Gayev Y. Models of easily penetrable roughness for problems of fluid mechanics and thermal physics.

Penetrable roughness (PR) is a submerged layer along the flow where the flow is decelerated by a number of obstructions, and this layer is a considerable portion of the whole flow where significant physical processes take place (Fig. 1.1,в). Examples of such PRs in nature and engineering are forests under atmospheric wind, droplet layer produced by spraying systems or by storming ocean, fluvial vegetation near beds or banks along rivers or channels, urban settlements etc as these have been overviewed in chapter 1. EPR flow is commonly referred to as a canopy flow as applied to vegetation in Western literature. Concept of easily penetrable roughness (EPR) has been suggested and proved experimentally and theoretically in this thesis as a general mathematical model (1.3) where mass force (1.2) and contaminent sources represent "smeared" effect of obstacles to the local flow, whereas individual force (1.1) and fluxes govern behaviour of obstacles as a continuum media. Internal motion of two or more couple d media, i.e. the carrying medium (of air or water) and the carried one(s), and external flow over the EPR are considered separately in the boundary-layer approach with conjugation conditions (1.4) on the interface surface representing their interaction. Chapter 2 provides evidence that such formulations may guarantee existence and uniqueness of the problem solution, and develops numerical performance method. Chapter 3 is devoted to the simplest EPR structure where obstacles constituting the EPR are immobile (model of a "forest"). Consideration of one-dimensional case (EPR in a duct, (3.1)) and two-dimensional boundary layer (3.5), vertically inhomogeneous EPR structure, heat and mass exchange between the flow and EPR elements has highlighted the structure of the flow formed by EPR: it consists of initial and main regions, and -- for certain values of the criteria (3.3) -- of a stagnation zone. Analytical representations have been found for velocity (3.6) and temperature distributions as well as for stagnatio n depth (3.4). Thermoanemometric measurements on two generic PR setups in wind tunnel (Fig. 5.3) provide more information concerning internal and external flows, and correspond qualitatively well to analytical and numerical results obtained. Chapter 4 considers EPR made up with mobile elements (a "droplet layer" model) by means of one-dimensional (4.3) and two-dimensional formulations (4.1) of fluid mechanical problems and heat and mass exchange problems. 1d simplifications are useful because, again, lead to some analytical estimations. Analogy between heat and mass processes becomes broken when both processes act simultaneously (§ 4.5). Unique vertical distributions of air flow quantities within and over droplet layer generated by large-scale spraying system were obtained in our "in-situ" measurements (Fig. 4.3). Algebraic model of the EPR turbulence (5.1) enables to construct analytical approximations (5.3) for mean velocity distribution over the main region of the EPR (chapter 5). Internal velocity decay (