## General

#### How to evaluate the difference of a local variable to its circumferential averaged value on a Turbo Surface?

• FAQ
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This can be achieved with the following steps: â€¢ Initialize the turbo components â€¢ Generate a Turbo Surface: Location > Turbo Surface â€¢ Define the Turbo Surface as required, e.g.: o Geometry > Method > Constant Streamwise Location o Color – Variable: Velocity – Circ Average: Length – Max Samples: 100 o Apply â€¢ When you click on â€œâ€¦â€ a new variable named â€œVelocity LCA on Turbo Surface 1â€ occurs * â€¢ Create an Expression: Insert > Expression > exp1 = Velocity – Velocity LCA on Turbo Surface 1 > Apply â€¢ Create a Variable: Insert > Variable > var1 > Expression: exp1 > Apply â€¢ Go to the Turbo Surface again o Variable: var1 o Circ Average: None o Apply The difference is now displayed on the turbo surface. * The abbreviation LCA means circumferentail averaging by length: When the Circ. Average setting is set to Length, circumferential averaging of values at a sampling point is carried out internally by forming a circular arc, centered about the turbo axis, passing through the sampling point. Values are interpolated to n equally-spaced locations along the arc, using values from nearby nodes, where n is a number that is inversely proportional to the mesh length scale, and limited by the Max. Samples setting. The n values are then averaged in order to obtain a single, circumferentially-averaged value for the sampling point.