Reaction product fluctuations in a sphere wake

Fluctuations of chemical reaction product were detected in the reacting and nonreacting wake of a sphere. Using the principle of conductometric titration, a single electrode microprobe was used to detect the local concentration of ammonium acetate produced when acetic acid and ammonium hydroxide solutions were injected into the wake of a sphere suspended in the test section of a water tunnel. Reacting and nonreacting wakes were produced when the reactants were injected separately or premixed, respectively. Measurements were taken in the reacting wake with a micro-pH probe in order to have an estimate of the extent of reaction. Data reduction was accomplished using digital techniques. Preliminary results have been obtained that indicate that the distribution of the salt concentration is nongaussian for both reacting and nonreacting wakes. Spectra have been calculated at two wake positions and have similar forms for reacting and non-reacting wakes except at low wavenumber. Inflections from inertial-convective fc~5/3 subranges to viscous-convective h~l subranges were observed at about -£$ of the Kolmogoroff wavenumber.