FLOW OVER A CYLINDER FOR DIFFERENT REYNOLD'S NUMBER (using SOLIDWORKS)
AIM:
To simulate the flow over a cylinder in a given computational domain for different Reynold's Number using SOLIDWORKS
OBJECTIVES:
- To understand the concept of Reynold's Number
- To simulate the flow of air over a cylindrical pipe and analysing it in SOLIDWORKS
- To create animation for different Reynold's Number
INTRODUCTION:
The Reynold's number is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities. A region where these forces change behavior is known as a boundary level, such as the bounding surface in the interior of a pipe. A similar effect is created by the introduction of a stream of high-velocity fluid into a low-velocity fluid, such as the hot gases emitted from a flame in air. This relative movement generates fluid friction, which is a factor in developing turbulent flow. Counteracting this effect is the viscosity of the fluid, which tends to inhibit turbulence. The Reynolds number quantifies the relative importance of these two types of forces for given flow conditions, and is a guide to when turbulent flow will occur in a particular situation.
The formula is as follows:
`R_e = (rhouD)/v`
where `R_e` = Reynold's Number
`rho` = density of the fluid = `1.184` kg/`m^3` at `25^oC`
`D` = diameter of the cross-section of pipe
`v` = dynamic viscosity of fluid = `1.849X10^(-5)` kg/(m.s) at `25^oC`
PROCEDURE:
- First, a cylindrical pipe of diameter `0.5m` and length `1m` was created.
- Then, flow simulation was created with a computational domain of `5.5m` length in x-axis and velocity given as `10` m/s in x-axis as in the 1st case.
- Then after the simulation end time was calculated as twice the time taken by the fluid (i.e. air here) to cover the whole computational domain.
- Then, animation was created for both pressure and velocity as contour plots.
- Then, the base Reynold's number was calculated and increased by `20%, 40%` and `100%` and further procedure was done as per above instructions.
OBSERVATIONS AND CALCULATIONS:
Case 1:
Velocity = `10` m/s
Computational domain = `5.5m`
Simulation end time = `1.1s`
Reynold's Number = `320207.066`
The simulation is as follows:
Case 2:
Velocity = `11.999` m/s
Computational domain = `5.5m`
Simulation end time = `0.917s`
Reynold's number = `384207.666`
The simulation is as follows:
Case 3:
Velocity = `13.999` m/s
Computational domain = `5.5m`
Simulation end time = `0.786s`
Reynold's Number = `448242.292`
The simualtion is as follows:
Case 4:
Velocity = `19.999` m/s
Computational domain = `5.5m`
Simulation end time = `0.55s`
Reynold's Number = `640346.132`
The simulation is as follows:
CONCLUSION:
- Reynold's Number affects velocity distribution a lot as it is directly stated in the formula. At lower Reynold's number, laminar flow occurs and at higher turbulent flow which tends to produces chaotic eddy currents, vortices and instabilities.
- As seen from the simulation, Reynold's Number has lesser impact on pressure distribution.