TY - JOUR
T1 - Controls on Yardang Development and Morphology
T2 - 2. Numerical Modeling
AU - Pelletier, Jon D.
N1 - Funding Information:
I wish to thank Giovanni Coco, Tom Barchyn, Doug Sherman, and an anonymous reviewer for comments that significantly improved the manuscript. This study was supported by NSF award 1323148. The source code and example files of the numerical model are available in Pelletier (). Any additional data or model results related to this paper are available upon request from the author.
Funding Information:
I wish to thank Giovanni Coco, Tom Barchyn, Doug Sherman, and an anon ymous reviewer for comments that sig nificantly improved the manuscript. This study was supported by NSF award 1323148. The source code and example files of the numerical model are available in Pelletier (2018). Any additional data or model results related to this paper are available upon request from the author.
Publisher Copyright:
©2018. American Geophysical Union. All Rights Reserved.
PY - 2018/4
Y1 - 2018/4
N2 - Here I present a set of mathematical modeling results, constrained by the results of the companion paper, aimed at improving our understanding of yardang development and controls on yardang morphology. The classic model for yardang development posits that yardangs evolve to an aspect ratio of ≈4 in order to minimize aerodynamic drag. Computational fluid dynamics model results presented here, however, demonstrate that yardangs with an aspect ratio of 4 do not minimize drag. As an alternative, I propose that yardang aspect ratios are primarily controlled by the lateral downwind expansion of wind and wind-blown sediments focused into the troughs among yardangs, which can be quantified using previous studies of wall-bounded turbulent jets. This approach predicts yardangs with aspect ratios in the range of 5 to 10, that is, similar to those of natural yardangs. In addition to aerodynamics, yardang aspect ratios are influenced by the strikes and dips of strata, as demonstrated in the companion paper. To better understand the aerodynamic and bedrock structural controls on yardang morphology, I developed a landscape evolution model that combines the physics of boundary layer flow and abrasion by eolian sediment transport with a model for the erosion of the tops and lee sides of yardangs by water-driven erosional processes. Yardang formation in the model is enhanced in substrates with greater heterogeneity (i.e., alternating strong and weak strata). Yardang morphology is controlled by the strikes and dips of strata as well as the topographic diffusivity associated with water-driven erosional processes.
AB - Here I present a set of mathematical modeling results, constrained by the results of the companion paper, aimed at improving our understanding of yardang development and controls on yardang morphology. The classic model for yardang development posits that yardangs evolve to an aspect ratio of ≈4 in order to minimize aerodynamic drag. Computational fluid dynamics model results presented here, however, demonstrate that yardangs with an aspect ratio of 4 do not minimize drag. As an alternative, I propose that yardang aspect ratios are primarily controlled by the lateral downwind expansion of wind and wind-blown sediments focused into the troughs among yardangs, which can be quantified using previous studies of wall-bounded turbulent jets. This approach predicts yardangs with aspect ratios in the range of 5 to 10, that is, similar to those of natural yardangs. In addition to aerodynamics, yardang aspect ratios are influenced by the strikes and dips of strata, as demonstrated in the companion paper. To better understand the aerodynamic and bedrock structural controls on yardang morphology, I developed a landscape evolution model that combines the physics of boundary layer flow and abrasion by eolian sediment transport with a model for the erosion of the tops and lee sides of yardangs by water-driven erosional processes. Yardang formation in the model is enhanced in substrates with greater heterogeneity (i.e., alternating strong and weak strata). Yardang morphology is controlled by the strikes and dips of strata as well as the topographic diffusivity associated with water-driven erosional processes.
KW - abrasion
KW - drag
KW - numerical modeling
KW - yardangs
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U2 - 10.1002/2017JF004462
DO - 10.1002/2017JF004462
M3 - Article
AN - SCOPUS:85046608783
SN - 2169-9003
VL - 123
SP - 723
EP - 743
JO - Journal of Geophysical Research: Earth Surface
JF - Journal of Geophysical Research: Earth Surface
IS - 4
ER -