Model Assumptions, Validity Ranges, and Physical Limitations
A transparent disclosure of the physical approximations, parameter validity boundaries, and excluded phenomena (e.g. moisture flier lies) within D-Plane Lab.
science · 7 min · NOT_CALCULATED_MVP
Scientific Integrity & Epistemic Badging
In scientific computing and simulation design, declaring what a model does not do is just as important as demonstrating what it does calculate. Many commercial golf simulators present complex numerical outputs without disclosing underlying approximations, leading players and coaches to mistake idealized geometric models for infallible truth.
D-Plane Lab applies an explicit Epistemic Classification System to every parameter and calculation:
EXACT_GEOMETRY: Pure Euclidean and trigonometric vector derivations (e.g., the D-Plane normal vector, spin-axis orthogonality, and path-shift math).EVIDENCE_BASED_APPROX: Approximation with a clearly identified evidence basis. This badge alone does not mean that this application’s coefficients were independently reproduced or calibrated against launch-monitor data.EDUCATIONAL_APPROX: Simplified, deterministic models intended to illustrate relationships and directional trends; coefficients are project assumptions unless a specific supporting measurement is identified.NOT_CALCULATED_MVP: Real-world phenomena that are acknowledged and explained conceptually, but excluded from real-time numerical simulation in the MVP release.
1. Primary Physical Assumptions in MVP
- Rigid-Body Impact Mechanics vs. Finite Element Analysis: The clubhead is modeled as a rigid body with lumped mass and Moments of Inertia ($I_{xx}, I_{yy}, I_{zz}$). In reality, during the $450,\mu\text{s}$ collision, the thin titanium face of a modern driver flexes like a trampoline (the COR/CT "spring-like effect"). While our model reflects ball speed transfer via smash factor formulas, it does not run real-time non-linear finite element structural grids.
- Atmospheric Inputs and Defaults: The flight solver accepts wind, temperature, and altitude inputs. Defaults are zero wind, sea-level altitude, and $20^\circ\text{C}$; air density is adjusted from temperature and altitude using a simplified implementation. This is not a full moist-air or weather model.
- Uniform Aerodynamic Coefficients: The implementation parameterizes drag as $C_D = 0.225 + 0.18S$ and lift using $S = r\omega/v$ plus the spin component perpendicular to relative airflow. These are compact educational polars, not CFD, source-equivalent ball-specific polars, or independently validated predictions.
2. Excluded Phenomena (NOT_CALCULATED_MVP)
- Turf Moisture & "Flier Lies":
Moisture and grass between the face and ball can change friction and spin, but the effect depends on lie, club, ball, and strike. This version does not calculate moisture-dependent friction or flier outcomes; no fixed spin or distance penalty is asserted here. The phenomenon is classified as
NOT_CALCULATED_MVP. - Dynamic Shaft Kick Geometry: Shaft deflection is parameterized through effective delivered angles (Dynamic Loft and Delivered Lie), rather than simulating multi-segment flexible Euler-Bernoulli beam vibrations.
3. Input Bounds
Interactive controls expose per-parameter ranges for editing. Those UI bounds are convenience limits, not physiological validity envelopes or guarantees about imported or programmatically supplied inputs. Range and validation behavior are parameter-specific and may differ between controls and session decoders.