FLOW SIMULATION FOR FLOW OVER A CYLINDER
AIM: TO RUN A FLOW SIMULATION FOR FLOW OVER CYLINDER USING SOLIDWORKS.
OBJECTIVE:
- To perform Flow simulation study.
- To calculate the Baseline case Reynolds number.
- To obtain a plot for velocity variation at a cut plane.
- To obtain a plot for pressure variation at a cut plane.
- To create the Animation video.
- To create flow simulation for three conditions-
|
Study number |
Increase in Reynolds number |
|
1 |
20% |
|
2 |
40% |
|
3 |
100% |
OVERVIEW:
External flows past objects have been studied extensively because of their many practical applications. For example, airfoils are made into streamline shapes in order to increase the lifts, and at the same time, reducing the aerodynamic drags exerted on the wings. On the other hand, flow past a blunt body, such as a circular cylinder, usually experiences boundary layer separation and very strong flow oscillations in the wake region behind the body. In certain Reynolds number range, a periodic flow motion will develop in the wake as a result of boundary layer vortices being shed alternatively from either side of the cylinder.
Flow Separation: The presence of the fluid viscosity slows down the fluid particles very close to the solid surface and forms a thin slow-moving fluid layer called a boundary layer. The flow velocity is zero at the surface to satisfy the no-slip boundary condition. Inside the boundary layer, flow momentum is quite low since it experiences a strong viscous flow resistance. Therefore, the boundary layer flow is sensitive to the external pressure gradient. If the pressure decreases in the direction of the flow, the pressure gradient is said to be favorable. In this case, the pressure force can assist the fluid movement and there is no flow retardation. However, if the pressure is increasing in the direction of the flow, an adverse pressure gradient condition as so it is called exist. In addition to the presence of a strong viscous force, the fluid particles now have to move against the increasing pressure force. Therefore, the fluid particles could be stopped or reversed, causing the neighboring particles to move away from the surface.This phenomenon is called the boundary layer separation.
CALCULATION:
Reynolds number, `Re= ρVD/μ`
Here,
ρ = Density of fluid (kg/m3)
V = Flow velocity (m/s)
D = Diameter of pipe (m)
µ = Dynamic viscosity of the fluid (pa.s)
here, Air is taken as a fluid so
ρ=1.2754 kg/m3
µ=1.81*10-5 pa.s
D=0.02 m
For Baseline calculation:
V=10 m/s
Re=14033 (calculated by the above formula)
Domain length = 0.2 m
Flow time = domain length/velocity = 0.2/10 = 0.02 s
End time = 2*Flow time = 0.04 s
For 20% Increased Reynolds number:
Re=14033*1.2 = 16840
V=12 m/s (calculated by the above formula)
Domain length = 0.2 m
Flow time = domain length/velocity = 0.2/12 = 0.0167 s
End time = 2*Flow time = 0.0334 s
For 40% Increased Reynolds number:
Re=14033*1.4 = 19646
V=14 m/s (calculated by the above formula)
Domain length = 0.2 m
Flow time = domain length/velocity = 0.2/14 = 0.0143 s
End time = 2*Flow time = 0.0286 s
For 100% Increased Reynolds number:
Re=14033*2 = 28066
V=20 m/s (calculated by the above formula)
Domain length = 0.2 m
Flow time = domain length/velocity = 0.2/20 = 0.01 s
End time = 2*Flow time = 0.02 s
PROCEDURE:
To start the flow simulation, we will provide some initial conditions like Unit System, Fluid type, Analysis type, Thermodynamic parameters etc.
Unit System
Fluid type
Analysis type
Thermodynamic parameters
Creating Cut plane for Pressure
Creating Cut plane for Velocity
Then by clicking on the “run”
RESULTS:
For Baseline study
Velocity
Animation video
Pressure
Animation video
Study-1 (20% Increased Reynolds number)
Velocity
Animation video
Pressure
Animation video
Study-2 (40% Increased Reynolds number)
Velocity
Animation video
Pressure
Animation video
Study-3 (100% Increased Reynolds number)
Velocity
Animation video
Pressure
Animation video
Link for Plots, Results –
https://drive.google.com/file/d/12TmT3kO0ORUHTfM0NfvVFrM6mFogI_aV/view?usp=sharing