Swim Cap Hydrodynamics & Boundary Layer Drag Simulator

p5.js Particle Boundary-Layer Flow Simulation

Laminar Boundary Streamlines

Boundary Separation / Wake Vortices

Skin Friction Roughness Drag

          Skin Friction ($C_{df}$)
          0.008
          Viscous Surface Shear
        

          Form Drag ($C_{dp}$)
          0.290
          Pressure Detachment
        

          Total Drag ($C_d$)
          0.298
          Combined Resistive Coeff
        

Power Saved 25.1 W vs Long Hair Baseline

Time Saved / 100m 8.42 s At Equal Effort

Hydrodynamic Profile Verified

Silicone Wrinkle-Free Cap @ 1.8 m/s

-38.6% Head Drag Force Reduction

Swimmer Presets

Head & Cap Surface Geometry

Fluid Parameters

Swimmer Velocity ($v$) 1.80 m/s

0.5 m/s (Relaxed) 1.5 m/s (Pace) 2.5 m/s (Sprint World Record)

Water Temperature ($T$) 25.0 °C

15°C (Dense Cold) 25°C (Olympic Standard) 30°C (Warm Pool)

Condition Comparison Table

Cap / Condition	$C_d$	Force (N)	Power (W)	$\Delta t$ /100m

Fluid Mechanics Physics Insight: Water is ~800 times denser than air. Loose hair causes boundary layer micro-turbulence, shifting the separation point forward and creating massive trailing pressure form drag ($C_{dp}$). Swim caps do not just keep hair out of eyes—they convert rough turbulent flow into smooth attached laminar flow, cutting head skin-friction drag by up to 60%.