Analysis of Flow Characteristics of Turbulent Plane Jets Based on Velocity and Scalar Fields Using DNS

Abstract

Turbulent plane jets are prototypical free shear flows on which fundamental research can expand the overall understanding of turbulent flows. In this study, flow characteristics of the turbulent plane jets are studied by means of direct numerical simulation (DNS) based on the finite difference method. The effects of the initial conditions at the jet exit (i.e. Reynolds number and velocity profile) on the spatial development of velocity and scalar fields are mainly investigated. Meanwhile the instantaneous coherent structures, based on the-criterion and the local minimum of pressure, are presented. The results suggest that the plane jet flow with the higher Re (= ⁄ : is the bulk mean velocity at the jet exit, is the slot width, and ν is the kinematic viscosity) and the parabola velocity profile at the jet exit will correspond to the shorter potential core, furthermore, the lower Re and the parabola velocity profile will strengthen the decay of the mean field in the process of flow transition to full turbulence. The flow self-similarity will be achieved at shorter streamwise distance from the jet exit for the higher Re and the parabola velocity profile at the jet exit. Moreover, the dependency of coherent structures on the initial Reynolds number is remarkable, especially in the flow development region, but the change of initial velocity profile at the jet exit hardly acts on the scale of coherent structures. It is also observed that the scalar field is more sensitive to changes of initial conditions than the velocity field.

Characteristics of small-scale shear layers in a temporally evolving turbulent planar jet

“…Wu et al. (2013) tested top-hat and parabolic profiles of the mean inflow velocity in DNS of a spatially evolving planar jet, and found that the evolution of velocity statistics is different for these profiles. The turbulent intensity defined as at the nozzle exit was also different among experiments and simulations.…”

Influence of Reynolds number on coherent structure, flow transition, and evolution of the plane jet

“…Uniform grids are set in the streamwise and spanwise direction. Non-uniform grids are set in the lateral direction, where the finer grids are set near the jet center, and the change of grid scale follows a hyperbolic tangent function, as used in our previous study (Wu et al, 2013).…”

“…In our previous publication (Wu et al, 2013), the Reynolds number dependency was proved important in the evolution of the plane jet. By the analysis of the mean and turbulent data of streamwise velocity and scalar, it is discovered that a large Reynolds number at the jet exit will assist the achievement of self-similarity and the development of turbulence.…”

“…Regarding another important study method for fluid dynamics, numerical simulation has been used to investigate the plane jet since the temporal simulation carried out by Comte et al (1989). After that, Dai et al (1994), Stanley and Sarkar (1997), Stanley et al (2002), Klein et al (2003), Liu et al (2008), Wu et al (2013), and others carried out the numerical simulation of plane jets separately.…”

Investigation of the influence of co-flow velocity ratio on a compressible plane jet exhausting into parallel streams

“…Sandberg et al [29] computed two-dimensional compressible pipe flow into a co-flow with direct numerical simulation and demonstrated self-preserving behavior of turbulence statistics at nozzle exit. Wu et al [23] analyzed the flow parameters of plane jet based on velocity and scalar fields with direct numerical simulation. Sabra Habli et al [33] showed the effect of the co-flow velocity ratio on two-dimensional turbulent plane jet in co-flow environment using RANS simulation.…”