The aim of this review is to show the relationships between the structure, the process, and the properties of biodegradable multiphase systems based on plasticized starch (PLS), the so‐called “thermoplastic starch.” These mutiphase materials are obtained when associating association between plasticized starches and other biodegradable materials, such as biodegradable polyesters [polycaprolactone (PCL), polyhydroxyalkanoates (PHAs), polylactic acid (PLA), polyesteramide (PEA), aliphatic, and aromatic copolyesters], or agro‐materials (ligno‐cellulosic fiber, lignin etc.). Depending on materials (soft, rigid) and the plastic processing system used, various structures (blends, composites, multilayers) can be obtained. The compatibility problematic between these hetero‐materials is analyzed. These starchy products show some interesting properties and have some applications in different fields: packaging, sports, catering, agriculture and gardening, or hygiene.

Biodegradable Multiphase Systems Based on Plasticized Starch: A Review

We consider the linear stability of the cocurrent flow of two fluids of different viscosity in an infinite region (the viscous analogue of the classical Kelvin-Helmholtz problem). Attention is confined to the simplest case, Couette flow, and we solve the problem using both numerical and asymptotic techniques. We find that the flow is always unstable (in the absence of surface tension). The instability arises at the interface between the two fluids and occurs for short wavelengths, when viscosity rather than inertia is the dominant physical effect.

Shear-flow instability at the interface between two viscous fluids

This paper gives an overview of the issues posed by the science and technology of transporting heavy oils in a sheath of lubricating water. It touches on measures of energy efficiency, industrial experience, fouling, stability, models of levitation, and future directions.

Core-annular flows

Providing a comprehensive introduction to the fundamentals and applications of flow and heat transfer in conventional and miniature systems, this fully enhanced and updated edition covers all the topics essential for graduate courses on two-phase flow, boiling, and condensation. Beginning with a concise review of single-phase flow fundamentals and interfacial phenomena, detailed and clear discussion is provided on a range of topics, including two-phase hydrodynamics and flow regimes, mathematical modeling of gas-liquid two-phase flows, pool and flow boiling, flow and boiling in mini and microchannels, external and internal-flow condensation with and without noncondensables, condensation in small flow passages, and two-phase choked flow. Numerous solved examples and end-of-chapter problems that include many common design problems likely to be encountered by students, make this an essential text for graduate students. With up-to-date detail on the most recent research trends and practical applications, it is also an ideal reference for professionals and researchers in mechanical, nuclear, and chemical engineering.

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Two-phase flow, boiling and condensation in conventional and miniature systems

Viscosity regularisation methods are probably the most popular current method for computing visco-plastic fluid flows. They are however generally used in an ad hoc manner. Here we examine convergence of regularised solutions to those of the corresponding exact models, in both mathematical and physical senses. Mathematically, the aim is to give practical guidance as to the order of error that one might expect for different regularisations and for different types of flow. Our theoretical results are illustrated with a number of computed example flows showing the orders of error predicted. Physically, the question is whether or not the regularised solutions behave in the same way as the exact solutions, qualitatively as well as quantitatively. We show that there are flows for which regularisation methods will generate their maximum errors, e.g. lubrication-type flows. In this context, we also consider the effects of regularisation on problems of hydrodynamic stability. For broad classes of problems, stability characteristics of the flow are incorrectly predicted by the use of viscosity regularisation methods.

On the usage of viscosity regularisation methods for visco-plastic fluid flow computation

The stability of a steady, axisymmetric, laminar, primary flow composed of two fluids flowing concentrically in a straight circular tube is investigated by the method of small perturbations. Both asymmetric and axisymmetric disturbances to the primary flow are considered. It is demonstrated that, regardless of the size of the Reynolds number, no situations are encountered for which the primary flow is stable to both types of disturbances, simultaneously. The primary cause of instability is found to be the difference in viscosities of the two fluids.

Instability due to Viscosity and Density Stratification in Axisymmetric Pipe Flow

A novel perturbation technique originally proposed by Benjamin is applied to the study of surface waves in axisymmetric, swirling flow of an inviscid fluid. A first approximation to finite amplitude waves of large wavelength is obtained. The results are found to correspond to the classical solitary and conidial wave solutions given by Korteweg and deVries.

Charles E. Hickox

Papers

Instability due to Viscosity and Density Stratification in Axisymmetric Pipe Flow

Surface waves of finite amplitude in axisymmetric swirling flow