Interaction of a gas-droplet turbulent jet with a cocurrent high-velocity high-temperature gas flow

A mathematical model and a method for calculating a gas-droplet turbulent jet with allowance for velocity nonequilibrium and virtual mass of the condensed phase during turbulent fluctuations and also heat and mass transfer within the three-temperature scheme are developed. Methodical calculations are performed. The results of these calculations are in reasonable agreement with available experimental data. The structure of the gas-droplet jet in a cocurrent high-velocity high-temperature gas flow is studied by numerical methods. The ratio of intensities of heat and mass transfer between the phases and turbulent diffusion transfers of substances is found to be different at the initial, transitional, and basic segments of the jet. This difference is responsible for the nonmonotonic axial distribution of vapor density and the lines of the halved mass flow of the condensed phase. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 85–94, May–June, 2008.     

Heat transfer in a wall jet propagating in a highly turbulent cocurrent flow

Heat transfer in a jet propagating in a cocurrent flow has been studied over wide ranges of the injection ratio (m=U_s/U₀<1 and m>1) and flow turbulence (Tu₀=0.2–25%). It is shown experimentally that for m<1, a 1% increase in turbulence leads to a 1% increase in heat transfer, and the wall adiabatic temperature and the relative heat-transfer function should be taken into account in heat-transfer calculations. For m>1, the flow turbulence does not affect the heat transfer and the heat production can be calculated using the laws typical of jet flows. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 3, pp. 119–125, May–June, 1998.     

Underexpanded wall jet in a cocurrent flow

The flow of a two-dimensional underexpanded wall jet flowing out of a sonic nozzle along a channel wall has been experimentally investigated. The dependence of the dimension of the first barrel of the jet on the underexpansion is obtained. It is shown that the flow of the jet in the channel is associated with a significant axial pressure gradient on the initial interval of the induced cocurrent flow and that this leads to a substantial change in the geometric dimensions of the jet.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 196–199, January–February, 1993.     

Large eddy simulation in a turbulent jet exhausting into a submerged space or a cocurrent flow

Results of large eddy simulations in a subsonic isothermal turbulent jet exhausting from a circular nozzle into a submerged space or a cocurrent flow are presented. The flow is described by space-averaged Navier-Stokes equations and by the RNG model of subgrid scale viscosity. Results computed for different values of the cocurrency parameter are compared with available results of numerical simulations and experimental data. The results obtained are found to agree well with measured data and to confirm the basic laws of variation of gas-dynamic and fluctuating parameters of submerged and cocurrent jets.     

The low Reynolds number turbulent flow and mixing in a confined impinging jet reactor

Turbulent mixing takes an important role in chemical engineering, especially when the chemical reaction is fast compared to the mixing time. In this context a detailed knowledge of the flow field, the distribution of turbulent kinetic energy (TKE) and its dissipation rate is important, as these quantities are used for many mixing models. For this reason we conduct a direct numerical simulation (DNS) of a confined impinging jet reactor (CIJR) at Re = 500 and Sc = 1. The data is compared with particle image velocimetry (PIV) measurements and the basic flow features match between simulation and experiment. The DNS data is analysed and it is shown that the flow is dominated by a stable vortex in the main mixing duct. High intensities of turbulent kinetic energy and dissipation are found in the impingement zone which decrease rapidly towards the exit of the CIJR. In the whole CIJR the turbulence is not in equilibrium. The strong mixing in the impingement zone leads to a rapid development of a monomodal PDF. Due to the special properties of the flow field, a bimodal PDF is generated in cross-sections downstream the impingement zone, that slowly relaxes under relaminarising conditions. The time required for meso-mixing is dominating the overall mixing performance.     

Interaction of plane turbulent jets in a confined space: mean flow characteristics

The present study deals with the experimental investigations of static pressure and mean velocity fields obtained as a result of the interaction of two plane turbulent jets at impingement angles of α equal to 30° and 45°, with an additional central jet in a confined space. The investigation is carried out for the velocity ratios of U _c/U _o=1.0, 2.0 and 3.0, where U _c and U _o are the velocities in the central plane at the exit of the central jet and the outer jets, respectively. The introduction of the central jet alters the various recirculation zones present in the flow field for all the cases considered above. Also, the change in the velocity ratio U _c/U _o has a significant effect on the pressure and mean velocity flow fields. Flow visualisation results are presented which give a better physical insight into the flow field considered. Received: 26 July 1999/Accepted: 14 February 2000     

Interaction between periodic disturbances and a turbulent jet

The results of a numerical and experimental investigation of the interaction between harmonic disturbances and a turbulent jet are presented. On the basis of large eddy simulation it is established that the narrow-band noise of a supersonic jet considerably increases, when the forcing amplitude amounts to thousandths and more of the total pressure of the flow within the nozzle. An analysis of the results of a laboratory experiment on the measurement of the longitudinal velocity spectra in the core of a low-velocity jet shows that the acoustic disturbances generated by a fan inside the nozzle lead to the generation of intense tonal hydrodynamic disturbances in the low-velocity jet.     

Partial-average-based equations of incompressible turbulent flow

This paper presents a detailed study of incompressible turbulent flow based on a newly developed statistical partial average scheme. As the ensemble average is taken on two groups of turbulent fluctuations separately, the partial average scheme is able to capture the first-order statistical moment of the fluctuation field, providing valuable information in addition to what have been known in the past from the conventional Reynolds average. The first-order statistical moment serves as the foundation in formulating theories of orthotropic turbulence and a momentum transfer chain in the modeling of second-order correlation terms, and eventually leads to a complete set of equations of incompressible turbulent flow. Without any empirical coefficients, the same set of the equations is used to simulate statistical mean behaviors and coherent structures of various benchmark turbulent flows. The simulated results are in good agreement with experimental data.     

Wavy flow of a liquid film in the presence of a cocurrent turbulent gas flow

Wavy downflow of viscous liquid films in the presence of a cocurrent turbulent gas flow is analyzed theoretically. The parameters of two-dimensional steady-state traveling waves are calculated for wide ranges of liquid Reynolds number and gas flow velocity. The hydrodynamic characteristics of the liquid flow are computed using the full Navier-Stokes equations. The wavy interface is regarded as a small perturbation, and the equations for the gas are linearized in the vicinity of the main turbulent flow. Various optimal film flow regimes are obtained for the calculated nonlinear waves branching from the plane-parallel flow. It is shown that for high velocities of the cocurrent gas flow, the calculated wave characteristics correspond to those of ripple waves observed in experiments.     

Velocity gradients in a turbulent jet flow

We present a selection of results from experiments on an air turbulent jet flow, which included measurements of all the three velocity components and their nine gradients with the emphasis on the properties of invariant quantities related to velocity gradients (enstrophy, dissipation, enstrophy generation, etc.). This has been achieved by a 21 hot wire probe (5 arrays x 4 wires and a cold wire), appropriate calibration unit and a 3-D calibration procedure [1]. A more detailed account on the results will be published elsewhere.     

Mixing in a confined turbulent impinging jet using planar laser-induced fluorescence

 The non-intrusive Planar Laser-Induced Fluorescence (PLIF) technique was applied to the study of the mixing of a turbulent water jet impinging orthogonally onto a flat surface. A procedure for calibrating the system at each pixel of a CCD camera array was first developed and tested. Post-processing of the PLIF data gave quantitative results of good quality. The mixing at the entrance of the deflection zone was also investigated. Average concentration fields in the centre plane of the jet were calculated and compared with Large Eddy Simulations (LES) and also with data from the literature. Probability density functions, space coefficients of correlation and radial concentration fluctuation profiles were calculated to further quantify the spreading of the jet, both in the free and deflection zones. Inside the deflection region, a slight tendency towards intensified mixing at the outer edge of the jet was found. This was attributed to a deceleration of the fluid which resulted in accelerated diffusion. Received: 11 July 1997 / Accepted: 9 January 1998     

High-order LES modeling of turbulent incompressible flow

This article presents the high-order algorithms that we have developed for large-eddy simulation of incompressible flows, and the results that have been obtained for the 3D turbulent wake of a cylinder at a Reynolds number of $\mathit{Re}=3900$. To cite this article: R. Pasquetti, C. R. Mecanique 333 (2005).     

Interaction of a circular turbulent jet with a flat target

Large eddy simulations are performed for an unsteady flow and heat transfer in the region of interaction of a circular turbulent jet with a normally positioned flat obstacle (target). Space-filtered Navier-Stokes equations are closed by the RNG model of eddy viscosity, which takes into account the curvature of streamlines in the region of flow turning. The computations are performed for different dimensionless distances between the nozzle exit and the target and for different Reynolds numbers. The dependence between the Nusselt number distribution over the target surface and the vortex structure of the jet is analyzed. The local and integral characteristics of the flow are compared with the data of a physical experiment. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 1, pp. 55–67, January–February, 2007.     

Interaction of a submerged turbulent jet with a solid wall

The turbulent layer of a wall jet has been analyzed in many theoretical and experimental studies [1–10]. Most theoretical investigations are based on the simultaneous solution of the equations of the turbulent jet and the boundary layer that forms at the wall. The differences lie in the methods used to correlate the velocity and temperature distributions, as well as in the friction and heat-transfer laws employed. In this article we present a method based on the further development of the idea of conservation of the laws governing wall turbulence with respect to change in boundary conditions.     

Conjugate heat transfer study of incompressible turbulent offset jet flows

In the present case, the conjugate heat transfer involving a turbulent plane offset jet is considered. The bottom wall of the solid block is maintained at an isothermal temperature higher than the jet inlet temperature. The parameters considered are the offset ratio (OR), the conductivity ratio (K), the solid slab thickness (S) and the Prandtl number (Pr). The Reynolds number considered is 15,000 because the flow becomes fully turbulent and then it becomes independent of the Reynolds number. The ranges of parameters considered are: OR = 3, 7 and 11, K = 1–1,000, S = 1–10 and Pr = 0.01–100. High Reynolds number two-equation model (k–ε) has been used for turbulence modeling. Results for the solid–fluid interface temperature, local Nusselt number, local heat flux, average Nusselt number and average heat transfer have been presented and discussed.     

An experimental examination of an impulsively started incompressible turbulent jet

The transient morphology and entrained fluid distribution of an impulsively started turbulent jet are studied in an experiment that examines a jet of dyed water injected into a large water reservoir. The images obtained, using a video recorder, are processed to determine the time-dependent length, tip velocity, and volume of the jet. Abel inversion is used in conjunction with digital images to examine the transient distribution of the ambient fluid entrained into the jet. Results from the analysis also describe the self-similarity of the jet’s flow and entrainment.