A laminar boundary layer separates in a region of adverse pressure gradient, undergoes transition, and finally the turbulent boundary layer reattaches, forming a laminar separation bubble (LSB). Laminar-turbulent transition within such a LSB is investigated by means of Laser-Doppler-Anemometry (LDA), Particle Image Velocimetry (mono PIV and stereoscopic PIV (SPIV)) and direct numerical simulati...

We propose a method for building a statistical model for the structural uncertainties in the k − ω turbulence model. An inverse RANS problem is solved for a collection of randomly generated geometries to determine the turbulent viscosity that produces the flow field closest to that predicted by direct numerical simulation (DNS). A statistical model of the uncertainty in the turbulent viscosity ...

The ability of three different crystal plasticity finite element models to predict deformation textures in face-centered cubic metals observed in experiments is assessed. These methods are: (i) Taylor averaging, in which the interactions of the grains are considered in a homogenized manner; (ii) low-resolution simulation (LRS), in which grain interactions are considered explicitly albeit with l...

NUMERICAL SIMULA nON OF THE AERODYNAMIC PERFORMANCE OF AN H-ROTOR YanChen August 1 st, 2011 Vertical axis wind turbines (VAWTs) are devices to convert wind energy into electricity. Unlike horizontal axis wind turbines (HA WT) where the main rotor shaft is set horizontally, VAWTs use vertical rotor shaft. Unlike HAWTs, VAWTs can be effectively used in urban environment where flow is characterize...

Direct numerical simulation (DNS) is performed to examine laminar to turbulent transition due to high-frequency secondary instability of stationary crossflow vortices in a subsonic swept-wing boundary layer for a realistic natural-laminar-flow airfoil configuration. The secondary instability is introduced via inflow forcing derived from a two-dimensional, partial-differential-equation based eig...

A direct search method in combination with a DNS/LES numerical approach is applied to optimize the control of the flow around a circular cylinder. The objective is the minimization of the drag coefficient and control is achieved via zero net mass flux actuators. The optimization process has been first evaluated and validated at Reynolds number 500 and then the more demanding flow at Reynolds nu...

We develop a model for second order statistics of turbulent channel flow using an associated linear stochastically forced input-output system. The correlation operator of the velocity fields is computed by solving the appropriate Lyapunov equations of a Galerkin approximation of the original system. We use a variety of excitation force correlations and show the dependence of the velocity fields...

Proper orthogonal decomposition (POD) is applied to the direct numerical simulation (DNS) of a turbulent boundary layer performed by Wu & Moin (2010), and the resulting POD modes of various scales are examined. The modes include structures resembling those observed in instantaneous flow fields, such as large-scale motions of streamwise velocity with ramp-like wall-normal growth. Other modes cor...

In this paper we present a new strategy to model the subgrid-scale scalar flux in three-dimensional turbulent incompressible flow using physics-informed neural networks (NNs). When trained from direct numerical simulation (DNS) data, state-of-the-art networks, such as convolutional may not preserve well known physical priors, which turn question their application real case-studies. To address i...

Statistical equations for inertial particle transport in turbulent boundary layers are usually closed using the quasi-Normal approximation (QNA), but this leads to large errors when inertia is significant. Here we develop a new closure based on an asymptotic solution exact equations, referred as ACA. Results show that ACA far better agreement with direct numerical simulation (DNS) data than QNA.