contribution to successful outcomes in many areas of contemporary academic life.

Ionization measurements in a super-orbital expansion tube

The flow in a new super-orbital expansion tube, X2, has been investigated using two optical techniques. X2 is capable of generating air flows at around 10 km/s simulating re-entry into Earths atmosphere by vehicles on interplanetary missions. Emission measurements identified sources of visible radiation which may influence optical measurements and can also contribute to radiative heat transfer. As well, Stark broadened hydrogen lines were used to measure electron concentrations between the bow shock and the body. Peak levels of around (3.5±0.5)xl016 cirf3 were observed. Two-wavelength holographic interferometry was used to provide two-dimensional density and electron concentration profiles of the flow. The results compared well with the emission measurements. A gradual increase in electron population was observed, reaching a maximum about one quarter of the distance from the body to the shock along the stagnation streamline. Thereafter the concentration decreased due to the influence of the body. Comparisons were also made between flows over different sized cylinders and between air and nitrogen flows.

Optical measurements for a superorbital expansion tube

The flow in a new super-orbital expansion tube, X2, has been investigated using two optical techniques. X2 is capable of generating air flows at around 10 km/s simulating re-entry into Earth’s atmosphere by vehicles on interplanetary missions. Emission measurements identified sources of visible radiation which may influence optical measurements and can also contribute to radiative heat transfer. As well, Stark broadened hydrogen lines were used to measure electron concentrations between the bow shock and the body. Peak levels of around (3.5±0.5)xl016 cm were observed. Two-wavelength holographic interferometry was used to provide two-dimensional density and electron concentration profiles of the flow. The results compared well with the emission measurements. A gradual increase in electron population was observed, reaching a maximum about one quarter of the distance from the body to the shock along the stagnation streamline. Thereafter the concentration decreased due to the influence of the body. Comparisons were also made between flows over different sized cylinders and between air and nitrogen flows.