Analysis of ground wind loads on launch vehicles using opensource software

Abstract

The process of launching vehicles into space is among the most significant developments that have occurred in the field of modern technology. This enables the successful completion of significant missions, such as the launch of satellites into space and the exploration of space by humans. As these complex machines ascend through the atmosphere of the Earth, they are forced to contend with an environment that is constantly shifting and frequently unpredictable, particularly in the atmospheric boundary layer (ABL). The atmospheric boundary layer (ABL), which is the turbulent lower section of the atmosphere that touches the surface of the Earth, makes it extremely challenging for launch vehicles to fly effectively, maintain structural integrity, and be controlled from an overall perspective. Due to the fact that the wind speed and direction are constantly shifting in a chaotic manner, this layer is turbulent. This places loads that are both intricate and subject to rapid change on the vehicle. Since the beginning of rocketry, one of the most important areas of research and development has been figuring out how to have a better understanding of ABL turbulence and how to decrease its potential impacts. A comprehensive investigation into the ways in which ABL turbulence influences the aerodynamics of launch vehicles is the objective of this master's thesis. In order to accomplish this, it will provide a comprehensive historical account of the ways in which our understanding has evolved over the course of time, the challenges that we have encountered, and the advancements in modeling and design that have been made in order to address these challenging occurrences. The primary objective of the simulation setup is to create an accurate representation of the turbulent ABL conditions that launch vehicles must go through prior to their launch. Ground winds, particularly when they are turbulent, have the potential to exert a significant amount of stress and motion on launch vehicles, which may have an impact on their structural integrity and safety while they are in operation . Therefore, in order to examine the aerodynamic and structural variables, it is important to conduct a simulation of these conditions that is extremely exact. In addition, one of the primary objectives of this research is to evaluate the precision of a Large Eddy Simulation (LES) framework that is entirely open-source by comparing it to well-known experimental data from the NASA TDT. Reynolds values up to 3.6 ×106 (model scaled) and turbulence spectra between 0.1 and 40 Hz (model scaled) are the primary areas of attention in this study. 0.25 is the Mach number that is being used for these ground wind simulations.To guarantee the extensive application and significance of the study, ABL profiles for three separate launch complexes were simulated: SLC-TX (A launch complex located in Texas), SLC-39 (Kennedy Space Center, Florida) and SLC-40 (Cape Canaveral Space Force Station, Florida). The selection of these sites is due to the significant variation in base altitudes for launch vehicles, which range from 12 to 78 feet above ground level, as well as the diverse surrounding topography. Due of these geographical disparities, the simulations must precisely replicate the distinct ABL velocity profiles and turbulence attributes associated with them. The research employed an open-source CFD platform. This decision renders aerospace engineering analysis more accessible, reproducible, and economical, providing an alternative to costly commercial software solutions. This research demonstrates that evaluating these frameworks using high-quality experimental data is crucial for establishing confidence in their predictive capabilities. LES was selected as the primary method for modeling turbulence. Reynolds-Averaged Navier-Stokes (RANS) models consider all turbulent scales, whereas Large Eddy Simulation (LES) focuses solely on the larger, energy-containing turbulent eddies and the smaller, more ubiquitous subgrid-scale (SGS) eddies. This technique is particularly effective for ABL flows characterized by substantial, transient turbulent structures, and for precisely forecasting flows with significant separation and instability, such as those surrounding a launch vehicle subjected to ground winds. To investigate aerodynamic instability, it is essential that LES accurately captures these complex flow events. In conclusion, this study highlights the substantial impact of ABL turbulence on the stability of launch vehicles during post-launch operations. This study provides a robust, widely accessible instrument for simulating turbulence-induced instabilities under realistic atmospheric circumstances by verifying an open-source Large Eddy Simulation (LES) framework against NASA's Transonic Dynamics Tunnel (TDT) experiments. The framework's capacity to delineate turbulence-induced vorticity and shear stress offers valuable insights for enhancing launchpad infrastructure, refining operational protocols, and mitigating aerodynamic hazards in advanced reusable launch systems. To reconcile computational and experimental aerodynamics, future endeavors aim to expand the computational model to incorporate other launch sites. This approach streamlines high-fidelity turbulence analysis for the aerospace sector by enhancing the precision of aerodynamic forecasts while diminishing reliance on expensive commercial tools.