Numerical study on mean flow field of turbulent dual offset jet

A numerical investigation on the mean flow and turbulence characteristics of dual offset jet for various separation distances between the two jets with a fixed offset height of the lower jet from the bottom wall is reported in this study. The numerical simulations have been performed by solving the Reynolds-averaged Navier-Stokes equations (RANS) with two-equation standard [Formula: see text] turbulence model. The Reynolds number based on the jet width and the inlet turbulence intensity are considered as 15,000 and 5%, respectively. The computational results for the mean flow reveal that after issuing from the nozzles, the adjacent shear layers of the offset jets meet together at the merging point and then the merged jets reattaches on the bottom wall at the reattachment point before they combine together at the combined point forming a single jet flow. In the far downstream, the flow field behaves like a classical single wall jet flow. The self-similarity of mean flow field is achieved at far down stream of combined point. An increase in separation distance between the two jets [Formula: see text] results in a decrease in magnitude of the streamwise maximum velocity of the combined jet but with same rate of decay. The converging region of the jets has depicted considerable growth of turbulence as the jet centrelines bend towards the merging point. According to the mean flow results, the distances of the reattachment point and the combined point from the nozzle exit gradually increase with the progressive increase in separation distance between the two jets within the range d/ w = 3–8.

Numerical investigation of turbulent offset jet flow over a moving flat plate using low-Reynolds number turbulence model

The present study reports the numerical simulation of turbulent plane offset jet flow over a moving plate. The effect of plate velocity on various flow characteristics are discussed in detail including the special case of a stationary plate. For turbulence closure, low-Reynolds number (LRN) model proposed by Yang and Shih (YS) is applied because it is computationally robust and reported to perform well in many complex flow situations. The computations have been carried out with a Reynolds number of 15000 for various offset ratios (OR=3, 7 and 11) for plate to jet velocity ratios in the range 0-2. Finite volume method with a staggered grid arrangement has been used to solve the transport equations. The application of LRN model along with integration to wall approach enables to capture one closed loop of Moffatt vortex near the left corner of the wall for the stationary plate case. The spreading of jet has been found to reduce with increase in the plate velocity. The jet half-width lies very close to the wall for the plate to jet velocity 1.5 and 2. For two extreme limits of plate velocity i.e. Uplate = 0 and 2, the nearly self-similar profiles are observed at different axial locations in the wall jet region. Also, the flow is observed to exhibit nearly self-similar behavior when velocity profiles are plotted for various offset ratios at a given axial location in the wall jet region for Uplate = 0 and 2.

Fluid flow analysis of a turbulent offset jet impinging on a wavy wall surface

The fluid flow characteristics of a turbulent offset jet impinging on a wavy wall surface has been investigated numerically. Two-dimensional Reynolds-averaged Navier–Stokes (RANS) equations are solved by the finite volume method. In the governing differential equations, the convective and diffusive terms are discretized by the power law upwind scheme and second-order central difference, respectively. The semi-implicit method for pressure linked equation algorithm is utilized to link the pressure to the velocity. The offset ratio is set to 7.0 and the Reynolds number is fixed to 15,000. The width of the jet is taken as the characteristic length. The amplitude of the wavy wall surface is varied from 0.1 to 0.7 with an interval of 0.1 and the number of cycle is fixed to 10. The results of fluid flow and turbulent characteristics of the offset jet are presented in the form of contours of streamline, velocity vector, turbulent kinetic energy, dissipation rate, pressure, and Reynolds shear stress. The variation in integral constant of momentum flux, wall shear stress, and pressure along the wall is presented and also compared. The decay in the maximum streamwise velocity in the downstream direction and jet half-width along the streamwise direction are also presented and discussed. The wavy surface introduces some remarkable features, which are not present in a normal plane wall case. These features have been discussed in detail.