Yasushi Nakabayashi

Parallel finite element fluid analysis on an element-by-element basis

A finite element fluid analysis code, which is based on an element-by-element scheme and the matrix-storage free formulation, is developed and implemented to the massively parallel computer; KSR1. Since the element-by-element scheme coupled with the CG-type iterative solver is suitable for parallel processing, the matrix-storage free formulation will enable the large-scale computation within a reasonable time.After the verification of the code by some numerical examples, the cavity flow and cyclinder flow, the parallel efficiency is discussed. In the analysis of cavity flow, the speed-up using 16 CPUs is 15.35, which corresponds to the parallel efficiency of 95.9%.

Large-scale finite element fluid analysis by massively parallel processors

Abstract A finite element fluid analysis code, which is based on the matrix-storage free formulation and the element-by-element computation strategy, is developed. The code has reduced memory requirements due to the matrix-storage free formulation. Simulations involving one million elements can be carried out with less than 208 Mbytes of memory. The code is implemented on the massively parallel computers, KSR1 and CRAY T3D. In the case of KSR1, high parallel efficiency is achieved, i.e. 95.9% with 16 CPUs. In the case of T3D, excellent scalability is achieved. Each time step of a 3D cavity flow problem with one million elements required 36.3, 18.7 and 9.8 s of CPU time by using 32, 64 and 128 processors, respectively.

Importance of Serum Amino Acid Profile for Induction of Hepatic Steatosis under Protein Malnutrition

We previously reported that a low-protein diet caused animals to develop fatty liver containing a high level of triglycerides (TG), similar to the human nutritional disorder “kwashiorkor”. To investigate the underlying mechanisms, we cultured hepatocytes in amino acid-sufficient or deficient medium. Surprisingly, the intracellular TG level was increased by amino acid deficiency without addition of any lipids or hormones, accompanied by enhanced lipid synthesis, indicating that hepatocytes themselves monitored the extracellular amino acid concentrations to induce lipid accumulation in a cell-autonomous manner. We then confirmed that a low-amino acid diet also resulted in the development of fatty liver, and supplementation of the low-amino acid diet with glutamic acid to compensate the loss of nitrogen source did not completely suppress the hepatic TG accumulation. Only a dietary arginine or threonine deficiency was sufficient to induce hepatic TG accumulation. However, supplementation of a low-amino acid diet with arginine or threonine failed to reverse it. In silico analysis succeeded in predicting liver TG level from the serum amino acid profile. Based on these results, we conclude that dietary amino acid composition dynamically affects the serum amino acid profile, which is sensed by hepatocytes and lipid synthesis was activated cell-autonomously, leading to hepatic steatosis.

APPLICATION OF THE EFMM TO FLUID-STRUCTURE COUPLED ANALYSIS AND ITS PARALLELIZATION METHOD

Abstract. There is a new fluid-structure coupled analysis method that combines a structure analysis method using Enriched Free Mesh Method (EFMM); a type of meshless analysis methods and a fluid analysis method using SUPG/PSPG stabilized FEM. in this study, solutions for problems during the parallelization of the abovementioned method are described. In EFMM, it is relatively easy to parallelize problems which do not require remeshing such as static analyses. Application of EFMM, on the other hand, becomes challenging on the problems needs remeshing due to issues in analysis algorithm of EFMM. Nevertheless, parallelization is essential in the fluid-structure coupled analysis. There fore, we propose a method for parallelization of EFMM in this study.

Fluid-Structure Coupled Analysis Using Enriched Free Mesh Method

Almost all the phenomena occurring around us are the coupled phenomena. In the field of numerical analysis, it is difficult to perform coupled analysis. Because, there are a lot of problems and these problems make coupled analysis difficult, so we have to resolve these problems to perform analyses with considering the coupling effect. At present, as the popularity of numerical analysis rising along advancement in computer performance, demand of numerical analyses with incorporating coupling effects will further increase. In this research, we propose a new fluid-structure coupled analysis method using SUPG/PSPG stabilized FEM and Enriched Free Mesh Method to eliminate a lot of problems occurring in the process of coupled analysis. As the feature of our proposed method, linear triangular elements are only used in the analysis.