OVERVIEW There are many two-fluid mixtures of practical interest. For example, mixtures of air and water or oil and water occur frequently in environmental and industrial processes. The existing modeling capability in FLOW-3D for mixtures of two fluids is the DRIFT routine that computes the relative motion of the two components arising from buoyancy and viscous forces. This model works quite well for many situations because of its simplicity and robustness.

Gas defects are often found in sand-cast parts that arise from gas generated by thermal decomposition of the sand binder. Typically, these defects occur with sand cores that have not been adequately vented. A new computational model has been developed that predicts the generation of decomposed binder gas and its transport within cores. The binder gas is treated as compressible to account for poor venting scenarios and for transport across core regions of steep temperature gradients. The model considers true molding geometry and actual core venting locations and can be used to predict the amount of gas that would enter liquid metal from any location on the surface of the core.

In free-surface flows the turbulence in a liquid may be sufficient enough to disturb its surface to the point of entraining air into the flow. The process of entraining air can be important in many applications including hydraulics and other areas. For example, in water treatment air is needed to sustain microorganisms for water purification and in rivers and streams to sustain a healthy fish population. Air entrainment is typically engineered into spillways downstream of hydropower plants to reduce the possibility of cavitation damage at the base of the spillway. There are also situations where air entrainment is undesirable such as in the sprue and runner systems used by metal casters, and in the filling of liquid containers used for consumer products. CFD can be used as an alternative to modeling such processes or as a compliment to experimental processes because it can quickly provide a large amount of information about flow. What makes it even more attractive is when conditions are difficult to reproduce experimentally or data is difficult to obtain (for example, regions that cannot be seen or are inaccessible to measurement). Unlike physical experiments, it is easy to measure quantities throughout the computational domain because all regions within that domain are accessible.

Overview Flows along rivers, through pipes and irrigation channels encounter resistance that is proportional to the roughness of bounding walls. Roughness can vary considerably from smooth steel, to concrete or sand, pebbles, and even large boulders. In traditional hydraulics the influence of roughness has been cataloged in the form of a roughness coefficient based on data obtained from a wide range of field and laboratory observations.

Slide-coating flow is widely used for the manufacturing of precision film-coating products. Considerable effort is being devoted toward a better understanding of slide-coating processes in hopes of increasing coating speeds and improving the performance of coated film. It has been demonstrated, for example Chen(1), that increasing coating speeds beyond well defined limits can result in a complete breakdown of the coating bead. In this paper we present simulation results of slide-coating flows obtained from a computational method capable of describing arbitrary, three-dimensional and time-dependent deformations of fluid surfaces. The method, which is available in the commercial program(2), uses a fixed grid through which fluid is tracked by a Volume-of-Fluid (VOF) technique(3,4). Surface tension, wall adhesion, fluid momentum, and viscous stresses are fully accounted for in our analysis.The basic method is illustrated through comparisons with dip-coating data(5). Then we present a discussion on how contact lines and dynamic contact angles are implicitly treated in our method. Because we use a VOF technique, we need only sum the forces acting on each control volume containing fluid. The location of contact lines and dynamic contact angles then arise automatically from the computed balance of forces. Our technique is illustrated with examples of startup and bead-breakup phenomena in coating flows. As will be shown, for rapid processes our approach offers efficiency and robustness for the simulation of coating process design and optimization that is difficult to achieve, with conventional analysis methods.

In this presentation we summarize the foundation and practical details of fractional-volume modeling methods. In particular, we shall demonstrate that these methods offer powerful computational approaches to a variety of physical phenomena in wind engineering. Use of volume-fraction methods is efficient because they typically require much less computer memory and less computational time than other techniques for modeling geometries. To be effective, however, these methods need to be supplemented with special considerations for boundary conditions and for numerical stability. A variety of examples will be used to demonstrate how fractional area/volume methods work.

SOLA-LOOP is designed for the solution of transient two-phase flow in networks composed of one-dimensional components. The fluid dynamics is described by a nonequilibrium, drift-flux formulation of the fluid conservation laws. Although developed for nuclear reactor safety analysis, SOLA-LOOP may be used as the basis for other types of special-purpose network codes. The program can accommodate almost any set of constitutive relations, property tables, or other special features required for different applications.