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As space exploration pushes boundaries, engineers face unique challenges ensuring spacecraft can endure intense conditions, particularly during launch, ascent, and descent. One of the most complex issues is aero vibroacoustics (AVA), specifically during the rocket¡¯s ascent phase, where turbulent airflows around the rocket excite the structure. These excitations can compromise sensitive equipment and payload integrity due to high sound pressure levels and vibrations.

To help engineers understand and address these phenomena, advanced simulation tools like VA One provide the precision and comprehensive analysis necessary to tackle AVA complexities in space. In this blog article, we'll explore the challenges of AVA in space and why VA One is the industry-preferred solution for vibroacoustic simulation.

The AVA simulation process involves calculating aerodynamic pressure fluctuations using either computational fluid dynamics (CFD) data or test data. There are three primary loading methodologies for vibroacoustic analysis, depending on the frequency range:

• Fluctuating Surface Pressure (FSP) for low-frequency analysis: This method converts Computational Fluid Dynamics (CFD) results into the frequency domain and applies them to a finite element model (FEM) of the structure and cavity. This helps predict how the structure will respond to the pressure fluctuations during ascent.
• General Surface Pressure (GSP) for high-frequency analysis: This method uses wave-number transformation to analyze pressure fluctuations and their impact on the structure. It converts CFD data into loads suitable for the Statistical Energy Analysis (SEA) method.
• Turbulent Boundary Layer (TBL): This method uses the chaotic, high-energy fluid regions along the spacecraft¡¯s surface to model the loads. It represents the interaction between turbulent airflow and the structure, approximating the load applied by turbulent flow on the surface (e.g., a fairing or vehicle body).

Each method focuses on assessing how aerodynamic loads affect structural vibrations and noise propagation within a cavity, such as a rocket fairing or vehicle cabin. The choice between TBL, FSP, and GSP depends on the frequency range and the complexity of the simulation.

Pre-test aero-vibro-acoustic analysis is essential for ensuring the reliability and performance of spacecraft. Using ESI¡¯s OpenFOAM, an open-source CFD toolbox, alongside VA One provides a comprehensive solution for this process. OpenFOAM generates pressure time histories on the surfaces, which are then integrated into VA One for advanced simulations. This integration reduces costs and streamlines the workflow by having both CFD and acoustic analysis from a single provider.

To model the ascent phase of a spacecraft, users can apply the loads experienced during ascent using three different methods: Turbulent Boundary Layer (TBL), Finite Structural Potential (FSP), or General Surface Pressure (GSP). These loads can be derived from either measured data (actual flow data collected during tests) or simulated data (flow data generated through simulations).

The wave-number transformation is important because it allows us to apply loads to the structure more accurately, without relying on simplified models like traditional TBL. By using the wave-number frequency spectrum directly, we can avoid assumptions and improve the accuracy of the results, especially when modeling how flow excites a structure and generates noise or convective energyvibrations.

Dr. Alexis Castel

Technical Expert, ¾ÅÓÎÌåÓý, a part of Keysight Technologies

Aero-vibro-acoustics presents significant challenges for engineers, especially as spacecraft are exposed to extreme aerodynamic forces during ascent and transonic flight. Accurate AVA simulation across a broad frequency range is essential for spacecraft integrity and mission success. VA One stands out as the preferred aero-vibro-acoustic simulation tool due to its comprehensive frequency analysis, CFD integration, advanced modeling techniques, and high-frequency simulation efficiency. These features provide engineers the confidence to tackle AVA challenges early in the design cycle and ensure rockets withstand immense ascent and transonic forces.