The flow field characteristics of a two-dimensional wall-attaching offset jet are experimentally investigated in comparison with a turbulent plane wall jet. And numerical computations are also conducted variants of k-ε turbulence models.
In the experimental investigation, even with the strong influence during its initial development by the suction pressure field in the recirculation bubble at the lower corner, it is found that there is close similarity between the wall-attaching offset jet in the wall jet region and the plane wall jet. Especially, the maximum velocity decay and the upper jet spread along the maximum velocity line are virtually the same as those of the plane wall jet. The mean velocity profile of the wall-attaching offset jet attains similarity rather fast after the jet impingement onto the lower plate. The development of the turbulent component intensities and the Reynolds shear stress are also compared between the two jets with the similarity scales. In addition to these, the higher order turbulent quantities are also represented. It can be seen that the large scale eddies formed in the pre-attachment region affect to the flow field development in the impingement region. It is interesting to note that the kurtosis distribution in the wall jet region mainly has the Gaussian value of 3.0.
In the computational study, three turbulence models (standard k-ε, Leschziner and Rodi's and Park's model) are tested and two different computational scheme are used. By comparing the computational results with the experimental data, it is found that the modified models give better overall prediction accuracy under the elimination of the numerical diffusion by using the skew-upwind scheme. The numerical scheme is found to have more prounounced effect on the accuracy of the computation than the turbulence models for this kind of flows.
