Numerical models of Rayleigh-Taylor instabilities superimposed upon convection
Numerical models of Rayleigh-Taylor instabilities superimposed upon convection
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对流叠加的瑞利-泰勒不稳定性数值模型
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发表时间：
1988
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通讯作者：
H. Schmeling
中科院分区：
文献类型：
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作者：
H. Schmeling
地壳中重力驱动的不稳定性是由倒置的密度分布引起的，这可能是成分和热（对流）起源的组合。一个数量级的估计表明，如果有效粘度小于101 H-1019 Pa·s，这种不稳定性可能在热异常区的下地壳中发展。为了比较成分驱动的重力翻转与对流不稳定性的活力，并描述它们对温度场的影响，引入了一个无量纲数Rt（“瑞利-泰勒数"）。“），它类似于用于对流的瑞利数Ra。Rt乘以取决于几何布置的因子C，描述了相对于传导的底辟热平流（即Rt C是底辟Peclet编号）。本文介绍了对流不稳定性叠加在组分（Rayleigh-Taylor）不稳定性上的数值模式。Ra-Rt空间被探索到Ra = 30000和Rt = 10000。几个f10 w制度被确定，在一般协议与以前的结果的基础上的线性稳定性分析，一个瑞利-泰勒推翻后的f10 w可能会变得稳定，它可能会振荡，也可能会继续对流在一个或两个层分离的不规则的倾斜界面。仅在成分密度对比的情况下，Rt给出了温度场或异常热流的畸变的良好量度：当Rt为几百或更大时，热的底辟平流变得显著。与底辟作用有关的热f10 w异常可以用包含有效粘度信息的Rt来解释。
Gravity driven instabilities in the earth's crust are caused by inverted density distributions which may be of combined compositional and thermal (convective) origin. An order of magnitude estimate suggests that such instabilities may develop in the lower crust of ther mally anomalous regions if the effective viscosity is less than 101H-1019 Pa s. To compare the vigour of compositionally driven gravity overturns with convection instabilities, and to describe their effect on the temperature field, a nondimensional number Rt ("Rayleigh Taylor number.") is defined, which is analogous to the Rayleigh number, Ra, used for con· vection. Rt, multiplied by a factor depending on the geometrical arrangement, C, describes the diapiric heat advection relative to conduction (i.e. Rt C is a diapiric Peclet no.). Nu merical models are presented in which convective instabilities are superimposed upon com positional (Rayleigh-Taylor) instabilities. Ra-Rt-space is explored up to Ra = 30000 and Rt = 10000. Several f10w regimes are identified, in general agreement with previous results based on linear stability analysis; after one Rayleigh-Taylor overturn the f10w may become stable, it may oscillate or it may continue to convect in either one or two layers separated by an irregular oblique interface. In the case of compositional density contrasts only, Rt gives a good measure for the distortion of the temperature field or the anomalous heat f1ow: diapiric advection of heat becomes significant for Rt of a few hundred or more. Heat f10w anomalies associated with diapirism may be interpreted in terms of Rt which contains infor mation about the effective viscosity.