This project aims to analyze and visualize the effect of various factors on the buoyant force experienced by a human body in water. Specifically, it compares how buoyancy is affected by:

• 🌡️ Water temperature (via changes in density)
• 🧥 Wetsuit thickness (neoprene adds both volume and weight)
• ⚖️ Body fat percentage (affects body density)

The model uses Archimedes’ Principle to estimate net buoyant force.

Without Dead Sea

Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. (Wikipedia)

We apply Archimedes' Principle:

F_buoyancy = ρ_water * g * (V_body + V_neoprene) - m_neoprene * g

See utils_physics.py for details.

• Fully submerged and static (no swimming, no lung inflation, no motion).
• Body modeled via two compartments:
  • Fat and Lean mass with fixed densities (harmonic mean).
• Body surface area computed via Du Bois formula.

• Covers 82% of body surface.
• Has uniform thickness and density.
• The wetsuit does not modify the body volume. Not true if you have ever worn in a wetsuit 😉
• No wetsuit compression due to depth - volume stays constant.
• Adds volume and weight (included in force calculations).

• Water density is computed as a function of temperature using a 5th-order polynomial approximation.
• Water is still (no motion or turbulence).
• Temperature is uniform throughout the water volume.

• Gravity is constant: g = 9.81 m/s².
• All densities and material constants are loaded from config.yaml.

To run the buoyant force simulations and generate plots:

python src/flotte/scripts/plot_impacts_on_buoyancy.py
# or
python -m flotte

You can adjust simulation parameters in config.yaml, such as:

• Body mass, height, and fat percentage
• Water temperature
• Wetsuit thickness

Also, you can add the Dead Sea as a reference value:

💡 Fun Fact: The Dead Sea provides about more than 4× more buoyant force increase than a 2.5mm wetsuit. This is due to its extreme salinity, raising water density to ~1240 kg/m³.

With Dead Sea

The output plot shows how buoyant force expressed in N (left y-axis) varies with each parameter (each subplot).

The plot also includes:

• Reference buoyant forces (RefBuoyF) computed for each body without wetsuit, in a 20°C fresh water environment.
• Percentage improvement in buoyant force over the RefBuoyF baseline (right y-axis).
• A summary table of body parameters used and resulting buoyant forces.
• Buoyancy reference forces (see parameters in config.yaml):
  • Body weight: the baseline force of gravity on the person.
  • Pull buoy: Simulated as 1500 cm³ of low-density foam → adds ≈15 N of buoyant force.
  • Maximum inhale: Simulated as 4.8 liters of air → adds ≈47 N of buoyancy.

Equilibrium occurs when buoyant force = body weight.
Positive buoyancy (floating) occurs when buoyant force > body weight.

Note: Wetsuits are typically 2–3 mm thick on average. Some panels may reach 5.0 mm, but overall body coverage averages lower.

• See example thickness maps in media, such as Mako wetsuit specs.

• 🧍 Without added air, all tested bodies sink in fresh water.
• ✅ A 7–8% increase in buoyancy is typically enough to reach neutral floatation.
• 💨 Air volume matters: A full inhale adds significant buoyancy (~47 N), enough to float lighter bodies.
• 🧘 Try it yourself: Inhale deeply while still in water - then exhale slowly and observe your own buoyancy change.

• 👙 Wetsuits (~+5%) increase buoyancy more than moderately salty water (~+3%) like the Mediterranean Sea.
• 🌊 The Mediterranean Sea gives a buoyancy boost similar to wearing a ~1.5 mm wetsuit.
• 🧂 The Dead Sea (+24%) offers the most dramatic boost - roughly 4–5× more buoyant than a 2.5 mm wetsuit.
  • Equivalent to wearing 4-5 wetsuits, or floating with 8 pull buoys!

• 🧊 Water temperature has minimal impact - its effect on density is too small to meaningfully change buoyancy.

• 🧬 Body fat influences buoyancy significantly - but often comes with added weight, which can offset gains.
  • Example: Bodies #2 and #3 have the same height.
    • Body #2 is lean (68 kg, 13% fat) and floats with an inhale.
    • Body #3 is muscular (75 kg, 10% fat) and sinks even after inhaling.