from Part I - Paradigms and Tools
Published online by Cambridge University Press: 31 January 2025
Originating from irreversible statistical mechanics, the Mori–Zwanzig (M–Z) formalism provides a mathematical procedure for the development of coarse-grained models of complex systems, such as turbulence, that lack scale separation. The M–Z formalism begins with the application of a specialized class of projectors to the governing equations. By leveraging these projectors, the M–Z procedure results in a reduced system, commonly referred to as the generalized Langevin equation (GLE). The GLE encapsulates the system’s behavior on a macroscopic (resolved) scale. The influence of the microscopic (unresolved) scales on resolved scales appears as a convolution integral – often referred to as memory – and an additional noise term. In essence, fully resolved Markovian dynamics is transformed into coarse grained non-Markovian dynamics. The appearance of the memory term in the GLE demonstrates that the coarse-graining procedure leads to nonlocal memory effects, which have to be modeled. This chapter introduces the mathematics behind the projection approach and the derivation of the GLE. Beyond the theoretical developments, the practical application of the M–Z procedure in the construction of subgrid-scale models for large eddy simulations is also presented.
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.