Numerical prediction of a turbulent curved wake and comparison with experimental data

Abstract

SUMMARYNumerical studies of the curved wake of a NACA 0012 airfoil of chord length 0:150 m are presented. The airfoil is placed in air at 10 m=s in the straight section of a duct of 0:457 m × 0:457 m cross-section followed by a 90• bend with a mean radius-to-height ratio of 1.17. The trailing edge is located at one chord length upstream of the bend entry plane. The authors' own measurements are used to deÿne the boundary conditions and for comparison with the predicted results.The numerical models are based on the time-averaged, three-dimensional conservation equations of uid ow, incorporating the k-, RNG k-, realizable k-and the Reynolds stress turbulence models. The results show that the models are capable of predicting the e ects of curvature on the wake development. However, quantitative di erences between prediction and experiment exist. The results obtained using the Reynolds stress model show better agreement with the experimental data, compared with the k-based models, but not consistently for all parameters. There are also better predictions by the RNG k-and realizable k-models compared with the standard k-model. The predicted results using the RNG k-are closer to experimental data than the realizable k-.

A large eddy simulation of an airfoil turbulent wake subjected to streamwise curvature

“…In Figure 5(b) in comparison to RSM the existence of a double peak in the profile is better depicted by the simulations, but the turbulence intensity is considerably overpredicted on the inner side for the dynamic SGS models in coarseLES. This is believed to stem from the overprediction of turbulence on the upper surface of the airfoil, which was also stated in [2]. The results indicate that the boundary layer predictions on the airfoil have worsened in the case of coarseLES leading to larger differences in the curved wake.…”

“…Experimental investigations of the curved wake of an airfoil [1] indicated enhancement of turbulence quantities on the inner-side wake and their suppression on the outer side. Steady-state Reynolds-averaged Navier-Stokes (RANS) computations [2] of the same flow field as in [1] with RSM qualitatively depicted the correct effects of curvature on 1234 E. FARSIMADAN AND M. R. MOKHTARZADEH-DEHGHAN turbulence. However, clear discrepancies were evident in the quantitative comparison of wake profiles and in regions where separation occurred.…”

“…This figure also presents new experimental data in the wake. The previous studies [1,2] showed that, relative to the duct centreline, the wake is shifted towards the convex wall at stations 2 and 3, and then towards the concave wall at stations 4 and 5. This was confirmed by the present simulations.…”

“…The outlet is placed 5.0H downstream of station 4, where H is the cross-sectional duct height (H = 0.457 m). In LES, the coarse spanwise resolution in the grid of [2] was considered to affect the boundary layer growth and the wake development. In response to this a refined grid was set up with a spanwise segment of the tunnel equal to 0.5c, with periodic conditions defined in this direction.…”

“…The majority of the simulations were conducted using the grid of [2], the results of which are referred to as coarseLES. This was in line with our initial aim to assess the degree of improvement, if any, which may be achieved using LES.…”