Video is a front view of the impingement of two, equal paper-thin sheets of water impinging at a 45^o angle to produce a mixed or combined sheet.  Single sheet thickness is about 80 microns at impingement and the impingement zone can clearly be seen as a thin arc segment line stretching across the fan shaped sheets.  Pressure drop is only 0.25 bar (3.6 psig) for a single-sheet flow rate of about 1.1 liters/minute and a single-sheet velocity of 6 m/s.

This photograph of a ThinSheet^TM injector shows that after about 4 to 5 ms virtually all of the droplets are yellow in color.  In the mixed sheet the excess acid has neutralized the base causing the phenol red to convert to it’s yellow form. From Demyanovich (2024a – see Publications below) the calculated neutralization time is 5 ms, which agrees well with the observed neutralization time. Operating conditions are single-sheet flowrate of 1.0 L/min, single-sheet thickness at impingement of 31 microns, distance to impingement of 2.25 cm, impingement angle of 40^o , injector pressure drop of 1.46 bar (21 psig), single-sheet velocity of 13.6 m/s, and energy dissipation rate in the impingement zone of just over 2 million W/kg (Demyanovich, 2024b; Demyanovich, 2021a). IZ – impingement zone.

This photograph of an impinging-jet injector with on-axis impingement shows a central core of liquid in the formed sheet that is still pink and has not been neutralized (despite the 20% excess acid).  Operating conditions are jet flowrate of 1.0 L/min,  jet diameter of 1.2 mm, distance to impingement of 1 cm, impingement angle of 60^o , injector pressure drop of 1.2 bar (17.6 psig), and jet velocity of 14.9 m/s.  At impingement the thickness of the equivalent single sheets is only 31 microns (a factor of 39 times less). IZ – impingement zone.

This photograph shows two jets impinging upon one another where the impingement of the 1.2 mm jets is offset by 0.2 mm. This off-axis impingement of the jets results in about 20 to 25% of the flow of each jet not impinging upon the other jet.  From the front, the liquid sheet formed by the slightly off-axis impingement is not visually affected; however, from the side, the sheet is turned about 10^o.  This off-axis impingement results in the portion of the pink base jet that does not impinge upon the clear acid jet flowing to the left and the corresponding portion of the acid jet that doesn’t impinge upon the base jet flowing to the right. Note that slight off-axis jet impingement cannot be visually observed without the aid of an indicator (in this case a color indicator).  Operating conditions are jet flowrate of 1.0 L/min, jet diameter of 1.2 mm, distance to impingement of 1 cm, impingement angle of 60^o, injector pressure drop of 17.5 psig (1.2 bar), and jet velocity of 14.8 m/s. IZ – impingement zone.