Huaibao Zhang

A data-driven adaptive Reynolds-averaged Navier–Stokes k–ω model for turbulent flow

Abstract This paper presents a new data-driven adaptive computational model for simulating turbulent flow, where partial-but-incomplete measurement data is available. The model automatically adjusts the closure coefficients of the Reynolds-averaged Navier–Stokes (RANS) k – ω turbulence equations to improve agreement between the simulated flow and the measurements. This data-driven adaptive RANS k – ω (D-DARK) model is validated with 3 canonical flow geometries: pipe flow, backward-facing step, and flow around an airfoil. For all test cases, the D-DARK model improves agreement with experimental data in comparison to the results from a non-adaptive RANS k – ω model that uses standard values of the closure coefficients. For the pipe flow, adaptation is driven by mean stream-wise velocity data from 42 measurement locations along the pipe radius, and the D-DARK model reduces the average error from 5.2% to 1.1%. For the 2-dimensional backward-facing step, adaptation is driven by mean stream-wise velocity data from 100 measurement locations at 4 cross-sections of the flow. In this case, D-DARK reduces the average error from 40% to 12%. For the NACA 0012 airfoil, adaptation is driven by surface-pressure data at 25 measurement locations. The D-DARK model reduces the average error in surface-pressure coefficients from 45% to 12%.

Simulation of Flow-tube Oxidation on the Carbon Preform of PICA

The oxidation of carbon fibers at high temperature is a subject of great interest in atmospheric re-entry science. To correctly evaluate the parameters involved, and test oxidation models, it is necessary to use a combination of flow and material solver. This works presents the full three-dimensional, implicit coupling of a computational fluid dynamics and material response solver, with the goal of reproducing the results of a series of flow-tube experiments recently performed. Results are presented for the geometry of interested, using a simplified numerical setup. This effort is the part of an ongoing project to develop a fully coupled system that solves fluid dynamics and material response under atmospheric entry conditions.

An introduction to the derivation of surface balance equations without the excruciating pain

Abstract Analyzing complex fluid flow problems that involve multiple coupled domains, each with their respective set of governing equations, is not a trivial undertaking. Even more complicated is the elaborate and tedious task of specifying the interface and boundary conditions between various domains. This paper provides an elegant, straightforward and universal method that considers the nature of those shared boundaries and derives the appropriate conditions at the interface, irrespective of the governing equations being solved. As a first example, a well-known interface condition is derived using this method. For a second example, the set of boundary conditions necessary to solve a baseline aerothermodynamics coupled plain/porous flow problem is derived. Finally, the method is applied to two more flow configurations, one consisting of an impermeable adiabatic wall and the other an ablating surface.