Ash accumulation in the channels of ceramic, honeycomb-type particulate filters is controlled by several key parameters, which are the focus of this study. Ultimately, it is the formation of ash deposits, their transport, and the manner in which the ash accumulates in the particulate filter, which determines the useful service life of the filter and its resulting impact on engine performance. Although significant variations in ash deposit properties and their spatial distribution within the filter channels have been reported, depending on the filter's application, understanding the key parameters and mechanisms, such as the effects of exhaust flow and temperature conditions, as well as the processes occurring during filter regeneration events (whether passive or active) are critical in developing improved filter ash management strategies.This work combines fundamental modeling studies with in-situ optical investigations clearly showing the processes whereby ash deposits are formed within the particulate filter, and subsequently transported down the length of the filter channel. A one-dimensional model was developed to describe the ash particle transport inside the filter channels, estimating the flow friction force imposed on the ash particles based on the local mean flow velocity. Size-dependent effects (critical mass) are accounted for in the model, which includes the re-entrainment of smaller, micron-sized ash particles, as well as the transport of larger agglomerated ash deposits (larger than 500 μm) through surface rolling or sliding. The results of the simplified 1-D model are compared and contrasted with experimental results from the in-situ optical studies, as well as three-dimensional analysis of the flow fields within particulate filter channels reported in the literature. Consistent with experimental observations, the theoretical analysis presented in this work provides a framework for understanding, and potentially controlling, the fundamental processes governing the mobility and accumulation of ash deposits within particulate filters, whether they are used as diesel particulate filters (DPF) or gasoline particulate filters (GPF).

Sea level rise (SLR) is placing both immediate and long‐term pressures on coastal communities to take protective actions. Projects in the United States, and in many locations throughout the world, generally involve local jurisdictions raising the elevation of shoreline protection elements, with limited or no analysis of the feedback between shoreline management decisions and the impacts to water levels regionally. Our study examines the impact of local shoreline development on regional flood risk and considers SLR scenarios up to 1.5 m using a large‐scale numerical model, as an example, for San Francisco Bay. Here we show that measures to prevent flooding along an embayment shoreline in one location or subregion may increase inundation elsewhere in the system. The network of interactions occurs not only within subbasins of the Bay but also across the greater geographic extent from one end of the Bay to the other, and local jurisdiction may have either reciprocal relationships with or asymmetric impacts on one other. Importantly, the nature of the interaction network is seen to evolve with SLR: interactions are purely subregional at current sea level but with higher sea level (e.g., 1 m of SLR), not only do the subregional interdependencies strengthen but also regional interdependences emerge.