Flow over a cylinder

AIM :

To simulate the transient state flow over a cylinder.

OBJECTIVES:

• Calculate the Reynolds number for the baseline simulation and Run the baseline simulation.
• Conduct transient flow simulation for an increasing Reynolds number by a factor of 20%, 40%, and 100% of the baseline Reynolds number.
• Create animation for pressure – velocity for all the three condition of Reynolds number.
  

INTRODUCTION :

In general, nearly every process or system has both a steady state and a transient state. Also, a steady state establishes after a specific time in your system. However, a transient state is essentially the time between the beginning of the event and the steady state.

PROCEDURE :

• Geometry Modelling of the cylinder -

  Prepare the cylinder for simulation of following dimensions

  Cylinder diameter = 0.04 m

  Cylinder length = 0.05 m

  
  
• Flow Simulation Setup -

  The characteristics of fluid flowing inside the pipe is given below,

  Fluid: Air

  Dynamic Viscosity: 0.00001825 N.S/m²

  Density: 1.225 kg/m

  Type of Flow : Laminar and Turbulant,

  Wall Conditions : Adiabatic with 0 micro-meter roughness,

  
  
• Calculation-

  Formula for Reynolds number: Re = rho*V*D/mu

  Where,

  Re = Reynolds number

  V = Flow velocity

  D = Diameter

  rho = density

  mu = dynamic viscosity

  Assumption:

  Surface of cylinder is smooth and roughness is considered zero.

  Effect of temperature are not considered in study.

  Re = (1.225 ×10 ×0.04)/0.00001825

  Case 1 : Re = 26849.3

  Similarly, Reynolds number at 20, 40 and 100% we get the following results as

  Case 2 : At 120% = Re = 32414.55

  Case 3 : At 140% = Re = 37817

  Case 4 : At 200% = Re = 54024.26

• Result :

Case 1 : Velocity distribution over cylinder for velocity 10m/s -

Pressure distribution over cylinder for velocity 10m/s -

Case 2 : For Re = 120% of 26849.3 =32219.1

Velocity distribution over cylinder for velocity 12m/s -

Pressure distribution over cylinder for velocity 12m/s -

Case 3 : For Re = 140% of 26849.3 =37589.02

Velocity distribution over cylinder for velocity 14m/s -

Pressure distribution over cylinder for velocity 14m/s -

Case 4 :For Re = 200% of 26849.3 =53698.6

Velocity distribution over cylinder for velocity 20m/s -

Pressure distribution over cylinder for velocity 20 m/s -

Conclusion :

• It is intelligible that increasing Re no increases the velocity of fluid.
• It is observed that the high pressure is created on the surface facing the inlet velocity.
• As velocity strikes the front face of cylinder, there is slight drop in the velocity and gradually increases over the cylinder.
• Vortex Formation takes place at the side of the cylinder which is opposite to velocity flow.
• Thiers no much of pressure change as compared to velocity change by Re no.
  

Animation videos:

https://drive.google.com/drive/folders/1VTdo9DeRZ_Q_jr1tts5vMsbJ_loP_nAR?usp=sharing