Nicholas Lawson

• Bachelor of Engineering - Mechanical Engineering
• Associate Professor at The University of Sydney

Range resolved interferometry (RRI) applied to the interrogation of an extrinsic Fabry-Perot based pressure sensor in laboratory and wind tunnel environments is presented. A simple, compact sensor head design was fabricated and subsequently characterised using RRI, which was shown to have a sensitivity of 1.627×10−3 rad/Pa with a noise standard dev...

Fibre-optic strain and shape sensing instrumentation were deployed on rotor blades during a full-speed helicopter ground run. Data were streamed wirelessly from rotor hub-mounted sensor interrogators, providing insights into the blade dynamics excited by pilot inputs to the controls and changes in rotation frequency. This paper explores the challen...

Optical fibre strain and shape measurement sensors were deployed on a 5-m long rotor blade during a full-speed (rotation rate 6.6 Hz) helicopter ground run, with real-time data wirelessly streamed from rotor hub-mounted sensor interrogators. In Part 1 of a 2-part paper series, the strain sensing capabilities of the two optical fibre-based sensing t...

Optical fibre strain and shape measurement sensors were deployed on a rotor blade during a full-speed helicopter ground run, with real-time data wirelessly streamed from rotor hub-mounted sensor interrogators. In part 2 of a 2-part paper series, two-dimensional direct fibre-optic shape sensing (DFOSS), using fibre segment interferometry-based inter...

Inlet flow distortion is expected to play a major role in future aircraft architectures where complex air induction systems are required to couple the engine with the airframe. The highly unsteady distortions generated by such intake systems can be detrimental to engine performance and were previously linked with loss of engine stability and potent...

This paper presents unsteady stall characteristics of a Slingsby T67M260 Firefly light aircraft from both a computational fluid dynamics (CFD) half model and flight tests. Initial results from the steady CFD, based on a RANS k−ω SST turbulence model, established the critical angle of attack of the stall to be αstall=16∘, with a maximum lift coeffic...

External velocity measurement in-flight by means of a LIDAR system allow for air flow measurements in front of an aircraft [1],[2]. This type of measurement offers the potential to anticipate the flowfield around the aircraft, without interfering the airflow ahead of the aircraft [3]. Anticipating the flowfield around the aircraft can be used to pr...

We hypothesized that an incorrect expectation due to spatial disorientation may induce roll reversal errors. To test this, an in-flight experiment was performed in which forty non-pilots rolled wings level after receiving motion cues. A No-leans condition (subthreshold motion to a bank angle) was included, as well as a Leans-opposite condition (lea...

A computational fluid dynamics (CFD) investigation was aimed at accurately predicting the air flow characteristics in the vicinity of underwing-mounted instruments on the Facility for Airborne Atmospheric Measurement's (FAAM) BAe-146-301. Perturbation of the free stream airflow as it passes through the region of detection of the underwing instrumen...

Numerical results from a three-dimensional (3D) computational fluid dynamics (CFD) model of the Jetstream 31 aircraft in conditions of one engine inoperative are presented. The objective of this work is to analyse the performance of the Jetstream 31 aircraft and provide transient data using an unsteady Detached-Eddy Simulation (DES) CFD approach an...

A ground-effect diffuser is an upwardly-inclined section of an automobile’s underbody which increases aerodynamic performance by generating downforce. To understand the diffuser flow physics (force behaviour, surface and offsurface flow features), we established the near-wake (within one vehicle width of the base) velocity profiles and flow structu...

This paper uses Stereoscopic Particle Image Velocimetry (SPIV) data from the near wake of a detailed sub-scale ½ model of a representative transport aircraft wing with leading and trailing edge high lift systems and outboard aileron representation, to analyse the influence of data-sampling period and frequency on the magnitude and position of the v...

A review of the development of flight test equipment throughout aviation history is presented, focusing specifically on the stall spin. The primitive, yet, ingenious solutions devised in the early twentieth century by the pioneers of this field, paved the way for the advancement in knowledge of the complex aerodynamic properties inherent during a s...

The influence of the laminar boundary-layer state on a wing operating in ground effect has been investigated using experiments with a model that provides two-dimensional flow. The effect of a boundary-layer trip placed at varying distances from the leading edge was observed at various incidences in terms of on-surface characteristics, including pre...

The Jetstream 31 G-NFLA aircraft is used as a national flying laboratory test vehicle for flight dynamics research and teaching purposes. It has been the subject of much theoretical and experimental modelling and therefore, the need for generating validation data through flight testing is critical. In this paper, the aircraft's short period pitch o...

Cranfield University's National Flying Laboratory Centre (NFLC) has developed a Bulldog light aircraft into a flight test facility. The facility is being used to research advanced in-flight instrumentation including fibre optic pressure and strain sensors. During the development of the test bed, Computational Fluid Dynamics (CFD) has been used to a...

A previous study analysing the local flow around angle of attack and sideslip angle vanes on a BAe Jetstream 3102 turboprop is extended to study the additional effects of bank angle. A full matrix of CFD simulations is carried out to investigate how the introduction of a bank angle affects vane performance for a range of flight conditions. An updat...

CFD modelling techniques are exploited to investigate the local velocity field around angle of attack and sideslip angle sensors fitted to the nose of a modified BAe Jetstream 3102 small airliner. Analysis of the flow angularity at the vane locations has allowed the vanes response to varying flight conditions to be predicted and errors in the readi...

Lift and drag flight test data is presented from the National Flying Laboratory Centre, Jetstream 31 aircraft. The aircraft has been modified as a flying classroom for completing flight test training courses, for engineering degree accreditation. The straight and level flight test data is compared to data from 10% and 17% scale wind tunnel models,...

Fibre optic based sensors are becoming increasingly viable as replacements for traditional flight test sensors. Here we present laboratory, wind tunnel and flight test results of fibre Bragg gratings (FBG) used to measure surface strain and an extrinsic fibre Fabry–Perot interferometric (EFFPI) sensor used to measure unsteady pressure. The calibrat...

In-flight testing of aircraft requires the measurement of many different parameters to ensure the aircraft meets the requirements for certification. Advanced optical methods offer opportunities to simplify and improve the quality of data obtained from flight test programs. With lead partner Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), the...

Wind tunnel and numerical results are presented from a 33% scale model of a Scottish Aviation Bulldog light aircraft. The model was developed using reverse engineering and computer aided design processes from a laser scan of the full scale aircraft. This solid model was subsequently used to provide a basic aerodynamic wind tunnel assessment of the...

A differential extrinsic optical fiber Fabry-Perot based pressure sensor has been developed and benchmarked against a conventional piezoresistive Kulite pressure sensor. The sensors were placed on the fuselage of a 1:10/3 sub-scale model of a Scottish aviation Bulldog, which was placed in a wind-tunnel. Pressure tappings that surrounded the sensors...

Particle image velocimetry data are presented from a scaled jet-lift aircraft ground vortex compressible flow. The scaled ground vortex is generated by a vertical compressible jet in cross-flow impinging on a moving ground plane. Particle image velocimetry is used to generate both transient and time-averaged flow statistics from the ground vortex r...

A low-cost imaging system for high magnification and high resolution was developed as an alternative to long-working-distance microscope-based systems, primarily for particle sizing applications. The imaging optics, comprising an inverted fixed focus lens coupled to a microscope objective, were able to provide a working distance of approximately 50...

The following paper presents detailed aerodynamic data of a Scottish Aviation Bulldog light aircraft. The data is taken from the pre-stall region of the aircraft flight envelope through two flight test methods and from a geometrically accurate computational fluid dynamics (CFD) model of the full scale aircraft, which was meshed in Ansys ICEM CFD an...

Wind tunnel testing is widely used for the development and testing of numerous aerodynamic systems. Mature laser based optical methods such as particle image velocimetry (PIV) also now offer detailed flow diagnostics in the wind tunnel environment. The majority of wind tunnels, however, cannot correctly scale both Reynolds and Mach number simultane...

This article briefly describes the basic principles of the flow field measurement technique PIV (Particle Image Velocimetry) and its application to flight testing.

The book presents a synopsis of the main results achieved during the 3 year EU-project "Advanced Inflight Measurement Techniques (AIM)" which applied advanced image based measurement techniques to industrial flight testing. The book is intended to be not only an overview on the AIM activities but also a guide on the application of advanced optical...

Wind tunnel testing is widely used for the development and testing of numerous aerodynamic systems. Mature laser based optical methods such as particle image velocimetry (PIV) also now offer detailed flow diagnostics in the wind tunnel environment. The majority of wind tunnels, however, cannot correctly scale both Reynolds and Mach number simultane...

Force and moment data are presented for an Ahmed reference model with backlight angles of 10°, 25° and 40° at various distances from a side wall. Tests were run at a freestream velocity of 25 m/s and a rolling road provided ground simulation. Six-component force data were recorded and compared with previous experimental data. It is found that the p...

An experimental and numerical study was performed on a Clark Y aerofoil with a 10% chord leading edge Kruger flap to examine its aerodynamic performance at Reynolds numbers of 0·6 × 106, 1 × 106, and 1·6 × 106, to help to identify the forces and moments acting on a basic configuration. A detailed comparison of the numerical and experimental data is...

Transonic flows are found across many aerodynamic applications. This chapter reviews fundamental aspects of external transonic flow aerodynamics and swept wing design. Initially, simple inviscid approximations are introduced to account for transonic effects and then the typical flow features found on actual 2D transonic aerofoils are outlined where...

The understanding of the behaviour of the flow around surface protuberances in hypersonic vehicles is developed and an engineering approach to predict the location and magnitude of the highest heat transfer rates in their vicinity is presented. To this end, an experimental investigation was performed in a hypersonic facility at freestream Mach numb...

Shock-wave/turbulent boundary-layer interactions (SWTBLIs) with separation are known to be inherently unsteady but their physical mechanisms are still not totally understood. An experimental investigation has been performed in a supersonic wind tunnel at a freestream flow Mach number of 2·42. The interaction between a shock wave created by a shock...

Applying advanced non-intrusive flow visualisation techniques to an in-flight environment is a challenging task which can provide invaluable data. The ability to capture complex flow structures under free atmospherical influences and in real flight conditions can potentially supply data for numerical technique validation and wind tunnel measurement...

An experimental investigation of the effects of planform shape on the flow structures generated by an insect-like flapping wing in hover are presented.This was performed with application to flapping-wing micro air vehicles (FMAVs) in mind.Experiments were accomplished with a first-of-its-kind mechanical flapping-wing apparatus capable of reproducin...

It is well known that the scatter of ultrasound by blood is mainly attributed to red blood cells (RBCs) and RBC aggregation. In the present review, researches of hemodynamic influence on RBC aggregation and ultrasound backscatter from blood were overviewed. ...

Surface protuberances are frequently unavoidable in the design of hypersonic vehicles in the form of control surfaces but also as smaller elements of the order of the boundary layer thickness such as instrumentation and cable protection pads, stiffeners, control modules and motors, feed and drain lines, etc. In any of these forms, the protuberance...

Experimental results of static pressure measurements from specially packaged pi-phase shifted optical fibre Bragg gratings (FBGs) that were installed into a 2D, 3 element high lift wing are presented. The static pressure measurements from the fibre sensors are found to be in good agreement with theory. Further pressure calibrations are currently un...

Experimental investigation is essential to improve the understanding of aerospace flows. During the last years, effort has been put on the development of optical diagnostics capable of imaging or yielding data from the flow in a nonintrusive way. The application of some of these techniques to supersonic and hypersonic flows can be highly challengin...

This paper presents an investigation of a transonic flow (M(infinity) = 0.85) over a rectangular cavity having a length-to-depth ratio of 5. Velocities were measured inside the cavity on the central plane and two off-centre planes using a two-component particle image velocimetry system. These measurements were supported by surface flow visualizatio...

A piezoelectric fan (piezofan) which couples a piezoelectric unimorph to an attached flexible blade is able to produce a large deflection especially at resonance. The fundamental resonant frequencies (fr) of the piezofan structures have been calculated by an analytical method and finite element modelling, and these were compared with experimental m...

The design or modification of an aircraft requires substantial numerical and experimental studies. The outcome of the design process and therefore the definitive quality of the aircraft will be verified during the flight tests for certification. The extrapolation of the data obtained during wind tunnel experiments or at low Reynolds number simulati...

Within the scope of the European project AIM several optical measurement techniques including Particle Image Velocimetry (PIV) are applied to flight tests. A large amount of challenges have to be accomplished including the large observation area, the time constraints given by the utilisation of the aircraft, interaction of the measurement system an...

A new method to measure shock wave unsteadiness is presented. Time-resolved visualizations of the flow field under investigation are obtained using a high-speed schlieren optical system and the motion of the shock wave is determined by means of digital image processing. Information on the shock's unsteadiness is subsequently derived with Fourier an...

Piezoelectric fans consisting of a piezoelectric layer and an elastic metal layer were prepared by epoxy bonding and a coupled flexible wing was formed by a pair of carbon fibre reinforced plastic wing spars and polymer skin attached to two piezoelectric fans. Two sinusoidal voltages with phase differences were then used to drive the coupled piezoe...

The results of an experimental investigation of the bootdeck flow structure of a 36 per cent scale model notchback car are presented together with a general review of advanced laser diagnostic techniques suitable for large-scale wind tunnel flow measurement. The tests were used to characterize the flow behaviour over the Reynolds number range 0.74...

Laser Doppler anemometry (LDA) data are presented for an Ahmed reference model employing various backlight angles. LDA velocity measurements are taken in a number of planes around and downstream of the model at a free-stream velocity of 25ms−1. During the testing a rolling road provided ground simulation and six-component force data were recorded....

The flow fields surrounding a sphere sedimenting through a liquid near a vertical wall are characterized using 3D stereoscopic particle-image velocimetry (PIV) experiments. Three different fluids, a Newtonian reference fluid, a constant (shear) viscosity Boger fluid, and a shear-thinning elastic fluid, are used to determine the effects of both elas...

A method for controlling the position of an oscillatory cavity jet flow is demonstrated. The method involves secondary injection of a lower mass flow control jet into the cross-flow region of the primary jet. The primary jet in this case is a turbulent jet (Re=55000) which when injected into the rectangular cavity with no secondary control, attains...

We describe and characterize an experimental system to perform shape measurements on deformable objects using high-speed close-range photogrammetry. The eventual application is to extract the kinematics of several marked points on an insect wing during tethered and hovering flight. We investigate the performance of the system with a small number of...

Some insects use leading-edge vortices to generate high lift forces, as has been inferred from qualitative smoke visualisations of the flow around their wings. Here we present the first Digital Particle Image Velocimetry (DPIV) data and quantitative analysis of an insect’s leading-edge vortex and near wake at two flight speeds. This allows us to de...

Actuator disc models of insect flight are concerned solely with the rate of momentum transfer to the air that passes through the disc. These simple models assume that an even pressure is applied across the disc, resulting in a uniform downwash distribution. However, a correction factor, k, is often included to correct for the difference in efficien...

An innovative method is presented for control of an oscillatory turbulent jet in a thin rectangular cavity with a thickness to width ratio of 0.16. Jet flow control is achieved by mass injection of a secondary jet into the region above the submerged primary jet nozzle exit and perpendicular to the primary nozzle axis. An experimental model, a 2-D a...

A method for controlling the position of an oscillatory jet cavity flow is demonstrated. The method involves secondary injection of a lower mass flow control jet into the cross-flow region of the primary jet. The primary jet in this case is a turbulent jet (Re=55000) which when injected into the rectangular cavity with no secondary control, attains...

Optically distinguishable seeding particles that emit light in a narrow bandwidth, and a combination of bandwidths, were prepared by encapsulating quantum dots. The three-dimensional components of the particles’ displacement were measured within a volume of fluid with particle tracking velocimetry (PTV). Particles are multiplexed to different hue b...

The flow fields for a sphere sedimenting through a Newtonian and two non-Newtonian liquids near a wall in a square tank are investigated using 3-D stereoscopic particle image velocimetry (PIV) and line integral convolution (LIC) methods. The PIV data were taken using an angular stereoscopic configuration with tilt and shift arrangements for the Sch...

Through the use of stereoscopic 3-D particle image velocimetry (3-D PIV), the flow field surrounding a sphere sedimenting at a distance of one, two and three ball diameters from the wall is measured. A Newtonian (constant shear viscosity, inelastic) fluid, a Boger (constant shear viscosity, elastic) fluid and a shear-thinning (variable shear viscos...

Here we present the first digital particle image velocimetry (DPIV) analysis of the flow field around the wings of an insect (the tobacco hawkmoth Manduca sexta, tethered to a 6-component force-moment balance in a wind tunnel). A leading-edge vortex (LEV) is present above the wings towards the end of the downstroke, as the net upward force peaks. O...

We describe and characterize an experimental arrangement to perform shape measurements on a deformable object through dynamic close-range photogrammetry; specifically, an insect in flight. The accuracy of shape measurements in photogrammetry is improved by increasing the number of camera views. In static close-range photogrammetry, one may increase...

The application of particle image velocimetry (PIV) to transonic cavity flows is presented. Data is recorded from rectangular cavities at a Mach number of 0.85 with length-to-depth ratios from ranging from l/h=5 to l/h=14 using a commercially available digital PIV acquisition system and in-house data processing software. Time averaged two-dimension...

Results are presented from a single and dual lens endoscopic PIV imaging system with a view to application of PIV where optical access is restricted such as internal flows. The dual lens PIV images were processed using cross-correlation, a cubic mapping function and standard stereoscopic relationships. For the single lens system, the images were pr...

Results are presented from a single and dual lens endoscopic PIV imaging system with a view to application of PIV where optical access is restricted, such as internal combustion engines and other internal flows. PIV images taken from the single lens system were processed using cross-correlation and a quadratic distortion-mapping function. The dual...

Laser Doppler anemometry (LDA) data and a 3D Fluent computational fluid dynamics (CFD) solution are presented from a 1044mm length Ahmed (1) reference model. LDA velocity measurements are taken from a transverse plane one model length downstream at a freestream speed of 25m/s with a moving ground plane, and are compared to the CFD model. Comparison...

The work described here concentrates on under-expanded, axisym-metric turbulent jets issuing into quiescent conditions. Under-expanded turbulent jets are applicable to most aircraft propulsion applications that use convergent nozzles. Experimental studies used laser doppler velocimetry (LDV) and pitot probe measurements along the jet centreline. Th...

The work described here concentrates on under-expanded, axisym-metric turbulent jets issuing into quiescent conditions. Under-expanded turbulent jets are applicable to most aircraft propulsion applications that use convergent nozzles. Experimental studies used laser doppler velocimetry (LDV) and pitot probe measurements along the jet centreline. Th...

Laser measurement techniques are becoming more commonly applied to many areas of thermofluids and heat transfer. An area of their application, which presents highly challenging requirements, is in the measurement of aerospace flows. In this case the experimentalist may encounter high mass flowrates, high-speed flows and in some cases high temperatu...

A simple jet flow vectoring control method for high Reynolds number confined flows in rectangular cavities is discussed, based on a laser Doppler anemometry (LDA) investigation. A baseline oscillatory turbulent jet flow (Re=55000) is used with a characteristic Strouhal number of S t,W=0.013. The jet, which is confined in a thin rectangular cavity w...

The sedimentation of a sphere through a fluid is a standard testbed problem in non-Newtonian fluid mechanics. The experimentally determined velocity fields may be compared with numerical predictions obtained using finite element simulations. In this work, the influence of an adjacent wall, in addition to elastic and shear thinning effects, on the v...

This paper discusses how the combined use of computational fluid dynamics and experimentation has been applied to three particular fluid dynamics problems: high-speed turbulent jet flow, transonic cavity flows and open-wheeled race car aerodynamics. In each case knowledge gathered from one analysis technique has been used to assist in the applicati...

Velocity measurements are presented from an open flow rectangular cavity with a length depth ratio (l/d) of 5 at freestream Mach number of M=0.82. Two-dimensional particle image velocimetry (PIV) results processed using a commercial and an in house developed correlation technique are compared with a two dimensional unsteady RANS based CFD model usi...

Two-dimensional Laser Doppler anemometry (LDA) and computational fluid dynamics (CFD) are used to investigate the influence of cross-flow and momentum addition on flow features of a submerged entry nozzle (SEN) jet in a rectangular cavity (Rejet ≈ 95000). Round sidewall control jets are used to attempt to deflect and attenuate the main jet oscillat...

PIV and LDA were used to study a scaled STOVL ground vortex flow. The flow included a compressible impinging jet in cross flow and a moving ground plane. PIV and LDA velocity data were recorded from the ground vortex about the jet centreline over a range of nozzle pressure ratios (NPRs) from 2.3 _ 3.7. Nozzle height to diameter ratios (h/dn) were a...

Laser Doppler anemometry (LDA) measurements are presented of the oscillatory flow in a 33% scale water model of thin slab casting mould when the flow enters as two lateral jets through a bifurcated nozzle. The submerged entry nozzle (SEN) and the mould were geometrically scaled to be representative of industrial thin slab casters. Mean and RMS LDA...

A particle image velocimetry (PIV) and laser Doppler anemometry (LDA) study of a scaled short take-off and vertical landing (STOVL) ground vortex flow is presented. The scaled flow features a compressible impinging jet in cross-flow with a moving ground plane. Mean and transient PIV and LDA velocity data are recorded from the ground vortex about th...

A novel three-dimensional particle image velocimetry technique is used to measure the planar three-dimensional flow field about the centreline of a sphere sedimenting in a rectangular shaped box. Measurements are made in the center of the container and also one diameter from a plane wall. Results are presented for a sphere falling in both a constan...

A torsionally driven cavity, consisting of a fully enclosed cylinder with rotating bottom lid, is used to examine the confined swirling flow of low-viscosity Boger fluids for situations where inertia dominates the flow field. Flow visualization and the optical technique of particle image velocimetry (PIV) are used to examine the effect of small amo...

A torsionally driven cavity has been used to examine the influence of elasticity on the swirling flow of constant-viscosity elastic liquids (Boger fluids). A wealth of phenomena is observed as the degree of inertia, elasticity and viscous forces are varied by using a range of low- to high-viscosity flexible polyacrylamide Boger fluids and a semi-ri...

Self-sustained oscillating jet flow of water in a rectangular cavity, having thickness which is small relative to its width, is measured using LDA and PIV, and predicted using a transient two-dimensional computational fluid dynamic model which incorporates a resistance coefficient for cross-flow. The basic geometry represents a scale model of a mou...

A computational model is presented for the simulation of solid/liquid mixing when neutrally buoyant solids are continuously dropped as a stream from above into a tank of liquid. Transient, two-phase calculations are performed for a two-dimensional model using a finite volume, Eulerian–Eulerian approach. The momentum equations for both phases are ad...

Laser Doppler anemometry (LDA) and cinematic particle image velocimetry (PIV) measurements of a low Strouhal number oscillatory jet are compared to two-dimensional computational fluid dynamic (CFD) model predictions. The LDA and PIV measurements are recorded from a water model consisting of a jet generated from a submerged entry nozzle (SEN) immers...

The application of LDA to a transient 1/3 scale (500 mm wide) water model of a mould typical of steel thin slab casting, is presented. The characteristics of a crossflow, associated with the oscillating jet emerging from a submerged nozzle (internal diameter 33 mm), were analyzed for a range of casting rates (0-2 m/min), nozzle submergences (20-120...

A low-cost 35 mm PIV stereoscopic system for liquid flows is presented which has an imaging component cost under US$9000. The system uses an angular configuration, rotating mirror image shifting and in-situ calibration techniques. Image processing algorithms based on cross correlation and bicubic interpolation are also used to calculate the 3D data...

The application of particle image velocimetry (PIV) to a Mach 1.4 de Laval expansion nozzle is described. Velocity measurements are taken inside and outside the nozzle and are compared to schlieren data. The PIV technique is shown to resolve a normal shock inside the nozzle and underexpanded shock cell structures outside the nozzle in the open jet...

 PIV measurement and numerical simulation of a large scale collapsing gas bubble that results from the burst of a balloon in a deep water pool are presented. There is seen to be excellent qualitative agreement between computation and experiment, and good quantitative agreement to within 8–10% when using a normalised error. This validation allowed s...