Momentum Flux in Plane, Parallel Jets

Abstract

The evolution of the streamwise momentum flux for two turbulent, plane, parallel jets discharging through slots in a direction normal to a wall was studied both numerically and experimentally. The numerical results, obtained by solving the Reynolds-averaged Navier-Stokes equations employing a standard k−ε turbulence model, predicted to within experimental error measured integrals of the momentum flux downstream of the merge point for jet spacing S/d=5. Integration of the streamwise component of the Reynolds-averaged Navier-Stokes equations over a control volume results in an integral constant that was evaluated numerically for jet spacings S/d=3, 5, 7, 9, and 11, and for different levels of turbulence kinetic energy and dissipation rate at the jet inlet boundaries. Results revealed that the integral constant is decreased as the jet spacing increases, and is also decreased as jet entrainment rates are increased due to higher levels of inlet turbulence kinetic energy, or alternatively, decreased levels of dissipation rate. Streamwise distance to the merge point was also found to decrease for increased levels of turbulence kinetic energy or decreased levels of dissipation rate at the jet inlet.

Joint probabilities and mixing of isolated scalars emitted from parallel jets

“…Interactions between multiple jets are a natural extension of this fundamental problem and are of interest for mixing studies in the areas of combustion, chemical mixing, pollutant transport and environmental processes. Velocity fields for multiple jets have been studied for inclined jets (Becker & Booth 1975;Wang, Lin & Sheu 1993;Villafruela, Castro & Parra 2008), coaxial jets (Champagne & Wygnanski 1971) and parallel jets both experimentally (Yuu, Shimoda & Jotaki 1979;Pani & Dash 1983;Lin & Sheu 1990;Anderson & Spall 2001;Fujisawa, Nakamura & Srinivas 2004;Bunderson & Smith 2005) and numerically (Spall, Anderson & Allen 2004;Zarruk & Cowen 2008).…”

Fluid Flow Characteristics of a Co-Flow Fluidic Slot Jet Thrust Augmentation Propulsion System

“…This process takes place in a region of the flow known as the shear layer which is developed due to the pressure differences and turbulence seen in the primary jet flows compared to the secondary entrainment flows. Spall has found that the merge point of the jet velocities moves downstream when the distance between the jets is increased and when the turbulent kinetic energy leaving the jets is increased [1].Tanaka also explains that increasing the spacing between the jets leads to a more dispersed distribution of turbulent intensities, an increase in half width distance from the jet centerline, and a sharper max axial velocity decrease in the combined flow region [15] [16].…”

“…Turbulent flow fields have become a widely studied topic due to its passive ability to provide many different benefits to a wide range of applications. Heating and air condition systems such as boilers and other industrial devices can see improved efficiencies through turbulent flows inducing higher energy transfer in the corresponding shear layers [1]. Turbulence between two substances create a turbulent mixing layer which can be used to increase combustion efficiency and the mixing rates between chemicals [2].…”

Computational study of periodically unsteady interaction between a wall jet and an offset jet for various velocity ratios

“…The two jets combine at the combined point, develop as a single jet in the combined region, and eventually display the characteristics of a free jet at a far downstream position. Miller and Comings [35], Tanaka [51] and [52], Ko and Lau [25], Elbanna and Sabbagh [12], Lin and Sheu [33] and Lin and Sheu [34], Nasr and Lai [39], Lai and Nasr [28], Anderson and Spall [4], Anderson et al [3], Fujisawa et al [16], Spall et al [50] and Bunderson and Smith [8] have thoroughly investigated the fundamental characteristics of two plane parallel jets.…”