Hi Raef, this is the problem description

The configuration consists of a 60 mm diameter pipe with the 90-degree bend (long elbow). Fluid (air and water annular flow horizontal pattern) flows in the pipe with entrained solid particles at 49 m/s normal velocity and the outlet is assumed to be pressure outlet boundary. Turbulent and transient conditions. Solid particles (sand) with 2650 kg/m3 density release from the inlet pipe with initial velocity same as phase 1 (air) 49 m/s. Mass flow rate 0.0084 kg/s.

For fluid flow consist of air with initial velocity 49 m/s and water 0.183 m/s. Center of inlet is the area of air initial velocity. Particle interacts with the continuous phase.

To solve this, I make detail configuration like this:

Type: Pressure-based

Velocity Formulation: Absolute

Time: Transient

VOF multiphase model

N of Eulerian Phase: 2

Formulation: Explicit

Interface Modelling: Sharp

k-epsilon realizable turbulence model

Phase 1: air

Phase 2: water

Surface tension: 0.072 constant

Inert particle: sand

Boundary Conditions:

Gas Inlet (velocity-inlet type)

V: 49 m/s

Initial Pressure: 0

TKE: 1.14

Epsilon: 1725

Phase 2 fraction: 0

DPM: escape

Water Inlet (velocity-inlet type)

V: 0.183 m/s

Initial Pressure: 0

TKE: 0.000167

Epsilon: 0.003047

Phase 2 fraction: 1

Outlet (outflow)

Flow Rate Weighting: 1

DPM: escape

Wall:

Stationary wall, no slip, standard wall roughness

DPM: reflect

Solution Methods:

Pressure-Velocity Coupled

Pressure: PRESTO!

Momentum: Second Order Upwind

Volume Fraction: Compressive

TKE: First Order Upwind

Turbulent Dissipation Rate: First Order Upwind

Transient Formulation: First Order Implicit

Solution Control:

Flow Courant: 100

Eexplicit RF

Momentum: 0.3

Pressure: 0.3

Under RF

Density: 1

Body Forces: 0.5

TKE: 0.6

TDR: 0.6

Turbulent Viscosity: 0.5

Discrete Phase: 0.9

Hybrid Initialization

Time step size: 0.001

N of time step: 1000