21-08-2013, 04:01 PM
ANSYS Workbench Tutorial – Minor Losses
ANSYS Workbench .pdf (Size: 361.51 KB / Downloads: 284)
Introduction
This tutorial provides instructions for meshing two
internal flows and for analyzing both of them in
FLUENT. The first flow is in a straight pipe, and the
second flow is in a pipe of the same length and diameter,
but with a 90° elbow. The pressure drop is calculated for
both cases. The difference in pressure drop between the
two cases is due solely to the elbow since the pipes are
the same length; this is the so-called “minor loss”. In Part
1 of this tutorial, a geometry and mesh like the one
shown to the right will be created. This tutorial shows
how to use “inflation” to generate a fine grid near a wall,
how to generate an unstructured quad mesh everywhere
else, and how to sweep the mesh along the pipe.
Set Workbench options for a new FLUENT project
1. This tutorial assumes that ANSYS Workbench is running but no projects are
open. If it is not running, open it before proceeding to the next step.
2. Under View, make sure that “Toolbox”, “Toolbox Customization”, and
“Project Schematic” each have a check mark next to them.
Check marks can be inserted by placing the cursor over the menu item
and LMB (click the left mouse button).
Placing a check mark next to a menu item opens its window. If you close the window, the
corresponding check mark will be removed from the View
menu.
3. In Toolbox Customization, verify that “Fluid Flow (FLUENT)”
has a check mark next to it.
If Column A is not shown in Toolbox Customization, 1
located to the left of “Name”.
If the box to the left of “Fluid Flow (FLUENT)” is
unchecked, LMB in the box to make it checked.
Depending on your system settings, it may be necessary to make Column B wider in order to
see the entirety of each entry.
To de-clutter your Workbench workspace, close or minimize the Toolbox Customization; it is
not needed after this step.
Iterate towards a solution
1. In the main FLUENT menu, Solve-Run Calculation. In the Run Calculation sub-window, change
Number of Iterations to 500, and change Reporting Interval to 10. Calculate. The main screen will
list the residuals after every 10 iterations, while the graphical display window will plot the residuals
as a function of iteration number. When the calculations are complete or converged, OK.
Sometimes you have to click Calculate twice to get it to work.
The residuals may rise at first, but should slowly start to fall. It is normal for the residuals to
fluctuate up and down. Do not be concerned if there are reverse flow warnings; these will
disappear in time.
2. At the end of these iterations, check to see how the solution is progressing. In the main FLUENT
menu, Display-Graphics and Animations-Vectors-Set Up [the upper
Set Up, not the lower one].
3. In the Vectors window that opens, under Surfaces, select only outlet.
Display. The graphical display window will show the velocity
vectors.
Run FLUENT for the pipe with elbow
1. To run the CFD analysis, follow the FLUENT instructions for the straight pipe above. Everything is
identical except that there is only one symmetry plane instead of two separate symmetry planes.
2. Calculate the pressure drop from the inlet to the outlet as was previously done for the straight pipe
and compare. The difference between the two pressures is due to the effects of the elbow alone,
since the two pipes are the same diameter and length, and since the fluid, flow rate, etc. are
identical