Flow over a cylinder Using SOLIDWORKS
ABSTRACT
In this Project, CFD analysis of a cylinder in which external flow takes place and running a baseline simulation and then calculating the Reynolds number and also the simulation end time. Then increase the Reynolds number by a factor of 20%, 40%, and 100% then run the transient flow simulation. Animations for pressure-velocity for all the three Reynolds number created.
INTRODUCTION
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.
The present study aims to analyze the fluid flow over a cylinder and calculate Reynold's number for baseline simulation and increase the calculated Reynolds number to a factor of 20%, 40%, & 100% and perform the simulation for all the three values of Reynold's number and create an animation file for velocity-pressure.
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 :
Simulation of Pressure Distribution :
Case 2: Increased Reynold's Number by 40%
Flow Through Time : 0.0321 Sec.
Simulation of Velocity Distribution :
Simulation of Pressure Distribution :
Case 3: Increased Reynold's Number by 100%
Flow Through Time : 0.0225 Sec.
Simulation of Velocity Distribution :
Simulation of Pressure Distribution :
Conclusion
for velocity distribution, we can say that the velocity of the air just before striking the cylinder is quite low but after striking the cylinder it passes over the cylinder with a high velocity and it comes down as the velocity decreases. For pressure distribution, As we know from the equation pv=mrt if velocity is greater then the pressure will be lesser to satisfy the equation and also we can see that a high-pressure region is created just before the air strikes the cylinder and low-pressure region is created where the velocity is high.