Free Form Surface

In the 21st Century, new geometrical forms in architecture and ecological concerns created the environment for search for new materials and new structural solutions. The use of curved shapes in a method of design grows enormously. The lack of appropriate materials for creating non-standard surfaces has led to the use of traditional materials in a new way. At the center of interest the architects specializing in the design non-linear shaped buildings was found glass panels New technologies allow fabricators to produce flat and curved glass more economically, while simultaneously expanding its design possibilities. Nowadays digital tectonics provide a new approach to structural design in which the essential elements of the structure are digitally represented, generated and modulated in digital morphogenetic processes. Digital technologies CAD / CAM have radically changed conceptual approach not only in architectural but also in the structural and material design. Computer generated form by using parametric tools of design will be the result of matching material characteristics with their respective environmental constraints and function as a load-bearing envelope. The final form will then be only a by-product derived from a natural way the form operates as a whole. The paper focused on the release a new method of panelization and subdivision of surfaces for creating nondevelopable freeform surfaces without being limited by facetted solutions, to realise freely curved architectural forms.

We present a simple comprehensive treatment on the use of free-form optical elements, and of nonuniform optical windows, either for increasing focal depth [by regulating the width of the axial point spread function (PSF)] or for tuning the depth of field by controlling the influence of focus error on the modulation transfer function (MTF)]. We employ the rising notation of pupil engineering, which incorporates techniques for controlling the spread of the axial PSF, as well as methods for governing the impact of focus errors on the MTF. Our discussion also includes the use of vortex lenses for designing nonconventional optical systems.

Ahşap ızgara kabuklar, serbest biçimleri nedeniyle karmaşık bir tasarım ve uygulama sürecine sahip olmasına rağmen; geniş açıklıkları minimum malzeme ile geçen en etkin taşıyıcı sistemlerden biridir. Çalışmada ahşap ızgara kabuk örneklerinin geçmişten günümüze gelişiminin, olumlu, olumsuz yönlerinin ve iki farklı tür (elastik ve rijit) ahşap ızgara kabuğun incelenmesi ve karşılaştırılması amaçlanmıştır. Bu kapsamda, inşa edildiği dönemde; tasarım ve uygulama açısından yeniliklere öncülük eden, farklı özelliklere sahip ahşap ızgara kabuk örnekleri seçilerek; bu örneklerin, tasarım, yapım yöntemi ve elemanları ile form oluşturma yöntemlerine ait verileri tablolar halinde sunulmuştur. Elde edilen sonuçlar ve yapılan değerlendirmelere göre, ahşap ızgara kabukların mimari ve yapısal açıdan gelişimine paralel olarak öneminin de giderek arttığı görülmektedir. Formun karmaşıklığı günümüzde sınırlayıcı bir faktör olarak görülmezken, yapısal karmaşıklığın artmasına bağlı olarak üretim sürecindeki zorluklar ve artan maliyet ahşap ızgara kabuk örneklerini müze, sergi salonları, spor alanları, vb. gibi sembolik yapılarla sınırlandırmıştır. Gelecekte, ahşap ızgara kabukların farklı konstrüksiyonları bir arada kullanan hibrid sistemler şeklinde uygulanabileceği öngörülmektedir.

This paper analyses the interaction between the
turbulence and free surface. The phenomenon takes place
in many natural flows and industrial processes. In the
present experiments, turbulence is generated by a vertically
oscillating grid moving beneath the free surface. Fluid
velocity has been measured through a hot-film anemometer,
and the free surface elevation has been measured by an
ultrasonic sensor. Integral length scales and several turbulence
estimators have been computed. In order to detect
the generation of turbulence near the free surface, the
correlation between free surface elevation and the underneath
flow velocity has been studied, as well as the time lag
between turbulence and free surface. The free surface
dynamics has been characterized by a velocity scale and a
length scale. The kinetic energy associated with the free
surface fluctuations increases with the Reynolds number at
a rate depending on the frequency of the grid movement.
For Reynolds number larger than &1000, however, the
relationships collapse to a single curve characterized by a
lower rate. The present experiments do not achieve the
inertial sub-range in the vertical velocity fluctuations, and
the estimated spectrum decays with an exponent smaller
than -3, which is the typical value for the two-dimensional
turbulence in the inertial sub-range. The macro length
scale, estimated by using the Taylor’s frozen turbulence
hypothesis, experiences a decay away from the grid, which
follows reasonably well the profile of Thompson and
Turner (J Fluid Mechanics 67: 349–368, 1975). The micro
length scale reduces immediately beneath the free surface,
which can be interpreted by the increase of dissipation rate
in the subsurface layer. The classification diagram by
Brocchini and Peregrine (J Fluid Mech 449: 225–254,
2001) indicates that most tests fall in the weak turbulence
domain, but some tests fall in the wavy domain. The vertical
velocity fluctuations and the free surface level show a
significant correlation with a negative phase lag, that is, the
free surface fluctuations are ahead of the vertical velocity
fluctuations.

Grid shells supporting transparent or opaque panels are largely used to cover long-spanned spaces because of their lightness, the easy setup, and economy. This paper presents the results of experimental static and dynamic investigations carried out on a large-scale free-form grid shell mock-up, whose geometry descended from an innovative Voronoi polygonal pattern. Accompanying finite-element method (FEM) simulations followed. To these purposes, a four-step procedure was adopted: (1) a perfect FEM model was analyzed; (2) using the modal shapes scaled by measuring the mock-up, a deformed unloaded geometry was built, which took into account the defects caused by the assembly phase; (3) experimental static tests were executed by affixing weights to the mock-up, and a simplified representative FEM model was calibrated , choosing the nodes stiffness and the material properties as parameters; and (4) modal identification was performed through operational modal analysis and impulsive tests, and then, a simplified FEM dynamical model was calibrated. Due to the high deformability of the mock-up, only a symmetric load case configuration was adopted.

Free-form architecture is one of the major challenges for architects, engineers, and the building industry. This is due to the inherent difficulty of manufacturing double curvature facades at reasonable prices and quality. This paper discusses the possibilities of manufacturing free-form facade panels for architectural envelopes supported by recent advances in CAD/CAM systems and digital processes. These methods allow for no-mould processes, thus reducing the final price. Examples of actual constructions will be presented to prove the viability of computer numerically controlled (CNC) fabrication technologies. Scientific literature will be reviewed. Promising fabrication methods (additive, subtractive, forming) to accomplish this proposal will be discussed. This research will provide valuable information regarding the feasibility of manufacturing free-form panels for architectural envelopes at lower prices.

Free-form  GRC  panels  are  widely  used  in  lightweight  facade  elements.  Such  panels  can  be  manufactured  through  a  variety of methods. Nevertheless, its advantages such as moldability, durability and lightness, are penalized by the high price of the corresponding molds, especially if there is not a sufficient repetition of units. New digital technologies enable innovative possibilities in the field of construction and manufacture of molds with complex geometries. In this paper, a series of manufacturing methods for free-form GRC panels are presented. Advantages and drawbacks of these methods are discussed, especially the role played by the mold and its economic impact. Finally, conclusions of this analysis about its technical feasibility and possibilities are drawn.

The representation and the variation of hull shapes are two challenging problems in naval architecture due to the complexity of the geometry and to the need to ensure the fairness of the surfaces. Conventional CAD techniques are widely used to accurately describe the hull shape. However, they are rather complex to be easily used to generate hull shape variations due to the great number of variables involved. We propose a study to highlight the pro and cons of the application of space reduction techniques, usually referred to as Reduced Order Models (ROMs), to create a parametric model for both global and local hull shape variations. A geometric transformation relying on the Proper Orthogonal Decomposition (POD) method is applied on top of a combined subdivision surface-Free Form Deformation (FFD) approach conceived for modeling and variation of hull shapes. The analysis focuses on highlighting the geometric meaning of the new POD basis functions and on how this model affects the variability of the explored design space. Two studies are developed in order to show possible applications of this technique. In the first one a new set of selection criteria for the POD modes based on geometric considerations are proposed to use it on uncorrelated geometric domains. In the latter the large-dimensional space of the so-called Design Velocities (DV), related to the shape sensitivity, is reduced by using the POD approach to create a new transformation of the hull shape.