Treating Complex Geometries with Cartesian Grids in Problems for Fluid Dynamics

2015 ◽  
pp. 528-535
Author(s):  
Igor Menshov
Keyword(s):  
Fluid Dynamics ◽  
Complex Geometries ◽  
Cartesian Grids

Efficiency prediction for storage chambers using computational fluid dynamics

1996 ◽  
Vol 33 (9) ◽  
pp. 163-170 ◽  
Author(s):  
Virginia R. Stovin ◽  
Adrian J. Saul
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Particle Tracking ◽  
Critical Value ◽  
Complex Geometries ◽  
Bed Shear Stress ◽  
Breadth Ratio ◽  
Computational Fluid Dynamics Cfd ◽  
Simulated Flow

Research was undertaken in order to identify possible methodologies for the prediction of sedimentation in storage chambers based on computational fluid dynamics (CFD). The Fluent CFD software was used to establish a numerical model of the flow field, on which further analysis was undertaken. Sedimentation was estimated from the simulated flow fields by two different methods. The first approach used the simulation to predict the bed shear stress distribution, with deposition being assumed for areas where the bed shear stress fell below a critical value (τcd). The value of τcd had previously been determined in the laboratory. Efficiency was then calculated as a function of the proportion of the chamber bed for which deposition had been predicted. The second method used the particle tracking facility in Fluent and efficiency was calculated from the proportion of particles that remained within the chamber. The results from the two techniques for efficiency are compared to data collected in a laboratory chamber. Three further simulations were then undertaken in order to investigate the influence of length to breadth ratio on chamber performance. The methodology presented here could be applied to complex geometries and full scale installations.

Efficiency limits of fans

2019 ◽  
Vol 234 (5) ◽  
pp. 739-748
Author(s):  
Konrad Bamberger ◽  
Thomas Carolus
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Geometrical Parameter ◽  
The Self ◽  
Complex Geometries ◽  
Relevant Parameter ◽  
Optimization Scheme ◽  
Loss Models ◽  
Definition Of

The purpose of this work is to identify upper efficiency limits of industrial fans such as axial rotor-only fans, axial with guide vanes, centrifugal rotor-only and centrifugal with volute. The efficiency limit is always a function of the class, the design point within the class and the definition of efficiency (total-to-static and total-to-total). The characteristic Reynolds number is another relevant parameter. First, based on analytical and empirical loss models, a theoretical efficiency limit is estimated. A set of idealizing assumptions in the loss models yields efficiencies which are assumed to be an insuperable limit but may be unrealistically high. Second, more realistic efficiency limits are estimated using a computational fluid dynamics-based optimization scheme, seeking for the best designs and hence the maximum achievable efficiencies in all classes. Given the self-imposed constraints in the geometrical parameter space considered, the thus-obtained practical efficiency limits can only be exceeded by admitting more complex geometries of the fans.

Robust and Efficient Setup Procedure for Complex Triangulations in Immersed Boundary Simulations

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Jianming Yang ◽  
Frederick Stern
Keyword(s):  
High Resolution ◽  
Grid Point ◽  
Immersed Boundary ◽  
Complex Geometries ◽  
Immersed Boundary Methods ◽  
Ray Casting ◽  
Cartesian Grids ◽  
Triangulated Surfaces ◽  
Boundary Methods ◽  
Fast Procedure

Immersed boundary methods have been widely used for simulating flows with complex geometries, as quality boundary-conforming grids are usually difficult to generate for complex geometries, especially when motion and/or deformation is involved. A major task in immersed boundary simulations is to inject the immersed boundary information into the background Cartesian grid, such as the inside/outside status of a grid point with regard to the immersed boundary and the accurate subcell position of the immersed boundary for a grid point next to it. Complex geometries in immersed boundary methods can be conveniently represented with triangulated surfaces placed upon underlying Cartesian grids in a Lagrangian manner. Regular, intuitive implementations using triangulations can be error-prone and/or cumbersome in dealing with robustness issues. In addition, they can be prohibitively expensive for high resolution simulations with complex moving/deforming boundaries. In this paper, a simple, robust, and fast procedure is developed for setting up complex triangulations in immersed boundary simulations. Central to this setup procedure are a ray casting and closest surface point computation algorithms. Several illustrative examples, including high resolution cases with Cartesian grids of up to 2.1 × 109 points and triangulations of up to 1.3 × 106 surface elements, are performed to demonstrate the robustness and efficiency of our procedure.

Turbomachinery computational fluid dynamics: asymptotes and paradigm shifts

2007 ◽  
Vol 365 (1859) ◽  
pp. 2553-2585 ◽  
Author(s):  
W.N Dawes
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Paradigm Shift ◽  
Computational Models ◽  
Complex Geometry ◽  
Three Dimensional ◽  
Complex Geometries ◽  
Paradigm Shifts ◽  
New Paradigm ◽  
Secondary Air

This paper reviews the development of computational fluid dynamics (CFD) specifically for turbomachinery simulations and with a particular focus on application to problems with complex geometry. The review is structured by considering this development as a series of paradigm shifts, followed by asymptotes. The original S1–S2 blade–blade-throughflow model is briefly described, followed by the development of two-dimensional then three-dimensional blade–blade analysis. This in turn evolved from inviscid to viscous analysis and then from steady to unsteady flow simulations. This development trajectory led over a surprisingly small number of years to an accepted approach—a ‘CFD orthodoxy’. A very important current area of intense interest and activity in turbomachinery simulation is in accounting for real geometry effects, not just in the secondary air and turbine cooling systems but also associated with the primary path. The requirements here are threefold: capturing and representing these geometries in a computer model; making rapid design changes to these complex geometries; and managing the very large associated computational models on PC clusters. Accordingly, the challenges in the application of the current CFD orthodoxy to complex geometries are described in some detail. The main aim of this paper is to argue that the current CFD orthodoxy is on a new asymptote and is not in fact suited for application to complex geometries and that a paradigm shift must be sought. In particular, the new paradigm must be geometry centric and inherently parallel without serial bottlenecks. The main contribution of this paper is to describe such a potential paradigm shift, inspired by the animation industry, based on a fundamental shift in perspective from explicit to implicit geometry and then illustrate this with a number of applications to turbomachinery.

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