Typescript, etc.

Typescript, etc.

Thesis (M.S.)--Ohio University, March, 2004. / Title from PDF t.p. Includes bibliographical references (leaves 226-232).

Icing can pose problems due to both accretions on aircraft aerodynamic surfaces as well as through shedding of large ice particles from aircraft surfaces. The shed ice causes damage by impacting downstream aerodynamic surfaces and on ingestion by aft mounted engines. Present ice trajectory simulation tools have limited capabilities due to the lack of experimental aerodynamic force and moment data for ice fragments and the large number of variables that can affect the trajectories of ice particles in the aircraft flowfield like the particle shape, size, mass, initial velocity, particle shedding location and orientation during shedding. A comprehensive literature review of experimental studies related to "random-shape" bluff body aerodynamics was conducted to support the development of a list of ice fragments for consideration in this research effort. Recommendations were also obtained from aircraft engine manufacturers and industry partners in developing the ice fragment list. Fifteen ice shapes were identified for aerodynamic testing and they were prioritized based on input from industry. The top three were selected for the present wind tunnel study. The ice fragments selected included a rectangular slab, a semicircular shell and a hemispherical shell. The literature review of experimental studies yielded a variety of methods employed by other investigators in obtaining force and moment data for randomshape bodies. However, in most previous experimental investigations force and moment data were obtained for infinite aspect ratio (2D) fragments. The research described in this thesis was performed to establish 3D six degree of freedom experimental force and moment data in the WSU 7-ft by 10-ft wind tunnel facility. The data obtained will be used in the probabilistic trajectory simulation methods of "random-shape" ice fragments employed at WSU. Experimental results are presented for five ice fragment configurations and include lift, drag and side force coefficients. In certain cases, the pitching, yawing and rolling moment coefficients are also provided. The data was reduced from the balance body axis system to the wind axis system. Transformations were developed to obtain the force and moment data at the model resolving center from the balance virtual center. The forces and moments were resolved by the WSU external balance at the virtual center. Detailed discussions are provided on the effects on the aerodynamic force and moment data due to the test mount, test section wall, model-mount interference, aspect-ratio, ice fragment shape and the associated Reynolds number. Moreover, the flowfield about selected ice fragments was computed using simulation tools like FLUENT (a Navier-Stokes solver) and GAMBIT (meshing preprocessor) to elucidate flow behavior and sting-model interference effects. Results from the computational effort are presented and include pressure coefficient contours and velocity colored streamlines. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering. / "December 2006." / Includes bibliographic references (leaves 134-140)

Thèse (D.Eng.) -- Université du Québec à Chicoutimi, 2006. / La p. de t. porte en outre: Thèse présentée à l'Université du Québec à Chicoutimi pour l'obtention du doctorat en ingénierie. CaQCU Bibliogr.: f. 260-264. Document électronique également accessible en format PDF. CaQCU

A detailed study is proposed for understanding the use of aircraft deicing and anti-icing fluids (ADAF) and optimal use of these fluids in airport operations. A detailed literature review of past and current technologies is conducted and possible opportunities to improve the use of ADAF and relevant recommendations are derived. Mathematical optimization models (e.g. MINLP with binary variables) based on a variety of objectives, which deal with exhaustive sets of system constraints are formulated, developed and applied to case studies. One real-life case study area which routinely carries out aircraft deicing is used for testing the mathematical optimization formulations for optimal use of fluids under budgetary and environmental compliance constraints. Based on the recommendations from one of the best optimization model formulations it is hoped that it will be used for a real-time implementation. Results from these formulations show the models to be robust and applicable. / by Scott E. Ornitz. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Thèse (M.Eng.)--Université du Québec à Chicoutimi, 2002. / Document électronique également accessible en format PDF. CaQCU

Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2007. / La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en ingénierie. CaQCU Bibliogr.: f. 137-143. Document électronique également accessible en format PDF. CaQCU

Note:

Ice accretion is a purely unsteady phenomenon that is presently approximated by most icing codes using quasi-steady modeling. The accuracy of ice prediction is thus directly related to the arbitrarily prescribed time span during which the impact of ice growth on both flow and droplets is neglected. The objective of this work is to remove this limitation by implementing a cost-effective unsteady approach. This is done by fully coupling, in time, a diphasic flow (interacting air and droplet particles) with the ice accretion model. The two-phase flow is solved using the Navier-Stokes and Eulerian droplet equations with dual-time stepping in order to improve computational time. The ice shape is either obtained from the conservation of mass and energy within a thin film layer for glaze and mixed icing conditions, or from a mass balance between water droplets impingement and mass flux of ice for rime icing conditions. The iced surface being constantly displaced in time, Arbitrary Lagrangian-Eulerian terms are added to the governing equations to account for mesh movement. Moreover, surface smoothing techniques are developed to prevent degradation of the iced-surface geometric discretization. For rime ice, the numerical results clearly show that the new full unsteady modeling improves the accuracy of ice prediction, compared to the quasi-steady approach, while in addition ensuring time span independence. The applicability of the unsteady icing model for predicting glaze ice accretion is also demonstrated by coupling the diphasic model to the Shallow Water Icing Model. A more rigorous analysis reveals that this model requires the implementation of local surface roughness and that previous quasi-steady validations cannot be carried out using a small number of shots, therefore the need for unsteady simulation.