Flow over a cylinder
Aim:
The aim of the project is to run an external flow baseline simulation over a cylinder and then calculating the Reynolds number for every 20, 40 and 100%. A transient simulation has to run and calculate the simulation end time.
Objective:
- Design the cylinder in solidworks and run a flow simulation
- Assign boundary conditions and create plots at various velocities and pressure
- Create animations for every plot.
Theory :
COMPUTATIONAL FLUID DYNAMICS: CFD has fascinated researchers, as it is a fast, accurate, and reliable method of analyzing the variation of hydrodynamic properties of the flow over and within a body. Computational Fluid Dynamics (CFD) is a branch of fluid mechanics that uses numerical methods and algorithms to solve complex problems involving fluid flow.
REYNOLD'S NUMBER: Reynolds number can reveal whether the flow is laminar or turbulent. The transition from laminar to turbulent flow depends on the surface roughness, flow velocity, geometry, surface temperature, and type of fluid, among others. Formula to calculate the baseline case Reynolds number.
`Re = (ρ*u*D)/μ`
where
- D= cylinder diameter in
- = dynamic viscosity in
- = density in
- u= inlet velocity in
GEOMETRY OF THE MODEL
In this project, a cylinder is created in SOLIDWORKS CAD software. The design parameters are as follows
Diameter of the cylinder = 0.06 m
Length of the cylinder = 0.1 m
BASELINE SIMULATION PARAMETERS
Initially, I considered the baseline velocity of air to be 10m/s. On the basis of initial velocity, Reynolds number is calculated.
Table 1.1: Parameters
Re = rho*U_inlet*D/mu ..........(1)
Re = rho*U_inlet*D/mu
D = cylinder diameter
mu = dynamic viscosity
rho = density
by Substituting the above values we get, the baseline case Reynolds number,
Re = 40518.19
Similarly, Reynold's number at 20, 40 and 100 % is calculated,
At 20% Re = 48621.83
At 40% Re = 56725.46
At 100% Re = 81036.38
Conducting the Baseline simulation
Table 1.2: Baseline simulation condition
CALCULATiNG SMULATION END TIME
Velocity = Distance / time
Time = Distance / velocity i.e. Time = 0.75/10 = 0.075 sec
The length of the domain along the X axis is 0.750 m
When the Velocity is 10 m/s for Re = 40518.19 then Simulation end time = 0.15 sec
Given that the end time should be 2 times the flow through time
At Baseline For V = 10 m/s , Re = 40518.19 , Simulation end time = 0.150 sec
At 20% For V = 12 m/s , Re = 48621.83 , Simulation end time = 0.125 sec
At 40% For V = 14 m/s , Re = 56725.46 , Simulation end time = 0.107 sec
At 100% For V = 20 m/s , Re = 81036.38 , Simulation end time = 0.075 sec
From this we can see that the Velocity increases the time decreases.
Results :-
Case 1: Increased Reynold's Number by 20%
Flow Through Time : 0.0375 Sec.
Simulation of Velocity Distribution :
https://drive.google.com/file/d/1PvdWC3Bav4Kh6UkoRu8jrLqaq_iUUEG_/view?usp=sharing
Simulation of Pressure Distribution :
https://drive.google.com/file/d/1e-28d2KCx5gewkFZT7ZSO7wz8B_65fI_/view?usp=sharing
Case 2: Increased Reynold's Number by 40%
Flow Through Time : 0.0321 Sec.
Simulation of Velocity Distribution :
https://drive.google.com/file/d/1XI54FeHSVpKUoFB1uXzGn_fpGMy8_O0Z/view?usp=sharing
Simulation of Pressure Distribution :
https://drive.google.com/file/d/1ibdO-nF8XrhoiJ2EEyeqi_DxzNoHw3qg/view?usp=sharing
Case 3: Increased Reynold's Number by 100%
Flow Through Time : 0.0225 Sec.
Simulation of Velocity Distribution :
https://drive.google.com/file/d/1SSRWnHIr5yzX0xpx8wWbitFqTekL2Zia/view?usp=sharing
Simulation of Pressure Distribution :
https://drive.google.com/file/d/1FTxkVY6dVVIc3MmSpM8hI_6guiIlfvUX/view?usp=sharing