Wednesday, November 29, 2017

Topology Optimization for Coupled Thermo-Fluidic Problems

Interesting video of a talk by Ole Sigmund on optimizing topology for fluid mixing or heat transfer.

Sunday, November 26, 2017

Installing ToPy in Fedora 26

This post summarizes the steps to install ToPy in Fedora 26.

Monday, November 20, 2017

Machine Learning for CFD Turbulence Closures

I wrote a couple previous posts on some interesting work using deep learning to accelerate topology optimization, and a couple neural network methods for accelerating computational fluid dynamics (with source). This post is about a use of machine learning in computational fluid dynamics (CFD) with a slightly different goal: to improve the quality of solutions. Rather than a focus on getting to solutions more quickly, this post covers work focused on getting better solutions. A better solution is one that has more predictive capability. There is usually a trade-off between predictive capability, and how long it takes to get a solution. The most well-known area for improvement in predictive capability of state-of-the-practice, industrial CFD is in our turbulence and transition modeling. There are a proliferation of approaches to tackling that problem, but the overall strategy that seems to be paying off is for CFD'ers to follow the enormous investment being made by the large tech companies in techniques, open source libraries, and services for machine learning. How can those free / low-cost tools and techniques be applied to our problems?

The authors of Machine Learning Models of Errors in Large Eddy Simulation Predictions of Surface Pressure Fluctuations used machine learning techniques to model the error in their LES solutions. See an illustration of the instantaneous density gradient magnitude of the developing boundary layer from that paper shown to the right. Here's the abstract,
We investigate a novel application of deep neural networks to modeling of errors in prediction of surface pressure fluctuations beneath a compressible, turbulent flow. In this context, the truth solution is given by Direct Numerical Simulation (DNS) data, while the predictive model is a wall-modeled Large Eddy Simulation (LES
). The neural network provides a means to map relevant statistical flow-features within the LES solution to errors in prediction of wall pressure spectra. We simulate a number of flat plate turbulent boundary layers using both DNS and wall-modeled LES to build up a database with which to train the neural network. We then apply machine learning techniques to develop an optimized neural network model for the error in terms of relevant flow features

Monday, November 13, 2017

Deep Learning to Accelerate Computational Fluid Dynamics

Lat-Net: Compressing Lattice Boltzmann Flow Simulations using Deep Neural Networks
I posted about a surprising application of deep learning to accelerate topology optimization. The thing I like about that approach is it's a strategy that could be applied to accelerate many different solvers that we use to simulate all sorts of continuum mechanics based on partial differential equations (i.e. computational fluid dynamics, structural mechanics, electrodynamics, etc.). With a bit of help from Google I found a neat paper and project on github doing exactly that for a Lattice-Boltzmann fluid solver.

Friday, November 10, 2017

Deep Learning to Accelerate Topology Optimization

Topology Optimization Data Set for CNN Training
Neural networks for topology optimization is an interesting paper I read on arXiv that illustrates how to speed up the topology optimization calculations by using a deep learning convolution neural network. The data sets for training the network are generate in ToPy, which is an Open Source topology optimization tool.