In the context of linear stability analysis, considering unsteady base flows is notoriously difficult. A generalisation modal allowing for arbitrarily over a finite time, therefore required. The recently developed optimally time-dependent (OTD) modes form projection basis tangent space. They capture leading amplification directions in state space under constraint that they an orthonormal at all...

The objective of this paper is to present the hybrid variational iteration method. The proposed algorithm is based on the combination of variational iteration and shooting methods. In the proposed algorithm the entire domain is divided into subintervals to establish the accuracy and convergence of the approximate solution. It is found that in each subinterval a three term approximate solution u...

An experimental study was performed to analyze the stability of localized streaky structure in a Blasius boundary layer. An artificial streaky structure was created by using suction or blowing through a thin spanwise slot at the wall. The velocity gradient generated by the suction or blowing was controlled by a damper. The Reynolds number based on the displacement thickness d1 was Red1 =280 at ...

The purpose of this study is to demonstrate the potential of Imperialist CompetitiveAlgorithm (ICA) for solving Blasius dierential equation. This algorithm is inspiredby competition mechanism among Imperialists and colonies and has demonstrated excellentcapabilities such as simplicity, accuracy, faster convergence and better global optimumachievement in contrast to other evolutionary algorithms...

Here we have demonstrated that small amplitude vibration can artificially excite both two dimensional (2D) and three (3D) instability modes. The 2D modes were typical of Tollmien–Schlichting (TS) waves provided the frequency excitation lies within unstable region neutral stability predicted by modal linear theory. However, even if mechanically forced mode was stable bounds curve harmonics gener...

On bou *A According to Lighthill (1995), Prandtl’s (1904) boundary layer has had the same transforming effect on fluid dynamics as Einstein’s 1905 discoveries had on other parts of physics, which, by the way, were celebrated in 2005 as the World Year of Physics. That the boundary layer becomes turbulent was formally known to Blasius (1908), though, of course, the origin of turbulence in a pipe ...

Round jets originating from a pipe nozzle are computed by large-eddy simulations (LES) to investigate the effects of the nozzle-exit conditions on the flow and sound fields of initially laminar jets. The jets are at Mach number 0.9 and Reynolds number 10, and exhibit exit boundary layers characterized by Blasius velocity profiles, maximum root-mean-square (r.m.s.) axial velocity fluctuations be...