[Abhinavmaurya]

Steps being followed:
(Before tracer injection)
1. Setup: realizable K-e, standard wall functions; Multiphase - VOF; Species transport: OFF
2. Side Inlet: Air (Vol. frac 0); Top Inlet: Water (Vol. frac 1)
Ran the simulation in steady state, obtained converged solution post 20000 iterations.

(During tracer injection) - Switched to Transient simulation
1. Setup: realizable K-e, standard wall functions; Multiphase - VOF; Species transport: ON
2. Side Inlet: Air (Vol. frac 0); Top Inlet: Water (Vol. frac 1 but tracer mass fraction = 1)
3. In the solution --> Controls --> Equation, Flow: Off, Volume Fraction: On, Turbulence: On, Tracer: On

(Post Tracer Injection)
[Method 1]
1. Setup: realizable K-e, standard wall functions; Multiphase - VOF; Species transport: ON
2. Side Inlet: Air (Vol. frac 0); Top Inlet: Water (Vol. frac 1 but tracer mass fraction = 0)
3. In the solution --> Controls --> Equation, Flow: On, Volume Fraction: On, Turbulence: On, Tracer: Off

[Method 2]
1. Setup: realizable K-e, standard wall functions; Multiphase - VOF; Species transport: ON
2. Side Inlet: Air (Vol. frac 0); Top Inlet: Water (Vol. frac 1 but tracer mass fraction = 0)
3. In the solution --> Controls --> Equation, Flow: On, Volume Fraction: On, Turbulence: On, Tracer: On

While following Method 1, tracer amount doesn't increase in tundish. However, if method 2 is followed, tracer amount increases.

P.S: I performed the simulation using method 2 for the homogeneous phase and the simulation ran smoothly