Analyzing the Variability in Low-Flow Projections under GCM CMIP5 Scenarios

Water Resources Management - The present study considered the impacts of global climate model (GCM) selection in the Couple Model Intercomparison Phase 5 (CMIP5) scenarios on the low-flow...     

A stochastic model to simulate the formation of a thermal spray coating

We present a three-dimensional, stochastic model of thermal spray coating. It is capable of predicting coating porosity, thickness, roughness, and the variation of these properties with spray parameters. The model assigns impact properties to molten droplets landing on the substrate by generating random values of process parameters, assuming that these properties follow normal distributions with user-specified means and standard deviations. We prescribed rules to calculate splat sizes after droplet impact and their interaction with each other. Porosity is assumed to be solely due to the curl-up of the splats as a result of thermal stresses. We use a Cartesian grid to define the computational domain and to track the shape and position of the deposited coating. The surface of the coating and the location of pores within it are specified using a variable known as the “volume fraction,” defined as the fraction of the volume of a computational cell occupied by coating material. Results are given for the variation of coating porosity, thickness and roughness with varying particle speed, size, and spraying gun speed. Predicted trends agree with experimental observation.     

Estimating direct, diffuse, and global solar radiation for various cities in Iran by two methods and their comparison with the measured data

Two computational methods for calculating hourly, daily, and monthly average values of direct, diffuse, and global solar radiation on horizontal collectors have been presented in this article for location with different latitude, altitude, and atmospheric conditions in Iran. These methods were developed using two different independent sets of measured data from the Iranian Meteorological Organization (IMO) for two cities in Iran (Tehran and Isfahan) during 14 years of measurement for Tehran and 4 years of measurement for Isfahan. Comparison of calculated monthly average global solar radiation, using the two models for Tehran and Isfahan with measured data from the IMO, has indicated a good agreement between them. Then these developed methods were extended to another location (city of Bandar-Abbas), where measured data are not available. But the work of Daneshyar [1] predicts its monthly global radiation. The maximum discrepancy of 7% between the developed models and the work of Daneshyar [1] was observed.     

Interactions between molten metal droplets impinging on a solid surface

We photographed molten tin droplets (2.2 mm diameter) landing off-center on a circular splat formed by the impact and solidification of another, identical drop. Final splat shapes were sensitive to the spacing between droplet centers, which was varied from 1.0 to 5.0 mm. We used a three-dimensional model of spreading and solidification to simulate interactions between droplets. The model applied a fixed-grid Eulerian control volume method to solve the fluid dynamics and energy conservation equations. A volume-of-fluid algorithm was used to track free surface deformation. Predictions of droplet shapes during impact from the model agreed well with photographs. By following temperature variations at different points on the surface of the first splat we could identify locations where remelting occurred and the splats fused together. Splat shapes observed in experiments with large tin droplets qualitatively resembled those obtained by plasma-spraying nickel powders on a steel surface.