Cascade CFD Simulation Training by Ansys Fluent

Cascade Project Description

The goal of this project is to simulate a cascade with an interrupted water inlet by ANSYS Fluent software. The Eulerian multiphase model has been used. The water is entering the domain with a speed of 0.3 m/s with gravity considered as -9.81 m/s-2 on the y-axis.

Geometry & Mesh

The 2-D geometry of the present model is carried out using Design Modeler software. The geometry consists two-section, the lower section is resident water, and the upper section contains outlet and velocity inlet; tank sides are considered as well.

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The meshing of this present model has been generated by Ansys Meshing software. The mesh grid is unstructured with no element quality lower than 0.53, and the total cell number is 110976.

Cascade CFD Simulation

To simulate the present model, several assumptions are considered, which are:

• The solver is pressure-based and transient.
• Simulation has only examined fluid behavior; in other words, heat transfer simulation has not been performed.
• The effect of gravity on the flow is considered to be 9.81 m.s-2 and along with the y-axis in the present model.

The following is a summary of the steps for defining the problem and its solution

Models
K-omega	Viscous model
SST	k-omega model
shear flow corrections	k-omega options
air	primary phase
water	secondary phase
explicit	formulation
Boundary conditions
Velocity-inlet		Inlet
0	initial gauge pressure	Mixture
0.3 m/s	velocity magnitude	Water
1	volume fraction
Pressure outlet		outlet
1	backflow volume fraction	Air
0	backflow volume fraction	Water
wall		Wall
stationary wall	wall motion
Solution Methods
Phase coupled		pressure-velocity coupling
PRESTO!	pressure
first-order upwind	momentum
first-order upwind	specific dissipation rate
first-order upwind	volume fraction
Initialization
standard	initialization method
0.3 m/s	water velocity (0,y,0)
0 m/s	air velocity (x,y,z)
1	the secondary phase volume fraction

Cascade Results

At the end of the solution process, two-dimensional and three-dimensional velocity, air and water volume fraction, and animation are obtained. This 2-D simulation shows water starts to fall cascade for 0.75 seconds. Then velocity cuts off to 0 m/s for 0.75 and continues with 0.3 m/s for another 0.75 seconds. This process repeats over and over again.