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.

This photograph of an impinging-sheet injector shows that the droplets formed at the end of the mixed sheet are all  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.  Time from impingement to mixed sheet breakup is ~ 5 ms.  Operating conditions are single sheet flowrate of 1.9 liters/minute, sheet thickness at impingement of 80 microns, impingement distance of 2 cm, impingement angle of 45^o and pressure drop of 0.69 bar (10 psig).

This photograph of an impinging-jet injector shows a central core of liquid in the formed sheet that is still red and has not been neutralized (despite the 20% excess acid).  Operating conditions are single jet flowrate of 1.9 liters/minute, jet diameter of 2 mm, impingement distance of 2 cm, impingement angle of 60^o and pressure drop of 0.69 bar (10 psig). At impingement the thickness of the equivalent single sheets is only 80 microns (a factor of 25 times less).

This photograph shows two jets impinging upon one another where the impingement is very slightly off axis.  The liquid sheet formed by the slightly off-axis impingement is not visually affected.  However, the acid and base are now segregated in the liquid sheet resulting in poor liquid-phase mixing. Note that slight off-axis jet impingement is difficult to observe visually without the aid of an indicator (in this case a color indicator). Operating conditions are single jet flowrate of 1.9 liters/minute, jet diameter of 2 mm, impingement distance of 2 cm, impingement angle of 60^o and pressure drop of 0.69 bar (10 psig).