## Calculating the Volume of an Iso-Surface

Question: How do I calculate the volume of a completely enclosed iso-surface? Solution: The volume of an iso-surface (no holes in it) may be calculated using 360’s data calculation, alteration and integration features by following these steps: A)   First, create a zone from your iso-surface: Display the iso-surface of choice by going to the side panel and clicking the Iso-Surfaces Details… button. Activate only one iso-surface group and ensure that […]

## Calculating Grid K Normal Nodal Values

Question: The symmetry of nodal Grid K Unit Normal values differ from the comparable cell-centered values (see Figure 1). How are nodal Grid K Unit Normal values calculated?1 Explaining the Question: In Figure 1, at nodes 1, 6, 11, 16, and 21 the X Grid K Unit Normal vectors are equal. However, on the data row below it (nodes 2, 7, 12, 17, and 22), the components of the X […]

## Unique Iso-surfaces in Multiple Zones with Equal Variables

Problem: How do I create iso-surfaces, exclusive to each zone, for the same iso-surface variable? As seen in Figure 1, Tecplot 360 will create iso-surfaces in both volume zones for the Mach variable because both zones contain this variable. What can be done if one iso-surface is to be seen in one zone, but not the other zone? Solution: Essentially, this procedure duplicates and renames a variable to each zone […]

## Weighted versus Arithmetic Averages and Tecplot

Question: Why is there a difference in Tecplot’s integration average results and the average, or mean, I am calculating over all the data values? Example:  I have nodal data and I want to calculate average U velocity on the following domain (see Figure 1). When I use the integration average feature (Analyze>Perform Integration…>Average>U), I calculate 38.90 m/s. But when I calculate the average over all the nodal U values in […]

## Verifying Surface Normals in Integral Calculations

Problem: How do I verify the direction of my unit surface normal vectors to make the correct integrations? If my surface normals point in an inconsistent direction from one timestep to another, how do I correct the value of my integral? From the User’s Manual: “Integrations involving surface unit normals, such as Mass Flow Rate, and Forces and Moments integration, rely on surface unit normals pointing in a consistent direction. […]

## Calculate Delta Criterion

Problem: How do I calculate Delta Criterion? Solution: The easiest way to do this is to use a Tecplot Macro to automate the calculation. Calculations are derived from http://www.ctr.maths.lu.se/media/thesis/2013/FMA820.pdf First, make sure Tecplot has established the velocity variables via the Field Variables dialog (Analyze -> Field Variables). Then, play the macro via the Scripting menu. The macro commands are as follows: Calculate the Velocity Gradient tensor. (Can also be calculated […]

## Calculating Average Normal Velocity to Iso-Surface

Problem: How do I calculate the average normal fluid velocity (or any vector variable) going through an iso-surface? Details: Or stated another way, “I am trying to use a vector dot product with unit normal integration to get the average normal velocity through an extracted iso-surface.”  This question originally relates to this scenario, but it can be used for calculating the average flux though a surface for various cases. Solution: […]

## Creating Streamtraces on a No-slip Boundary Surface with Multiple Surrounding Volume Zones

Problem: How do I create streamtraces on a no-slip boundary surface with multiple surrounding volume zones? In more detail: In the User’s Manual in the section titled “Surface Streamtraces on No-slip Boundaries”, it describes how to create these surface streamtraces in the context of an ASCII file with one parent (volume) zone. However, if other data file types are used or multiple parent zones, these instructions do not apply. Solution: […]

## Vortex Core Extraction Method

Problem: How is the Vortex Core calculated in Tecplot 360? Solution: The exact Vortex Core extraction method is defined in an AIAA paper called “Identification of Swirling Flow in 3-D Vector Fields” by David Sujudi and Robert Haimes of the Massachusettes Institute of Technology. Abstract An algorithm for identifying the center of swirling flow in 3-D discretized vector fields has been developed. The algorithm is based on critical point theory and […]