**Abbreviations**

The following abbreviations are used in this manuscript:


#### **Appendix A. Simulated Case Study**

The results from the simulated case study are shown in Figure A1 regarding the direction of the forced air flow and in Figure A2 for the design of the nozzle setup. Analyzing the direction of the air flow focuses on areas that exhibit low air flow velocities (*u* < 0.36 m <sup>s</sup><sup>−</sup><sup>1</sup>). The air stays in the same place in these areas and is consequently heated by the hot cylinder. Therefore, there will be a refractive index gradient in these areas at a magnitude comparable to the gradient without air flow. For the given reasons, the air flow should be applied comparable to Case (a), i.e., perpendicular to the cylinder main axis. In all cases, the measurement system should be placed near the forced air flow actuator to avoid areas of low air flow velocities interfering with the measurement light.

Focusing on the nozzle setup, a case study was conducted using ANSYS Discovery AIM. The examined cases are shown in Figure A2. The results are comparable to the ones in Figure 5 while showing a slightly different excerpt from the simulation field. Analyzing the case study, an homogeneous velocity profile of 250 mm at a distance of 500 mm to the nozzles (cf. dashed lines in Figure A2) is considered to be desirable (cf. Section 5). A sectional view through the simulated velocities fields is shown in Figure A3. The simulated profiles are symmetrical to *x* = 0 mm. The setup using three nozzles and an angle of 5° show a nearly homogeneous profile at approximately 3.0 m s<sup>−</sup><sup>1</sup> for −125 mm < *x* < 125 mm. This is the chosen nozzle configuration for the suppression device.

**Figure A1.** Results from the simulated case study examining different forced air flow *vf f* = 1.0 m s<sup>−</sup><sup>1</sup> directions in relation to a cylinder. The direction is varied by tilting the object and is described by the cylinder main axis **c***m* in world coordinates. The vector for the direction of the forced air flow is (1, 0, <sup>0</sup>)*<sup>T</sup>*. (**a**) **c***m* = (0, 1, <sup>0</sup>)*<sup>T</sup>*; (**b**) **c***m* = (1, 1, <sup>0</sup>)*<sup>T</sup>*; (**c**) **c***m* = (1, 0, <sup>0</sup>)*<sup>T</sup>*.

**Figure A2.** Results from the simulated case study using multiple nozzles. A positive angle value indicates nozzles pointing towards each other, and a negative value indicates nozzles pointing away from each other. The dashed line depicts the design distance, in which an homogeneous field is desired. Air flow velocities *vf f* < 1.0 m s<sup>−</sup><sup>1</sup> are masked and depicted in white. (**a**) Two nozzles 400 mm apart with an angle of −10°; (**b**) two nozzles 200 mm apart with an angle of 0°; (**c**) two nozzles 200 mm apart with an angle of 5°; (**d**) three nozzles with an angle of 0°; (**e**) three nozzles with an angle of 5°; (**f**) three nozzles with an angle of 10°.

**Figure A3.** Sectional view through the air flow velocities profiles of Figure A2 (dashed lines).

#### **Appendix B. 3D Geometry Reconstructions**

An example set of reconstructed height maps *<sup>z</sup>*(**<sup>u</sup>***p*) is shown in Figure A4. These height maps are the fundamentals to calculate the deviations maps *Em*(**<sup>u</sup>***p*). There is one height map for each camera-camera and camera-projector pair. The height maps reconstructed from cameras on the same side of the measurement setup are omitted (explained in detail in [15]).

**Figure A4.** Example of a set of reconstructed height maps, depicted as the map of the corresponding *z*-values. (**<sup>a</sup>**–**h**) Height maps from each camera-camera pair and each camera-projector pair, respectively; (**i**) average height map of all available sets. All points are masked that are not present in each height map. Masked points are not considered when calculating the reconstruction quality metric.
