Laminar gas jets in high-temperature atmospheres
Numerical and asymptotic methods are used to describe the structure of low-temperaturelaminar gas jets discharging into a hot atmosphere of the same gas in the limit of small jet-to-ambienttemperature ratios =Tj /To<<1. In the limitε →0, heat conduction cannot modify significantlythe temperature in the cold gas, leading to a two-region flow structure consisting of a neatly definedunperturbed cold jet for r＜rf (x), where T =T0/To = and u =U0/Uj =1, surrounded by a hot gas.These two region are separated by a transition layer where T- ￠ and 1-u<<1. In planar jetsthe front thickens with distance achieving thickness of order unity at axial distances x ￠ - (1+¨B) Reaforcing the near-axis uid to change slowly its velocity and temperature, being necessary distancesx ￠ - 2 Rea to reach values of T and 1-u of order unity. In round jets the front remains at r =a upto distances x ￠ - (1 - ¨B) (log - 1 ) 2 where the front is forced to move radially towards the axis of thejet, reaching r =0 at x ￠ - 1 log - 1 Rea. The arrival of the front forces the change of the velocity andtemperature in the near-axis region, reaching values of order unity in a far field region of characteristiclength x~ε- 1 log ε-1 Rea, distance comparable to that needed by the front to achieve the axis. Inboth geometries, the distance necessary for the fully development of the cold jet is considerably longerthan that required by the isothermal jet x~ Rea.
laminar cold gas jet front compressible asymptotic
M.S′anchez-Sanz A.L.S′anchez A.Liuan′an
Area de Mec′ anica de Fluidos, Universidad Carlos III de Madrid, 28911 Legan′es, Spain E.T.S.I.Aeron′ auticos, Pl.Cardenal Cisneros 3, 28040 Madrid, Spain
国际会议
The Fifth International Conference on Fluid Mechanics(第五届国际流体力学会议)
上海
英文
2007-08-15（万方平台首次上网日期，不代表论文的发表时间）