SATPC0038854 Tab 04 4 SOW.pdf

STATEMENT OF WORK

1. Objective/Requirements

Background: Laminar-turbulent transition in boundary layer flows is a major contributor to overall uncertainty in predicting aerodynamic heating, drag, and overall performance of high-speed flight vehicles. Engineering predictions of hypersonic boundary layer transition (BLT) utilizes various modeling approaches, ranging from empirical correlations, linear stability correlations (i.e., N-factor methods), parabolized stability equations (PSE), and RANS-like, auxiliary transport equations. A major challenge in all these approaches is the extreme sensitivity of transition location to freestream disturbances. Quiet hypersonic wind tunnels can reasonably mimic the BLT scenarios in low-disturbance flight environments, but they face significant limitations in replicating actual flight conditions, especially the full-scale Reynolds number. In contrast, conventional wind tunnels are significantly noisier, and hence, do not permit an accurate extrapolation of the transition behavior to flight configurations. Additionally, current instrumentation capabilities do not allow accurate and sufficiently in-depth characterization of the freestream disturbances in high-speed wind tunnels.

Numerical experiments can offset the limitations of high-speed transition experiments by synthesizing the natural, stochastic disturbance environment in high-speed wind tunnels and simulating the laminar, transitional, and turbulent flows in such environments. Such high-fidelity simulations effectively amount to "digital wind tunnels" that can help bridge the gap between ground testing and in-flight transition, ultimately improving our predictive capabilities for hypersonic vehicle design.

A research effort within the Computational AeroSciences Branch of the NASA Langley Research Center seeks to improve the accuracy of boundary-layer transition prediction on high-speed flight vehicles by using data and insights from Direct Numerical Simulations (DNS) to guide the development of suitable engineering models. Specifically, the planned research will extend previous, first-principles simulations of freestream disturbance environment in a 2D nozzle with two wind tunnel walls to a rectangular section nozzle with four walls. These freestream disturbance simulations represent the first step toward high-fidelity simulations of hypersonic transition and their application to engineering models of transition that would allow more reliable extrapolation from ground data to flight. To achieve this goal in a timely manner, the DNS code required for such simulations cannot be developed as part of the NASA effort and an off-the-shelf capability must be acquired. Prof. Duan from the Ohio State University has developed used a DNS code with partial capability of this type and demonstrated it on a problem of direct relevance to the targeted NASA simulations of a rectangular cross-section nozzle at hypersonic speeds. Acquisition of the DNS code and the associated utilities under the current task order is critical to the timely completion of the NASA effort, paving the way for comparisons with experimental measurements and the development of improved transition models.

Scope of Work: This task order will support the delivery of an improved version of previously demonstrated computational methodology to simulate the fully 3D boundary-layer flow on the interior walls of a rectangular nozzle similar to the 31 Inch Mach 10 Wind Tunnel at NASA Langley Research Center. Specifically, the Contractor will deliver the DNS code(s) with verified solid-wall boundary conditions along all four walls of the rectangular test section. The codes will include preprocessing and postprocessing utilities to set up the numerical simulation and analyze the results in terms of mean-flow and fluctuation characteristics, including their 2nd order statistics, both single point and multi-point (i.e., frequency and wavenumber spectra). The documentation should be sufficient to allow the NASA personnel to setup, execute, and analyze the simulations, make appropriate modifications to the code if necessary, and aid troubleshooting.

Objectives: NASA’s research in support of high-speed research goals of the Aeronautics Research Mission Directorate includes the study of acoustic radiation from turbulent boundary layers along the walls of the 31 Inch Mach 10 wind tunnel at NASA Langley, with the eventual goal of developing and improving the methodology for digital wind tunnel simulations of laminar-turbulent transition in conventional hypersonic facilities. Such simulations will complement the wind tunnel measurements and provide crucial data toward the development of accurate models for boundary-layer transition on high-speed flight vehicles. The objective of this task order is to facilitate the turbulent boundary layer simulations for a 3D setting, including the boundary layers on all four sides of a rectangular cross-section nozzle. These simulations will be performed using an enhanced version of the DNS code that was used in prior quasi-2D simulations involving just two opposite walls.

The enhanced code and auxiliary pre-processing and post-processing utilities will be provided by the Contractor. NASA may run multiple simulations to achieve the desired quality of results in terms of accuracy and resolution of the simulated acoustic field as well as the tunnel wall boundary layer. Appropriate changes to the baseline code will be made if necessary to support the goals of these simulations.

The results of these simulations will be used toward future simulations of hypersonic transition.

Description of the Work/Contractor Tasks: The following pre-requisites should have been met before the beginning of this task order effort.

(i) The DNS codes and pre/post-processing utilities have been used by the Contractor/Vendor in previous simulations of acoustic disturbance environment in a high-speed boundary layer and the transition process over a relevant body shape such as circular cone. These results shall have been documented in peer reviewed publications to provide necessary confidence in the accuracy of future simulations

(ii) Given the target timeframe of NASA’s simulations of acoustic environment in a 3D hypersonic nozzle, the contractor/Vendor must have previously documented the applications of these codes and utilities to a representative case so that it can be used as a guide during the NASA project.

The Contractor shall perform the following tasks:

• Deliver the DNS codes that can be used to simulate the flow as well as the freestream disturbance environment in a rectangular cross-section nozzle designed for hypersonic Mach number (Sep. 30, 2025). The codes should have been assessed using a preliminary simulation of prototype case with solid surfaces along two distinct computational planes (e.g., planes normal to j and k coordinate axes).

• Deliver associated preprocessing and postprocessing codes to aid the setup of NASA’s simulations and the analysis of the resulting numerical data. (Sep. 30, 2025)

Deliverables: The Contractor shall deliver electronic files containing the DNS codes, preprocessing, and postprocessing utilities, and auxiliary files for the illustrative case, including a sample input deck and the description of output data for the test case, to the Technical POC by the task order expiration. The estimated period of performance for is 07/10/2025 through 09/30/2025.

The information listed below is required to complete this purchase.

2. Characteristics, Scope, and Specs

LINE DESCRIPTION QTY.

1 OSU High-Speed Direct Numerical Simulation Software Development and

Testing

Other Considerations:

Milestones:

1. Delivery of the DNS codes with required capability, along with auxiliary files related to the sample case. (09/30/2025) – see Task 4.1

2. Delivery of the preprocessing and postprocessing codes. (09/30/2025)

Government-furnished property – N/A

Government-furnished information – If necessary, the government will share non-sensitive aspects of the targeted simulation(s), to aid the troubleshooting of NASA computations by the contractor. This information will not include potentially sensitive information such as the configuration geometry.

3. Place of Performance NASA Langley Research Center

4. Period of Performance 07/10/2025 - 09/30/2025