Include Page 

 FLUENT Google Analytics 

 FLUENT Google Analytics 


Include Page 

 Unsteady Flow Past a Cylinder  Panel 

 Unsteady Flow Past a Cylinder  Panel 


Unsteady Flow Past a Cylinder
Created using ANSYS 13.0
Problem Specification
Consider the unsteady state case of a fluid flowing past a cylinder, as illustrated above. For this tutorial we will use a Reynolds Number of 120. In order to simplify the computation, the diameter of the cylinder is set to 1 m, the x component of the velocity is set to 1 m/s and the density of the fluid is set to 1 kg/m^3. Thus, the dynamic viscosity must be set to 8.333x10^3 kg/m*s in order to obtain the desired Reynolds number.
Compared to the steady case, the unsteady case includes an additional timederivative term in the NavierStokes equations:
Wiki Markup 

{latex}
\begin{eqnarray}
\frac{\partial \vec{u}}{\partial t} + \rho (\vec{u}\cdot \triangledown)\vec{u} = \triangledown p + \mu \triangledown^{2} \vec{u}
\end{eqnarray}
{latex} 
The methods implemented by FLUENT to solve a time dependent system are very similar to those used in a steadystate case. In this case, the domain and boundary conditions will be the same as the Steady Flow Past a Cylinder. However, because this is a transient system, initial conditions at t=0 are required. To solve the system, we need to input the desired time range and time step into FLUENT. The program will then compute a solution for the first time step, iterating until convergence or a limit of iterations is reached, then will proceed to the next time step, "marching" through time until the end time is reached.
Go to Step 1: PreAnalysis & StartUp
Go to all FLUENT Learning Modules