CFD ANALYSIS OF FLOW OVER A CYLINDER SIMULATION USING SOLIDWORKS
AIM: CFD Analysis of Simulation of the flow over a cylinder for different conditions.
OBJECTIVES:
1) Run a study with baseline parameters and calculate the Reynolds number for that study.
2) Run the study for increased Reynolds number in order to 20%, 40% and 100% increament in initial Re.
3) Run different studies and obtain the velocity & pressure plots and animations.
FLOW OVER A CYLINDER:
> In mathematics, potential flow around a circular cylinder is a classical solution for the flow of an inviscid, incompressible fluid around a cylinder that is transverse to the flow. Far from the cylinder, the flow is unidirectional and uniform. The flow has no vorticity and thus the velocity field is irrotational and can be modeled as a potential flow. Unlike a real fluid, this solution indicates a net zero drag on the body, a result known as d'Alembert's paradox.
PROCEDURE:
> In this flow simulation, we're required to alter the value of Reynolds no., which means we've three different inlet velocities. But first we need to run a Baseline simulation where we do not consider the Reynolds no. and depending on the inlet velocity we'll calculate the constant value later.
> First we begin with the creation of the geometry i.e. our cylinder, using the 'Extrude boss/base' command. Here the geometrical parameters of the cylinder are:diameter D = 0.05m and length L = 0.1m. To start with the baseline simulation, we consider the inlet velocity in x-dir as 0.75 m/s.
> Click on Wizard option, give a proper name to the project, Select the units system and here the flow is over the cylinder hence, the type of analysis is External. After setting up the initial conditions, we have to fulfill a condition where the complete time of simulation must be in relation to the inlet velocity and the length of the Computational domain. Hence, with Vin = 0.75 m/s and Computational domain length decided as 2m our flow through time is 0.4 sec and the end time as 2x of flow through time i.e. 0.8 sec. For mesh size, we're refining the mesh so as to get more accuracy.
> After running the analysis we get the result. As we're interested in the Pressure and Velocity(x) also the animations for both. We create two cut plots one each
for Velocity(x) and for Pressure.
CALCULATION OF REYNOLDS NUMBER FROM ABOVE STUDY:
> For Air:
`rho = 1.225 kg//m^3`
`mu = 1.81 xx 10^-5 kg//m*s`
`D = 0.05 m`
`v = 0.75 m//s`
> Formula for Reynolds Number:
`Re = (rho*v*D)/mu`
> After substituting all values in above equation the value for Reynolds number obtained is'
Re = 2538
CASES:
1) Increase Re by 20% = 3045.6
2) Increase Re by 40% = 3553.2
3) Increase Re by 100% = 5076
> Velocities calculated for these values of Reynolds numbers are:
1) v1 = 0.9 m/s
2) v2 = 1.05 m/s
3) v3 = 1.50 m/s
CASE 1:
VELOCITY:
PRESSURE:
CASE 2:
VELOCITY:
PRESSURE:
CASE 3:
VELOCITY:
PRESSURE:
CONCLUSION:
1) After observing the cut plots for Pressure and Velocity for different Reynolds no., it may be concluded that the Pressure plot remains unaffected though the magnitude of the is increasing at the outlet for different Re.
2) The Velocity plot show a considerable change as in baseline simulation there's a low velocity region at the surface where the Air strike and just around that there's a high velocity region. As the Air leaves the outlet its produces the tail, where the velocity is gradually increasing.
3) With increase in the velocity, the region of velocity at inlet remains almost similar to that of Baseline condition. But we can observe that the air leaving the geometry is increased and so the plot is slightly changed w.r.t. baseline simulation.
4) With V = 1.50 m/s, we observe a considerable change in the plot as in this case we've doubled the inlet velocity. The inlet portion shows an accumulation of the velocity and at the outlet the velocity is increased greatly.
5) The Reynolds number are from every type of flow like the first case is from Laminar flow, Second case is from Transitional Flow and the third one is from Turbulant flow. Therefore they behaving according to that.
NOTE: Due to technical errors I cannot make Animation files but the observations are made from the simulation played in solidworks software.