Abstract
In the present paper, direct numerical simulation (DNS) and particle image velocimetry (PIV) have been applied complementarily in order to generate a database of near-wall turbulence properties of a highly turbulent jet impinging on a solid surface under different inclination angles. Thereby, the main focus is placed on an impingement angle of 45 ∘ , since it represents a good generic benchmark test case for a wide range of technical fluid flow applications. This specific configuration features very complex flow properties including the presence of a stagnation point, development of the shear boundary layer and strong streamline curvature. In particular, this database includes near-wall turbulence statistics along with mean and rms velocities, budget terms in the turbulent kinetic energy equation, anisotropy invariant maps, turbulent length/time scales and near-wall shear stresses. These properties are useful for the validation of near-wall modeling approaches in the context of Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulations (LES). From this study, in which further impingement angles ( 0 ∘ , 90 ∘ ) have been considered in the experiments only, it turns out that (1) the production of turbulent kinetic energy appears negative at the stagnation point for an impingement angle other than 0 ∘ and is balanced predominantly by pressure-related diffusion, (2) quasi-coherent thin streaks with large characteristic time scales appear at the stagnation region, while the organization of the flow is predominantly toroidal further downstream, and (3) near-wall shear stresses are low at the stagnation region and intense in regions where the direction of the flow changes suddenly.
Highlights
Impinging jets are used in a variety of engineering applications as they enable localized heat and mass transfer, e.g., cooling of electronic components, quenching of metals and glass, cooling of turbine-blades or drying of paper and other materials
This study revealed that the turbulence is almost in an axisymmetric state at the stagnation point and that negative production of turbulent kinetic energy takes place in the vicinity of the wall, which is compensated by the pressure diffusion
The 0◦ -configuration resembles a boundary layer flow, while the stagnation region and wall-jets are predominant in the 90◦ -configuration
Summary
Impinging jets are used in a variety of engineering applications as they enable localized heat and mass transfer, e.g., cooling of electronic components, quenching of metals and glass, cooling of turbine-blades or drying of paper and other materials. Characterized by a strong wall/flow interaction process, impinging jets feature very complex flow properties including the presence of a stagnation point, shear boundary layer development in the free jet region and strong streamline curvature In this respect, several experimental and direct numerical simulations (DNS) studies have been carried out in the past (e.g., [5,6,7,8,9,10,11,12,13,14,15,16,17]) in order to provide a deeper understanding about the underlying physical effects in such flows. This specific jet configuration serves as a model geometry for a wide range of engineering application and is often used to validate turbulence models in the context of Reynolds-averaged Navier–Stokes (RANS) [18,19,20] and large-eddy simulations (LES) [21,22,23]
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