George Boole, in the 1840s, proposed that variables could represent more than just numbers. Boole’s work, published in “An Investigation of the Laws of Thought” (1854), introduced algebra with two values: 1 (true) and 0 (false). Instead of traditional algebraic operations, Boolean algebra uses AND, OR, and NOT, also known as conjunction, disjunction, and complement. …

# Category Archives: Numerics

## Additional Thoughts on Half-Equation Model of Johnson and King

The Johnson King turbulence model represented a significant advancement in the understanding and modeling of turbulent flows. Introduced amidst the exploration of first and second equation models, the Johnson King model distinguished itself through the innovative concept of a half-equation model, emphasizing the critical role of memory in turbulence phenomena. The early stages of turbulence …

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## An Improbable Life by D.C. Wilcox, and the $k-\omega$ Model

I just finished reading the autobiography of D. C. Wilcox. He wrote a number of books that were published through his own company. One of the most popular is on fluid dynamics. A less known book is on turbulence modeling. He was famous for a particular two-equation turbulence model in the form of $k-\omega$. It …

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## Toward Exascale Computation for Turbomachinery Flows

Citation: Yuhang Fu, Weiqi Shen, Jiahuan Cui, Yao Zheng, Guangwen Yang, Zhao Liu, Jifa Zhang, Tingwei Ji, Fangfang Xie, Xiaojing Lv, Hanyue Liu, Xu Liu, Xiyang Liu, Xiaoyu Song, Guocheng Tao, Yan Yan, Paul Tucker, Steven Miller, Shirui Luo, Seid Koric, and Weimin Zheng, “Toward Exascale Computation for Turbomachinery Flows,” Gordon Bell, High Performance Computing, …

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## Split-Step Simulations to Assess the Effects of Atmospheric Boundary Layer Turbulence on the Dose Variability of N-Waves and Shaped Booms

My former student, Dr. Alex Carr, along with Dr. J. Lonzaga, who are both of NASA Langley Research Center, and myself published an article on the propagation of sonic boom through the turbulent atmosphere. Abstract: The effects of atmospheric boundary layer turbulence on the loudness variability of a sonic boom N-wave and shaped boom are …

## Fall 2023

Who would have thought that 7 years go by so quickly at the University of Florida. This year I am teaching introduction to computational fluid dynamics. The last time I taught it was before COVID in the fall of 2020. I am working on a new design program for nozzles. I am basing it on …

## Aeroacoustic and Aerodynamic Interaction Effects Between eVTOL Rotors

My student presented his MS thesis on the aerodynamics and aeroacoustics of rotors. Abstract: Electric vertical take-off and landing (eVTOL) aircraft are characterized by their unconventional wing and electric rotor configurations, which involve both side-by-side and tandem rotor configurations. These configurations create unique aerodynamic and aeroacoustic flow-fields. We numerically investigate the interaction effects between rotor …

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## AIAA SciTech 2023

This year, some of my students and collaborators are going to the AIAA SciTech conference in the DC area in the National Harbor, MD. We are presenting two particular papers. The first involves hypersonic flow-fields and the second involves acoustics and aerodynamic experiments. The citations, papers, and presentations are:

## The prediction of cross-spectra from first mode instability waves within high-speed flow over sharp and blunt cones with plasma actuation

Abstract: Leading edge geometries, such as cones, moving at high-speed undergo intense loading due to the growth of instability waves and turbulent transition. These instability waves are highly spatially coherent. Aerodynamic loading related to instability waves and transition cause large-amplitude vibrations within the underlying structure, which may lead to flight-vehicle failure. We examine the effect …

## On Large-Scale HPC from Viewpoint of Cebeci

One other aspect should be mentioned. When the program was transferred to El Segundo from Santa Monica, I naturally duplicated some runs. The printout was eight-decimal places, I believe. For a number of steps the new and old tab sheets would check exactly. But then after a while there would be a gradual drift; first …

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