DNS Study on Mechanism of Formation of Lambda Rotational Core in Late Boundary Layer Transition
نویسندگان
چکیده
Λ-vortex plays a critical role in the boundary layer transition process. In this paper, the mechanism of Λ-shaped rotational core formation is studied by DNS. The Blasius velocity profile is found to be the vorticity resource. The aggregation of vorticity (vortex filaments) is caused by the 2-D T-S wave. The mechanism of clustering of spanwise vorticity by 2-D T-S wave to form vortex tubes is studied. After that, the 3D TS wave is amplified due to its linear growth and begins to effect the direction of the vortex filaments. The bended Λ-shaped rotation core is generated by the 3D TS wave which is gradually growing. The perturbation in normal and spanwise directions suddenly becomes very large due to the vorticity conservation and the streamwise vorticity formation. Nomenclature ∞ M = Mach number Re = Reynolds number in δ = inflow displacement thickness w T = wall temperature ∞ T = free stream temperature in Lz = height at inflow boundary out Lz = height at outflow boundary Lx = length of computational domain along x direction Ly = length of computational domain along y direction in x = distance between leading edge of flat plate and upstream boundary of computational domain
منابع مشابه
Numerical Study on Randomization in Late Boundary Layer Transition
The mechanism of randomization in late boundary layer transition is studied carefully by high order DNS. The randomization was originally considered as a result of background noise. It was addressed that the large ring structure is affected by background noises first and then the change of large ring structure affects the small length scale quickly, which directly leads to randomization and for...
متن کاملDNS Study on the Evolution of Vortical Packets and Their Interactions in Boundary Layer
Vortical structures like the Λ-vortex and ring-like vortex play a critical role in the boundary layer transition process. In this paper, the mechanisms of the formation of the vortical packets and their mutual interactions are studied by DNS. It is found that the shear layer instability is the key of the vortex generation. On the other hand, in the process of evolution of vortical packets, the ...
متن کاملNannostratigraphy and paleoenvironmental study of the lower boundary of the Kalat Formation in East and West of Kopeh- Dagh, Northeast Iran
This study presents the nannostratigraphy and nannofossil events in the lower boundary of Kalat Formation in the East and West of the Kopeh- Dagh basin. The Kalat Formation comprises of coarse grained detritus limestone with subordinate sandstone intercalations. In the current study, six sections have been chosen in the East and West of the basin which are as follow: Dobaradar section, Kalat se...
متن کاملInvestigation of Thermal Nonequilibrium on Hypersonic Boundary-Layer Transition by DNS
High-temperature gas effects are known as the physical processes which result in a deviation of the behavior of the calorically perfect gas in the hypersonicflow regime. These effects may have a significant impact on laminar-turbulent transition of the boundary layer, and thus affect the heat loads of hypersonic vehicles. In the present paper we deal with thermal effects, i.e. rotational and vi...
متن کاملStagnation-point flow of a viscous fluid towards a stretching surface with variable thickness and thermal radiation
In the present analysis, we study the boundary layer flow of an incompressible viscous fluid near the two-dimensional stagnation-point flow over a stretching surface. The effects of variable thickness and radiation are also taken into account and assumed that the sheet is non-flat. Using suitable transformations, the governing partial differential equations are first converted to ordin...
متن کامل