Reynolds stresses and turbulence closure
Research context
research method · conditional · As of 2026-10-10
For constant-density incompressible flow, averaging u=U+u′ adds the Reynolds stress R_ij=⟨u′_iu′_j⟩ to the mean momentum equation.
Key knowledge
For constant-density incompressible flow, averaging u=U+u′ adds the Reynolds stress R_ij=⟨u′_iu′_j⟩ to the mean momentum equation. Its transport introduces higher correlations, so averaging does not close the equations. Eddy-viscosity, Reynolds-stress and data-informed closures encode different assumptions; a fitted mean velocity alone does not validate every stress or transient.
Values and equations
∂_tU_i+U_j∂_jU_i=−ρ⁻¹∂_iP+ν∇²U_i−∂_jR_ij
- U_i
- Mean velocity m s⁻¹
- P
- Mean pressure Pa
- ρ
- Constant mass density kg m⁻³
- ν
- Kinematic viscosity m² s⁻¹
- R_ij
- Velocity covariance m² s⁻²
- t,x_j
- Time and spatial coordinates s; m
Conditions and scope
- Averaging must commute with the required derivatives. The displayed equation assumes no body force, or a conservative body force absorbed into pressure; density-weighted compressible averaging is a different formulation.
- Specify inflow, walls, forcing, averaging interval and Reynolds number. Statistical sampling error, model discrepancy and discretization error require separate checks.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Inspected all three pages: Reynolds decomposition, averaged incompressible equation and extra stress closure; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication. Inspected calculation verification and comparisons with uncertain experimental observables for a declared application; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication.
2026-10-10 · Author source inspection of the displayed claim, model assumptions and equations; independent exact-content and branch-inventory review is a separate gate. Contemporary status is a dated snapshot, not a promise of ongoing monitoring.
Entry details
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- research-physics-rans-stress-closure
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference