The water entry of everything … a unifying approach

The water entry of spheres has been shown to cause cavity formation above a critical impact velocity. Yet, previous foundational studies conflict over whether this finding applies at high contact angles. Through experimentation, we look closer at this conflict and show that cavity formation can occur well below the critical impact velocity as well. We also elucidate how changing the static contact angle alters the cavity shapes or regimes (e.g., quasi-static, shallow, deep and surface). Our findings indicate an alternate scaling for the Bond and Weber numbers that unifies the cavity regimes for many impacting body types (e.g., spheres, multi-droplet streams and jets). Our findings show that solid-liquid impact is quite similar to liquid-liquid impact and that both impact types should be considered as one in the same.