Direct numerical simulation of turbulent flow and heat transfer in a square duct roughened by longitudinal ribs
| dc.contributor.author | Tachie, Mark Sedem | |
| dc.contributor.examiningcommittee | Ormiston, Scott (Mechanical Engineering) | |
| dc.contributor.examiningcommittee | Essel, Ebenezer (Mechanical Engineering) | |
| dc.contributor.supervisor | Wang, Bing-Chen | |
| dc.date.accessioned | 2025-06-16T19:08:42Z | |
| dc.date.available | 2025-06-16T19:08:42Z | |
| dc.date.issued | 2025-06-15 | |
| dc.date.submitted | 2025-06-16T03:22:47Z | en_US |
| dc.degree.discipline | Mechanical Engineering | |
| dc.degree.level | Master of Science (M.Sc.) | |
| dc.description.abstract | This thesis provides a detailed study of turbulent heat and fluid flow within a longitudinally-rib-roughened square duct using direct numerical simulations (DNS). To understand the rib effects on the velocity and temperature fields, DNS of turbulent convection in a smooth-wall duct is also performed which serves as a baseline case of comparison. The research consists of three major parts. In Part I, turbulent flow through a longitudinally-rib-roughened square duct is studied at a nominal bulk Reynolds number of $Re^{N}_{b}=4410$. It is observed that the mean pattern of the secondary flows is sensitive to the presence of the ribs, and tertiary flows form at the roofs and roots of the ribs, leading to enhanced momentum transport throughout the cross-stream plane. The effects of ribs on the velocity field are further studied through analyses of the Reynolds stresses, budget balance of turbulence kinetic energy (TKE), and skewness and flatness factors of velocity fluctuations. In Part II, the influence of ribs on the statistical moments of the vorticity and velocity fields are demonstrated through analyses of the transport equation of the mean streamwise vorticity, enstrophy, as well as the joint probability density function (JPDF) of velocity fluctuations. Through a spectral analysis, it is found that the characteristic wavelength of the most energetic turbulent eddies is shortened in the ribbed duct. In Part III, turbulent heat transfer in three longitudinally-ribbed duct flows at nominal bulk Reynolds numbers of $Re^{N}_{b}=2730$, 4410 and 9650 are studied. It is observed that the presence of longitudinal ribs strengthens the secondary flows, which become intensified as Reynolds number increases, leading to enhanced thermal energy transport. It is also observed that the presence of longitudinal ribs does not result in increased hydraulic losses. As the value of Reynolds number increases, the heat transfer coefficient increases monotonically. The effects of longitudinal ribs and Reynolds number on turbulent heat transfer in a square duct are further examined by analyzing the turbulent heat fluxes, budget balance of the temperature variance transport equation, and thermal structures in both the physical and spectral spaces. | |
| dc.description.note | October 2025 | |
| dc.description.sponsorship | University of Manitoba Graduate Fellowship | |
| dc.identifier.uri | http://hdl.handle.net/1993/39118 | |
| dc.language.iso | eng | |
| dc.subject | Direct numerical simulation | |
| dc.subject | Turbulence | |
| dc.subject | Heat transfer | |
| dc.subject | Duct flow | |
| dc.subject | Longitudinal ribs | |
| dc.title | Direct numerical simulation of turbulent flow and heat transfer in a square duct roughened by longitudinal ribs | |
| local.subject.manitoba | yes | |
| oaire.awardTitle | Master's (CGS M) program | |
| oaire.awardURI | https://www.nserc-crsng.gc.ca/students-etudiants/pg-cs/cgsm-bescm_eng.asp | |
| project.funder.identifier | https://doi.org/10.13039/501100000038 | |
| project.funder.name | Natural Sciences and Engineering Research Council of Canada |