Space–time VMS computational flow analysis with isogeometric discretization and a general-purpose NURBS mesh generation method

Element-free methods (EFreeMs) are expected to eliminate the mesh generation task. However, a computer aided engineering (CAE) system by EFreeM for complex three-dimensional (3D) objects has not yet been developed. This paper discusses the obstacles to the CAE and way to solve them. A 3D groundwater flow analysis system with an EFreeM is presented as a practical CAE. In the system, instead of pursuing mesh-less CAE, a unique mesh is employed to achieve the practical CAE. Some 3D examples show the performance and usefulness of the system. Two serious drawbacks of the EFreeM are also discussed from the viewpoint of the practical CAE.

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Space–Time Gradient Method for Unsteady Bladerow Interaction—Part II: Further Validation, Clocking, and Multidisturbance Effect

Journal of Turbomachinery ◽

10.1115/1.4031464 ◽

2015 ◽

Vol 137 (12) ◽

Cited By ~ 2

Author(s):

L. He ◽

J. Yi ◽

P. Adami ◽

L. Capone

Keyword(s):

Case Studies ◽

Flow Analysis ◽

Space Time ◽

Inlet Temperature ◽

Turbine Stage ◽

Two Stage ◽

Transonic Compressor ◽

Surface Time ◽

Blade Row ◽

Speed Up

For efficient and accurate unsteady flow analysis of blade row interactions, a space–time gradient (STG) method has been proposed. The development is aimed at maintaining as many modeling fidelities (the interface treatment in particular) of a direct unsteady time-domain method as possible while still having a significant speed-up. The basic modeling considerations, main method ingredients and some preliminary verification have been presented in Part I of the paper. Here in Part II, further case studies are presented to examine the capability and applicability of the method. Having tested a turbine stage in Part I, here we first consider the applicability and robustness of the method for a three-dimensional (3D) transonic compressor stage under a highly loaded condition with separating boundary layers. The results of the STG solution compare well with the direct unsteady solution while showing a speed up of 25 times. The method is also used to analyze rotor–rotor/stator–stator interferences in a two-stage turbine configuration. Remarkably, for stator–stator and rotor–rotor clocking analyses, the STG method demonstrates a significant further speed-up. Also interestingly, the two-stage case studies suggest clearly measurable clocking dependence of blade surface time-mean temperatures for both stator–stator clocking and rotor–rotor clocking, though only small efficiency variations are shown. Also validated and illustrated is the capacity of the STG method to efficiently evaluate unsteady blade forcing due to the rotor–rotor clocking. Considerable efforts are directed to extending the method to more complex situations with multiple disturbances. Several techniques are adopted to decouple the disturbances in the temporal terms. The developed capabilities have been examined for turbine stage configurations with inlet temperature distortions (hot streaks), and for three blade-row turbine configurations with nonequal blade counts. The results compare well with the corresponding direct unsteady solutions.

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Computing Equidistant Curves and Surfaces

19th Design Automation Conference: Volume 2 — Design Optimization; Geometric Modeling and Tolerance Analysis; Mechanism Synthesis and Analysis; Decomposition and Design Optimization ◽

10.1115/detc1993-0413 ◽

1993 ◽

Author(s):

R. Sarma ◽

D. Dutta

Keyword(s):

Fluid Flow ◽

Mesh Generation ◽

Flow Analysis ◽

Parametric Surface ◽

Engineering Applications ◽

Parametric Curve ◽

Curves And Surfaces ◽

Fluid Flow Analysis

Abstract The problem of computing equidistant curves and surfaces between a point and (i) a parametric curve and (ii) a parametric surface is considered. This problem is important since it can form a basis for further generalizations of the problem, viz., computing equidistant curves and surfaces between a pair of curves and a pair of surfaces. Engineering applications of such equidistant curves and surfaces include fluid flow analysis, mesh generation and shape interrogation.

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Space–Time Variational Multiscale Isogeometric Analysis of a tsunami-shelter vertical-axis wind turbine

Computational Mechanics ◽

10.1007/s00466-020-01910-5 ◽

2020 ◽

Vol 66 (6) ◽

pp. 1443-1460 ◽

Cited By ~ 3

Author(s):

Yuto Otoguro ◽

Hiroki Mochizuki ◽

Kenji Takizawa ◽

Tayfun E. Tezduyar

Keyword(s):

Unsteady Flow ◽

Wind Turbine ◽

Mesh Generation ◽

Isogeometric Analysis ◽

Flow Analysis ◽

Vertical Axis ◽

Moving Mesh ◽

Vertical Axis Wind Turbine ◽

Accurate Representation ◽

Variational Multiscale

AbstractWe present computational flow analysis of a vertical-axis wind turbine (VAWT) that has been proposed to also serve as a tsunami shelter. In addition to the three-blade rotor, the turbine has four support columns at the periphery. The columns support the turbine rotor and the shelter. Computational challenges encountered in flow analysis of wind turbines in general include accurate representation of the turbine geometry, multiscale unsteady flow, and moving-boundary flow associated with the rotor motion. The tsunami-shelter VAWT, because of its rather high geometric complexity, poses the additional challenge of reaching high accuracy in turbine-geometry representation and flow solution when the geometry is so complex. We address the challenges with a space–time (ST) computational method that integrates three special ST methods around the core, ST Variational Multiscale (ST-VMS) method, and mesh generation and improvement methods. The three special methods are the ST Slip Interface (ST-SI) method, ST Isogeometric Analysis (ST-IGA), and the ST/NURBS Mesh Update Method (STNMUM). The ST-discretization feature of the integrated method provides higher-order accuracy compared to standard discretization methods. The VMS feature addresses the computational challenges associated with the multiscale nature of the unsteady flow. The moving-mesh feature of the ST framework enables high-resolution computation near the blades. The ST-SI enables moving-mesh computation of the spinning rotor. The mesh covering the rotor spins with it, and the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-IGA enables more accurate representation of the blade and other turbine geometries and increased accuracy in the flow solution. The STNMUM enables exact representation of the mesh rotation. A general-purpose NURBS mesh generation method makes it easier to deal with the complex turbine geometry. The quality of the mesh generated with this method is improved with a mesh relaxation method based on fiber-reinforced hyperelasticity and optimized zero-stress state. We present computations for the 2D and 3D cases. The computations show the effectiveness of our ST and mesh generation and relaxation methods in flow analysis of the tsunami-shelter VAWT.

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