基于最小熵产生与耗散结构和混沌理论的河床演变分析

Analysis of river bed changes based on the theories of minimum entropy production dissipative structure and chaos

阐述了最小熵产生、耗散结构和混沌理论的基本原理和研究方法,并介绍了如何应用这些理论和方法对河床演变过程进行分析。认为:河流只可能处于近平衡态和远离平衡态。河流处于近平衡态时,遵循最小熵产生原理或最小能耗率原理,其演变过程表现为逐渐趋向于与外界条件相适应的相对平衡状态,在相对平衡状态水流的熵产生或能耗率为最小值。当作用在河流上的约束条件发生变化后,河流就会离开原来的相对平衡状态,寻求与新的约束条件相适应的相对平衡状态。在这个调整过程中,熵产生或能耗率并不是单调减少,而是有增有减,直到新的相对平衡状态,水流的熵产生或能耗率一定是与新的约束条件相适应的最小值。河流处于远离平衡态时,其演变过程可以经受突变,导致河型转化发生。河型转化是在外界条件缓慢变化过程中,超过某一临界值而发生的突变,这种突变相当于热力学中的非平衡相变,因而可以用耗散结构和混沌理论解释河型转化。

This paper expounds the basic principle and research method of the theories of minimum entropy production, dissipative structure and chaos, and introduces how to apply the theories and methods to analyze the river bed changes process. It considers that there are only two states for rivers including the near balance state and far from balance state. Rivers bed changes follow the principle of minimum entropy production or principle of the minimum rate of energy dissipation when it is near the balance state and its variation process tends to the relative balance state adapted to external conditions, and in which the entropy production or the rate of energy dissipation of water is minimum. Rivers will leave the primary relative balance state, and seek relative balance state adapted to new constraint conditions after the constraint conditions on the river change. In this adjustment process, the entropy production or the rate of energy dissipation is not drably decreased, but sometimes increased and sometimes decreased, until the new state of rela- tive balance whose entropy production or the rate of energy dissipation is the minimum adapted to the new constraint conditions. The river bed changes process can undergo mutation, causing the change of river patterns when it is far from the balance state. The change of river patterns is a mutation when it surpasses a certain critical value in the transformation process of gradual change of external conditions which is equivalent to the non-equilibrium phase transition of thermodynamics, so that it can be explained by the theories of dissipative structure and chaos.