| Summary: | 碩士 === 國立交通大學 === 機械工程系 === 90 === Flow field and heat transfer for argon gas flows surrounding a circular cylinder at low Reynolds numbers in the transitional regime is simulated using the unstructured-mesh, parallel direct simulation Monte Carlo [DSMC] method. A grid-overlapping method is designed to speed up accumulating an appreciable number of samples within wake region. Flow conditions include free-stream Knudsen numbers in the range of 0.02-2, free-stream Reynolds numbers in the range of 10-75, free-stream Mach number in the range of 0.1-3, and surface temperature of the cylinder in the range of 300-900K. Numerical results show that the size of symmetric recirculating bubble behind the cylinder increases with increasing Reynolds numbers at constant Knudsen number, while it decreases with increasing Knudsen numbers at constant Reynolds numbers. In other words, rarefaction tends to destroy the formation of recirculating bubble behind the cylinder. In addition, heat transfer from the surface of the cylinder correlates strongly with the existence of the recirculating bubble behind the cylinder.
|
|---|
