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Author: Cristale D. Garnica Vallejo Publisher: ISBN: Category : Aerospace engineering Languages : en Pages : 236
Book Description
"Understanding wall-jet-induced turbulence and mixing is an important challenge in modern engineering, as drag reduction and mixing enhancement are attainable by modifying the flow development. Simulations are performed to investigate the effect on skin friction and flow mixing due to introducing controlled perturbations, at the initial shear layer of a planar wall-jet using jet inlet cyclic pulsing. The billow production by the Kelvin-Helmholtz instability, the instability that drives turbulence in a wall-jet, is modified by the excitation of the inlet velocity profile by a sine wave perturbation. Two types of wall-jet simulations are carried out, a two-dimensional compressible case at Rein = 5000 using the PyFR solver and a three-dimensional incompressible case at Rein = 6000 using the Nek5000 solver. The compressible wall-jet simulation indicates that the addition of a sine wave perturbation of 1% on the inlet velocity, at the initial shear layer, increases the wall-normal turbulence intensity at a Strouhal number (Sr) of 0.05 and reduces the turbulence intensity in all directions at a Sr of 0.25. The incompressible wall-jet simulations show that a perturbation of magnitude 40% of the inlet velocity at a low Sr number of 0.0048 damps turbulence and leads to skin friction reduction. The forced wall-jet experiences a repetitive re-laminarization process that delays transition as well as separation from the wall. A qualitative parametric analysis of the perturbation of the global behavior of the flow development on a plane wall-jet under forced velocity profiles is also presented. Cases at Sr = 0.0048 experience a reduction in the number of turbulent structures while becoming more stable, indicating potential drag reduction. Cases at Sr = 0.02 experience a frequent energy re-supply from the inlet that helps maintain large turbulent structures at further downstream locations, useful for mixing related applications."--Abstract.
Author: Cristale D. Garnica Vallejo Publisher: ISBN: Category : Aerospace engineering Languages : en Pages : 236
Book Description
"Understanding wall-jet-induced turbulence and mixing is an important challenge in modern engineering, as drag reduction and mixing enhancement are attainable by modifying the flow development. Simulations are performed to investigate the effect on skin friction and flow mixing due to introducing controlled perturbations, at the initial shear layer of a planar wall-jet using jet inlet cyclic pulsing. The billow production by the Kelvin-Helmholtz instability, the instability that drives turbulence in a wall-jet, is modified by the excitation of the inlet velocity profile by a sine wave perturbation. Two types of wall-jet simulations are carried out, a two-dimensional compressible case at Rein = 5000 using the PyFR solver and a three-dimensional incompressible case at Rein = 6000 using the Nek5000 solver. The compressible wall-jet simulation indicates that the addition of a sine wave perturbation of 1% on the inlet velocity, at the initial shear layer, increases the wall-normal turbulence intensity at a Strouhal number (Sr) of 0.05 and reduces the turbulence intensity in all directions at a Sr of 0.25. The incompressible wall-jet simulations show that a perturbation of magnitude 40% of the inlet velocity at a low Sr number of 0.0048 damps turbulence and leads to skin friction reduction. The forced wall-jet experiences a repetitive re-laminarization process that delays transition as well as separation from the wall. A qualitative parametric analysis of the perturbation of the global behavior of the flow development on a plane wall-jet under forced velocity profiles is also presented. Cases at Sr = 0.0048 experience a reduction in the number of turbulent structures while becoming more stable, indicating potential drag reduction. Cases at Sr = 0.02 experience a frequent energy re-supply from the inlet that helps maintain large turbulent structures at further downstream locations, useful for mixing related applications."--Abstract.
Author: Ann R. Karagozian Publisher: Springer ISBN: 3709127920 Category : Technology & Engineering Languages : en Pages : 304
Book Description
Fundamental Non-Reactive Jets in Crossflow and Other Jet Systems; Background on Modeling, Dynamical Systems, and Control; Reactive Jets in Crossflow and Multiphase Jets; Controlled Jets in Crossflow and Control via Jet Systems;
Author: August Verhoff Publisher: ISBN: Category : Jets Languages : en Pages : 383
Book Description
For the case of the steady, plane turbulent wall jet, the growth of the jet and decay of maximum velocity are predicted based upon the assumption that the shear stress distribution as well as the velocity distribution across the jet remain similar over the useful range of downstream positions. A suggested form for the velocity distribution is compared with the experimental results of this investigation and with the results of several previous investigators. The approach used in the analysis of the plane turbulent wall jet is then extended to the more general case of a steady turbulent wall jet beneath a secondary uniform stream. The experimental results of this investigation and other previous investigations are compared with the velocity profiles as predicted by the analysis. The case of a pulsating wall jet flow field was also analyzed; a simplified theoretical model is presented based upon the experimentally observed discrete vortex pattern produced by the unsteady jet. The analysis for both zero and nonzero secondary flow velocity relies to a large extent on many of the results of potential flow theory and the known characteristics of turbulent vortex structure. Experimental data consisting of instantaneous velocity measurements obtained by means of a hot-wire anemometer system and information obtained from visual flow field studies are compared with the results of the theoretical analysis. (Author).
Author: Joseph A. Schetz Publisher: ISBN: Category : Science Languages : en Pages : 232
Book Description
Good,No Highlights,No Markup,all pages are intact, Slight Shelfwear,may have the corners slightly dented, may have slight color changes/slightly damaged spine.
Author: D. E. Chriss Publisher: ISBN: Category : Gas flow Languages : en Pages : 52
Book Description
An experimental investigation of ducted, two stream, subsonic, reactive, turbulent jet mixing with recirculation was conducted. A primary jet of air at a mass flow rate of 0.075 lb/sec and velocity of 700 ft/sec was surrounded by an outer, low velocity, hydrogen stream. Data were obtained with hydrogen-air ratios of 0.143 and 0.107. The duct-to-inner nozzle diameter ratio was ten. Radial distributions of hydrogen mass fraction, mean axial velocity, turbulence intensity, and total pressure as well as axial distributions of wall hydrogen mass fraction and wall static pressure are presented for axial stations from one-half to five duct diameters from the nozzle exit plane. Comparison of the experimental data with calculations assuming frozen or equilibrium chemistry indicate that he measured velocity, pressure, and composition data are, in general, self-consistent. The maximum turbulent intensities which occurred in the center of the mixing layer and within the recirculation eddy were very high having values of 20 percent of the jet exit velocity. The velocity and composition field indicate that, while and mixing in the reactive flow field is slower than for the nonreactive case, the reaction had little effect on the size and location of the recirculation zone within the mixing duct.
Author: Venkata-Ramya Pasumarti Publisher: ISBN: Category : Eddies Languages : en Pages :
Book Description
The jet-in-crossflow problem has been extensively studied, mainly because of its applications in film cooling and injector designs. It has been established that in low-speed flows, pulsing the jet significantly enhances mixing and jet penetration.: This work investigates the effects of pulsing on mixing and jet trajectory in high speed (compressible) flow, using Large Eddy Simulation. Jets with different density ratios, velocity ratios and momentum ratios are pulsed from an injector into a crossflow.
Author: V. Kruka Publisher: ISBN: Category : Languages : en Pages : 1
Book Description
The wall-jet is the flow of fluid emanating from a narrow slot and blowing over a rigid wall. The width of the slot is of the order of the boundary layer on the infinite wall and the jet, in this case, mixes with a stream moving with constant velocity. This flow has drawn considerable basic and applied interest in the past few years for it has the characteristics of both a boundary layer and a free mixing flow. The present experimental investigation of a plane, steady, turbulent wall-jet with negligible longitudinal pressure gradients in a constant moving stream, with varying ratios of jet to free stream velocity definitely supports Glauert's reasoning (The Wall-Jet. J. Fluid Mech., v.1, part 6, 1956), though the precise point of partition of the flow might be in question. The inner layer is constantly losing momentum due to the frictional stresses at the wall, while the outer layer preserves its momentum; the division now occurring at the point of zero shear which is not at the maximum velocity. The analysis and experimental results are compared with those of previous investigators and a definite comparison of this work with those performed in a quiescent free stream is achieved through transformation of coordinates. (Author).
Author: Cristale D. Garnica Vallejo
Author: Cristale D. Garnica Vallejo
Author: Ann R. Karagozian
Author: Jack Duane Wilson
Author: August Verhoff
Author: 
Author: Joseph A. Schetz
Author: D. E. Chriss
Author: Venkata-Ramya Pasumarti
Author: Taghi Karimipanah
Author: V. Kruka