# Numerical Results — Lesson 7

### Contour Plots of Axial Velocity

Note that there are two types of velocities in an LES simulation — instantaneous velocity and mean velocity. The instantaneous velocity is the actual velocity at any time instant in the domain. When we collect the statistics, the instantaneous velocity is time-averaged to obtain the mean velocity. Let us make a mid-plane in the domain to look at the contour plots of instantaneous axial velocity and the mean axial velocity.

(Click) Graphics and Animation > Contours > Set Up.. as shown in the figure below. In the Contours window, click on New Surface > Plane... as shown below. In the Plane Surface window, click Point and Normal. Under Points, choose (x0 (m), y0 (m), z0 (m)) = (0,0.0635,0) and under Normal choose (ix (m), iy (m), iz (m)) = (1,0,0). Name the surface as midplane_les under New Surface Name. Click Create. The plane can be viewed using Graphics and Animations > Mesh > Set Up.... Go back to the Contours window and select Velocity... and Y Velocity under Contours of and under Surfaces choose midplane_les and click Display.The figure below shows the contour plot of instantaneous axial velocity. For the contour plot of the mean axial velocity, select Unsteady Statistics... and Mean Y Velocity under Contours of and under Surfaces choose midplane_les and click Display For the contour plot of the mean axial velocity, select Unsteady Statistics... and Mean Y Velocity under Contours of and under Surfaces choose midplane_les and click Display. In the Solution XY Plot window, click on New Surface > Line/Rake... as shown below. In the Line/Rake Surface window, under End Points choose (x0 (m), y0 (m), z0 (m)) = (0,0.03175,0) and (x1 (m), y1 (m), z1 (m)) = (0,0.03175,0.00635). Name the surface as midline_les under New Surface Name. Click Create. The line can be viewed using Graphics and Animations > Mesh > Set Up.... Go back to the Solution XY Plot window and select Unsteady Statistics... and Mean Y Velocity under Y Axis Function and under Plot Direction choose (X,Y,Z) = (0,0,1). Choose midline_les under Surfaces and click Plot. The figure below shows the contour plot of instantaneous axial velocity. To save the line plot, select Write to File in the Solution XY Plot window and click Write. Select a location and save the file as MeanYVel_LES.xy. Save the project and close Fluent.