Computational Physicist - Fluid Dynamics

Xcimer Energy leverages decades of research on Inertial Fusion Energy (IFE) combined with groundbreaking new laser architecture. Our mission is to deploy fusion power plants to meet global decarbonization goals as fast as possible. Xcimer has assembled a team of leaders in tough tech, fusion science, and manufacturing with a track record of rapid execution. Supported by leading investors, Xcimer is uniquely positioned to deliver limitless, clean, fusion power to combat climate change. Join us in powering a better world with inertial fusion!

This is a full-time, onsite role based at our headquarters in Denver, CO.

As a Computational Physicist (Fluid Dynamics) at Xcimer, you will contribute to the theoretical and computational development of multi-material radiation hydrodynamics models that support inertial confinement fusion (ICF). This role focuses on numerical methods for computational fluid dynamics (CFD), with emphasis on high-fidelity modeling of complex multi-physics systems relevant to fusion energy.

You will work closely with senior scientists and software engineers to develop, analyze, verify, and validate numerical methods and simulation capabilities within Xcimer's radiation hydrodynamics codebase. This is a hands-on technical role that blends mathematical modeling, numerical analysis, and high-performance scientific computing.

The ideal candidate brings deep expertise in numerical methods for fluid dynamics, hands-on experience with invariant-domain preserving (IDP) methods, strong experience with finite element frameworks (particularly deal.II), and the ability to contribute meaningfully to code development, scientific publications, and collaborative research efforts.

Responsibilities

Multi-Material & Radiation Hydrodynamics Modeling

• Implement and improve multi-material modeling approaches (e.g., interface tracking/capturing, mixture models, or related techniques).

• Support coupling of hydrodynamics with radiation transport and other relevant physics modules for various equation of state and opacity models.

• Assist in developing robust algorithms for extreme thermodynamic and flow regimes relevant to ICF.

Numerical Methods & Theoretical Development

• Develop and analyze certifiably robust, invariant-domain preserving (IDP) numerical methods for computational fluid dynamics with emphasis on multi-material flows.

• Contribute to mathematical modeling for multi-material systems relevant to inertial confinement fusion.

• Support development of radiation hydrodynamics formulations, discretizations, and stabilization strategies.

• Investigate accuracy, stability, and convergence properties of numerical schemes.

• Contribute to solving complex inverse and forward problems in high-energy-density physics.

Verification, Validation & Scientific Rigor

• Collaborate with Xcimer's verification and validation function to validate multi-material numerics, contributing domain expertise on expected physical behavior.

• Contribute multi-material test problems and physical judgment to the shared benchmark suite.

• Help ensure multi-material results are reproducible and scientifically credible, in partnership with the team that owns V&V methodology.

Communication & Collaboration

• Collaborate closely with physicists, applied mathematicians, and software engineers.

• Contribute to internal technical documentation and external scientific publications.

• Present findings in technical meetings and contribute to peer-reviewed journal articles and conference papers.

Qualifications

• Education: Ph.D. in Mathematics (preferred), Applied Mathematics, Computational Physics, or a closely related field, with a focus on numerical methods for fluid dynamics.
• Strong background in numerical analysis for PDEs, particularly for fluid dynamics.
• Hands-on experience with invariant-domain preserving (IDP) methods or comparable certifiably robust discretization frameworks for hyperbolic/compressible flow.
• Experience with finite element methods and hands-on development using deal.II (strongly preferred) or similar frameworks.
• Experience developing scientific software in C++.
• Experience working in high-performance computing environments (MPI-based parallelism and large-scale simulations).
• Familiarity with multi-material modeling techniques in CFD.
• Experience with verification and validation of numerical methods.
• Strong written and verbal communication skills, with demonstrated ability to contribute to scientific publications.
• Must be a U.S. citizen or national, U.S. permanent resident (current Green Card holder), or lawfully admitted into the U.S. as a refugee or granted asylum.

Desired

• Background in radiation hydrodynamics, high-energy-density physics, or related multi-physics domains.
• Experience with mathematical modeling for multi-material compressible flows.
• Experience coupling hydrodynamics with radiation transport.
• Experience contributing to large, research-grade scientific codebases.
• Demonstrated ability to balance theoretical rigor with practical computational implementation.