Mechanical Engineering - Theses
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ItemBiomechanical changes at the knee after anterior cruciate ligament reconstruction( 2022-11)Due to its frequent injury, the Anterior Cruciate Ligament (ACL) at the knee is one of the most researched ligaments. Anterior cruciate ligament reconstruction (ACLR) surgery is performed to restore knee stability and function and preserve joint health. However, clinical studies with long-term follow-up indicate that up to 90 percent of individuals undergoing ACL reconstruction have radiographic evidence of osteoarthritis in both the tibiofemoral and patellofemoral joints within 10 years of the surgery. One way to understand the effects of these changes is to understand the change in the biomechanical function of the knee joint. The aim of this thesis was to understand the biomechanical changes at the knee, primarily focusing on the changes in the net external moments at the lower extremities, changes in the knee extensor moment arm, and changes in the ligament lengths after ACLR surgery. The specific aims of this thesis were to (1) measure the net external moments at the lower extremities and compare them between the ACLR and the contralateral knee; (2) measure the patellar tendon moment arm (PTMA) and compare it between the ACLR and contralateral knees to understand the effect of ACLR surgery on the knee extensor mechanism; and (3) understand the geometrical changes in the ACL, such as attachment sites, length, and orientation while performing functional activities after ACLR surgery. Accurate measurements of six degrees of freedom tibiofemoral and patellofemoral kinematics of ten subjects who underwent unilateral ACLR (which were measured as part of a different study by other members at the Bio-motion lab at the University of Melbourne) were used to calculate the PTMA and the ligament lengths for an entire cycle of gait. Measuring the net external moment at the lower extremity resulted in statistically significant differences in the knee moments, specifically in the transverse plane, while performing level walking. The ACLR knees exhibited lower internal rotation moments compared to the contralateral knees. Differences were also observed in the sagittal plane moments for downhill walking, where the ACLR knee showed lower knee extension moments than the contralateral knee. The mean moment arm of the knee extensor mechanism (PTMA) calculated over one complete gait cycle was significantly higher by 1.5 mm in the ACLR knee compared to the contralateral knee. A significant difference in the PTMA is also observed for downhill walking, but only at certain knee flexion angles. The results of aim 3 indicated that the attachment sites of the ACL graft on the tibia and femur shifted significantly. Specifically, the attachment of the ACL graft on the tibia shifted posteriorly by 6 mm compared to the intact ACL. The shift in the attachment site of the ACL graft on the tibia and femur has reduced the ACL graft's length throughout the gait cycle by around 5 mm compared to the intact ACL. Interestingly, the shift in the attachment site did not affect the pattern of the ligament length throughout the gait cycle. Understanding the function of the knee joint after ACLR is crucial for developing better surgical procedures and rehabilitative methods post and pre-surgery and preventing further degradation of the joint. The biomechanical changes measured through this study can give further insight into the function of the ACLR knees and will help design better rehabilitation techniques and improved surgical procedures. The cruciate ligament geometry and the PTMA can be used to develop accurate computational knee models and better understand ACLR surgeries. The net external moments at the lower extremities can be used to design post and pre-rehabilitation techniques to avoid re-injury of the ACL graft and injury to the other lower extremity joints.
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ItemPredicting turbulent heat transfer over rough surfaces( 2023-04)When fluids such as air or water flow over solid surfaces, a transfer of heat between the fluid and solid interface occurs. This heat transfer underpins numerous industrial and natural systems, making routine predictions for heat transfer of paramount interest. In practice this is no easy feat. The fluid flow is often turbulent and the underlying surface is often rough, both of which must be accounted for in accurate predictions. Unfortunately, current state-of-the-art models for this purpose are insufficient, as these models are usually restricted to empirical fits, which admit a diverse set of behaviours in their predictions. To rectify this current ambiguity in rough-wall heat transfer, we have systematically conducted high-fidelity direct numerical simulations (DNSs), aiming to unveil the physical mechanisms governing rough-wall heat transfer. In these comprehensive datasets, we cover a wide array of roughness regimes (controlled by the roughness Reynolds number k+), whilst simultaneously varying the working fluid (dictated by the Prandtl number Pr ). A further dataset is also considered where we vary both k+ and the roughness topography, which we control through the frontal solidity, defined as the frontal projected area divided by the total plan area. These simulations are conducted using the minimal channel framework (MacDonald et al., 2017), which can accurately resolve the near-wall roughness sublayer flow at affordable cost, thus enabling the comprehensive parameter sweep. We examine the disagreements which currently linger regarding the prediction of fully rough (high-k+ ) heat transfer. We focus on the fully rough phenomenologies. Although we find the mean heat transfer favours the scaling of Brutsaert (1975), the Prandtl–Blasius boundary-layer ideas associated with the Reynolds–Chilton–Colburn analogy of Owen & Thomson (1963); Yaglom & Kader (1974) can remain an apt description of the flow locally in regions exposed to high shear. Sheltered regions, meanwhile, violate this behaviour and are instead dominated by reversed flow, where no clear correlation between heat and momentum transfer is evident. The overall picture of fully rough heat transfer is then not encapsulated by one singular mechanism or phenomenology, but rather an ensemble of different behaviours locally. Building on this intuition of distinct heat transfer behaviours locally, we develop a predictive model which idealises the total heat transfer as being comprised of two competing heat transfer mechanisms: exposed heat transfer, which follows a Reynolds–Analogy-like scaling and sheltered heat transfer, which is spatially uniform. The summation of these contributions, each weighted by their individual area fractions yields the total rough-wall heat transfer, and is ultimately dependent on the roughness topography controlled by the frontal solidity. We show that a simple ray-tracing model parameterised solely by a sheltering angle is capable of capturing this sheltered and exposed area partition. Finally, we provide a view to transitionally rough, low-k + heat transfer. Here, we have demonstrated that the virtual-origin framework of Luchini (1996) can provide a valid avenue for the prediction of transitionally rough heat transfer.
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ItemRoughened Ultra High-Lift Blades with Grooves for Drag Reduction( 2023-03)Transitional boundary layers on low-pressure turbines (LPT) are prone to separation on the suction surface of the blade under strong local adverse pressure gradients. Intermittent free-stream turbulence, periodic wakes shed by the upstream blades, and surface roughness due to in-service degradation of the blades are shown to suppress the separation. Although this generally leads to a profile loss reduction, some of the benefits are offset by a loss increase associated with an increased turbulent wetted area. In this work, we explore a strategy where the losses in both the transitional and turbulent boundary layers can be reduced. In particular, we employ surface roughness in the transitional regime to reduce the separation bubble-related losses and riblets in the turbulent regime to further reduce the losses due to the turbulent wetted area. The efficacy of this ‘rough-riblet blade surface’ is studied using high fidelity scale resolving simulations on the configuration of a flat surface subjected to a streamwise varying pressure gradient. In the first phase of this investigation, the effects of riblet shapes, riblet tip curvature and the positioning of the riblets at different regimes of the flow are investigated under both zero-pressure gradient and a streamwise varying pressure gradient. Of all these considerations, it turns out that the most important aspect is the way in which riblets are positioned with respect to the flat surface level. This work shows that in order to achieve both a reduction in the skin-friction drag and boundary layer losses riblets have to flush mounted with reference to the flat suction surface. In the second phase of this investigation, a series of high-fidelity eddy resolving simulations were further carried out to discern the sensitivity of riblet dimensions to the profile loss. The performance of different riblet shapes and riblet dimensions are analysed by examining various first and second order statistical quantities in detail. In particular, the streamwise evolution of skin-friction coefficient, boundary layer integral parameters and shape factor are compared and contrasted among riblets of different dimensions. The instantaneous flow features and second order statistics such as the Reynolds stress, turbulent kinetic energy and its production are analyzed for different test cases to determine the impact of riblets on these quantities. When compared to the roughness alone configuration, the scalloped shape riblets with s^+ = 17 and h^+ = 22 reduced the net skin-friction drag by 7.3% and the trailing edge momentum thickness by 14.5% thereby demonstrating the efficacy of riblets in reducing the mixing losses under adverse pressure gradients. Through an analysis of flow blockage introduced by the application of riblets, the deleterious effects of increasing the riblet height along with the necessity of optimizing the riblet ramp are highlighted.
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ItemNo Preview AvailableTurbulent drag reduction using polymer additives( 2022-12)Skin-friction drag in turbulent flows accounts for a significant energy loss in engineering applications dealing with liquid flows, e.g. oil transportation, irrigation systems, and cargo ships. Since the discovery that polymers with long, flexible, and linear chains can significantly reduce drag, many studies have been performed to describe such a phenomenon, which is known as Toms phenomenon. A review of the literature reveals that polymers are one of the promising drag-reduction methods in external flow applications. The experimental study in the current work investigates the drag-reducing polymer effect on the outer region of the turbulent boundary layer to provide further insight into the polymer/turbulence interactions. The presented experiments were performed in the tow tank facility located at the University of Melbourne. The facility provides streamwise/wall-normal plane PIV measurements with a unique frame of reference that allows capturing time-resolved spatially-evolved PIV measurements of the evolving drag-reduced turbulent boundary layer for different polyacrylamide concentrations. Three different concentrations of uniform polyacrylamide-water solutions were used to conduct the current analysis, namely 25, 50, and 100 ppm, covering a broad range of drag-reduction regimes. The statistical analysis of the drag-reduced turbulent boundary layer reveals an increase in the logarithmic region slope of the inner-scaled mean streamwise velocity profile with a drag-reduction increase. A quadratic model is proposed that links the logarithmic region slope with the drag-reduction percentage for 20 < %DR < MDR. Additionally, the investigation of polymer chain scissoring in the current experiments suggests the presence of a new cause for the drag-reduction decrease with boundary layer development other than polymer degradation. The turbulent/non-turbulent interface of the drag-reduced turbulent boundary layer was studied to identify the causes for the significant reduction in the boundary layer thickness with polymer concentration increase. The analysis suggests that drag-reducing polymers reduce the boundary layer growth rate by affecting both potential flow entrainment processes (engulfment and nibbling). Hence, a significant reduction in the boundary layer thickness is observed. The unique frame of reference for the current measurements allows tracking of large-scale structures within the developing turbulent boundary layer. The coherent structures convect past the field of view in the conventional frame of reference (wind tunnel frame of reference). In contrast, in the current unique frame of reference, any large-scale structure moving with a convection velocity close to the free-stream velocity will appear stationary in the field of view. Therefore, acquiring time-resolved measurements in such a unique frame of reference enables the analysis of the internal shear layers convection velocities. The internal shear layers for the drag-reduced flow present elongated features in the streamwise direction with an inclination angle that increases with polymer concentration increase. The convection velocity of the internal shear layer decreases in the vicinity of the wall while increasing away from the wall with polymer concentration increase. This implies the stretching of the shear layer in drag-reduced flow. The shear layer inclination angle was used to indicate the interaction between the large-scale structures in the outer region of the turbulent boundary layer. The instantaneous velocity fields indicate less turbulent mixing in the drag-reduced flow as deduced from the large time interval of the eruption events and the lower standard deviation of the shear layer inclination angle. Although we could not measure the near-wall region of the boundary layer, we were able to fully investigate the outer region to reveal the polymer/turbulence interactions, which is essential for understanding the evolution of the drag-reduced turbulent boundary layer. More investigation still needs to be done into polymer/turbulence interactions. However, the current study will likely have implications on the boundary layer predictive models and mixing applications.
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ItemAn experimental study of fluid flow and dispersion in Triply Periodic Minimal Surface (TPMS) porous media( 2022-09)Biological systems in nature consist of cellular materials that have unique topologies and structures at different length scales. Compared with man-made structures, cellular materials demonstrate much higher multifunctionalities such as high stiffness-to-weight ratio, heat dissipation control, and enhanced mechanical energy absorption. Such outstanding properties have fascinated many scientists and engineers and led them to manufacture bio-inspired structures artificially. Among these, Triply Periodic Minimal Surface (TPMS) porous media have drawn more attention due to their advantages over other similar lattice structures. TPMS are surfaces generated by mathematical expressions that have zero mean curvature and three-dimensional (3D) periodicity. Due to these advantages, TPMS porous media have been of great interest to engineers and biologists. With the development of the additive manufacturing known as 3D-printing, many researchers have manufactured a variety of TPMS porous media using different methods, and then studying their mechanical behaviours. However, less attention is devoted to fluid dynamics in TPMS porous media. Although some researchers have investigated fluid flow in TPMS porous media, their studies mainly focus on low flow rates and permeability in Darcy’s flow regime. When they conducted experiments to measure pressure drops, their sample specimens were relatively small and their experimental setup were not designed well for the correct pressure drop measurement, which led to uncertainty in their conclusions. This led us to explore fluid dynamics in TPMS porous media at a variety of flow rates to highlight their topological advantages and expand their engineering applications in other fields. Based on the author’s knowledge, none of the current literature present pressure drop results especially at high flow rates. In addition, more importantly, we are not aware of any studies where fluid velocity within TPMS porous media has ever been measured. To investigate fluid behaviour in TPMS porous, we conduct a comprehensive experimental study with TPMS porous media namely gyroid, primitive, and Body Centered Cubic (BCC). Among many of the different TPMS geometries, we select “gyroid” because of its complex internal architecture, “primitive” due to its distinguishable features, and lastly “TPMS-based body-centered cubic (BCC)” owing to its open cell structure. With three different TPMS porous media, we design new experimental measurement systems to obtain experimental data for a comprehensive study of fluid behaviour in TPMS porous media. To achieve this goal, three different experiments are conducted:(i) pressure drop measurements for three different TPMS geometries at various porosities resulting in different flow regimes; (ii) 2D-2C particle tracking velocimetry (PTV) measurement by refractive-index matching the fluid and the 3D-printed TPMS structure, and (iii) longitudinal dispersion in a particular geometry. In this thesis, the high precision experimental data is compared with the well-known Ergun equation for spherical packed beds to understand the macroscopic behaviour. Based on the pressure drop results, this thesis presents high-resolution velocity field in TPMS porous media to understand different flow behaviours at pore level by identifying three different flow regimes. Lastly, longitudinal dispersion coefficients of gyroid at different length scales are presented.
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ItemPlanar buoyant plume in a channel with cross flow( 2023)Discharge of buoyant harmful gases or liquid within enclosed spaces, such as tunnels and rivers, may have an adverse effect on human health, environmental risk, and destruction of the water ecosystem balance. The study of the mixing of fluid within a crossflow is an important exercise for obvious reasons. However, conducting simulations with realistic parameters for practical geometric configurations without any modelling remains prohibitively expensive using the computers available today. Hence, in this thesis, we will study the more simplified fundamental problem of a buoyant plume in cross-flow. It is anticipated that results from this study will give pertinent insights into the dynamics of small and large-scale motions of the buoyant plume in crossflow. This study will use data from direct numerical simulation (DNS) of a planar buoyant plume in cross-flow in a channel and is intended to complement the fundamental understanding of entrainment and mixing of the buoyant plume in a crossflow. To this end, the investigation covers a range of crossflow Reynolds numbers, source Reynolds numbers, Richardson numbers, heat release rates, and jet Reynolds numbers. The study presented here will be broadly grouped into three main topics: i) the buoyant plume in laminar crossflow; ii) the planar jet and/or buoyant plume in turbulent channel crossflow; iii) instability of a buoyant plume in crossflow. In the study of the buoyant plume in laminar crossflow, the plume originates from a line heat source at the bottom channel wall, impinging on the top wall, and propagates downstream and/or upstream based on the strength of the cross-flow. I study the critical velocity, defined as the minimum cross-flow velocity which prevents negative backlayering length from occurring. For cross-flow velocities higher than the critical velocities, all the plume generated from the source would be forced downstream and the location of the backlayering front would move downstream. I also visualise the structure of the plume for different source Reynolds numbers, which indicates that the backlayering is thicker at lower source Reynolds numbers. The thicker backlayering acts like a blockage, which changes the direction of the cross-flow velocity downstream of the source. In addition, an investigation into the relationship between critical velocity, source Reynolds number and the heat release rate has been carried out. An empirical relationship has been established between the critical heat release rates, which follows a power law with an exponent of one-third. The obtained result is in concurrence with the findings reported in prior investigations. For a fixed heat release rate, the critical velocity increases with increasing source Reynolds number. However, the critical velocity approaches an asymptotic value when the source Reynolds number is sufficiently high. In addition, I present data from the DNS of a planar buoyant plume in turbulent cross-flow in a channel. The Navier-Stokes equations are solved numerically using the Boussinesq approximation to simulate buoyancy effects. In particular, I study the effect of source buoyancy and momentum (defined as the source Richardson number) on the development of the plume. The size of the re-circulation zone immediately downstream of the plume is computed and shows good agreement with the existing experimental and numerical data. The results reflect that the length and height of this re-circulation zone, as well as the turbulence intensity, are affected by the buoyancy flux of the source. The mean jet normal velocity and temperature along the jet trajectory are found to be reasonably self-similar. The turbulent structures in the flow field are visualised and the flow statistics are calculated for different values of heat fluxes used to generate the plume. It is demonstrated that the findings in this chapter can assist in parameterising the unclosed turbulent terms within integral models that can be used in field applications. For the stability analysis, as a validation of the numerical tools, I first present the 2D global linear stability results using the spectral-element code Nektar++ as well as 1D stability with the primitive method solved by Matlab to investigate and validate the dynamics of the nonlinear flows of two-dimensional Rayleigh-Benard-Poiseuille flow. I then study the nonlinear direct numerical simulations of a two-dimensional buoyant plume in a channel with laminar crossflow under the Boussinesq buoyancy approximation. I observe that the mushroom-shaped vortices are generated by the buoyancy-related mechanism from the heat source, as the buoyant plume progresses downstream, it undergoes a transition into shear-induced instability. The shedding frequency of the vortices is also investigated. Global and local linear stability analysis is carried out on the buoyant plume in a channel with crossflow and the eigenfunctions are presented. The spatial structure of the eigenfunction visualized from the global stability analysis shows similarities to the structures found in DNS. The local perturbation kinetic energy analysis using the eigenfunctions is conducted to show the physical contributions to the growth rate. It is found that stability is primarily shear-related. The buoyancy effect acts to perturb the flow to form the structure that is subsequently enhanced by the shear instability near the source.
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ItemParticle-induced modulation and dispersion of inertial particles in turbulent wall flows( 2023)Turbulent wall flows laden with dispersed particles represent a significant canonical problem in modern turbulence research. The modelling of fluids laden with a dispersed phase has received substantial attention by fluid mechanicians and indeed physicists---from Einstein's effective eddy viscosity for dilute suspensions of small rigid spheres to sonoluminescence where collapsing bubbles excite such strong energy that light emission occurs, part of Lohse's wide investigation into bubble puzzles. This thesis drives further physical understanding of particle-fluid flows by simulations performed on state-of-the-art heterogeneous computing architectures. So, the generated data illuminates mathematical modelling from the twentieth century of some particles in turbulence scenarios. Restricting attention firstly to the underlying fluid, chapter 3 in this thesis devotes attention to the spatial requirements for accurate numerical calculation of the turbulent fluid. Then, the migration of inertial solid dense spherical particles in wall-bounded turbulence is studied, which represents a scenario where a dilute loading of particles is present. The findings support turbophoretic drift modelling of and `roll-off' extension of that relates particle accumulation at walls with the viscous Stokes number, validating and contextualising these models. Thereafter, the modification of turbulence by the presence of a higher particle loading reveals similarity between two canonical flows, pipes and channels. It was found that near to the wall, there is remarkable agreement in the modification of turbulent scales because heavy inertial sub-Kolmogorov particles deplete turbulent structures. Finally, Reynolds number effects are studied in classical Taylor dispersion of solutes. When characterisation of the particles is based off the small-scale motions, it is found that increasing Reynolds number leads to scale separation whereby inertial effects of particles are diminished. There is also a dramatic reduction in skewness of particle dispersion as Reynolds number increases due to enhanced radial mixing.
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ItemAccurate Forecasting of Distributed Solar Generation using Time Series and Deep Learning Methods( 2022)The number of small-scale distributed solar photovoltaic (PV) systems on the rooftops of residential and commercial buildings (i.e., behind-the-meter PV) has been rapidly rising in recent years due to the high demand for solar energy as a clean and renewable energy source. Despite the environmental and economic benefits of such PV systems, integrating high amounts of rooftop solar PV has introduced challenges in operating and managing electrical grids due to the variable and non-dispatchable nature of PV generation. Accurately forecasting the future solar generation is becoming important to overcome such challenges. This thesis investigates novel data-driven methods (i.e., methods based on historical power generation data) to forecast solar generation from rooftop PV systems. Forecasting methods have varying performances in specific prediction intervals (i.e., time horizons) and resolutions (i.e., frequency of the data). However, the required time resolution and horizon of forecasts may differ based on the application of interest. Therefore, this thesis first proposes a forecast combination method based on particle swarm optimisation to combine forecasts from multiple diverse methods to accurately forecast the solar generation across different time resolutions and horizons. During short-time horizons, fluctuations in solar generation are primarily caused due to the movement of clouds. Predicting the cloud movement using images of the clouds (e.g., satellite imagery) is therefore vital to predict solar generation. Deep neural networks, in particular, attention-based networks that focus on important regions of an input, have shown pre-eminent success in many computer vision tasks, including in spatiotemporal applications. However, their applicability in similar cloud forecasting tasks and subsequent impact on solar forecasting methods are poorly studied. Therefore, this thesis next proposes novel attention-based networks adapted to forecast cloud movement and investigates their impact towards solar forecasting. Forecasting the aggregated solar power generation from all distributed PV systems installed across an entire region (i.e., regional solar power forecasting) is essential to manage the energy demand and supply. As the final contribution, this thesis proposes novel deep learning-based methods that can improve regional forecasts by incorporating large volumes of time series data available for a region. The proposed methods and findings discussed in this thesis enable grid operators to better plan electricity grid operations to facilitate the integration of more rooftop solar PV into existing electricity grids through accurate solar forecasts.
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ItemExperimental Investigation of Ship Air-Wake Effects on Helicopter Landing( 2022)Helicopter landing on a continuously moving ship landing deck is classified as a high-risk marine operation. One parameter that significantly contributes to the operation adversity is the highly fluctuating, three-dimensional and unsteady flow over the landing deck, commonly known as the ship air-wake. Therefore, it is essential to understand the air-wake turbulence characteristics and how the unsteady flow affects the ship-helicopter landing operation. A review of the literature reveals that the air-wake high complexity is affected by several physical parameters. In this study, we investigate the contributions of two parameters: inflow conditions and superstructure geometries. The investigation is performed by comparing wind tunnel experimental results with two inflow conditions: a simulated Atmospheric Boundary Layer (ABL) and without ABL simulation; and two simplified ship models: Simplified Frigate Ship No.2 (SFS2) and NATO–Generic Destroyer (NATO-GD). Particle Image Velocimetry (PIV) and single-point time-series measurements over the landing deck center line show that the ABL inflow increases the flow fluctuations but reduces the length of the wake. Furthermore, we observed an enhancement of turbulence energy on the ship landing deck when the ABL is simulated. The experimental data also show that the topside arrangement, especially at the hangar elevation upstream of the landing deck, plays an essential role in the air-wake over the ship center line. There are significant differences in flow re-circulation regions, turbulence structure and energy content. The instantaneous velocity snapshots show that the flow over the landing deck is multi-scale, and the size of the turbulent eddies changes significantly in size over time. More importantly, there is a consistent stream of turbulent eddies with a comparable size to the helicopter that is likely to cause the most problem for the pilots. We identify two possible extreme events for the helicopter during the landing operation. The first extreme event is when the helicopter navigates in a region with a stronger down-wash (descending flow coming over the superstructure) than the time-averaged condition, and the second event is when it hovers in a region with a strong wall-normal velocity spatial gradient (dw/dx). In the first condition, the helicopter will experience a high vertical drag that may introduce altitude loss, while in the second condition, the helicopter receives an intense pitching moment that can rotate the helicopter. Our preliminary investigations show that these extreme events can produce significant aerodynamic forces on the helicopter. Based on a turbulence structure and energy spectrum analysis, as well as the extreme event characteristics observed with zero degrees angle of attack, we highlight regions with a possible increased safety risk for both models. Over the SFS2 center line, regions with an increased safety risk are located directly above the landing deck. Meanwhile on the NATO-GD center line, they are located at non-critical locations unlikely to be included in the helicopter landing trajectory, i.e., high above the landing deck and close to the hangar edge. We also present a new methodology that could be used to estimate landing safety risk based on the probability distribution function for a flow quantity of interest. The method requires a threshold for some turbulence quantity; for illustrative purposes only, we employ civil helicopter operations guidelines, which specify a threshold of vertical velocity fluctuations for safe landings. This study also presents preliminary results from the first ship air-wake experiment completed in a wind-wave facility where the boundary layer is naturally developed over the water wave surface. It is shown that for a static ship, the obtained air-wake turbulence characteristics are comparable to the typical ABL simulations completed in a wind tunnel. Specifically, we show that the turbulence kinetic energy on the landing deck increases linearly with both the background turbulence and the reference mean velocity.
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ItemClinically practical technology-assisted measures of upper limb spasticity( 2022)Spasticity is a motor disorder with high prevalence and important consequences following neurological injuries. Accurate measurement of spasticity is critical to direct management strategies and evaluate treatments' effectiveness. However, spasticity is commonly measured using clinical scales which lack specificity and reliability. Thus, technology-assisted measures have been developed as objective and accurate alternatives. Still, many of these methods have not been widely adopted in clinical settings, possibly due to their low feasibility and practicability. This work thus intends to identify and evaluate clinically practical technology-assisted measures of spasticity which have the potential and ability to be adopted into clinical practice. To achieve this objective, this work starts from systematically identifying and characterising existing technology-assisted measures of spasticity in the literature. An evaluation and comparison of psychometric properties and usability for each approach is then conducted. In addition, a validation of a potential practical robotic measure of elbow spasticity, using an upper limb rehabilitation device, is proposed. The discriminant validity and concurrent validity of this method is investigated. Finally, the possibility of using frequency information of neuromuscular signals to distinguish between spastic muscle reactions and voluntary muscle contractions is explored as a potential solution to overcome the limitations of existing muscle activity based measures. This work concludes that there is no ready-to-use valid and practical alternative to existing clinical scales. Still, among the promising methods, this work shows the possibility of using a robotic measure to evaluate elbow spasticity and provides future research directions for the use of frequency information to improve muscle activity measurements in spasticity detection.