1,720,986 research outputs found
Numerical solution of partial differential equations in random domains: An application to wind engineering.
No full textAn application of recent uncertainty quantification techniques to Wind Engineering is presented. In particular, the study of the effects of small geometric changes in the Sunshine Skyway Bridge dock on its aerodynamic behavior is addressed. This results in the numerical solution of a proper PDE posed in a domain affected by randomness, which is handled through a mapping approach. A non-intrusive Polynomial Chaos expansion allows to transform the stochastic problem into a deterministic one, in which a commercial code is used as a black-box for the solution of a number of Reynolds-Averaged Navier-Stokes simulations. The use of proper Gauss-Patterson nested quadrature formulas with respect to a Truncated Weibull probability density function permits to limit the number of these computationally expensive simulations, though maintaining a sufficient accuracy. Polynomial Chaos approximations, statistical moments and probability density functions of time-independent quantities of interest for the engineering applications are obtained
Determination of flutter derivatives for streamlined bodies throughout a modified indicial approach by means of CWE: part II - Sensitivity to physical parameters
No full textDetermination of flutter derivatives for streamlined bodies throughout a modified indicial approach by means of CWE: part I - Mathematical and computational modeling
No full textEvaluation of Reynolds number effects on flutter derivatives of a flat plate by means of a computational approach
No full textEvaluation of Reynolds number effects on flutter derivatives of a flat plate by means of a computational approach
No full textDetermination of the Aeroelastic Transfer Functions for Streamlined Bodies by means of a Navier-Stokes Solver
No full textThis paper proposes a method to determine the flutter derivatives of two-dimensional streamlined cylinders by means of a modified indicial approach adapted to a Navier-Stokes solver using an Arbitrary Lagrangian Eulerian formulation. The method relies on heave or pitch motion imposed onto the section according to smoothed-ramp time-histories and on the computational evaluation of the transient forces arising on the obstacle. Hence, the indicial transfer function relating the plate motion to the induced force in the frequency domain is obtained. Application to a flat plate of finite thickness and length is proposed. The steady viscous flow simulated around the motionless plate is compared with the well-known Blasius solution. The computed flutter derivatives are compared both with those obtained from the Theodorsen function in the frame of the thin airfoil theory and with those resulting from previous methods in the frame of the computational approac
Sand transverse dune aerodynamics: 3D coherent flow structures from a computational study
Full text linkThe engineering interest about dune fields is dictated by their interaction with a number of human infrastructures in arid environments. Sand dunes dynamics is dictated by wind and its ability to induce sand erosion, transport and deposition. A deep understanding of dune aerodynamics serves then to ground effective strategies for the protection of human infrastructures from sand, the so-called sand mitigation. Because of their simple geometry and their frequent occurrence in desert area, transverse sand dunes are usually adopted in the literature as a benchmark to investigate dune aerodynamics by means of both computational and experimental approaches, usually in nominal 2D setups. The present study aims at evaluating 3D flow features in the wake of a idealized transverse dune, if any, under different nominal 2D setup conditions by means of computational simulations and to compare the obtained results with experimental measurements available in the literatur
Edge degree-of-sharpness and integral length scale effects on the aerodynamics of a bridge deck
No full textThis paper discusses the sensitivity of the aerodynamic behaviour of a trapezoidalshaped bridge deck cross-section to its lower corner degree-of-sharpness and to the incoming flow turbulence integral length scale in conjunction with low turbulence intensity. Since these features are hard to set and measure in experimental facilities, the aerodynamic behaviour of the body has been investigated through the computational simulation of the flow around it. The results are given in term of force coefficients, Strouhal number, pressure distribution along its surface, and the mean and instantaneous flow patterns. Dramatic changes in the force coefficients and Strouhal number occur following small changes in the parameters' values. These changes have been found to be due to significant modifications in the topological structure of the flow. Special emphasis has been given to the analysis of the separation and reattachment points, the recirculation bubble length, the vortex shedding mechanisms and the wake structures. On the basis of the obtained results, four aerodynamic regimes have been pointed out in analogy with the well-known individual Re number regimes. Some of these regimes have also been recognized on the Sunshine Skyway Bridge cross-section, even when the sharping aerodynamic devices at the lower corners are taken into consideratio
Probabilistic evaluation of the aerodynamic behaviour of a bridge deck
No full textThe study of the probabilistic response of wind-excited structures and their reliability analysis need to take into account for the influence of a large number of uncertain parameters ascribed to meteorological data, structural characteristics and aerodynamic/aeroelastic behaviour. Although the latter one plays a key role in the reliability analysis and it shows high sensitivity to a number of parameters, the probabilistic description of the aerodynamic and aeroelastic forces remains scarce in literature. The present work aims at giving a contribution to the probabilistic evaluation of the aerodynamic behaviour of a bluff body, namely a bare bridge deck with trapezoidal cross section. The lower edge degree of sharpness and the oncoming turbulence length scale are retained as random variables. The computational solution of the resulting Stochastic Navier-Stokes Equations is performed by means of the adaptive form of the Multi-Element generalized Polynomial Chaos. As a result, the stochastic aerodynamic coefficients are described by their approximate probability density functions, which are related in turn to the aerodynamic regimes recognised for the case study
Using delayed detached Eddy simulation to create datasets for data-driven turbulence modeling: A periodic hills with parameterized geometry case
Full text linkDespite the emerging field of data-driven turbulence models, there is a lack of systematic high-fidelity datasets at flow configurations changing continuously with respect to geometrical/physical parameters. In this work, we investigate the possibility of using Delayed Detached Eddy Simulation (DDES) to generate reliable datasets in a significantly cheaper manner compared to the DNS or LES counterparts. To do that, we perform 25 simulations with geometrically-parameterized periodic hills geometries to deal with different hills steepness. We firstly check the accuracy of our results by comparing one simulation with the benchmark case of Xiao et al.. Then, we use such database to train the turbulent viscosity-Vector Basis Neural Network data-driven turbulence model. The latter outperforms the classic k-omega SST RANS model, proving that our generated dataset can be useful for data-driven turbulence modeling and opening the opportunity to exploit DDES to create systematic datasets for data-driven turbulence modeling
- …
