Taking a lead from the humpback whale flukes, characterized by a series of bumps that result in a sinusoidal-like leading edge, this paper reports on a three-dimensional numerical study of sinusoidal leading edges on cambered airfoil profiles. The turbulent flow around the cambered airfoil with the sinusoidal leading edge was computed at different angles of attack with the open source solver OpenFOAM, using two different eddy viscosity models integrated to the wall. The reported research focused on the effects of the modified leading edge in terms of lift-to-drag performance and the influence of camber on such parameters. For these reasons a comparison with a symmetric airfoil is provided. The research was primarily concerned with the elucidation of the fluid flow mechanisms induced by the bumps and the impact of those mechanisms on airfoil performance, on both symmetric and cambered profiles. The bumps on the leading edge influenced the aerodynamic performance of the airfoil, and the lift curves were found to feature an early recovery in post-stall for the symmetric profile with an additional gain in lift for the cambered profile. The bumps drove the fluid dynamic on the suction side of the airfoil, which in turn resulted in the capability to control the separation at the trailing edge in coincidence with the peak of the sinusoid at the leading edge

No abstract

The Y Zβ shock-capturing technique, which is residual-based, was introduced in conjunction with the Streamline-Upwind/Petrov-Galerkin (SUPG) formulation of compressible flows in conservation variables. It was later also combined with the variable subgrid scale (V-SGS) formulation of compressible flows in conservation variables and successfully tested on 2D and 3D computation of inviscid flows with shocks. In this paper we extend that combined method to inviscid flow computations with particle tracking and particle-shock interaction. Particles are tracked individually, assuming one-way dependence between the particle dynamics and the flow. We present two steady-state test computations with particle-shock interaction, one in 2D and one in 3D, and show that the overall method is effective in particle tracking and particle-shock interaction analysis in compressible flows.

No abstract

In this paper we discuss a computational method focused on the prediction of unsteady aerodynamics, adequate for industrial turbomachinery. Here we focus on a single rotor device selected from a new family of large tunnel ventilation axial flow fans. The flow field in the fan was simulated using the open source code OPENFOAM, with a large-eddy simulation (LES) approach. The sub-grid scale (SGS) closure relied on a one-equation model, that requires us to solve a differential transport equation for the modeled SGS turbulent kinetic energy. The use of such closure was here considered as a remedial strategy in LES of high-Reynolds industrial flows, being able to tackle the otherwise insufficient resolution of turbulence spectrum. The results show that LES of the fan allows to predict the pressure rise capability of the fan and to reproduce the most relevant flow features, such as three-dimensional separation and secondary flows

This paper reports on the application of unsteady Reynolds averaged Navier-Stokes (U-RANS) and hybrid large-eddy simulation (LES)/Reynolds averaged Navier-Stokes (RANS) methods to predict flows in compressor cascades using an affordable computational mesh. Both approaches use the zeta-f elliptic relaxation eddy-viscosity model, which for U-RANS prevails throughout the flow, whereas for the hybrid the U-RANS is active only in the near-wall region, coupled with the dynamic LES in the rest of the flow. In this 'seamless' coupling the dissipation rate in the k-equation is multiplied by a grid-detection function in terms of the ratio of the RANS and LES length scales. The potential of both approaches was tested in several benchmark flows showing satisfactory agreement with the available experimental results. The flow pattern through the tip clearance in a low-speed linear cascade shows close similarity with experimental evidence, indicating that both approaches can reproduce qualitatively the tip leakage and tip separation vortices with a relatively coarse computational mesh. The hybrid method, however, showed to be superior in capturing the evolution of vortical structures and related unsteadiness in the hub and wake regions

Flow and heat transfer through a matrix of 8 x 8 cylindrical adiabatic rods in a staggered arrangement and connecting two non-isothermal walls of a plane channel have been studied with LES using an in-house unstructured finite-volume computational code. The results for the mean flow properties agree well with the experimental data of Ames et al. [1]. The instantaneous velocity and temperature fields, vortical structures and their wall-signatures, unsteadiness and three-dimensionality -none of which is accessible to experiments, have been analyzed to gain a better insight into the flow dynamics and its effects on the local and averaged heat transfer.

No abstract