The Department of Defense, specifically the Navy, is seeking proposals for the development of hypersonic computational fluid dynamics (CFD) heat flux sub-models as part of the Small Business Innovation Research (SBIR) program. The objective is to enhance modeling and simulation of Navy-relevant hypersonic flows by creating or improving turbulence-heat flux sub-models that can be integrated into existing CFD solvers, demonstrating improved predictive capabilities through verification and validation against hypersonics datasets. This initiative is crucial for advancing the accuracy of heat flux predictions in hypersonic environments, which has significant implications for both military applications and commercial sectors such as turbomachinery and internal combustion engines. Interested parties should note that the solicitation will open on April 23, 2025, with proposals due by May 21, 2025, and can find more information at the official DOD SBIR/STTR website.

## Description

At present, CFD prediction of heat flux in hypersonic flows relies on simplified approximation of the relationship between fluid transport, turbulence, and heat flux. These models are not rooted in fundamental physics and are typically &ldquo;tuned&rdquo; to yield reasonable agreement with a select number of canonical sub- and transonic flows. Consequently, existing turbulence models can produce larger errors when attempting to predict heat flux for hypersonic flows. The objective of this topic is to enhance M&amp;S of Navy-relevant hypersonic flows through the development and/or improvement of CFD turbulence-heat flux sub-models. Proposers should define a framework for heat flux modeling of the Favre-averaged, reacting Navier-Stokes equations, develop a heat flux sub-model that can be easily integrated into existing RANS-based CFD solvers, and demonstrate the predictive capability of the model through verification and validation (V&amp;V) against existing hypersonics datasets.

## Objective

Enhance Modeling and Simulation (M&amp;S) of Navy-relevant hypersonic flows through the development and/or improvement of Computational Fluid Dynamics (CFD) turbulence-heat flux sub-models.

## Phase I

Develop and present a turbulence modeling framework based on the Favre-averaged, reacting Navier-Stokes equations. Provide a heat flux sub-model for hypersonic, turbulent flows that shows improvements in physical realism, predictive capability, and numerical performance/robustness over existing heat flux sub-models. Ideally, the model should be generalizable across flight conditions (i.e., subsonic to hypersonic). The functional form of the heat flux sub-model must be capable of seamless integration into existing compressible RANS and hybrid RANS/LES turbulence modeling frameworks, i.e., the model should take as inputs only those variables used/stored by industry-standard RANS/LES algorithms and their sub-models, be continuous in form, rely only on local data, and should ideally be turbulence model agnostic.The Phase I effort will include prototype plans to be developed under Phase II.

## Phase II

Refine the form of the model(s) and define any constants needed to close the model. Constants and model specifics should be driven by a combination of first principles and existing experimental/flight test data. Collaborate with the High Performance Computing Modernization Program (HPCMP) CREATE Air Vehicle (CREATE-AV) development team to incorporate the model(s) into a CFD architecture, verify the model implementation, and validate the model against existing hypersonics databases using best V&amp;V practices. Further refine the model form, constants, and implementation based on V&amp;V activities. Finalize the heat flux sub-model by demonstrating model integration into an existing turbulence modeling framework plus improvements in predictive capability for Navy-relevant hypersonic flows, and transitioning the model to CREATE tools.

## Phase III: Dual Use Applications

Transition the finalized model(s) along with all supporting documentation, rationale, and source code to the HPCMP CREATE development team for (1) implementation into its Kestrel CFD solver, (2) standard verification testing, and comparison to/validation against existing databases,. Complete any necessary alterations to the model or its source code requested by the HPCMP CREATE team.Improved heat flux modeling will benefit commercial computational fluid dynamics solvers and commercial entities that utilize CFD for design and analysis. In addition to hypersonic systems, improved heat flux modeling will benefit commercial sectors producing turbomachinery, internal combustion engines, and other problems where heat transfer due to fluid-solid-interaction plays an important role in design, performance, and sustainment.

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