Senior Research Engineer, CFD Algorithm Development

About SandboxAQSandboxAQ is a high-growth company delivering AI solutions that address some of the world's greatest challenges. The company’s Large Quantitative Models (LQMs) power advances in life sciences, financial services, navigation, cybersecurity, and other sectors.We are a global team that is tech-focused and includes experts in AI, chemistry, cybersecurity, physics, mathematics, medicine, engineering, and other specialties. The company emerged from Alphabet Inc. as an independent, growth capital-backed company in 2022, funded by leading investors and supported by a braintrust of industry leaders.At SandboxAQ, we’ve cultivated an environment that encourages creativity, collaboration, and impact. By investing deeply in our people, we’re building a thriving, global workforce poised to tackle the world's epic challenges. Join us to advance your career in pursuit of an inspiring mission, in a community of like-minded people who value entrepreneurialism, ownership, and transformative impact.The Opportunity SandboxAQ is seeking a hands on computational scientist or engineer to lead the CFD Algorithm Development Project. This team is focused on building AI driven, physics based optimization tools for next generation catalytic reactors, combining technical depth in CFD, GPU programming, and differentiable simulation with practical experience in model validation and high-performance computing (HPC).The AI Simulation Team are looking for a CFD Algorithm Development Lead to join our team. This role is central to our efforts to develop and deploy a differentiable Computational Fluid Dynamics (CFD) framework on multi-GPU and multi-node systems to optimize chemical reactor designs. This person will lead the CFD Algorithm Development Project, deliver critical milestones that advance our mission, and bridge the gap between differentiable simulation and high-performance computing. This role is ideal for a candidate who thrives on delivering technical breakthroughs and wants the unique opportunity to lead the development of cutting-edge optimization tools that solve complex challenges in chemical reactor design.Key ResponsibilitiesDevelop Differentiable Solvers: Lead the creation of differentiable CFD frameworks in JAX, extending capabilities to complex geometries and non-periodic boundary conditions using immersed boundary methods.Scalable GPU Engineering: Design, implement, and containerize code (Docker/enroot) to ensure reproducibility and scalability across multi-node GPU HPC environments.Numerical Optimization: Develop optimized parallel linear solvers (FFT or matrix decompositions) and gradient-based scripts to iteratively modify reactor designs based on catalyst activity.Validate & Benchmark: Rigorously validate simulation accuracy against benchmark results and fixed-bed reactor configurations for both non-reactive and reactive flow regimes.Cross-Functional Collaboration: Partner with AI model developers to integrate property predictions and generate comprehensive technical reports summarizing algorithm scalability and differentiability.Essential Skills & ExperiencePhD or MS in Computational Physics, Mechanical/Chemical Engineering, Computer Science, or equivalent.3+ years (including PhD) of hands-on experience in CFD code development, specifically on GPUs.Scientific Software Expertise: Proven ability to build scalable software on multi-GPU systems using JAX, PyTorch, CUDA, or MPI frameworks.Numerical Mastery: Full fluency in numerical linear algebra, PDE numerical methods, sparse/dense linear solvers, and immersed boundary methods.Python & JAX: Excellent Python programming skills, with JAX proficiency as a prerequisite.Documentation: Ability to manage multiple deliverables and produce clear technical documentation for milestone reviews.Highly Desired Skills & ExperienceAdvanced Industry Experience: PhD + 3 years of industry experience in a related computational field.Reactive Flow Modeling: Proven expertise in non-isothermal flow, transport equations, and chemical reactor multi-physics (e.g., mass transport in fixed-bed systems).Differentiable Simulation: Expertise in adjoint optimization or auto-diff for gradient-based optimization of complex CFD objectives.DevOps for Science: Experience with the full stack of scientific development, including CI/CD, unit testing, and deployment via K8s, Slurm, or Google Cloud Batch.Track Record: Demonstrated ability to deliver complex project milestones and publish high-quality technical results.Why Join Us?We offer a comprehensive and competitive benefits package designed to support your health, financial well-being, and life outside of work.Compensation: Competitive base salary, performance-based incentives or bonuses (where applicable), and equity participation.Benefits: Comprehensive medical, dental, and vision coverage for employees and dependents with generous employer premium contributions, retirement savings with company matching, paid parental leave, and inclusive family-building benefits.Work-Life Balance: Flexible paid time off, company-wide seasonal breaks, and support for flexible work arrangements that enable sustainable performance.Career Development: Opportunities for continuous learning and growth through on-the-job development, cross-functional collaboration, and access to internal learning and development programs.SandboxAQ Welcomes AllWe are committed to fostering a culture of belonging and respect, where diverse perspectives are actively sought and valued. Our multidisciplinary environment provides ample opportunity for continuous growth - working alongside humble, empowered, and ambitious colleagues ready to tackle epic challenges.Equal Employment Opportunity: All qualified applicants will receive consideration regardless of race, color, ancestry, religion, sex, national origin, sexual orientation, age, citizenship, marital status, disability, gender identity, or Veteran status.Accommodations: We provide reasonable accommodations for individuals with disabilities in job application procedures for open roles. If you need such an accommodation, please let a member of our Recruiting team know.Read: Guidance for candidates on using AI Tools in interviews