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Support Corner – Calculator Performance Tip

Here’s an interesting calculator problem,

You know that
var{5} is the value of the variable at timestep 5
and
var{0} is the value of the variable at timestep 0.

If you want to know the difference between the two,
you can put the following expression in the calculator.

var{5} – var{0]

but, for models of any size, it is so slow it appears to hang.

Why?

If you include a reference to a variable from two or more different
timesteps, the calculator will change back and forth between timesteps element 
by element or node by node and take a considerable amount of time. If you
need to do a calculation with two different timesteps, assign each of the
timesteps to a temporary variable, then use the temporary variables in your
calculation.

For example,

var{5} – var{0}

is prone to drastic slowdown in EnSight. Whereas

temp5 = var{5}
temp0 = var{0}
temp5-temp0

will run much faster.

This is documented in Knowledge Base under Calculator Variable Problems, and now in ch 7 of the User Manual.

Signed – EnSight Support

Distance Field Calculator Function

What is a Distance Field and Why Do I Care?

Before we begin, we should define the signed distance field being computed by this new function. Put simply, the distance field is a nodal, scalar quantity which is the minimum distance from each node to any node on a target part. In EnSight, the field is estimated from the individual node positions. No consideration is given to element boundaries in the computation. In this sense, it is a purely nodal computation and thus its accuracy is strongly linked to spatial nodal density.

“Clearance” Computation

How might one use a distance field?  A classic example is the computation of “clearance” or the minimum distance between two parts that are moving relative to each other over time. In the example below, some ordinance is simulated dropping from the wing of a plane. We use the Dist2Part() function to compute a “clearance” field that is the minimum distance between each node on the dropping ordinance and the nodes on the parts that make up the plane model.

Read more

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