Transient Flow Simulation over a cylinder in Solidworks
Aim:
To model and simulate transient flow over a cylinder in Solidworks.
Objective:
- To simulate the flow over a cylindrical geometry.
- To increase the Reynolds number by a factor of 20 %, 40 % and 100 % and observe the changes.
Theory:
Flow over a cylinder for various Reynolds number is shown below.
Reynolds number: is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. It is used to predict the transition from laminar to turbulent flow, and is used in the scaling of similar but different-sized flow situations. It is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities, which is known as a boundary layer in the case of a bounding surface such as the interior of a pipe.
The Reynolds number is defined as
Where,
ρ is the density of the fluid (kg/m^3)
u is the velocity of the fluid with respect to the object (m/s)
L is a characteristic linear dimension (m)
μ is the dynamic viscosity of the fluid (Pa·s or N·s/m^2 or kg/m·s)
ν is the kinematic viscosity of the fluid (m^2/s).
In our Case:
Air is used as a medium. Which has,
Viscosity = 1.81 x 10^−5 pa.s
Density = 1.225 kg/m^3
Length = 30 mm
Thus,
for inlet velocity = 10 m/s, R = 20,303
for inlet velocity = 12 m/s, R = 24,364
for inlet velocity = 14 m/s, R = 28,425
for inlet velocity = 20 m/s, R = 40,606
Setup Explanation:
- First, the cylinder is modelled using appropriate dimensions as shown. In my case it has 30 mm diameter and 60 mm length.
- Then, under flow simulation option click on wizard tool and create a new setup with default options, external flow time dependent study of 0.1 second duration and 0.01 second interval with air as the working fluid. Set velocity in X direction as 10 m/s for the first case.
- Keep the mesh setting to default level 3.
- Set the computational domain dimensions as inlet velocity times half the duration, i.e. 0.05 seconds. For the first case, this will be 5 meters as shown.
- Insert a velocity and pressure cut plot parallel to the flow.
- Insert animations of scenario type for the velocity and pressure using the wizard tool for a duration of 10 seconds.
- Do the above process for velocity of 12, 14 and 20 m/s as well using the appropriate computational domain dimensions.
Results:
- Velocity:
- For 10 m/s: https://youtu.be/oW0kquWNKPE
- For 12 m/s: https://youtu.be/0RztlKVSa8E
- For 14 m/s: https://youtu.be/mT1ltvLHJ80
- For 20 m/s: https://youtu.be/M4ilyHKwIFY
- Pressure:
- For 10 m/s: https://youtu.be/nS0swosVRBQ
- For 12 m/s: https://youtu.be/0wR_1l-AR8Q
- For 14 m/s: https://youtu.be/_wP_KR48lKg
- For 20 m/s: https://youtu.be/7HkMZkCYVs4
Conclusions:
- From the velocity plot, the blue region indicates that voids are created and that the flow is turbulent. This is also visible in the pressure plots.
- As the velocity increases, the flow becomes more and more turbulent.
File Link:
https://drive.google.com/drive/folders/14NRna3S_Utnr9Ilsb9BD8hjS9iA72KAc?usp=sharing