Parametrically forced stably stratified flow in a three-dimensional rectangular container

In stably stratified flow over a three-dimensional hill, we can define a dividing streamline that separates those streamlines that pass around the hill from those that pass over the hill. The height Hs of this dividing streamline can be estimated by Sheppard's simple energy argument; fluid parcels originating far upstream of a hill at an elevation above Hs have sufficient kinetic energy to rise over the top, whereas those below Hs must pass around the sides. This prediction provides the basis for analysing an extensive range of laboratory observations and measurements of stably stratified flow over a variety of shapes and orientations of hills and with different upwind density and velocity profiles. For symmetric hills and small upwind shear, Sheppard's expression provides a good estimate for Hs. For highly asymmetric flow and/or in the presence of strong upwind shear, the expression provides a lower limit for Hs. As the hills become more nearly two-dimensional, these experiments become less well defined because steady-state conditions take progressively longer to be established. The results of new studies are presented here of the development of the unsteady flow upwind of two-dimensional hills in a finite-length towing tank. These measurements suggest that a very long tank would be required for steady-state conditions to be established upstream of long ridges with or without small gaps and cast doubt upon the validity of previous laboratory studies.

Download Full-text

COHERENT STRUCTURE IN THE NEAR WAKE FROM A HEATED OR UNHEATED CIRCULAR CYLINDER IMMERSED IN A STABLY STRATIFIED FLOW

Proceeding of International Heat Transfer Conference 11 ◽

10.1615/ihtc11.3220 ◽

1998 ◽

Author(s):

Kyung Chun Kim

Keyword(s):

Circular Cylinder ◽

Coherent Structure ◽

Stratified Flow ◽

Near Wake ◽

Stably Stratified Flow

Download Full-text

AN EFFICIENT APPROACH FOR THE THREE-DIMENSIONAL CONTAINER PACKING PROBLEM WITH PRACTICAL CONSTRAINTS

Asia Pacific Journal of Operational Research ◽

10.1142/s0217595904000254 ◽

2004 ◽

Vol 21 (03) ◽

pp. 279-295 ◽

Cited By ~ 26

Author(s):

ZHIHONG JIN ◽

KATSUHISA OHNO ◽

JIALI DU

Keyword(s):

Three Dimensional ◽

Real Life ◽

Packing Problem ◽

Utilization Rate ◽

Benchmark Problems ◽

Rectangular Container ◽

Efficient Packing ◽

High Degree ◽

Practical Constraints ◽

Inherent Stability

This paper deals with the three-dimensional container packing problem (3DCPP), which is to pack a number of items orthogonally onto a rectangular container so that the utilization rate of the container space or the total value of loaded items is maximized. Besides the above objectives, some other practical constraints, such as loading stability, the rotation of items around the height axis, and the fixed loading (unloading) orders, must be considered for the real-life 3DCPP. In this paper, a sub-volume based simulated annealing meta-heuristic algorithm is proposed, which aims at generating flexible and efficient packing patterns and providing a high degree of inherent stability at the same time. Computational experiments on benchmark problems show its efficiency.

Download Full-text

The two-sided lid-driven cavity: experiments on stationary and time-dependent flows

Journal of Fluid Mechanics ◽

10.1017/s0022112001006267 ◽

2002 ◽

Vol 450 ◽

pp. 67-95 ◽

Cited By ~ 49

Author(s):

CH. BLOHM ◽

H. C. KUHLMANN

Keyword(s):

Three Dimensional ◽

Standing Waves ◽

Reynolds Numbers ◽

Time Dependent ◽

Flow State ◽

Incompressible Fluid Flow ◽

Velocity Measurements ◽

Driven Cavity ◽

Rectangular Container ◽

Hot Film

The incompressible fluid flow in a rectangular container driven by two facing sidewalls which move steadily in anti-parallel directions is investigated experimentally for Reynolds numbers up to 1200. The moving sidewalls are realized by two rotating cylinders of large radii tightly closing the cavity. The distance between the moving walls relative to the height of the cavity (aspect ratio) is Γ = 1.96. Laser-Doppler and hot-film techniques are employed to measure steady and time-dependent vortex flows. Beyond a first threshold robust, steady, three-dimensional cells bifurcate supercritically out of the basic flow state. Through a further instability the cellular flow becomes unstable to oscillations in the form of standing waves with the same wavelength as the underlying cellular flow. If both sidewalls move with the same velocity (symmetrical driving), the oscillatory instability is found to be tricritical. The dependence on two sidewall Reynolds numbers of the ranges of existence of steady and oscillatory cellular flows is explored. Flow symmetries and quantitative velocity measurements are presented for representative cases.

Download Full-text