In the traditional approaches to the level of detail (LoD) control of polygonal datasets, local features, such as curvature and distance energy, have been used as representative control parameters. However, when our targets are restricted to digital elevation models (DEMs), features of differential topology are expected to play a key role as global features in determining the LoD of these shapes. This paper proposes a novel method of simplifying a given DEM while keeping this kind of features as much as possible. Two sample datasets are used to demonstrate the feasibility of the proposed method.

View full abstract

Small scale multi-blade fan being used in automobile air conditioning system is one of the well-established fluid machinery, however further improvement of performance and noise reduction are required in the situation of total advancement of automobile engineering. In order to meet the requirement, experimental analysis of 3D flow in it is useful to understand physical phenomena generated in it and to improve the performances. Stereoscopic PIV (SPIV) is promising technique for this case, however there are some difficulties in practical measurements of the flow field in a multi-blade fan having complicated geometry. The feasibility and applicablity of SPIV have been investigated by applying to measurements of the inflow structure of the multi-blade fan for two different types of impeller. The basic interests on the inflow are the flow through the inlet bell-mouth of the fan casing and the three-dimensional velocity field at the inlet part of the impeller. In the case of measurement of three-components of flow velocity at the section of the bell-mouth, the common optical arrangement of SPIV is applied, but in the latter case, a different type of camera arrangement must be applied. In the arrangement, two cameras are set at large stereoscopic viewing angle and with long focal length. In this case, a modified optical arrangement of SPIV and Schiempflug configuration of camera lens are adapted successfully. The results obtained give the three-dimensional features of inflow of the fan and the understanding of fan characteristics. From these results, the usefulness of SPIV for 3D flow analysis in a practical model of fluid machinery has been verified.

View full abstract