THE CALCULATION OF UPSTREAM CONCENTRATIONS FROM DOWNSTREAM DATA FOR A2-LAYER FLOW

Is it possible to infer the time-dependent cross-sectionally uniform c oncentration at the entry to a sampling tube from concentration flux m easurements at the exit? Alas, if the shear dispersion within the samp ling tube is modelled by a constant-coefficient diffusion equation, th e answer is no: the inversion problem is ill-posed. However, the close ly related and more accurate telegraph equation can be inverted. As th e separation between entry and exit increases, the deconvolution formu la grows exponentially and oscillates more rapidly. This has severe re percussions upon the frequency and accuracy with which the exit measur ements need to be made.