Reproduction de : Thèse de doctorat : Mécanique des fluides : Poitiers : 2009. / Titre provenant de l'écran-titre. Bibliogr. 130 réf.

Thesis (Ph. D.)--School of Chemical Engineering, Georgia Institute of Technology, 2004. Directed by Sue Ann Bidstrup. / Includes bibliographical references (leaves 165-168).

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xii, 113 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 95-98).

Thesis (Ph. D.)--Florida State University, 2002. / Advisor: Dr. Horst Wahl, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (Oct. 6, 2003). Includes bibliographical references.

The present study combines modern jet reconstruction algorithms and particle identification (PID) techniques in order to study the enhancement of proton/pion ratio at mid transverse momentum ([mathematical symbols] 1.5 - 4.0 GeV/c) observed in central Au + Au collisions at [mathematical symbols] = 200 GeV. The ratio enhancement is thought to be caused by recombination processes and/or parton fragmentation modification of jets in relativistic heavy ion collisions. The fragmentation modification hypothesis is tested in this analysis by reconstructing and selecting energetic jets presumably biased to fragment outside of the medium created in Au + Au collisions and comparing their particle composition to the recoiling (medium-traversing) jets. The bias assumption is confirmed by comparing jets in central collisions, where the effect of proton/pion enhancement is present, with peripheral ones where no medium effects are expected. The selected jets are reconstructed by using the anti-k[subscript T] algorithm from the modern FASTJET package. The PID in the p[subscript T] region of interest is possible by combining measurements of the particles' energy deposition and velocity from the Time Projection Chamber and the recently installed (2009-2010) Time of Flight detectors at STAR. The acceptance of these detectors, [eta] < 1.0 and full azimuth, make them extraordinary tools for correlation studies. These features allow for the measurement of relative azimuth ([phi] [subscript jet] - [phi] [subscript pion,proton]) distributions by using the selected jet axis in order to disentangle the uncorrelated background present in the high multiplicity heavy ion collisions. The proton/pion ratios in two different centrality bins and p[subscript T] = 1.2 - 3.0 GeV/c are presented for biased (vacuum fragmenting) jets and their recoiling counterparts / text

Indoor jets considerably dominate air movement and distribution of temperature and velocity, as well as transport of particles and other pollutants. Indoor air temperature and velocity distribution substantially impact occupants’ thermal comfort and productivity, heat and mass transfer on indoor surfaces. In addition, jets produced by human respiratory activities, such as coughing and sneezing, enhance the spread of particles that might carry bacteria or viruses. Understanding and characterizing indoor jets and their impacts on air distribution, temperature and velocity fields, and particle transport are crucial for advancing heating, ventilation, and air conditioning (HVAC) systems when considering thermal comfort and developing strategies for exposure mitigation. This dissertation contributes to the scientific understanding regarding to indoor air distribution and particle transport associated with indoor air jets. Current HVAC system design defines indoor air distribution related to the selection of diffusers/ grilles that distribute supply air jets, according to the specifics of the space and internal heating and cooling loads. However, current design guidance was developed over 40 years ago. It requires expansion of diffuser/ grille types and the update for air distribution by diffuser/ grille air jets supplying warm air at heating mode. Unlike jets from diffusers/ grilles, jets created by human activities are inherently transient in nature and might perform quite differently from steady-state ones. Understanding the dynamics of unsteady-state jets, such as coughs, enhances the current state of understanding of the mechanisms of respiratory disease transmission, which enables development of exposure reduction measures. The investigations presented in this dissertation extend the state-of-the-art knowledge on indoor jets and analyze the effect of steady-state and unsteady-state jets on particle transport in indoor environments. Figure 1 illustrates the two objectives and six investigations conducted in this dissertation. The first objective includes four investigations that address air distribution and particle transport associated with steady-state jets created by diffusers/ grilles, and the remaining two investigations relate to the second objective on unsteady-state cough jets. The first objective of this dissertation characterizes air distribution and particle transport in a space with steady-state jets created by diffusers/ grilles. One of the major contributions of this objective to the-state-of-the-art knowledge on indoor air distribution is the newly developed method for diffuser performance assessment and design when considering heating mode. It advances the current diffuser/ grille selection guide that was outdated decades ago. Furthermore, based on 650 experimental set-ups this objective provides a systematic analysis of indoor air velocity that can be further used in indoor heat transfer and pollutant emission and transport. The second objective investigates velocity fields in unsteady-state cough jets and transport of coughed particles. This objective provides a theoretical analysis of the dynamics of cough jets and examines how human thermal plume affects the exposure to coughed particles when considering different particle sizes. Ultimately, these investigations fill the knowledge gaps in indoor air distribution and particle transport associated with steady-state and unsteady-state jets in spaces using all-air HVAC systems. The newly developed diffuser guideline will improve HVAC design for both heating and cooling conditions when considering thermal discomfort or air stagnant zones caused by a wrong diffuser selection. In addition, the systematic analysis of indoor air velocity will improve the prediction of indoor heat transfer, mass transfer, particle resuspension rate, pollutant emission rate from the floor and other indoor surfaces. Finally, the theoretical analysis of unsteady-state jets contributes the knowledge for fluid dynamics of unobstructed human coughs and also transport of coughed particles, including the distribution in the vicinity of an exposed person. / text

Not available / text

Not available / text

published_or_final_version / abstract / toc / Civil Engineering / Doctoral / Doctor of Philosophy

No description available.