Multiscale Parallelized Computational Fluid Dynamics Modeling Toward Resolving Manufacturable Roughness

Abstract

Typical turbomachinery aerothermal problems of practical interest are characterized by flow structures of wide-ranging scales, which interact with each other. Such multiscale interactions can be observed between the flow structures produced by surface roughness and by the bulk flow patterns. Moreover, additive manufacturing (AM) may sooner or later open a new chapter in the way components are designed by granting designers the ability to control the shape and patterns of surface roughness. As a result, surface finish, which so far has been treated largely as a stochastic trait, can be shifted to a set of design parameters that consist of repetitive, discrete micro-elements on a wall surface (“manufacturable roughness”). Considering this prospective capability, the question would arise regarding how surface microstructures can be incorporated in computational analyses during designing in the future. Semi-empirical methods for predicting aerothermal characteristics and the impact of manufacturable roughness could be used to minimize computational cost. However, the lack of element-to-element resolution may lead to erroneous predictions, as the interactions among the roughness micro-elements have been shown to be significant for adequate performance predictions (Kapsis and He, 2018, “Analysis of Aerothermal Characteristics of Surface Micro-Structures,” ASME J. Fluids Eng., 140(5), p. 051104). In this paper, a new multiscale approach based on the novel block spectral method (BSM) is adopted. This method aims to provide efficient resolution of the detailed local flow variation in space and time of the large-scale microstructures. This resolution is provided without resorting to modeling every single ones in detail, as a conventional large-scale computational fluid dynamics (CFD) simulation would demand, but still demonstrating similar time-accurate and time-averaged flow properties. The main emphasis of this work is to develop a parallelized solver of the method to enable tackling large problems. The work also includes a first of the kind verification and demonstration of the method for wall surfaces with a large number of microstructured elements.

On locally embedded two-scale solution for wall-bounded turbulent flows

“…This should be the case for many practical wall-bounded turbulence flows where a time-averaged flow is smooth while being inhomogeneous in two wall-parallel directions. As indicated in the introduction, the present work stems from a two-scale block spectral method development aimed at more specific practical problems, such as surface micro-structures, micro/effusion-cooling (He 2018;Kapsis et al 2020) and aerothermal analyses of multiple blade passages and rows (He 2021), commonly subject to non-uniform flow conditions and geometries. The work presented in this paper should provide a more fundamental while generalizable underpinning of the two-scale methodology, as motivated.…”

Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion

“…The multiscale method is a source term-based approach that has been developed by solving different regimes with markedly different length and time scales [34][35][36]. The multiscale method so far has been typically used to deal with problems of many repetitive fine-scale element such as film and effusion cooling holes [37] as well as the additively manufactured pattern [38]. In the current framework, we adopt the multiscale method in a global manner, i.e.…”

Impact of Wall Temperature on Aerothermal Characteristics of an Array of Surface Microstructures

“…Recently, He [25] has developed a two-scale block-spectral approach for unsteady flows capable of resolving the flow field around surface microstructures at an affordable cost. The development of multi-scale methods presents considerable potential for applications to AM manufacturable surface micro-structures as indicated by Kapsis et al [26].…”