Pressure projection often limits the scalability of incompressible Navier–Stokes solvers because exact incompressibility requires a globally coupled Poisson solve. We develop Locality-Certified Screened Projection (
LCSP), which replaces the classical projection with a screened pressure correction and combines exponentially localized tile solves
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Pressure projection often limits the scalability of incompressible Navier–Stokes solvers because exact incompressibility requires a globally coupled Poisson solve. We develop Locality-Certified Screened Projection (
LCSP), which replaces the classical projection with a screened pressure correction and combines exponentially localized tile solves with face-correction overlap–restrict (
FCOR) assembly on a staggered grid. The screening parameter sets the localization length and makes the residual divergence explicit. For a spectrally commensurate class of two-dimensional periodic flows, each patch spans one spatial subperiod, so the assembled local correction reproduces the global screened solution without iterative interface communication. Double-precision tests on
512
2
and
1024
2
grids give assembly errors below
3.30×
10
−
15
, velocity errors below
9.83×
10
−
3
relative to the classical projection, and compatible-divergence ratios below
4.83×
10
−
2
. Time-dependent tests remain stable to
T
=
2
and agree with the global screened reference to roundoff. Communication traces record no inter-rank exchange, collective operation, or global reduction during the local correction, and a fixed-work batch attains a speedup of
3.99
on four graphics processing units (GPUs). These results establish a mathematically controlled communication-free screened pressure correction for this periodic class.
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