Werner 9526439 New models and computational techniques in nonlinear dynamics and improved instrumentation for field studies motivate a re-examination of the problem of eolian dune formation. The goals of the proposed investigation are to be advance models for the origin and evolution of eolian dunes and dune fields, to work out the predicted consequences of these models, and to subject them to rigorous field testing. The study will follow an integrated approach, bringing together computer simulation, field observation and experimentation, and analytical models. The work plan for the study proceeds in step-wise fashion from consideration of sand patch (incipient dune) nucleation, continuing with investigation of isolated bedforms, graduating to treatment of interactions between bedforms, and ending with study of the overall dynamics of dune fields. At the sand-patch level, computer simulations of saltation over sand patches plus field experimentation are aimed at understanding why and how nucleation first occurs and growth follows. At the bedform level, computer simulation of airflow and saltation over developing bedforms, tested and constrained by detailed field measurements, will be used to explore the conditions under which evolution to dune forms with slipfaces occurs. At the bedform-bedform interaction level, extensive field measurements of airflow lateral and downwind from dunes will be performed to probe the regulating effects of dunes on their neighbors. The interactions between a variety of constructed dunes under a range of conditions will be documented to produce a functional map describing the results of dune-dune interactions. These results will be compared to simplified computer simulations of bedform mechanics. It is expected that an analytical model of dune field development, based on simplifying assumptions emerging from the simulation nd field efforts, will result. Throughout the entire study, factors that may affect bedforms at any of the levels of development and interaction, such as wind velocity and variability and sand supply, will be explored. Predictions of the resulting model will be compared with the morphology of natural dune fields.
