Expedited Award for Novel Research: Deterministic Chaos in Nucleate Boiling

这项研究的目的是确定饱和核态沸腾中的气泡从单个位置通过可重复的分叉序列从周期到混沌的脱离，目的是寻找适合这一现象的低维模型。对电热圆柱腔进行了实验研究，以确定其周期性。将绘制从孤立气泡到连续蒸汽柱的路线图。建立一个基于分叉和动力系统理论的模型。有许多机制负责从沸腾表面到饱和液体的热传递。对这些过程的理论研究认识到气泡频率、成核点密度和气泡直径等因素的重要性。它们都依赖于热通量、表面过热度和空腔大小，但人们对此并不完全了解。本提案的结果将通过确定汽泡离开成核点的频率及其随热流的定性和定量变化来帮助理解这一现象的一部分。将有可能找出气泡偏离频率的统计分布是否是由于确定性混沌。因此，这些实验在评估低维模型以模拟一系列热通量的过程中也将是至关重要的。

The goal of this research is to determine if the detachment of bubbles in saturated nucleate boiling from a single site goes from periodic to chaotic through a reproducible sequence of bifurcations, with the purpose of searching for a suitable low- dimensional model of the phenomenon. An experimental study of an electrically heated cylindrical cavity will be performed to determine the periodicity. The route from isolated bubbles to continuous vapor columns will be mapped. A model based upon bifurcations and dynamical systems theory will be developed. There are many mechanisms which are responsible for the heat transfer from a boiling surface to a saturated liquid. Theoretical studies of these processes recognize the importance of factors such as bubble frequency, nucleation site density and bubble diameter. They all depend on the heat flux, surface superheat and cavity size in ways that are not entirely understood. The results of the present proposal will help in understanding part of the phenomenon by determining the frequency with which vapor bubbles leave a nucleation site as well as its qualitative and quantitative change with heat flux. It will be possible to find out whether the statistical distribution of bubble departure frequencies is due to deterministic chaos. Thus the experiments will also be vital in evaluating a low- dimensional model to simulate the process over a range of heat fluxes.