Pressure Fields & Fluid Acceleration A hundred thousand tracer particles stream past a cylinder. They pile up and slow at the nose (red, high pressure), race around the shoulders (blue, low pressure), then slow again at the back. Where the streamlines curve, a sideways pressure difference must be there to bend them: ∂p/∂n = −ρV²/R. The journey: Euler’s equation is just F = ma for a fluid blob. Split the acceleration along and across a streamline and out fall Bernoulli (fast = low pressure) and the curved-streamline rule. Drag Γ to spin the cylinder and watch the flow — and the lift — go asymmetric.