A Computational Analysis of Flow Development through a Constant Area C- Duct
This paper represents the results of an experimental work with measurement of mean velocity along with total pressure contours in 2-D form and validation of the same with numerical results based on the wall y + approach for various turbulent models like, Spalart Alamras, k-e model, k-ω model and RSM models are used to solve the closure problem. The turbulence models are investigated in the commercial CFD code of Fluent using y + as guidance in selecting the appropriate grid configuration and turbulence model. The experiment is carried out at mass averaged mean velocity of 40m/s and the geometry of the duct is chosen as rectangular cross-section of 90 curved constant area duct .In the present paper the computational results obtained from different turbulence models are compared with the experimental result along with the near-wall treatments are investigated for wall y + 30 in the fully turbulent region. It is concluded in the present study that the mesh resolving the fully turbulent region is sufficiently accurate in terms of qualitative features. Here RSM turbulence model predicts the best results while comparing with the experimental results.
Wall y+ approach for dealing with turbulent flows over a surface mounted cube: part 2 - high Reynolds number
An approach for dealing with turbulent flows over a surface-mounted cube using the wall y + as guidance in selecting the appropriate grid configuration and corresponding turbulence models are investigated using Fluent. The study is divided into two parts- Part I and Part II, dealing with low and high Reynolds number, respectively. Part I dealt with a low Reynolds number of 1,870. In Part II presented here, a Reynolds number of 40,000 based on cube height and bulk velocity is investigated and the computational results are compared with experimental data from Martinuzzi et al. (1993) on „the flow around surface-mounted, prismatic obstacles placed in a fully developed channel flow‟. The standard ke, standard k-ω, Reynolds Stress Model (RSM), SpalartAllmaras (SA) and renormalization group (RNG) k-e models are used to solve the closure problem. Their behaviour together with the accompanying near-wall treatments is investigated for wall y + ≈5 covering the viscous sublayer, y + ≈22 the buffer region and y + ≈33 resolving the log-law region, unlike the previous study (Part I – Ariff et al., 2009) which could only resolve the viscous sublayer and buffer region due to the comparatively lower Reynolds number. It is concluded that the mesh resolving the log-law region is sufficiently accurate without incurring additional computational cost. RSM turbulence model best predicts the flow separation region above the cube whereas the standard k-e performs better in the flow reattachment and recovery regions.
On the ontology of particle mass and energy in special relativity
Einstein claimed that the fundamental dynamical insight of special relativity was the equivalence of mass and energy. I disagree. Not only are mass and energy not equivalent (whatever exactly that means) but talk of such equivalence obscures the real dynamical insight of special relativity, which concerns the nature of 4-forces and interactions more generally. In this paper I present and defend a new ontology of special relativistic particle dynamics that makes this insight perspicuous and I explain how alleged cases of mass–energy conversion can be accommodated within that ontology.