Mean Flow and Thermal Characteristics of a Turbulent Dual Jet Consisting of a Plane Wall Jet and a Parallel Offset Jet

Abstract

The standard high-Reynolds number two-equation k À e model is used to study the flow and thermal characteristics of a dual jet consisting of a plain wall turbulent jet and a parallel turbulent offset jet (hereafter, dual jet). The flow and thermal characteristics are presented in the form of streamlines, mean velocity vector, turbulent kinetic energy, dissipation of turbulent energy, Reynolds stresses, and isothermal contour plots. The variation in local heat flux and local Nusselt number on the bottom wall is also presented. The finite-volumemethod-based SIMPLE algorithm is utilized for understanding the complex nature of flow arising due to a dual jet. The convective flux is discretized using the power-law upwind scheme, while the diffusive term is discretized using the central difference scheme. To study the effect of offset ratio, which is defined as the ratio of height of the jet from the horizontal wall to the width of the jet (nozzle), it is varied between 3 and 15 at an interval of 2. It is noted that the presence of a wall jet in addition to the parallel offset jet has a significant effect on flow and thermal characteristics.

Enhancement of heat transfer using turbulent wall jet

“…The decay of normalized maximum velocity (Umax) in the streamwise direction is shown in Figure 4(b) for various amplitudes (0.1,0.3,0.5 and 0.7) of the sinusoidal wavy wall surface. The present results of wavy surface are also compared with the numerical results of Kumar, 41 Vishnuvardhanarao and Das, 42 Pramanik and Das 2 and Bannyassady and Piomelli 43 and experimental results of Lai and Lu 44 and Eriksson et al. 37 of plane wall surface.…”

“…The decay of normalized maximum velocity ðU max Þ in the streamwise direction is shown in Figure 4(b) for various amplitudes (0:1, 0:3, 0:5 and 0.7) of the sinusoidal wavy wall surface. The present results of wavy surface are also compared with the numerical results of Kumar, 41 Vishnuvardhanarao and Das, 42 Pramanik and Das 2 and Bannyassady and Piomelli 43 and experimental results of Lai and Lu 44 and Eriksson et al 37 of plane wall surface. The maximum velocity ðU max Þ of Vishnuvardhanarao and Das 42 and Pramanik and Das 2 remains almost constant till the potential core is consumed; the potential core is consumed near the axial location of X ¼ 10 and X ¼ 6 respectively.…”

“…Kumar 41 used k-ɛ model while Dejoan and Leschziner 45 used LES to calculate U max for the plane wall surface. Kumar 41 and Dejoan and Leschziner 45 noticed that U max remains constant till the potential core is completely consumed up to an axial location of X = 6. Thereafter, the U max decreases in the downstream direction.…”

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

“…Even though similarity solution is achieved for all the cases, the trend is entirely different than the case of a plane wall. 40,41,45 The similarity solution at the crest is different than at the trough. Moreover, the similarity solution is even different for the case of A = 0.7 (see Figure 15(e) and (f)).…”

“…The minimum value of ɛn is noticed in the recirculation region and it decreases continuously along the flow direction. Kumar 41 calculated the maximum value of dissipation rate (ɛmax) of an offset jet ( OR = 7.0) for the plane wall as 0.039, while Pramanik and Das 43 noticed the maximum value of ɛ max of offset jet ( OR = 6.5) for inclined plane wall as 0.065. When the wavy surface is used, it is found that the value of ɛ max is located above the nozzle and it decreases as the amplitude of the wavy surface increases.…”