The aim of this study is to extend a parallel Fortran90 code to compute three&ndash / dimensional laminar and turbulent flowfields over rotary wing configurations. The code employs finite volume discretization and the compact, four step Runge-Kutta type time integration technique to solve unsteady, thin&ndash / layer Navier&ndash / Stokes equations. Zero&ndash / order Baldwin&ndash / Lomax turbulence model is utilized to model the turbulence for the computation of turbulent flowfields. A fine, viscous, H type structured grid is employed in the computations. To reduce the computational time and memory requirements parallel processing with distributed memory is used. The data communication among the processors is executed by using the MPI ( Message Passing Interface ) communication libraries. Laminar and turbulent solutions around a two bladed UH &ndash / 1 helicopter rotor and turbulent solution around a flat plate is obtained. For the rotary wing configurations, nonlifting and lifting rotor cases are handled seperately for subsonic and transonic blade tip speeds. The results are, generally, in good agreement with the experimental data.

Sandwich panels comprise a thick, light-weight plastic foam such as polyurethane, polystyrene or mineral wool sandwiched between two relatively thin steel faces. One or both steel faces may be flat, lightly profiled or fully profiled. Until recently sandwich panel construction in Australia has been limited to cold-storage buildings due to the lack of design methods and data. However, in recent times, its use has increased significantly due to their widespread structural applications in building systems. Structural sandwich panels generally used in Australia comprise of polystyrene foam core and thinner (0.42 mm) and high strength (minimum yield stress of 550 MPa and reduced ductility) steel faces bonded together using separate adhesives. Sandwich panels exhibit various types of buckling behaviour depending on the types of faces used. Three types of buckling modes can be observed which are local buckling of plate elements of fully profiled faces, flexural wrinkling of flat and lightly profiled faces and mixed mode buckling of lightly profiled faces due to the interaction of local buckling and flexural wrinkling. To study the structural performance and develop appropriate design rules for sandwich panels, all these buckling failure modes have to be investigated thoroughly. A well established analytical solution exists for the design of flat faced sandwich panels, however, the design solutions for local buckling of fully profiled sandwich panels and mixed mode buckling of lightly profiled sandwich panels are not adequate. Therefore an extensive research program was undertaken to investigate the local buckling behaviour of fully profiled sandwich panels and the mixed mode buckling behaviour of lightly profiled sandwich panels. The first phase of this research was based on a series of laboratory experiments and numerical analyses of 50 foam-supported steel plate elements to study the local buckling behaviour of fully profiled sandwich panels made of thin steel faces and polystyrene foam core covering a wide range of b/t ratios. The current European design standard recommends the use of a modified effective width approach to include the local buckling effects in design. However, the experimental and numerical results revealed that this design method can predict reasonable strength for sandwich panels with low b/t ratios (< 100), but it predicts unconservative strengths for panels with slender plates (high b/t ratios). The use of sandwich panels with high b/t ratios is very common in practical design due to the increasing use of thinner and high strength steel plates. Therefore an improved design rule was developed based on the numerical results that can be used for fully profiled sandwich panels with any practical b/t ratio up to 600. The new improved design rule was validated using six full-scale experiments of profiled sandwich panels and hence can be used to develop safe and economical design solutions. The second phase of this research was based on a series of laboratory experiments and numerical analyses on lightly profiled sandwich panels to study the mixed mode buckling behaviour due to the interaction of local buckling and flexural wrinkling. The current wrinkling formula, which is a simple modification of the methods utilized for flat panels, does not consider the possible interaction between these two buckling modes. As the rib depth and width of flat plates between the ribs increase, flat plate buckling can occur leading to the failure of the entire panel due to the interaction between local buckling and wrinkling modes. Experimental and numerical results from this research confirmed that the current wrinkling formula for lightly profiled sandwich panels based on the elastic half-space method is inadequate in its present form. Hence an improved equation was developed based on validated finite element analysis results to take into account the interaction of the two buckling modes. This new interactive buckling formula can be used to determine the true value of interactive buckling stress for safe and economical design of lightly profiled sandwich panels. This thesis presents the details of experimental investigations and finite element analyses conducted to study the local buckling behaviour of fully profiled sandwich panels and the mixed mode buckling behaviour of lightly profiled sandwich panels. It includes development and validation of suitable numerical and experimental models, and the results. Current design rules are reviewed and new improved design rules are developed based on the results from this research.

Transition delay in boundary-layer flows is achieved via reactive control of flow instabilities, i.e. Tollmien-Schlichting (TS) waves. Adaptive and model-based control techniques are investigated by means of direct numerical simulations (DNS) and experiments. The action of actuators localised in the wall region is prescribed based on localised measurement of the disturbance field; in particular, plasma actuators and surface hot-wire sensors are considered. Performances and limitations of this control approach are evaluated both for two-dimensional (2D) and three-dimensional (3D) disturbance scenarios. The focus is on the robustness properties of the investigated control techniques; it is highlighted that static model-based control, such as the linear-quadratic- Gaussian (LQG) regulator, is very sensitive to model-inaccuracies. The reason for this behaviour is found in the feed-forward nature of the adopted sensor/actuator scheme; hence, a second, downstream sensor is introduced and actively used to recover robustness via an adaptive filtered-x least-mean-squares (fxLMS) algorithm. Furthermore, the model of the flow required by the control algorithm is reduced to a time delay. This technique, called delayed-x least-mean-squares (dxLMS) algorithm, allows taking a step towards a self-tuning controller; by introducing a third sensor it is possible to compute on-line the suitable time-delay model with no previous knowledge of the controlled system. This self-tuning approach is successfully tested by in-flight experiments on a motor-glider. Lastly, the transition delay capabilities of the investigated control con- figuration are confirmed in a complex disturbance environment. The flow is perturbed with random localised disturbances inside the boundary layer and the laminar-to-turbulence transition is delayed via a multi-input-multi-output (MIMO) version of the fxLMS algorithm. A positive theoretical net-energy- saving is observed for disturbance amplitudes up to 2% of the free-stream velocity at the actuation location, reaching values around 1000 times the input power for the lower disturbance amplitudes that have been investigated. / I den här avhandlingen har reglertekniska metoder tillämpats för att försena omslaget från ett laminärt till ett turbulent gränsskikt genom att dämpa tillväxten av små instabiliteter, så kallade Tollmien-Schlichting vågor. Adaptiva och modellbaserade metoder för reglering av strömning har undersökts med hjälp av numeriska beräkningar av Navier-Stokes ekvationer, vindtunnelexperiment och även genom direkt tillämpning på flygplan. Plasmaaktuatorer och varmtrådsgivare vidhäftade på ytan av plattan eller vingen har använts i experimenten och modellerats i beräkningarna. Prestanda och begränsningar av den valda kontrollstrategin har utvärderats för både tvådimensionella och tredimensionella gränsskiktsinstabiliteter. Fokus har varit på metodernas robusthet, där vi visar att statiska metoder som linjär-kvadratiska regulatorer (LQG) är mycket känsliga för avvikelser från den nominella modellen. Detta beror främst på att regulatorer agerar i förkompenseringsläge (”feed-foward”) på grund av strömningens karaktär och placeringen av givare och aktuatorer. För att minska känsligheten mot avvikelser och därmed öka robustheten har en givare införts nedströms och en adaptiv fXLMS algoritm (filtered-x least-mean-squares) har tillämpats.                  Vidare har modelleringen av fXLMS-algoritmen förenklats genom att ersätta överföringsfunktionen mellan aktuatorer och givare med en lämplig tidsfördröjning.  Denna  metod som kallas för dxLMS (delayed-x least-mean-squares) kräver att ytterligare en givare införs långt uppströms för att kunna uppskatta hastigheten på de propagerande instabilitetsvågorna. Denna teknik har tillämpats framgångsrikt för reglering av gränsskiktet på vingen av ett segelflygplan. Slutligen har de reglertekniska metoderna testas för komplexa slumpmässiga tredimensionella störningar som genererats uppströms lokalt i gränsskiktet. Vi visar att en signifikant försening av laminärt-turbulentomslag äger rum med hjälp av en fXLMS algoritm. En analys av energibudgeten visar att för ideala aktuatorer och givare kan den sparade energiåtgången på grund av minskad väggfriktion vara upp till 1000 gånger större än den energi som använts för reglering.

The Master´s thesis is focused on the assessment basic parts of the story building. All construction is made from reinforced concrete. The columns, flat plate slabs, flanges and stairways are between the design constructions. The thesis includes working-out of static calculation, drawing shape, reinforcement drawing of all design constructions and results from computer sofware.

Turbulent boundary layers approximating those found on the NASA Orion Multi-Purpose Crew Vehicle (MPCV) thermal protection system during atmospheric reentry from the International Space Station have been studied by direct numerical simulation, with the ultimate goal of reducing aerothermodynamic heating prediction uncertainty. Simulations were performed using a new, well-verified, openly available Fourier/B-spline pseudospectral code called Suzerain equipped with a ``slow growth'' spatiotemporal homogenization approximation recently developed by Topalian et al. A first study aimed to reduce turbulence-driven heating prediction uncertainty by providing high-quality data suitable for calibrating Reynolds-averaged Navier--Stokes turbulence models to address the atypical boundary layer characteristics found in such reentry problems. The two data sets generated were Ma[approximate symbol] 0.9 and 1.15 homogenized boundary layers possessing Re[subscript theta, approximate symbol] 382 and 531, respectively. Edge-to-wall temperature ratios, T[subscript e]/T[subscript w], were close to 4.15 and wall blowing velocities, v[subscript w, superscript plus symbol]= v[subscript w]/u[subscript tau], were about 8 x 10-3 . The favorable pressure gradients had Pohlhausen parameters between 25 and 42. Skin frictions coefficients around 6 x10-3 and Nusselt numbers under 22 were observed. Near-wall vorticity fluctuations show qualitatively different profiles than observed by Spalart (J. Fluid Mech. 187 (1988)) or Guarini et al. (J. Fluid Mech. 414 (2000)). Small or negative displacement effects are evident. Uncertainty estimates and Favre-averaged equation budgets are provided. A second study aimed to reduce transition-driven uncertainty by determining where on the thermal protection system surface the boundary layer could sustain turbulence. Local boundary layer conditions were extracted from a laminar flow solution over the MPCV which included the bow shock, aerothermochemistry, heat shield surface curvature, and ablation. That information, as a function of leeward distance from the stagnation point, was approximated by Re[subscript theta], Ma[subscript e], [mathematical equation], v[subscript w, superscript plus sign], and T[subscript e]/T[subscript w] along with perfect gas assumptions. Homogenized turbulent boundary layers were initialized at those local conditions and evolved until either stationarity, implying the conditions could sustain turbulence, or relaminarization, implying the conditions could not. Fully turbulent fields relaminarized subject to conditions 4.134 m and 3.199 m leeward of the stagnation point. However, different initial conditions produced long-lived fluctuations at leeward position 2.299 m. Locations more than 1.389 m leeward of the stagnation point are predicted to sustain turbulence in this scenario. / text

Splitter plates are passive flow control devices for reducing drag and suppressing vortex shedding from bluff bodies. Most studies of splitter plates involve the flow around an “infinite” circular cylinder, however, in the present study the flow around a surface-mounted finite-height circular cylinder, with a wake-mounted splitter plate, was studied experimentally in a low-speed wind tunnel using a force balance and single-component hot-wire anemometry. Four circular cylinders of aspect ratios AR = 9, 7, 5 and 3 were tested for a Reynolds number range of Re = 1.9×10^4 to 8.2×10^4. The splitter plates had lengths, relative to the cylinder diameter, of L/D = 1, 1.5, 2, 3, 5 and 7, thicknesses ranging from T/D = 0.10 and 0.15, and were the same height as the cylinder being tested. The cylinders were partially immersed in a flat-plate turbulent boundary layer, where the range of boundary layer thickness relative to the cylinder diameter was δ/D = 1.4 to 1.5. Measurements were made of the mean drag force coefficient, the Strouhal number at the mid-height position, and the Strouhal number and power spectra along the cylinder height. For all four finite circular cylinders, the splitter plates were effective at reducing the magnitude of the Strouhal number, and weakening or even suppressing vortex shedding, depending on the specific combination of AR and L/D. Compared to the case of an infinite circular cylinder, the splitter plate is less effective at reducing the mean drag force coefficient of a finite circular cylinder. The largest drag reduction was obtained for the cylinder of AR = 9 and splitter plates of L/D = 1 to 3, while negligible drag reduction occurred for the shorter cylinders.