Channel flow simulation using CONVERGE CFD
Aim:
To simulate flow of air through a 2D channel and to compare results of various grid sizes.
Governing Equation:
In 2D channel flow following governing equations are used.
1) Navier-Stokes Equation in X-direction(X-momentum Eqn)
`frac{del}{delt)(rho*u)+frac{del}{delx)(rho*u*u)+frac{del}{dely)(rho*v*u)=-frac{delp}{delx}+mu(frac{del^2u}{delx^2}+frac{del^2u}{dely^2})`
2) Navier-Stokes Equation in Y-direction(Y-momentum Eqn)
`frac{del}{delt)(rho*v)+frac{del}{delx)(rho*u*v)+frac{del}{dely)(rho*v*v)=-frac{delp}{dely}+mu(frac{del^2v}{delx^2}+frac{del^2v}{dely^2})`
3) Continuity Equation (Mass Conservation Equation)
`frac{delu}{delx}+frac{delv}{dely}=0`
Above Equations are discretised and solved for each and every control volume. There are two different methods for solution of these equations.
1) Stream-Vorticity Function Formulation
2) Pressure Correction Method on Staggered OR Collocated Grid
Two Algorithms can be used :
1)SIMPLE( Semi-Implicit Method for Pressure Linked Equations)
2)PISO(Pressure-Implicit with Splitting of Operators)
Objective:
Objective of this simulation is to obtain parabolic velocity profile induced in channel.
Workflow:
1)Geometry Setup
2)Case Setup
3)Post-Processing of 3D Files in VTK format
4)Result Analysis in paraview and Line Plotting Module.
Description:
1)Geometry
In 2D channel flow we will first take a geometry which is actually 3D but we are going to ignore the dimensions in z-direction.
So while setting up geometry dimesions are
2)Case Setup
We will setup a case by using time based simulation
Then setting up default values for gas simulation and global transport properties.We add species O2 and N2.
Then Setting up inflow outflow wall and 2d wall boundary with their corresponding values
Setting up simulation run parameter
steady state monitor
simulation time parameters and solver parameters.
Monitoring Average velocities at inlet and outlet
then setting up grid
and finally setting up the variables which we need in post processing and output files parameters.
2)Simulation Results:
Case1: dx=2e-4 m dy=2e-4 m dz=2e-4 m
Mesh:
Cell Count:
Velocity:
Pressure:
Velocity Plot:
case 2: dx=1.5e-4 dy=1.5e-4 dz=1.5e-4
mesh
Cell Count:
Velocity:
Pressure:
Velocity plot:
case3:
dx=1e-4 m dy=1e-4 m dz=1e-4 m
mesh:
Cell Count:
Velocity:
pressure:
Velocity Plot:
Animation:
Conclusion:
1)As mesh size increases the cycles taken for obtaining steady state of monitored variable increases.
2)The velocity profile is parabolic which is zero at both walls and maximum at centre.
3)Cell count increases as mesh size decreases.