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Journal ArticleDOI

Interaction between particle-laden underexpanded twin supersonic jets

01 Sep 2010-Vol. 224, Iss: 9, pp 1005-1025
TL;DR: In this article, the effects of particle-laden twin-round jets operating in underexpanded mode, with special emphasis on the effect of particles on jet flow expansion were analyzed.
Abstract: This paper presents numerical results on the near-field interactions of particle-laden twin supersonic jets operating in underexpanded mode, with special emphasis on the effects of particles on jet flow expansion. Although plane jets have been considered primarily, a few cases of twin round jets have also been simulated for the sake of comparison. Three turbulence models (Spalart—Allmaras, k—ɛ (realizable), and k—ω (sst)) have been considered for incorporating turbulent interaction effects in two-phase supersonic jets. In general, the k—ω (sst) model gives better predictions in the reverse flow as well as in the shock regions. The recirculatory flow is enhanced at high underexpansion (UE) ratios, and the size and strength of the recirculation region are much smaller for twin round jets than those for plane jets. In particle-laden jets, small particles (corresponding to Stokes number less than 0.05) are entrained in the recirculation zone, whereas particles of larger size are not trapped. With larg...
Citations
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Journal ArticleDOI
TL;DR: In this paper, a computational fluid dynamics (CFD) description of the spray flame originating from a twin-fluid atomizer and coaxial diffusion burner was combined with droplet and nanoparticle dynamics.

86 citations

Journal ArticleDOI
TL;DR: In this article, the authors present an overview on progress and perspectives of the jet impingement research for rocket launching and discuss the interaction of impinging jets with multiphase flows.

31 citations

Journal ArticleDOI
TL;DR: In this paper , the effects of different parameters such as eddy viscosity and pressure ratio on the behavior of the jet are studied, and the results are validated using available experimental data.
Abstract: Supersonic turbulent high-pressure jet flows, which are discharging in low-pressure quiescent ambient, are recognized as imperfectly expanded turbulent jet. Steady-state imperfectly expanded jet flow has been already studied analytically; however, the transient flow has not been thoroughly studied. In the present study, the transient imperfectly expanded jet flow with focus on fuel spray in combustion is investigated analytically employing two-step separation of variables method and Fourier-Bessel expansion. The results are validated using available experimental data. The effects of different parameters such as eddy viscosity and pressure ratio on the behavior of the jet are studied. Results show that increasing the eddy viscosity decreases the velocity magnitude and required time to reach fully developed jet. Increasing the pressure ratio almost linearly increases the required time to reach steady state. The density distribution which affects the combustion performance is reported for different axial and radial positions. In the transient region, tip penetration is obtained and validated with the experimental results in the literature, and the velocity profile at different times is presented. The simplicity and accuracy are key advantages of the developed method compared with the experimental and numerical methods. The analytical method proposed in the present research helps to understand the behavior of jet flows from transient to steady state condition without using expensive and time-consuming numerical or experimental techniques.
References
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Journal ArticleDOI
TL;DR: In this article, the authors describe a theoretical investigation into the response of a spherical particle to a one-dimensional fluid flow, and the motion of the spherical particle in a uniform 2D fluid flow about a circular cylinder.
Abstract: This paper describes a theoretical investigation into (i) the response of a spherical particle to a one-dimensional fluid flow, (ii) the motion of a spherical particle in a uniform two-dimensional fluid flow about a circular cylinder and (iii) the motion of a particle about a lifting aerofoil section. In all three cases the drag of the particle is allowed to vary with (instantaneous) Reynolds number by using an analytical approximation to the standard experimental drag-Reynolds-number relationship for spherical particles.

2,401 citations

Journal ArticleDOI
TL;DR: It is proposed that, in moderate Mach number homogeneous turbulence, the compressible component of the turbulence is in quasi-equilibrium with respect to the incompressible turbulence.
Abstract: It is shown that the dilatational terms that need to be modeled in compressible turbulence include not only the pressure-dilatation term but also another term - the compressible dissipation. The nature of these dilatational terms in homogeneous turbulence is explored by asymptotic analysis of the compressible Navier-Stokes equations. A non-dimensional parameter which characterizes some compressible effects in moderate Mach number, homogeneous turbulence is identified. Direct numerical simulations (DNS) of isotropic, compressible turbulence are performed, and their results are found to be in agreement with the theoretical analysis. A model for the compressible dissipation is proposed; the model is based on the asymptotic analysis and the direct numerical simulations. This model is calibrated with reference to the DNS results regarding the influence of compressibility on the decay rate of isotropic turbulence. An application of the proposed model to the compressible mixing layer has shown that the model is able to predict the dramatically reduced growth rate of the compressible mixing layer.

735 citations

Journal ArticleDOI
TL;DR: In this paper, the mean and fluctuating velocities of both phases as well as particle mass fluxes were completed in turbulent, particle-laden jets containing monodisperse particles with well-defined initial and boundary conditions.
Abstract: Measurements of mean and fluctuating velocities of both phases as well as particle mass fluxes were completed in turbulent, particle-laden jets containing monodisperse particles with well-defined initial and boundary conditions. The new measurements were used to evaluate a stochastic separated flow model of the process which treated effects of interphase slip and turbulent dispersion using random-walk computations for particle motion. The continuous phase was treated using a modified k-epsilon model allowing for direct contributions of interphase transport to both mean and turbulence properties. The model performed reasonably well over the new data base, with all empirical parameters fixed from earlier work. In contrast, simplified models ignoring either interphase slip or turbulent dispersion yielded poor agreement with the measurements.

237 citations

Journal ArticleDOI
TL;DR: In this article, the authors developed a linear shock cell model for non-axisymmetric supersonic jets from convergent-divergent nozzles operating at off-design conditions, where the mixing layer of the jet is approximated by a vortex sheet.

166 citations

Journal ArticleDOI
TL;DR: In this paper, it is suggested that the K-e model, together with the Pope and Sarkar terms for nonplanar and high convective Mach number flow corrections, does contain the essential ingredients of turbulence physics for adequate jet mean flow prediction.
Abstract: It is known that the standard K-e model does not provide an accurate prediction of the mean flow of turbulent jets. This is so even when the Pope and Sarkar correction terms are included. It is suggested that the K-e model, together with the Pope and Sarkar terms for nonplanar and high convective Mach number flow corrections, does contain the essential ingredients of turbulence physics for adequate jet mean flow prediction. The problem lies in the standard coefficients that were calibrated by using boundary-layer and low Mach number plane mixing layer data. By replacing these coefficients by a new set of empirical coefficients, it is demonstrated that the model can offer good predictions of axisymmetric, rectangular, and elliptic jet mean flows over the Mach number range of 0.4-2.0 and jet total temperature to ambient temperature ratio of 1.0-4.0. The present result conveys the message that it is possible that there is no universally applicable turbulence model. The reason is that although the characteristics and dynamics of fine-scale turbulence may be the same for all turbulent flows, the large turbulence structures, having dimensions comparable to the local length scale of the flow, are significantly influenced by local boundary conditions and geometry. Thus overall turbulence dynamics are somewhat problem type dependent.

150 citations