Role of appropriate permeability model on numerical prediction of macrosegregation
- PDF / 291,710 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 0 Downloads / 163 Views
ODUCTION
SOLIDIFICATION is an integral part of many manufacturing processes and has been a topic of active research for a long time. With the advent of digital computer and mathematical modeling techniques in the last four decades, numerical modeling of solidification phenomena has become an important tool for analysis. Excellent reviews on numerical models of melting and solidification are available in the literature.[1,2,3] The objectives of these models are manifold, viz. prediction of microstructure, macrostructure, microsegregation, macrosegregation, temperature profile, rate of solidification, etc.[4] Macrosegregation, which is one of the major casting defects, has also been extensively investigated with the help of mathematical models in the past. Excellent reviews on the subject are available in the literature.[4,5,6] From these studies, it is evident that mathematical models, in general, have provided good insight into the formation of macrosegregation. Broadly, two types of models are employed in the study of macrosegregation: ‘‘single-phase models’’ and ‘‘multiphase models.’’ In single-phase models, only one set of governing equations is used to describe the transport phenomena in all three phases, namely, the solid, the liquid, and the mush. In this approach, there is no need for tracking the interface explicitly and a fixed grid can be employed for numerical simulations.[2] However, there are some disadvantages of this approach. Consideration of relative motion between the solid and the liquid (as is the case during equiaxed solidification) requires special treatment. Besides this, specific assumptions are invoked with regard to the solute undercooling and the averaging of solute in the mushy region.[2] In contrast, the basic formalism of multiphase models is more robust. Sophisticated models have been A.K. SINGH, Scientist, is with the Tata Research Development and Design Centre, Pune 411013, India. Contact e-mail: amarendra.singh@tcs. com B. BASU, formerly Scientist, Tata Research Development and Design Centre, is Vice President, Corporate Technology Strategy and Services, Aditya Birla Management Corporation Limited, Mumbai 400093, India. Contact e-mail: [email protected] A. GHOSH, formerly Professor, Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur 208016, India, is retired. Contact e-mail: ahindra258@ yahoo.com.in Manuscript submitted November 23, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS B
developed, which account for convection in the presence of simultaneous columnar and equiaxed solidification.[2] These state-of-the-art models attempt to comprehensively capture the physics of the process. However, additional computational resources, requirements of complex algorithms for tracking the solid-liquid interface, and the nonavailability of a large number of thermophysical data make the use of multiphase models difficult.[5] For these reasons, singlephase models are preferred in the study of macrosegregation. There are two basic formulations to arrive at a
Data Loading...
