Flow over a cylinder
flow over cylinder
Aim:- Run external flow over cylinder simulation in SolidWorks with increasing flow velocity by 20%,40%100%
introduction:- The Reynolds no. is an important dimensionless quantity in fluid mechanics used to help to predict flow patterns in a different fluid flow situations
- computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structure to analyze and solve problems that involve fluid flows
- In this pipe flow simulation, we are going to run the pipe flow simulation to understand the behavior of velocity with respect to Reynolds no in a close bound pipe.
- in solid works flow simulation, we can set up the problem in various circumstances to observe the behavior of the flow of gaseous and liquid material. in computational fluid dynamics, this simulation is used to analyze the flow.
Theory:-
- Reynolds number is the ratio of inertial forces to viscous forces within a fluid that is subjected to relative internal movement due to different fluid velocities.
ρ is the density of the fluid ( KG/M3 )
u is the flow speed (m/s)
D is the diameter of the tube (m)
μ is the dynamic viscosity of the fluid (Pa·s or N·s/m2 or kg/(m·s))
ν is the kinematic viscosity of the fluid (m2/s).
- Boundary layer:- the layer of fluid in the immediate vicinity of the bounding surface where the effect of viscosity is significant. The boundary layer is a region where these forces change behavior.
- boundary layer separation: Whenever there is relative movement between a fluid and a solid surface, whether externally round a body or internally in an enclosed passage, a boundary layer exists with viscous force present in the layer of fluid close to the surface. Boundary layers can be either laminar or turbulent. A reasonable assessment of whether the boundary layer will be laminar or turbulent can be made by calculating the Reynolds number of the local flow conditions.
- Flow separation is the detachment of a boundary layer from a surface into awake. Separation occurs inflow that is slowing down, with pressure increasing, after passing the thickest part of a streamlined body.
calculation
computational flow domain consired 0.5m
type of fluid flow: air
ρ= 1.225 KG/M3
u= 10m/s
D=0.02m
μ=1.81*10^-5 kg/(m·s)
from reynolds number equation
- for baseline flow simulation flow speed (u) =10m/s Re=13535 flow time0.05s
- for 20% incresed reynolds number =16245 flow speed =12m/s time = 0.045s
- for 40% incresed reynolds number =18950 flow speed =14m/s time = 0.035s
- for 100% incresed reynolds number =27070 flow speed =20m/s time = 0.025s
model
culinder diameter 20mm
cylinder length 50mm
Mesh parameter setup
type: automatic
global mesh setting level 5
radio factor 2
advance channel refinement
computational domain setup
Size
X min: -0.200 m Y min: -0.140 m Z min: -0.120 m
X max: 0.300 m Y max: 0.140 m Z max: 0.170 m
X size: 0.500 m Y size: 0.280 m Z size: 0.290 m
case 1
External flow simulation wizard setup
project name: flow_over_cylinder_10
(keeping the default setting except for the following parameter)
analysis type: external
time-dependent
time0.01s ( animation time should be double)
fluids: air
velocity parameter
velocity in x-direction 10m/s
case 1
Results
velocity plot
velocity animation
pressure plot
pressure animation
case 2
External flow simulation wizard setup
project name: flow_over_cylinder_12
(keeping the default setting except for the following parameter)
analysis type: external
time-dependent
time0.009s ( animation time should be double)
fluids: air
velocity parameter
velocity in x-direction 12m/s
case 2
Results
velocity plot
velocity animation
pressure plot
pressure animation
case 3
External flow simulation wizard setup
project name: flow_over_cylinder_14
(keeping the default setting except for the following parameter)
analysis type: external
time-dependent
time0.007s ( animation time should be double)
fluids: air
velocity parameter
velocity in x-direction 14m/s
case 3
Results
velocity plot
velocity animation
pressure plot
pressure animation
case 4
External flow simulation wizard setup
project name: flow_over_cylinder_20
(keeping the default setting except for the following parameter)
analysis type: external
time-dependent
time0.005s ( animation time should be double)
fluids: air
velocity parameter
velocity in x-direction 20m/s
case 4
Results
velocity plot
velocity animation
pressure plot
pressure animation
Result table
| flow velocity (m/s) | reynolds number |
min velocity (near cylinder)(m/s) |
max velocity(in the domain)(m/s) | min pressure(pa) | max pressure(pa) |
| 10 | 13535 | 1.806 | 12.874 | 101297.89 | 101384.59 |
| 12 | 16245 | 1.185 | 15.588 | 101284.73 | 101412.83 |
| 14 | 18950 | 1.375 | 18.210 | 101270.20 | 101444.55 |
| 20 | 27070 | 1.997 | 26.077 | 101211.68 | 101569.5 |
observations:
- in all the cases result from table max flow velocity is increased by120% of the initial velocity
- min flow velocity is observed near the cylinder in the boundary layer separation area
- the pressure and velocity is vice versa in the computational domain
- max flow velocity is observed near to the cylinder as the flow separation reduces the flow velocity is returned to normal
conclusion:
this flow simulation over the cylinder proves the theory of boundary layer separation and relation between the velocity and pressure.