Adjoint Topology Optimization: Flow through a U-Bend

Simcenter STAR-CCM+ provides adjoint topology optimization as a method for finding optimized designs for complex flow problems. Topology optimization can aid in the design of, for example, components found in aeroplanes or ground transportation vehicles such as air ducts by improving performance and efficiency.

Adjoint topology optimization determines the optimal distribution of material within a domain in order to meet a single objective and any constraints placed on it. Topology optimization provides valuable solutions for a chosen criterion, without defining any initial shape or topology prior to the optimization process. The optimization uses adjoint-based sensitivities to advance a level set equation that tracks the fluid-solid interface, thus varying the topology at each step in the optimization. Topology optimization provides valuable solutions by distributing a volume of material in a selected design domain through optimization

The objective of this tutorial is to determine the optimal flowpath of water through a U-bend configuration by minimizing the pressure drop between inlet and outlet. The optimization is constrained in that the proportion of solid in the fluid-solid material distribution for describing the topology must not be less than 65%. The following diagram shows the geometry:

Water enters the inlet channel through a velocity inlet boundary with a velocity of 0.05 m/s and leaves it through a pressure outlet boundary at atmospheric pressure. The geometry is divided into three regions: the inlet channel, the outlet channel, and the topology optimization domain. The topology optimization is performed in the topology optimization domain only, by associating a solid phase, defined by the Topology Physics model, with the region. The fluid-solid material distribution is given by a scalar field—the material indicator field.

Adaptive mesh refinement (AMR) is used to locally refine the mesh along the solid-fluid interface. Topology Physics Mesh Adaptation method is used to adjust the mesh. This model identifies the solid-fluid interface cells for refinement based on the gradient of the material indicator field, therefore the mesh is refined only at the volume close to the interface.

After the topology optimization has finished, you can extract a closed surface from the computed material indicator field. This extracted surface is automatically added as a geometry part to the simulation tree. You can then mesh this optimized geometry part and run a flow simulation with it in order to validate the new design.