Transient Simulation of Flow Over A Cylinder

Introduction:

External flow past around a circular cylinder has been extensively studied by the fluid community because of their practical applications. Flow over heat exchanger tubes and civil structures are such examples. The flow past a circular cylinder experiences a boundary layer separation and very strong flow oscillations in the wake region behind the body. The flow pattern is dependent on the Reynolds number and is affected by the surface roughness, compressibility of the fluid and other factors.

Objective:

To perform a transient flow over a circular cylinder and post-process the results in SolidWorks Flow Simulation to understand the effect of vortex shedding due to the change in the Reynolds number.

Geometry:

A circular cylinder of diameter 50 mm was modeled in SolidWorks and imported into SolidWorks Flow Simulation Add-ins.

Calculating Velocity Based on the Reynolds Number:

Formula Used:

Where,

Re - Reynolds Number,

ρ = density of the fluid,

V = velocity of the fluid,

μ = viscosity of fluid,

L = length or diameter of the object..

Calculation:

On calculating the Velocity of the fluid, here are the corresponding values and their units

Constant Parameters	Value	Units
Reynolds Number	37	No unit
Diameter of Cylinder	0.05	m
Dynamic Viscosity of Air	1.729E-5	kg/ms
Kinematic Viscosity of Air	1.338E-5	sq.m/s
Density of Air	1.274	kg/cu.m

Velocity of fluid = 0.01 m/s.

Computational Domain:

A computational domain is a region which refers to the simplified form of the physical domain in which the physical equations of fluid flow are solved. Here, a 2-D computational domain has been created as the flow over cylinder is symmetrical about the Z - axis. The size of the computational domain has been shown below with a negligible thickness of 1 mm in the Z - axis.

Meshing:

In SolidWorks, the computational domain has to be broken down into individual volumes called cells to solve the governing equation. The mesh can have any shape in any size and is discretized based on the model requirement. Here, a fine mesh of 151 cells in the X - axis and 80 cells in the Y - axis has been created.

Results:

The results obtained from the simulation are as follows

Velocity Profile:

The above figure shows the velocity contour at a Reynolds number of 50 and 225. Here, the shape of the streamline is symmetrical around the cylinder’s upper side to the lowerto the lower side and also from front to rear side of the cylinder. around the front to rear side of the cylinder.