The three-dimensional unsteady boundary layer induced by a vortex filament moving outside a circular cylinder is considered. In the present paper, we focus attention on the situation where the inviscid flow is fully three-dimensional but is symmetric with respect to the top centreline of the cylinder. The motion of the vortex toward the cylinder leads to separation of the boundary layer; in the present work a large unsteady adverse pressure gradient develops as well. Results for the three-dimensional streamlines, the vorticity distribution, and the velocity component normal to the cylinder indicate the presence of a region of unsteady three-dimensional secondary flow structure of rather complex shape located deep within the boundary layer. Within this three-dimensional secondary flow the fluid is progressively squeezed into a narrow region under the main vortex and it is expected that a local three-dimensional jet will develop sending boundary-layer fluid out into the main stream. It is pointed out that such three-dimensional eruptive behaviour has been observed in experiments. The results indicate the development of a three-dimensional singularity in the boundary-layer equations.
The spin transition temperature of the Cu(ii)-nitroxide complex was found to shift by approximately 100 K toward higher temperatures when the hydrostatic pressure increased to ∼0.04 GPa.
In this paper the solution to the three-dimensional and unsteady
interacting boundary-layer equations for a vortex approaching a cylinder
is calculated. The flow is three-dimensional and unsteady.
The purpose of this paper is to enhance the understanding
of the structure in three-dimensional unsteady boundary-layer separation
commonly
observed in a high-Reynolds-number flow. The short length scales associated
with
the boundary-layer eruption process are resolved through an efficient and
effective
moving adaptive grid procedure. The results of this work suggest that like
its
two-dimensional counterpart, the three-dimensional unsteady
interacting boundary layer
also terminates in a singularity at a finite time. Furthermore,
the numerical calculations
confirm the theoretical analysis of the singular structure in two dimensions
for the
interacting boundary layer due to Smith (1988).
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