Velocity-Dependent Quantum Fluctuation Energy in a Structured Vacuum Framework

We develop a self-consistent and mathematically rigorous phenomenological framework in which quantum vacuum fluctuation energy depends on velocity relative to a preferred vacuum rest frame Σ₀. Starting from the exact relativistic Doppler transformation applied mode by mode, we prove that the isotropically averaged zero-point energy per vacuum mode is QFE (v) = γ (ℏω₀/2) = ℏω₀ / (2√ (1 − v²/c²) ), where γ = (1 − v²/c²) ^ (−1/2) and v is velocity relative to Σ₀. The directional β cosθ anisotropy integrates exactly to zero over the full sphere; the γ factor arises solely from the isotropic part. We derive the modified vacuum energy density ρᵥac (v) = γ ρᵥac (0), construct and analyse the phenomenological Lagrangian, perform a complete non-relativistic expansion to fourth order in β, and contrast the result with the Unruh effect at the level of the stress-energy tensor. A full derivation of the velocity-dependent Casimir force is given from the modified mode sum, including boundary conditions, plate geometry, and a quantitative experimental proposal specifying plate separation, material, orientation, and required sensitivity. Systematic experimental error sources are analysed for all three predictions. The coupling constant λ is constrained against the full landscape of Standard-Model Extension (SME) experiments — birefringence, time-of-flight, Penning trap, and gravitational wave bounds — and shown to be consistent with all current null results. Three parameter-free predictions follow: a fractional Casimir force shift ΔF/F₀ ≈ β²/2 ≈ 7. 6 × 10⁻⁷, a vacuum noise anisotropy of amplitude 2β ≈ 2. 5 × 10⁻³, and an atomic clock fractional offset ∼ αQED β²/2 ≈ 5. 5 × 10⁻⁹, all relative to the CMB rest frame with β_⊙ ≈ 1. 23 × 10⁻³.