The Formation of Channels, Gullies and Sediment Waves by Turbidity Currents: A Navier-Stokes Based Framework

Meiburg 0854338这项研究将建立一个新的框架，分析浊流/沉积物床的相互作用的基础上的Navier-Stokes方程，而不是深度平均浅水方程。研究重点是线性稳定性框架，以提供洞察的渠道，冲沟和沉积物波的形成浊流。同时还将进行直接纳维尔-斯托克斯模拟。这一领域的基本进展将加强对沉积物沉积结构的预测，从而导致更有效的深水油气藏勘探战略。该研究建立在初步调查的PI到形成顺流渠道的浊流。具体而言，一种新的不稳定性被证明是发生，如果由单向浊流基流施加的剪切应力衰减更快地与沉积物床的距离比基流泥沙浓度。这项调查是基于假设，这种新发现的线性不稳定机制也适用于流向扰动。因此，根本上重要的问题出现对流或绝对性质的流向不稳定性，沿着与他们的潜力，引起线性和非线性的全球模式。基于新的Navier-Stokes方法，这些问题将作为控制参数的函数进行研究。将与阿伯丁大学石油地质学教授Ben Kneller博士和Ecole Polytechnique的Lesshafft博士密切合作，就线性稳定性问题评价预期结果对深水沉积物的适用性。纳维尔-斯托克斯方法不是求平均值，而是解决水流和沉积物结构，从而可以研究三维扰动速度和沉积物浓度场之间的反馈机制。解决这些问题将有助于深入了解世界底部大量沉积物的时空演变？沉积物波浪、涟漪、沙丘和反沙丘等现象造成的海洋。对浊流/沉积床耦合动力学的深入了解将改进深水油气藏勘探战略，减少钻探，提高采收率，从而节省大量资金，减少对环境的影响。这项研究将进一步培养本科生和研究生在计算线性稳定性分析和科学计算。

Meiburg0854338This research will establish a novel framework for analyzing turbidity current/sediment bed interactions based on the Navier-Stokes equations, rather than the depth-averaged shallow water equations employed to date. The study focuses on the linear stability framework to provide insight into the formation of channels, gullies and sediment waves by turbidity currents. Accompanying Direct Navier-Stokes simulations will be carried out as well. Fundamental progress in this area will enhance prediction of the architecture of sediment deposits, thereby leading to more effective exploration strategies for deep-water hydrocarbon reservoirs. The study builds on a preliminary investigation by the PI into the formation of streamwise channels by turbidity currents. Specifically, a novel instability was shown to occur if the shear stress imposed by the unidirectional turbidity current base flow decays more rapidly with the distance from the sediment bed than the base flow sediment concentration. This investigation is based on the hypothesis that this newly discovered linear instability mechanism also applies to streamwise perturbations. Thus, fundamentally important questions arise regarding the convective or absolute nature of streamwise instabilities, along with their potential for giving rise to linear and nonlinear global modes. Based on the novel Navier-Stokes approach, these issues will be investigated as functions of the governing parameters. The applicability of the anticipated results to deep-water sediments will be evaluated by a close collaboration with Dr. Ben Kneller, Professor of Petroleum Geology at the University of Aberdeen and with Dr. Lesshafft at Ecole Polytechnique, for questions on questions of linear stability. Rather than averaging, the Navier-Stokes approach will resolve flow and sediment structures within the current, and thereby allow for the study of feedback mechanisms between the three-dimensional perturbation velocity and the sediment concentration field. Resolving these issues will provide insight into the spatio-temporal evolution of the vast sediment deposits at the bottom of the world?s oceans caused by phenomena such as sediment waves, ripples, dunes and antidunes. The advanced understanding of coupled turbidity current/sediment bed dynamics will improve strategies for the exploration of deep-water hydrocarbon reservoirs, for reduced drilling, and for improved recovery rates, thereby resulting in large financial savings and a reduced environmental impact. This research will furthermore train undergraduate and graduate students in computational linear stability analysis and scientific computing.