On the nonlinear viscosity of the orthotropic bulk rheology

Autor: Nicholas M. Rathmann, David A. Lilien

Publikováno v: Journal of Glaciology, Vol 68, Pp 1243-1248 (2022)

We compare different ways the bulk flow nonlinearity of glacier ice can be captured in an orthotropic rheology. Specifically, we compare the unapproximated orthotropic rheology, derived from plastic potential theory, to existing approximations that a

Externí odkaz: https://doaj.org/article/83ccacc3b5614adb8cb8d60bc9861d7c

Inferred basal friction and mass flux affected by crystal-orientation fabrics

Autor: Nicholas M. Rathmann, David A. Lilien

Publikováno v: Journal of Glaciology, Vol 68, Pp 236-252 (2022)

We investigate the errors caused by neglecting the crystal-orientation fabric when inferring the basal friction coefficient field, and whether such errors can be alleviated by inferring an isotropic enhancement factor field to compensate for missing

Externí odkaz: https://doaj.org/article/9cc26a5085d142e29434bbc4b84fe851

Simulating higher-order fabric structure in a coupled, anisotropic ice-flow model: application to Dome C

Autor: David A. Lilien, Nicholas M. Rathmann, Christine S. Hvidberg, Aslak Grinsted, M. Reza Ershadi, Reinhard Drews, Dorthe Dahl-Jensen

Publikováno v: Journal of Glaciology, Pp 1-20

Ice-crystal fabric can induce mechanical anisotropy that significantly affects flow, but ice-flow models generally do not include fabric development or its effect upon flow. Here, we incorporate a new spectral expansion of fabric, and more complete d

Externí odkaz: https://doaj.org/article/4f5e29f2070b4296988606c2ae08e9fa

Elastic wave propagation in anisotropic polycrystals: inferring physical properties of glacier ice

Autor: Nicholas M. Rathmann, Aslak Grinsted, Klaus Mosegaard, David A. Lilien, Julien Westhoff, Christine S. Hvidberg, David J. Prior, Franz Lutz, Rilee E. Thomas, Dorthe Dahl-Jensen

Publikováno v: Rathmann, N M M, Grinsted, A, Mosegaard, K, Lilien, D A A, Westhoff, J, Hvidberg, C S S, Prior, D J J, Lutz, F, Thomas, R E E & Dahl-Jensen, D 2022, ' Elastic wave propagation in anisotropic polycrystals : inferring physical properties of glacier ice ', Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, vol. 478, no. 2268, 20220574 . https://doi.org/10.1098/rspa.2022.0574

An optimization problem is proposed for inferring physical properties of polycrystals given ultrasonic (elastic) wave velocity measurements, made across multiple sample orientations. The feasibility of the method is demonstrated by inferring both the

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4e3c66f4d39be305ea2adafc4ce98de7
https://doi.org/10.1098/rspa.2022.0574

Effect of an orientation-dependent non-linear grain fluidity on bulk directional enhancement factors

Autor: David A. Lilien, Nicholas M. Rathmann, Aslak Grinsted, Dorthe Dahl-Jensen, Christine S. Hvidberg

Publikováno v: Rathmann, N M, Hvidberg, C S, Grinsted, A, Lilien, D A & Dahl-Jensen, D 2021, ' Effect of an orientation-dependent non-linear grain fluidity on bulk directional enhancement factors ', Journal of Glaciology, vol. 67, no. 263, pp. 569-575 . https://doi.org/10.1017/jog.2020.117

Bulk directional enhancement factors are determined for axisymmetric (girdle and single-maximum) orientation fabrics using a transversely isotropic grain rheology with an orientation-dependent non-linear grain fluidity. Compared to grain fluidities t

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::e2dd38d285bfa4a0eb5ce73ef7b24ec9
https://doi.org/10.1017/jog.2020.117