Finite Duct Research Articles

Effects of wall admittance changes on duct transmission and radiation of sound

This paper is concerned with the effect of changes in duct wall acoustic properties on the transmission of sound through ducts. Two special problems are considered. The first problem is that of a rectangular infinite-length duct with airflow and a single change in duct wall acoustic admittance. The second problem is that of an axisymmetric field in a finite circular duct without airflow and with an arbitrary number of duct wall acoustic admittance changes. Results for the first problem show the effect of wall admittance change and flow on the acoustic power transmission within the duct. Results for the second problem show the interactive effects of multiple duct liner sections on power radiated from a finite duct.

Limiting nusselt numbers in finite MHD ducts

Limiting nusselt numbers in finite MHD ducts

The Effects of Variable Properties on MHD Flow in Finite Ducts

Numerical solutions are obtained of the coupled partial differential equations which describe variable property MHD flow in finite rectangular ducts. The fluid properties are allowed to vary to the extent that electrical conductivity and viscosity are assumed to be temperature-dependent. It is shown that it is not possible to account for fluid property variations in terms of “weighted” fluid parameters such as average Hartmann numbers. Analysis leads to the conclusion that it is the nature of the current distributions in the duct which is important in predicting the behavior of nonisothermal MHD duct flow. It is possible that this conclusion may aid in the evaluation and correlation of experimental data. It is also shown that consideration of variable fluid properties results in friction factors and flow rates which differ from constant property solutions by as much as a factor of two and by 50 percent, even for small variations.