This article aims at predicting the oscillation frequency of open-channel lateral cavities, which are common sheltered zones of riverine environments, and have important ecological impact. Using a theoretical analysis based on an existing model for acoustic cavities and a free-surface lateral cavity experiment, we show that the vortex shedding in the mixing layer between the cavity and the open channel is always constrained by gravity waves even for low Froude numbers ($F<0.6$). This expands previous results from the literature showing the impact of gravity waves on the vortex shedding frequency for high Froude number ($F>0.6$). Measurements of the free-surface oscillation and transverse velocity oscillation frequencies reveal a unique frequency along the mixing layer, equal to the free-surface oscillation frequency anywhere in the cavity. Hence, it is shown that the vortex shedding frequency in an open-channel lateral cavity always equals a match between a natural frequency of the cavity and a solution of the feedback model developed herein for low to moderate Froude numbers.

The following is a description of Limochores bimacula, Scuds ♂ , Hesperia acanoatus, Scudd., which I drew up some time ago:-

Dark brown marked with chrome yellow.

Above: head, thorax, abdomen and antennae black, the head and abdomen having a few yellow hairs. Both wings dark olive brown; primaries with a indistinct spot a little above and beyond the outer termination of the disk; a large patch extends over the middle third from the outer margin to the disc, and is crossed by a black velvety dash, which if continued would bisect the apical angle

We present a combined theoretical and experimental study of the adsorption of two pairs of organic isomers, (i) acetic acid AA (CH3COOH) and methyl formate MF (HCOOCH3), and (ii) ethanol EtOH (CH3CH2OH) and dimethyl ether DME (CH3OCH3), onto crystalline water ice surfaces at low temperatures. Both approaches show that, for each pair, the most stable isomer from a thermodynamical point of view, i.e. AA and EtOH, is also the one which is the more tightly bound to the water ice surface compared to the less stable isomers (MF and DME). This finding, which can be explained by the ability of AA or EtOH to efficiently interact with the ice surface via hydrogen bondings, may have important consequences in an astrophysical context, since it could explain why the most stable isomer is not the most abundant observed in the interstellar gas phase.