The velocity fields of high Reynolds number, turbulent, wall boundary layers in non-equilibrium pressure gradients are experimentally investigated. Experiments in two wall configurations were performed; one with a hydrodynamically smooth test wall composed of flat aluminum panels, and the other with a rough surface consisting of 2 mm tall, staggered, circular cylindrical elements. A representative set of pressure gradient distributions were generated on the research wall by a systematically rotated NACA 0012 airfoil placed in a wind tunnel section to determine the functional dependence of the boundary layer formation on pressure gradient. Particle image velocimetry (PIV) was the primary measurement technique used to determine time-resolved features of the velocity flow field. newline{}newline{} It is shown that regardless of wall condition and Reynolds number, the non-equilibrium turbulent boundary layers exhibit increasingly non-local behavior with streamwise development. This is apparent as a lag to the pressure gradient distribution observed in the streamwise developing integrated boundary layer parameters. These ``history effects" are also prevalent in mean velocity profiles which are exhibited as a cross-over of the favorable and adverse pressure gradient profiles in the logarithmic layer. Similar cross-over points are observed in the Reynolds shear and normal stresses, particularly at the streamwise station downstream of the pressure gradient switch. The primary effect of the rough wall is to increase the magnitude of flow scales, and, while they exhibit the same qualitative history effects as the smooth wall, the rough wall flows show an earlier relaxation to equilibrium. Despite inherent uncertainties of indirect skin friction methods for the rough wall, the effective sandgrain roughness parameter k_s does not show a functional dependency to pressure gradient history. An evaluation of the wall-similarity hypothesis solely based on boundary layer thickness to roughness parameter ratios delta/k_s is insufficient and additional parameters such as pressure gradient histories, local roughness Reynolds numbers, and bias uncertainties due to instrument spatial resolution must be considered. / Doctor of Philosophy / In the interface between a surface and a moving fluid is the boundary layer where high shear and viscous stresses cause the bulk velocity to decrease to zero. When turbulent, this region of fluid is characterized by random, chaotic, and fluctuating motions of varying sizes. Parameters such as pressure gradients and geometric irregularities of the surface, referred to as roughness, can increase fluctuating pressures and velocities within the boundary layer and cause unwanted noise, vibration, and increased drag. Although many studies have evaluated boundary layers with either roughness or pressure gradient independently, most surfaces in practical application are susceptible to the compounding influences of both of these parameters. Thus, it is necessary to expand the current knowledge database to include complex flow fields necessary to improve data driven modeling and vehicle design.newline{}newline{} This study focuses on experimental observations of the turbulent velocity field developing in both a rough and smooth wall boundary layer that is induced to a family of bi-directional pressure gradients generated by the pressure field of a rotating airfoil inside in a wind tunnel. Through statistical observations of the velocity field it was found that the varying pressure gradients caused the flow to develop non-local dependencies such that the response of the downstream boundary layer was dependent on the upstream flow history. The principal effect of roughness was to increase the magnitude of turbulent scales, but to show the same qualitative response to the pressure gradient history as seen in a smooth wall flow. However, direct comparison of rough and smooth wall turbulence statistics by means of the ``wall-similarity hypothesis" requires careful consideration of multiple parameters including these flow histories, scales prescribed by roughness parameters, and bias errors from experiment under-resolution of the velocity field.

As mental health care increasingly embraces recovery principles, the role of peer support workers (PSWs) has gained recognition. The work that mental health PSWs do became particularly important during the COVID-19 pandemic, when increased needs for mental health care became apparent but were often unmet. This article-based doctoral thesis adopts an interdisciplinary perspective that combines research on management and organization with research on health care and systems. The thesis examines the mental health peer support role and its integration within teams, organizations and health systems. It also considers the peer support role as it was enacted in a virtual space, which became a requirement due to pandemic work-from-home mandates. Within the context of the virtual space, PSWs confronted work-life boundaries that they had to navigate as they enacted their work roles. The virtual space also presented technological and social challenges to and opportunities for peer support, which are examined in this thesis from the points of views of PSWs and peers. Overall, this thesis attends to the PSW role more generally, and to peer support work in the specific context of a virtual environment. The thesis is composed of three studies, the second and third of which had to be adapted to the unexpected challenges and opportunities posed by the COVID-19 pandemic. Study 1 (presented in Chapter 2) is a narrative review that synthesizes the literature on factors influencing formal PSW role implementation in mental health systems. The findings are synthesized in a multilevel framework consisting of macro, meso and micro level influences. The analysis reveals that macro-level influences on PSW role implementation include socio-cultural, regulatory, political and economic factors, most of which act as obstacles. At the meso level, organizational culture, leadership, and human resource management policies play a significant role. Micro-level influences center around PSWs' relationships with team members. Interlevel interactions are also discussed. This study is co-authored with Professor Samia Chreim and was published in Administration and Policy in Mental Health and Mental Health Services in February 2022. For Studies 2 and 3, qualitative data were collected from members of a peer support organization situated in Ottawa. This organization is a publicly funded, not-for-profit organization that provides services free of charge to people experiencing mental health and addictions challenges. Due to the pandemic, all services and operations of this organization transitioned to remote services involving virtual platforms. Study 2 (presented in Chapter 3) is a qualitative case study that delves into the work-life boundary challenges and management of PSWs who were providing virtual mental health support during the pandemic. The study identifies temporal, physical, and task-related boundary challenges in work-life domains. Strategies employed by PSWs to manage these boundaries include segmenting and integrating work and personal domains. The study highlights the importance of self-care and the need for training on work-life boundary management for mental health workers. This research is co-authored with Professor Samia Chreim and is published in BMC Public Health. Study 3 (presented in Chapter 4) focuses on the transition from in-person to virtual mental health peer support services. Through semi-structured interviews with PSWs and service users (or peers), the research examines how technological factors act as bridges and boundaries to mental health peer support services, and whether and how a sense of community can be built or maintained among PSWs and peers in a virtual space when connections are mediated by technology. The findings highlight the mental health peer support needs that were (un)met through virtual services, the technology-based boundaries that were manifested and the steps taken to remove some of these boundaries, and the strategies employed by the organization and its members to establish and maintain a sense of community in a virtual environment marked by physical distancing and technology-mediated interrelations. The manuscript pertaining to this study is co-authored with Professor Samia Chreim and will be submitted soon to an academic journal. Overall, this thesis presents a unique and multi-faceted exploration of the implementation of peer support worker roles in mental health systems and their adaptation to virtual environments. It makes a number of contributions. The multilevel framework developed in Study 1 not only advances knowledge in the field but also offers a structured approach for policymakers and organizations to enhance the formal incorporation of PSW roles into mental health systems. Study 2 provides valuable insights into the nature of work-life boundaries in a virtual space, an important topic at a time when peer support workers and organizations are considering whether and how to maintain some form of virtual work post-pandemic. Study 3 adds to knowledge by highlighting the significance of virtual peer support beyond pandemic conditions. It also enhances understanding of the need for technological adaptation in mental health services and for community building regardless of the model of service. Limitations and implications for research, practice and policy are addressed.

QC 20100927

An artificial neural network (ANN) method was developed for solving boundary value problems (BVPs) on an arbitrary irregular domain in such a manner that all Dirichlet and/or Neuman boundary conditions (BCs) are automatically satisfied. Exact satisfaction of BCs is not available with traditional numerical solution techniques such as the finite element method (FEM). The ANN is trained by reducing error in the given differential equation (DE) at certain points within the domain. Selection of these points is significantly simpler than the often difficult definition of meshes for the FEM. The approximate solution is continuous and differentiable, and can be evaluated at any location in the domain independent of the set of points used for training. The continuous solution eliminates interpolation required of discrete solutions produced by the FEM. Reducing error in the DE at a particular location in the domain does not necessarily imply improvement in the approximate solution there. A theorem was developed, proving that the solution will improve whenever error in the DE is reduced at all locations in the domain during training. The actual training of ANNs reasonably approximates the assumptions required by the proof. This dissertation offers a significant contribution to the field by developing a method for solving BVPs where all BCs are automatically satisfied. It had already been established in the literature that such automatic BC satisfaction is beneficial when solving problems on rectangular domains, but this dissertation presents the first method applying the technique to irregular domain shapes. This was accomplished by developing an innovative length factor. Length factors ensure BC satisfaction extrapolate the values at Dirichlet boundaries into the domain, providing a solid starting point for ANN training to begin. The resulting method has been successful at solving even nonlinear and non-homogenous BVPs to accuracy sufficient for typical engineering applications.

La simulation d’écoulements incompressibles pose de nombreuses difficultés. Une première est la question de savoir comment traiter la contrainte d’incompressibilité et le couplage vitesse/pression afin d’obtenir une solution précise à moindre coût. Pour cela, nous nous intéressons en particulier à deux méthodes de time splitting : la correction de pression et la correction de vitesse. Une seconde difficulté porte sur des conditions limites de sortie. Nous nous intéressons ici à deux d’entre elles : la condition limite de traction et la condition limite d’Orlanski. Après avoir détaillé les difficultés pouvant apparaître lors de l’implémentation des méthodes de time-splitting, nous proposons une nouvelle implémentation de la condition limite de traction qui permet d’améliorer les ordres de convergence obtenus. Nous nous intéressons ensuite à la condition limite d’Orlanski qui nécessite une certaine vitesse d’advection C dans la direction normale à la limite dont nous proposons ici une nouvelle définition. Nos propositions sont confrontées à de multiples écoulements physiques afin de valider leurs comportements : l’écoulement en aval d’une marche descendante, l’écoulement au niveau d’une bifurcation,l’écoulement autour d’un obstacle et des écoulements de Poiseuille-Rayleigh-Bénard. / One of the understudied difficulties in the simulation of incompressible flows is how to treat the incompressibilityconstraint and the velocity/pressure coupling in order to obtain an accurate solution at low computationnalcost. In this context, we develop two methods: pressure-correction and velocity-correction. An anotherdifficulty is due to the boundary conditions. We study here two of them : the traction boundary condition andthe Orlanski boundary condition. After having developed the difficulties that appears when implementing timesplittingmethods, we propose a new way to enforce the traction boundary condition which improves the orderof convergence. Then we propose a new definition of the advective velocity C which is needed for the Orlanskiboundary condition. Our propositions are validated against multiple physical flows: flow over a backward facingstep, flow around a biffurcation, flow around an obstacle and several Poiseuille-Rayleigh-Bénard flows.

Mathematical theory of partial differential equations (PDEs) is a pretty old classical area with wide range of applications to almost every branch of science and engineering. With the advanced development of functional analysis and operator theory in the last century, it became a topic of analysis. The theory of homogenization of partial differential equations is a relatively new area of research which helps to understand the multi-scale phenomena which has tremendous applications in a variety of physical and engineering models, like in composite materials, porous media, thin structures, rapidly oscillating boundaries and so on. Hence, it has emerged as one of the most interesting and useful subject to study for the last few decades both as a theoretical and applied topic. In this thesis, we study asymptotic analysis (homogenization) of second-order partial differential equations posed on an oscillating domain. We consider a two dimensional oscillating domain (comb shape type) consisting of a fixed bottom region and an oscillatory (rugose) upper region. We introduce optimal control problems for the Laplace equation. There are mainly two types of optimal control problems; namely distributed control and boundary control. For distributed control problems in the oscillating domain, one can apply control on the oscillating part or on the fixed part and similarly for boundary control problem (control on the oscillating boundary or on the fixed part the boundary). We consider all the four cases, namely distributed and boundary controls both on the oscillating part and away from the oscillating part. The present thesis consists of 8 chapters. In Chapter 1, a brief introduction to homogenization and optimal control is given with relevant references. In Chapter 2, we introduce the oscillatory domain and define the basic unfolding operators which will be used throughout the thesis. Summary of the thesis is given in Chapter 3 and future plan in Chapter 8. Our main contribution is contained in Chapters 4-7. In chapters 4 and 5, we study the asymptotic analysis of optimal control problems namely distributed and boundary controls, respectively, where the controls act away from the oscillating part of the domain. We consider both L2 cost functional as well as Dirichlet (gradient type) cost functional. We derive homogenized problem and introduce the limit optimal control problems with appropriate cost functional. Finally, we show convergence of the optimal solution, optimal state and associate adjoint solution. Also convergence of cost-functional. In Chapter 6, we consider the periodic controls on the oscillatory part together with Neumann condition on the oscillating boundary. One of the main contributions is the characterization of the optimal control using unfolding operator. This characterization is new and also will be used to study the limiting analysis of the optimality system. Chapter 7 deals with the boundary optimal control problem, where the control is applied through Neumann boundary condition on the oscillating boundary with a suitable scaling parameter. To characterize the optimal control, we introduce boundary unfolding operators which we consider as a novel approach. This characterization is used in the limiting analysis. In the limit, we obtain two limit problems according to the scaling parameters. In one of the limit optimal control problem, we observe that it contains three controls namely; a distributed control, a boundary control and an interface control.

Wall transpiration, in the form of wall-normal suction or blowing through a permeable wall, is a relatively simple and effective technique to control the behaviour of a boundary layer. For its potential applications for laminar-turbulent transition and separation delay (suction) or for turbulent drag reduction and thermal protection (blowing), wall transpiration has over the past decades been the topic of a significant amount of studies. However, as far as the turbulent regime is concerned, fundamental understanding of the phenomena occurring in the boundary layer in presence of wall transpiration is limited and considerable disagreements persist even on the description of basic quantities, such as the mean streamwise velocity, for the rather simplified case of flat-plate boundary-layer flows without pressure gradients. In order to provide new experimental data on suction and blowing boundary layers, an experimental apparatus was designed and brought into operation. The perforated region spans the whole 1.2 m of the test-section width and with its streamwise extent of 6.5 m is significantly longer than previous studies, allowing for a better investigation of the spatial development of the boundary layer. The quality of the experimental setup and measurement procedures was verified with extensive testing, including benchmarking against previous results on a canonical zero-pressure-gradient turbulent boundary layer (ZPG TBL) and on a laminar asymptotic suction boundary layer. The present experimental results on ZPG turbulent suction boundary layers show that it is possible to experimentally realize a turbulent asymptotic suction boundary layer (TASBL) where the boundary layer mean-velocity profile becomes independent of the streamwise location, so that the suction rate constitutes the only control parameter. TASBLs show a mean-velocity profile with a large logarithmic region and without the existence of a clear wake region. If outer scaling is adopted, using the free-stream velocity and the boundary layer thickness (δ99) as characteristic velocity and length scale respectively, the logarithmic region is described by a slope Ao=0.064 and an intercept Bo=0.994, independently from the suction rate (Γ). Relaminarization of an initially turbulent boundary layer is observed for Γ&gt;3.70×10−3. Wall suction is responsible for a strong damping of the velocity fluctuations, with a decrease of the near-wall peak of the velocity-variance profile ranging from 50% to 65% when compared to a canonical ZPG TBL at comparable Reτ. This decrease in the turbulent activity appears to be explained by an increased stability of the near-wall streaks. Measurements on ZPG blowing boundary layers were conducted for blowing rates ranging between 0.1% and 0.37% of the free-stream velocity and cover the range of momentum thickness Reynolds number 10000&lt;Reθ&lt;36000. Wall-normal blowing strongly modifies the shape of the boundary-layer mean-velocity profile. As the blowing rate is increased, the clear logarithmic region characterizing the canonical ZPG TBLs gradually disappears. A good overlap among the mean velocity-defect profiles of the canonical ZPG TBLs and of the blowing boundary layers for all the Re number and blowing rates considered is obtained when normalization with the Zagarola-Smits velocity scale is adopted. Wall blowing enhances the intensity of the velocity fluctuations, especially in the outer region. At sufficiently high blowing rates and Reynolds number, the outer peak in the streamwise-velocity fluctuations surpasses in magnitude the near-wall peak, which eventually disappears. / Genom att använda sig av genomströmmande ytor, med sugning eller blåsning, kan man relativt enkelt och effektivt påverka ett gränsskikts tillstånd. Genom sin potential att påverka olika strömningsfysikaliska fenomen så som att senarelägga både avlösning och omslaget från laminär till turbulent strömning (genom sugning) eller som att exempelvis minska luftmotståndet i turbulenta gränsskikt och ge kyleffekt (genom blåsning), så har ett otaligt antal studier genomförts på området de senaste decennierna. Trots detta så är den grundläggande förståelsen bristfällig för de strömningsfenomen som inträffar i turbulenta gränsskikt över genomströmmande ytor. Det råder stora meningsskiljaktigheter om de mest elementära strömningskvantiteterna, såsom medelhastigheten, när sugning och blåsning tillämpas även i det mest förenklade gränsskiktsfallet nämligen det som utvecklar sig över en plan platta utan tryckgradient. För att ta fram nya experimentella data på gränsskikt med sugning och blåsning genom ytan så har vi designat en ny experimentell uppställning samt tagit den i bruk.Den genomströmmande ytan spänner över hela bredden av vindtunnelns mätsträcka (1.2 m) och är 6.5 m lång i strömningsriktningen och är därmed betydligt längre än vad som använts i tidigare studier. Detta gör det möjligt att bättre utforska gränsskiktet som utvecklas över ytan i strömningsriktningen. Kvaliteten på den experimentella uppställningen och valda mätprocedurerna har verifierats genom omfattande tester, som även inkluderar benchmarking mot tidigare resultat på turbulenta gränsskikt utan tryckgradient eller blåsning/sugning och på laminära asymptotiska sugningsgränsskikt. De experimentella resultaten på turbulenta gränsskikt med sugning bekräftar för första gången att det är möjligt att experimentellt sätta upp ett turbulent asymptotiskt sugningsgränsskikt där gränsskiktets medelhastighetsprofil blir oberoende av strömningsriktningen och där sugningshastigheten utgör den enda kontrollparametern. Det turbulenta asymptotiska sugningsgränsskiktet visar sig ha en medelhastighetsprofil normalt mot ytan med en lång logaritmisk region och utan förekomsten av en yttre vakregion. Om man använder yttre skalning av medelhastigheten, med friströmshastigheten och gränsskiktstjockleken som karaktäristisk hastighet respektive längdskala, så kan det logaritmiska området beskrivas med en lutning på Ao=0.064 och ett korsande värde med y-axeln på Bo=0.994, som är oberoende av sugningshastigheten. Om sugningshasigheten normaliserad med friströmshastigheten överskrider värdet 3.70x10^-3 så återgår det ursprungligen turbulenta gränsskiktet till att vara laminärt. Sugningen genom väggen dämpar hastighetsfluktuationerna i gränsskiktet med upp till 50-60% vid direkt jämförelse av det inre toppvärdet i ett turbulent gränsskikt utan sugning och vid jämförbart Reynolds tal. Denna minskning av turbulent aktivitet verkar härstamma från en ökad stabilitet av hastighetsstråken närmast ytan. Mätningar på turbulenta gränsskikt med blåsning har genomförts för blåsningshastigheter mellan 0.1 och 0.37% av friströmshastigheten och täcker Reynoldstalområdet (10-36)x10^3, med Reynolds tal baserat på rörelsemängds-tjockleken. Vid blåsning genom ytan får man en stark modifiering av formen på hastighetesfördelningen genom gränsskiktet. När blåsningshastigheten ökar så kommer till slut den logaritmiska regionen av medelhastigheten, karaktäristisk för turbulent gränsskikt utan blåsning, att gradvis försvinna. God överens-stämmelse av medelhastighetsprofiler mellan turbulenta gränsskikt med och utan blåsning erhålls för alla Reynoldstal och blåsningshastigheter när profilerna normaliseras med Zagarola-Smits hastighetsskala. Blåsning vid väggen ökar intensiteten av hastighetsfluktuationerna, speciellt i den yttre regionen av gränsskiktet. Vid riktigt höga blåsningshastigheter och Reynoldstal så kommer den yttre toppen av hastighetsfluktuationer i gränsskiktet att överskrida den inre toppen, som i sig gradvis försvinner. / <p>QC 20171101</p>

The initial slow viscous growth of the Tollmein-Schlichting wave in a canonical boundary layer transition is absent in bypass and wake-induced transitions. Although there have been a great deal of studies pertaining to bypass transition in boundary layers, the underlying breakdown mechanism is not clearly understood and it continues to be a subject of interest. Similarly, a wake-induced transition caused by Karman wake in the freestream remains poorly understood. The breakdown in this case is caused by anisotropic disturbances containing large scale unsteadiness in the freestream. Differing view points among workers on the transition process have also added to the complexities. In this thesis, bypass and wake-induced boundary layer transitions studied experimentally towards understanding various flow breakdown features are reported. The measurements were made on a flat plate boundary layer in a low-speed wind tunnel. The particle image velocimetry (PIV) technique was extensively used. Various grids were used to generate nearly isotropic freestream turbulence. A circular cylinder was placed at different heights from the plate leading edge to generate Karman wake in the freestream. Two cylinders of different diameters were used to vary the Reynolds number(based on the cylinder diameter). The PIV measurements being simultaneous over a large spatial domain enabled to assess various spatial transitional flow structures. In the case of bypass transition, the streamwise velocity fluctuation, u, is found to exhibit some organized negative and positive fluctuations that dominate the flow during transition, and confirm the simulation results reported in the literature. These positive and negative u fluctuations are found to be associated with the streak unsteadiness. By conditional sampling of these positive and negative u fluctuations, we find that urms (root-mean-squaredof u)can be expressed as a linear combination of urms,f and urms,b,i.e. urms = a(urms,f + urms,b); ais constant, and the subscripts fand bdenote the positive and nega-tive ufluctuations, respectively. Both urms,f and urms,b arefoundto follow the non-modal growth distribution. The wall-normal results clearly show that an inclined shear layer is often associated with an organized structure of negative ufluctuations and an inflectional in-stantaneous velocity profile. These inclined shear layers appear to be similar to those in ribbon-induced transition. The turbulent spot precursor appears to be the vortex shedding from an oscillating in-clined shear layer. Interestingly, the normalized vortex shedding fre-quency is found to be Reynolds number invariant, as in the case of ribbon-induced transition. The present study also confirms the sim-ulated turbulent spot features, including a thin log-law at the break-down stage. The spanwise plane PIV results reveal the signature of streak secondary instability in the flow in terms of symmetric and anti-symmetric streaks oscillations. The initial growth of streak amplitude is followed by a slow decay. The maximum streak amplitude is well above30% of the freestream velocity. These two aspects provide support to the streak instability analysis reported in the literature. While the present wake-induced transition study provides some sup-port to the available numerical simulation and experimental results, some new results have also emerged. The measured sharp rise in the disturbance energy during transition is found to be closer to the simulated result, compared to the difference reported in the literature. The spanwise vortices in the early stage, as also seen in other experimental studies, deform leading to the formation of lambda structures, the signature of which is found by the linear stochastic analysis. With increased Reynolds number and decreased cylinder height from the plate, the physical size of the lambda structure is found to decrease. These lambda structures are often found to appear in a staggered manner in the spanwise plane, as in the case of sub-harmonic boundary layer transition. Although a sub-harmonic peak in the frequency spectra is reported in the literature, as also in the present study, the clear staggered pattern went unnoticed. Streamwise streaks are subsequently generated due to the mean shear stretching of these lambda vortices. The spanwise spacing of these streamwise streaks is found to be comparable with the recent simulation results. Also, these streaks are found to undergo somewhat sinuous-like oscillations, compared to the only varicose type oscillations reported in the literature. The streak amplitude is found to saturate at about 35% of the freestream speed. Here again an inclined shear layer in the wall-normal plane is associated with organized negative u fluctuations and an inflectional instantaneous velocity profile. The movement of the peak urms towards the wall is found to be due to the positive u fluctuation, which follows a hairpin-like structure. The inclined shear layers herein are associated with the lambda or a hairpin-like structure. As in a by-pass transition, an inclined shear layer, vortex shedding from it, the imprint of which is also found in the linear stochastic analysis are present. The normalized high frequency shed vortices is found to be Reynolds number invariant in the present wake-induced transition, as in ribbon-induced and bypass transitions. Compared to the re-cent suggestion that the parent-offspring mechanism is the governing self-sustaining mechanism in the boundary layer, the present study suggests that streak-instability mechanism is also present. The proper orthogonal decomposition(POD) analysis of the experimental data was carried out with an emphasis on the bypass transition case studied. The first few energetic POD modes are found to capture the dominant flow structures, i.e. the organized positive and negative u fluctuations. In the case of bypass transition, the first two energetic POD modes are self-similar, i.e. independent of the freestream turbulent intensity and the Reynolds number. An attempt is also made to construct a low-dimensional model with the POD eigenfunction modes to predict the qualitative dynamics of bypass transition. This has revealed the existence of a traveling disturbance in the bypass transition. On the whole, the present study shows some similar breakdown features in bypass and wake-induced transitions, although more studies in this regard are essential.

ICTs have enabled increased mobility and created a new era of workplace connectivity. Due to changes in work organization, global operations, increased mobility, and the new opportunities they are creating; work requires more coordination, more travel and a higher frequency of boundary spanning. ICTs have infiltrated into the personal life of individuals, while similarly, having an increasing impact on how organizations manage their workers‘ work-life balance. This research investigates the work boundary negotiation process in ICT-enabled work.Using an in-depth case study supplemented with visual data, this thesis studies the case of Sigma, an international consulting firm, that serves clients located in a large geographical area. It explores how consultants exhibiting mobile work practices, use ICTs to negotiate work boundaries. It draws on the structurational model of technology and complements it with the boundary object construct. The utilisation of this combined approach allows further understanding of work boundary negotiation.The research reveals that some ICTs as technological artefacts are boundary objects bridging between different groups of actors, crossing work boundaries, and allowing actors to negotiate their work boundaries while challenging traditional boundaries. Thus, allowing consultants to use their ICTs (specifically their smartphone) to negotiate their work boundaries on a need to basis. The boundary negotiation process (as revealed by the structuration process) is the means by which consultants try to make the most out of existing social structures – in this case specifically domination – in their organizational context. The ICT becomes a source of power and is mainly used to manifest domination over available resources. Consultants use them to maintain control over their life, increase their legitimacy and convey that they are professional experts. ICTs allow consultants to continuously redefine their work boundaries which become dynamic, fluid and contextual; the research reaffirms the sociotechnical nature of work boundaries.The thesis also develops a conceptual model of work boundary negotiation that conceptually illustrates how boundary negotiation is the outcome of the structuration process and the negotiation of existing structures of domination, legitimation and signification.

The main aim of this thesis was to understand the mechanism behind the classical transition scenario inside the boundary layer over an airfoil and eventually attempting to control this transition utilizing passive devices for transition delay. The initial objective of analyzing the transition phenomenon based on TS wave disturbance growth was conducted at 90 Hz using LDV and CTA measurement techniques at two different angles of attack. This was combined with the studies performed on two other frequencies of 100 and 110 Hz, in order to witness its impact on the neutral stability curve behavior. The challenges faced in the next phase of the thesis while trying to control the transition location, was to understand and encompass the effect of adverse pressure gradient before setting up the passive control devices, which in this case was miniature vortex generators. Consequently, several attempts were made to optimize the parameters of the miniature vortex generators depending upon the streak strength and stability. Finally, for 90 Hz a configuration of miniature vortex generators have been found to successfully stabilize the TS wave disturbances below a certain forcing amplitude, which also led to transition delay.