Classical generalized constant coupling model for geometrically frustrated antiferromagnets

A generalized constant coupling approximation for classical geometrically frustrated antiferromagnets is presented. Starting from a frustrated unit we introduce the interactions with the surrounding units in terms of an internal effective field which is fixed by a self consistency condition. Results for the magnetic susceptibility and specific heat are compared with Monte Carlo data for the classical Heisenberg model for the pyrochlore and kagome lattices. The predictions for the susceptibility are found to be essentially exact, and the corresponding predictions for the specific heat are found to be in very good agreement with the Monte Carlo results.Comment: 4 pages, 3 figures, 2 columns. Discussion about the zero T value of the pyrochlore specific heat correcte

Supersonic mixing and combustion control using streamwise vortices

In this paper, we present our experimental and numerical results for the supersonic mixing and combustion control. Our strategy of enhancing supersonic mixing is to use streamwise vortices. The reasons are (1) that in supersonic flows streamwise vortices can be generated quite easily and almost without additional losses in total pressure such as those due to shock waves, (2) that their breakdown into smaller scale, which is essential for mixing enhancement, can be controlled by their geometry in spanwise row configurations and by various combinations of their scales, intensity of circulation and rotational directions, and (3)that the hydrogen fuel can be injected into their core region. Several kind of alternating wedge struts are tested to examine the effects of the cited various combinations on the mixing enhancement. By presenting those results, we will discuss the formation mechanism of streamwise vortices and their downstream development, in particular the interaction between themselves in spanwise row configurations, their eventual breakdown into turbulent eddies. Firing tests are also carried out and the results for alternating wedge strut will be presented together with the results for a generic fuel injection strut for comparison. The results show the effectiveness of the present streamwise vortices for supersonic mixing enhancement and combustion control