Origin of transverse ridges on the surfaces of catastrophic mass flow deposits on the Earth and Mars
Origin of transverse ridges on the surfaces of catastrophic mass flow deposits on the Earth and Mars
复制标题
地球和火星灾难性物质流沉积物表面横脊的起源
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
B. C. Bruno
中科院分区：
文献类型：
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作者：
S. Baloga;B. C. Bruno
灾难性质量流沉积物（如滑坡、泥石流和火山泥流）表面的横向隆起可能是在传输过程中产生的表面波的残余物。这种波的形成可能是由于流动不稳定，或由于源处物质释放的不规则或脉冲。我们首先考虑物质在流中的稳态释放。通过考虑经典的流体动力学稳定性标准，我们表明，已知导致翻滚波的流动不稳定性似乎可能适用于在地球和火星上研究的质量流沉积物。由于动力波形成的合理性，我们通过对动量和体积守恒方程进行详细的数学分析，考虑了更现实的情况，即物质随时间释放到流动中。结果表明，在某些流动条件下，源条件下的任何扰动都不受约束地向下游发展，很像经典的流体动力不稳定性。据推测，这种状态可能导致类似的横摇波。然而，在其他情况下，流源处边界条件的任何不规则性都会衰减，例如在稳定的流体流动中。描述稳定和不稳定状态的一个关键参数是源处流深衰减的时间常数。当表面波被保存在长跳动、灾难性质量流的沉积物中时，我们的结果提供了一种新的诊断方法来限制放置条件和流动在运输过程中的流变。
[1] Transverse ridges on the surfaces of catastrophic mass flow deposits such as landslides, debris flows, and lahars may be the remnants of surface waves that originated during transit. Such waves can form as a result of a flow instability or from irregularities or pulses in the release of material at the source. We first consider a steady state release of material into the flow. By considering classic fluid dynamic stability criteria, we show that flow instabilities known to lead to roll waves seem likely for the mass flow deposits studied on Earth and Mars. Motivated by the plausibility of dynamic wave formation, we consider the more realistic case of a time-dependent release of material into the flow by performing a detailed mathematical analysis of the momentum and volume conservation equations. The results show that for some regimes of flow conditions, any disturbances in the source conditions grow downstream without bound, much like a classical fluid dynamic instability. It is conjectured that this regime may lead to analogs of roll waves. In other regimes, however, any irregularities in the boundary conditions at the source of the flow decay, as in a stable fluid flow. One critical parameter delineating the regimes of stability and instability is the time constant for the decay of the flow depth at the source. When surface waves are preserved in the deposits of long runout, catastrophic mass flows, our results provide a new diagnostic for constraining the emplacement conditions and the rheology of the flow during transit.