honeycomb straightener

Test Methods for Honeycomb Straighteners in Wind Tunnel Applications

Honeycomb straighteners are mainly for making flow more uniform. In a wind tunnel, you can’t tell by looking. You have to measure.

Below are the test methods commonly used.

1. Airflow uniformity

Usually we measure velocity at multiple points downstream. A pitot tube grid or multi-point probe is common.

You set a grid, take readings point by point, then look at variation. If some points are much higher or lower, the straightener is not uniform. Often this is due to installation. If the panel is tilted or not fixed flat, the result changes.

2. Pressure drop

Pressure drop is measured across the straightener. Differential pressure sensors are used before and after.

Test at different flow speeds. Pressure drop increases with speed, but if it is too high, it could mean blocked cells or uneven cell size. In a tunnel, a high pressure drop affects the fan and limits speed range.

3. Turbulence intensity

Measure turbulence upstream and downstream. Hot-wire probes are typical.

If turbulence increases after the straightener, it usually means the panel is deformed or the cells are inconsistent. Even small bends can cause local turbulence. This is common when the straightener is thin and not supported well.

4. Visual and dimensional checks

Before airflow tests, check flatness and dimensions.

If the panel is warped or the cells are not aligned, the flow will not be uniform. Sometimes the straightener looks fine, but under clamping it bends. That changes performance.

5. Repeatability

Run the same test multiple times. The result should be similar.

If the result varies, check how the panel is installed. Different clamping force or different position changes the flow. The test record should include how the panel was fixed and where the probes were placed.