Panelling planar graphs

The skeleton of a spherical polyhedron may also be viewed as the skeleton of other panelled structures. We characterize those collections of cycles of a planar graph that bound the panels of hinged-panel structures, and distinguish those that arise from spherical polyhedra

Analysis and design of planar and non-planar wings for induced drag minimization

The goal of the work reported herein is to develop and validate computational tools to be used for the design of planar and non-planar wing geometries for minimum induced drag. Because of the iterative nature of the design problem, it is important that, in addition to being sufficiently accurate for the problem at hand, these tools need to be reasonably fast and computationally efficient. Toward this end, a method of predicting induced drag in the presence of a free wake has been coupled with a panel method. The induced drag prediction technique is based on the application of the Kutta-Joukowski law at the trailing edge. Until now, the use of this method has not been fully explored and pressure integration and Trefftz-plane calculations favored. As is shown in this report, however, the Kutta-Joukowski method is able to give better results for a given amount of effort than the more commonly used techniques, particularly when relaxed wakes and non-planar wing geometries are considered. Using these methods, it is demonstrated that a reduction in induced drag can be achieved through non-planar wing geometries. It remains to determine what overall drag reductions are possible when the induced drag reduction is traded-off against increased wetted area. With the design methodology that is described herein, such trade studies can be performed in which the non-linear effects of the free wake are taken into account

Lightweight conical components for rotational parabolic domes: geometric definition, structural behaviour, optimisation and digital fabrication

Although initially intended for academic purposes, the research shown in this paper was drawn towards the development of hollow lightweight conical com-ponents to materialise rotational parabolic domes. The starting point is a projec-tive interpretation of an Archimedean property of rotational paraboloid planar sections. This is used to discretise the parabolic surface with a set of tangent ellipses obtained via planar circle-packing algorithms. The ellipses are then mate-rialised with components composed of three truncated conical surfaces, which may be composed of several laminar materials. The geometry and economy of the material, the good structural behaviour, the simple solution for fabrication and assembly, and the tests on a full-scale prototype prove this component to be an efficient self-supporting system for wide-span structures against the use of solid boundary rings, not only for rotational parabolic domes, but also for a possible translation to other types of surface

Analysis and design of planar and non-planar wings for induced drag minimization

The goal of the work was to develop and validate computational tools to be used for the design of planar and non-planar wing geometries for minimum induced drag. Because of the iterative nature of the design problem, it is important that, in addition to being sufficiently accurate for the problem at hand, they are reasonably fast and computationally efficient. Toward this end, a method of predicting induced drag in the presence of a non-rigid wake is coupled with a panel method. The induced drag prediction technique is based on the Kutta-Joukowski law applied at the trailing edge. Until recently, the use of this method has not been fully explored and pressure integration and Trefftz-plane calculations favored. As is shown in this report, however, the Kutta-Joukowski method is able to give better results for a given amount of effort than the more common techniques, particularly when relaxed wakes and non-planar wing geometries are considered. Using these tools, a workable design method is in place which takes into account relaxed wakes and non-planar wing geometries. It is recommended that this method be used to design a wind-tunnel experiment to verify the predicted aerodynamic benefits of non-planar wing geometries

PAN AIR: A computer program for predicting subsonic or supersonic linear potential flows about arbitrary configurations using a higher order panel method. Volume 3: Case manual (version 1.0)

Numerous applications of the PAN AIR computer program system are presented. PAN AIR is user-oriented tool for analyzing and/or designing aerodynamic configurations in subsonic or supersonic flow using a technique generally referred to as a higher order panel method. Problems solved include simple wings in subsonic and supersonic flow, a wing-body in supersonic flow, wing with deflected flap in subsonic flow, design of two-dimensional and three-dimensional wings, axisymmetric nacelle in supersonic flow, and wing-canard-tail-nacelle-fuselage combination in supersonic flow

NASA Ames potential flow analysis (POTFAN) geometry program (POTGEM), version 1

A computer program known as POTGEM is reported which has been developed as an independent segment of a three-dimensional linearized, potential flow analysis system and which is used to generate a panel point description of arbitrary, three-dimensional bodies from convenient engineering descriptions consisting of equations and/or tables. Due to the independent, modular nature of the program, it may be used to generate corner points for other computer programs

Large amplitude fish swimming

A fish swims by stimulating its muscles and causing its body to "wiggle", which in turn generates the thrust required for propulsion. The relationship between the forces generated by the fish muscles and the observed pattern of movement is governed by the mechanics of the internal structure ofthe fish, and the fluid mechanics of the surrounding water. The mathematical modell ing of how fish swim involves coupling the external "biofluiddynamics" to the body's internal solid mechanics. The best-known theory for the hydrodynamics of fish swimming is Lighthill's elongated body theory (Lighthill, 1975). In Lighthill's theory the curvature of the fish is assumed small and the effect on the fish of the vortex wake is neglected. Cheng et al. (1991) did not make these simplifications in developing their vortex lattice panel method, but the fish was assumed to be infinitely thin and its undulations of small amplitude. Lighthill's "recoil correction" is the addition of a solid-body motion to ensure that an imposed "swimming description" satisfies the conservation of momentum and angular momentum. A real fish is expected to minimize such sideways translation and rotation to avoid wasteful vortex shedding. Cheng and Blickhan (1994) found that the panel method model required a smaller recoil than did Lighthill's model. Our approach is to extend Cheng's model to large amplitude. Thus we include the effect of the wake on the fish, and the self-induced deformation of the wake itself. In studying the internal mechanics of the body we model the fish as an active bending beam. Using the equations of motion of cross-sectional slices of the body we can form a set of coupled differential equations for the bending moment distribution. At large amplitude the bending moment equations involve the tangential forces acting on the body (which may be neglected in the small amplitude version). Consequently we include the boundary layer along the fish in order to estimate the viscous drag directly. The panel method has been used successfully for the fluid mechanical calculations associated with large-amplitude fish swimming. We are able to use its results as input to calculate the bending moment distribution. The boundary layer calculations are based on a crude model; solutions to the large amplitude bending moment equations should also be considered in this light

Analysing Sound Environment and Architectural Characteristics of Libraries through Indoor Soundscape Framework

This study presents the indoor soundscape framework in detail by describing the variables and factors that form an indoor soundscape study. The main objective is to introduce a new indoor soundscaping framework and systematically explain the variables that contribute to the overall evaluation of an indoor soundscape. Hence, the dependencies of physical and psychoacoustical factors of the sound environment and the spatial factors of the built entity are statistically tested. The new indoor soundscaping framework leads to an overarching evaluation perspective of enclosed sound environments, combining objective room acoustics research and noise control engineering with architectural analysis. Therefore, it is hypothesised that case spaces with certain plan organisations, volumetric relations, and spatial referencing lead to differentiated sound pressure level (SPL) and loudness (N) values. SPL and N parametric variances of the sound environments are discussed through the statistical findings with respect to the architectural characteristics of each library case space. The results show that the relation between crowd level variances and sound environment parametric values is statistically significant. It is also found that increasing the atrium height and atrium void volume, the atrium’s presence as a common architectural element, and its interpenetrating reference and domain containment results in unwanted variances and acoustic formations, leading to high SPL and N values

Industrial Explosions Modelling; Special Case An Lpg Explosion

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2007Bu çalışmada endüstride en sık karşılaşılan iki patlama türü yer almaktadır. Bunlar gaz ve toz patlamalarıdır. Toz patlamaları ile ilgili, tarihte meydana gelen toz patlamaları, toz patlama beşgeni, toz patlamalarını tetikleyen etkenler, birincil ve ikincil toz patlamaları, toz patlama mekanizması ve toz patlama şiddetini etkileyen faktörler özetlenmiştir. Sonraki bölümde gaz patlamaları yer almaktadır. Sınırlı gaz patlamaları, kısmi sınırlı gaz patlamaları, kuşatılmamış gaz patlamaları, BLEVE olayı ve buhar bulutu yayılım modelleri açıklandı. Ayrıca mevcut gaz patlama modelleri incelenerek, bunların zayıf ve güçlü noktaları özetlendi. İncelenen gaz patlama modelleri sırası ile amprik modeller, fenomen modeller, CFD modelleri ve gelişmiş CFD modelleridir. Yine aynı bölümde mevcut gaz modelleme yazılımları özetlenmiştir. Uygulama bölümünde bir LPG dolum tesisinde meydana gelebilecek çeşitli kaza ve patlama senaryoları modellendi, ayrıca İTÜ Maslak kampüsünde bulunan LPG tankın kaza ve patlama senaryosu için modelleme yapıldı. Modelleme için ALOHA programı kullanılmıştır. Son bölümde endüstride patlama modellemelerinin kullanılmasının sağladığı faydalar ve bundan sonraki çalışmalar için bilgiler verildi.In this study the two main hazards in industry are discussed; gas explosions and dust explosions. In the first part dust explosion case history, the dust explosion pentagon, what triggers dust explosions, primary and secondary dust explosions, dust explosion mechanism, and the dust explosability factors are summarized. In the next part the gas explosions are presented. Confined gas explosions, partially confined gas explosions, unconfined gas explosions, BLEVE and vapour cloud dispersion models are presented. The current gas explosion models which are empirical models, phenomenological models, CFD models and advanced CFD models are summarised with their strong and weak points. Modelling software is presented. An experimental study was done at the LPG filling station and LPG storage tank at the İTÜ Maslak campus. The experimental chapter contains different simulation scenarios for failure and explosion of LPG tanks. Modelling was done by ALOHA program. Last chapter contains advantages of using explosion modelling in industry and recommendation for future work.Yüksek LisansM.Sc