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Chapter 24: Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder

This tutorial is divided into the following sections:

24.1.Introduction

24.2.Prerequisites

24.3.Problem Description

24.4.Setup and Solution

24.5.Summary

24.1. Introduction

ANSYS Fluent’s adjoint solver is used to compute the sensitivity of quantities of interest in a fluid system with respect to the user-specified inputs, for an existing flow solution. Importantly, this also includes

the sensitivity of the computed results with respect to the geometric shape of the system. The adjoint design change tool is a powerful component that can use the sensitivity information from one or more adjoint solutions to guide systematic changes that result in predictable improvements in the system performance, which can be made subject to various types of design constraints if desired.

This tutorial provides an example of how to generate sensitivity data for flow past a circular cylinder, how to postprocess the results, and how to use the data to perform a multi-objective design change that reduces drag and increases lift by morphing the mesh. The tutorial makes use of a previously computed flow solution, and demonstrates how to do the following:

•Select the observable of interest.

•Access the solver controls for advancing the adjoint solution.

•Set convergence criteria and plot and print residuals.

•Advance the adjoint solver.

•Postprocess the results to extract sensitivity data.

•Use the design change tool to modify the cylinder shape to simultaneously reduce the drag and increase the lift.

24.2. Prerequisites

This tutorial is written with the assumption that you have completed one or more of the introductory tutorial Fluid Flow and Heat Transfer in a Mixing Elbow (p. 35) found in this manual and that you are familiar with the ANSYS Fluent tree and ribbon structure. Some steps in the setup and solution procedure will not be shown explicitly.

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