Wyniki wyszukiwania - BazTech

1

Representing 3D Topological Adjacencies between Volumes Using a 36-Intersection Model

Salleh Syahiirah, Ujang Uznir, Azri Suhaibah

Geomatics and Environmental Engineering

|

2022

|

Vol. 16, no. 2

127--155

EN

Topological properties of objects should be maintained and preserved to concisely represent objects. However, the implementation of 2D topological rules requires the decomposition of 3D objects into lower dimensions to determine topological relationships. This results in 2D topological relationships although the connected objects are in 3D. Hence, accurate representation of 3D connectivity in 3D models is limited. 3D topological rules can be implemented to include topological connectivity in 3D space. This paper implemented an extension of the 27-Intersection Model (27-IM) called the 36-Intersection Model (36-IM) to represent 3D topological adjacencies of two objects in 3D space. This resulted in a 12 × 3 intersection matrix or 36-IM that represented the intersections in terms of dimension and number of separations. Six cases were tested, consisting of “meets”, “disjoint” “intersects at a line”, “intersects at a point”, “contains”, and “overlaps”. The resulting 36-IM matrices provided an accurate representation of how the objects in 3D space were related and their dimension of intersections. The formalisms of the 36-IM matrices were also interoperable which allowed the interpretation of 36-IM using the 9IM and DE-9IM to determine general topological relationships. By examining the intersection of interiors, boundaries and exteriors of 3D objects without object decomposition, 3D topological relationships can be determined as well as the dimension and manner of intersection.

2

Study of topology and vortex structure in turbine cascades with tip clearance under different incidence angles

Yan P. G., Qiang X. Q., Teng J. F., Han W. J.

Journal of Theoretical and Applied Mechanics

|

2013

|

Vol. 51 nr 2

363--373

EN

Three sets of conventional straight, positive curved and negative curved turbine cascades with tip clearance were tested with experimental measurement. The impact of incidence angles and blade bending on the tip leakage was studied under larger clearance (0.036 of span). An ink trace visualization of the wall flow and topology theory was adopted and thus the topological structures of the blade surface, the upper and lower end wall were analyzed in this paper. It was found that, compared with the same cascade under the zero incidence angle, the saddle points all move to the upstream, the scope of the separation expands along the flow and span direction, and the separation line of the upper and lower passage vortex climb to the middle span of the blade when the flow incidence angle increased from zero to 20º. Under the condition of zero and 20º incidence angle, the positive curved blade will eliminate the upper passage vortex. The numbers of singular points are reduced and the interaction loss between the passage vortex and the leakage vortex is greatly reduced too. On the other hand, it also strengthens the blocking effect of the end wall cross flow on the leakage flow, thereby reduces the relative leakage flow rate.

PL

W pracy zaprezentowano wyniki pomiarów eksperymentalnych trzech zestawów konwencjonalnych palisad turbin o prostym, dodatnio i ujemnie zakrzywionym profilu. Zbadano wpływ kąta natarcia oraz efekt zginania łopatek na straty wskutek upływu przy luzie wierzchołkowym sięgającym 3.6% rozpiętości łopatek. Do analizy zastosowano wizualizację śladów pozostawianych barwnikiem oraz teorię topologii, tj. struktur topologicznych reprezentujących powierzchnię łopatki oraz górnej i dolnej ściany krańcowej. Zaobserwowano, że w porównaniu do analogicznej palisady o zerowym kącie natarcia wszystkie punkty siodłowe przesuwają się w gorę przepływu, a obszar oderwania strugi rozszerza się wzdłuż promienia łopatki. Jednocześnie granica oderwania górnego i dolnego wiru przemieszcza się ku środkowi łopatki, gdy kąt natarcia narasta od zera do 20◦. Przy tych granicznych wartościach kąta natarcia łopatki o dodatniej krzywiźnie profilu eliminują górny wir podczas przejścia. Ponadto okazało się, że liczba punktów osobliwych zmniejszyła się podobnie, jak osłabiła się interakcja pomiędzy wirami przejścia i wirami upływu. Stwierdzono, że wzmacnia to efekt blokowania upływu poprzecznym przepływem na krańcowej ścianie łopatki, co ostatecznie redukuje straty indukowane upływem.

3

Zastosowanie zaawansowanych reguł topologicznych w procesie budowania baz danych przestrzennych wspomagających wycenę nieruchomości

Cichociński P.

Roczniki Geomatyki

|

2007

|

T. 5, z. 3

29-35

EN

An essential attribute of real estates, having influence on their cadastral value, is their location, and thereby the neighbourhood, both of other real estates and other objects. In order to efficiently carry out the valuation,, spatial information on these objects should be collected in an appropriate database. This information could come from GIS databases, encompassing land and buildings cadastre, spatial registration of utility infrastructure, topographical objects with digital terrain model, as well as various environmental elements. It can be assumed that the necessity of integration of these data sets will also appear during the creation of national spatial data infrastructures. This will include both aggregation of neighbouring data sets of the same object types (.horizontal.) and adjustment of the content of different data sets describing the same part of the space (.vertical.). Previous experiences of users working in Poland with different kinds of topographical databases showed, however, the possibility of considerable inconsistencies among them of both geometrical and attribute character , due to different temporal periods and methods of data acquisition, and also due to different data sources. It is likely that the same problem will happen with large scale data. This can be resolved by the use of topology .description of spatial relationships between geographical objects. Originally, this term referred to such simple rules describing the internal correctness of data sets as: .lines shall not intersect and must not overlap., .line shall only touch other lines at endpoints ., .polygons shall not overlap and shall not have gaps., necessary to carry out any spatial analyses. However, in last few years the term of topology was extended and now includes also description of relationships between objects coming from different object classes. The list of available rules was considerably extended. Among other things it now contains the following statements: .boundaries of polygon features in feature class A shall be covered by boundaries of polygon features in feature class B., .objects of feature class A shall be contained within polygons of feature class B., .objects of feature class A shall be covered with objects of feature class B.. The paper presents the use of these topological rules available in advanced GIS software to describe the required mutual spatial relationships between objects coming from different, mentioned above databases and to analyse occurring violations of these rules. Besides methods of detection of these inaccuracies, the methodology of their removal was also proposed, using analytical and data processing GIS tools. The technology called conflation can also be used here. It refers to joining of at least two different data sets to create a new data set. It is necessary to make suitable modifications of objects from both data sets. To carry out this operation on a wider scale it is required to use tools automating this process to the greatest degree possible in order to reduce the participation of the operator to the interventions in few non-typical cases. It is expected that the results of conducted works will be applicable not only to the valuation of real estates, but in every case when the use of many potentially inconsistent sources of geographical data is required