Validation of large eddy simulation of flow behind a circular cylinder

Abstract

The flow in the wake behind a circular cylinder in a cross-flow at Reynolds number of 4815 was studied both experimentally and via mathematical modeling. The mathematical model was performed as a Large Eddy Simulation (LES), while the experiments were carried out using the time-resolved variant of the Particle Image Velocimetry (PIV) method. Both the simulation and experiment took into account the dynamical aspects of the studied phenomenon, which enabled a detailed validation of the mathematical model. The overall statistical properties of the simulated flow were validated via comparing the time-averaged measured and computed velocity and vorticity fields. To validate the dynamical behavior, the velocity spectra were examined first. Next, the Proper Orthogonal Decomposition (POD) of the spatio-temporal velocity data was performed on both the experimental and numerical data and a comparison of the obtained energetic modes was carried out. All the performed validations have shown a satisfactory agreement between the simulation and the experiment.

Convergence of POD Modes for Cylinder Wake Flow

“…The second and third meshes are constructed with the mesh cell size 2 ∆, and 4 ∆, respectively, and the velocity is interpolated during preprocessing. Note that the cell size 4 ∆ (mesh in the first row in Figure 4) conforms to the experimental PIV resolution used in [7].…”

“…A numerical simulation of the cross flow around a circular cylinder was performed utilizing the OpenFOAM open-source CFD library [8], which is based on the finite volume method (FVM). The model itself and its validation on experimental data are described in detail in [7]. The fluid density, ρ, fluctuations are neglected, and the flow is assumed to be governed by the Navier-Stokes equations for an incompressible and isothermal flow of a Newtonian fluid,…”

“…The geometry of the model is inspired by an experimental device, which is significantly larger than the region of interest behind the cylinder, see [7]. To efficiently handle flow in the entire spatial computational domain, we employ a hybrid LES-RANS turbulence model introduced by Strelets [9] and known as the detached eddy simulation (DES), which utilizes a single turbulence model serving as SGS model in regions with high grid resolution and as an (U)RANS model in the remainder of the computational domain.…”

“…Moreover, note that although the wall functions are prescribed for the turbulence variables (k and ω) at the test section walls and cylinder, the mesh resolution 62 Prague, February 21-23, 2024 _______________________________________________________________________ is high enough so they are effectively turned off for most of the test-section and affect the flow solution only downstream from the region of interest. For additional information on the full CFD model geometry, used computational mesh, and validation on PIV experimental data, the reader is referred to our previous work [7].…”

“…In this work, we focus on POD analysis of flow field data obtained for a crossflow around a circular cylinder at Reynolds number of 4815. We build on our previous work [7], where the computational fluid dynamics (CFD) model of this case was presented and validated against the particle image velocimetry (PIV) experiment. Here, we leverage the available CFD results, for which we further extended the sampling interval T , and attempt to evaluate the discrete POD convergence towards time-continuous results.…”