Three-Dimensional, Parallel Implementation of Entropic Lattice Boltzmann Method for Compressible Flows

Date

2024-9-4

Author

Selimhocaoğlu, Bahri Tuğcan

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Among the Lattice Boltzmann (LB) methods the entropic variant, called Entropic Lattice Boltzmann Method (ELBM) has become popular in solving compressible flows. The fundamental logic behind this method is the expansion of double equilibrium distribution functions under entropy constraints as well as using higher-order multi-speed lattices and dividing the collision process into two parts consisting of a quasi-equilibrium state. ELBM is an inherently unsteady and explicit calculation method. This thesis provides a short description of the method in terms of the core principles, mathematical framework, followed by a 3D parallel implementation with different Entropic Relaxation Factor calculation methods added as well. The parallel performance of this implementation is studied and found out to be acceptable. The method is validated via different cases in the compressible regime, both of steady and unsteady nature like flow around both circular and square cylinders at low compressible regime, the shock tube problem, flow around a supersonic sphere, and NACA0012 airfoil at different compressible flow regimes. The results of a flow around a cubic diamond resulting in a three dimensional and highly unsteady wake at both low compressible and transonic regime are also presented to demonstrate the capabilities of the method. It is demonstrated that ELBM was able to capture the complex unsteady nature of this case with local changes in the compressible regime. With the computational power available, the highest Re investigated was 10000, which is within the laminar flow regime. As a result, ELBM was found out to be a very capable method which is able to capture unsteady wake-driven physics in the compressible regime.

Subject Keywords

Computational Fluid Dynamics, Entropic Lattice Boltzmann Method, Parallel Implementation, Compressible Flow

URI

https://hdl.handle.net/11511/111415

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Graduate School of Natural and Applied Sciences, Thesis