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A hydrogel‐capped hair‐cell flow microsensor, which closely mimics a superficial neuromast of a fish, is introduced. By encapsulating the hair sensor into the artificial hydrogel cupula a dramatic increase in hair‐sensor sensitivity to the oscillating and the steady flow is achieved. It opens the way toward the remote monitoring of the underwater environment by autonomous, unmanned microvehicles with self‐navigating capability.

Readmission rates after radical cystectomy are significant, approaching 27% within the first 90 days. Gender and age adjusted Charlson comorbidity index were independent predictors providing preoperative information identifying patients more likely to require readmission or possibly to benefit from a longer initial hospital stay.

Calculated values of the three velocity components and measured values of the longitudinal component are reported for the flow of water in a 90° bend of 40 x 40mm cross-section; the bend had a mean radius of 92mm and was located downstream of a 1[sdot ]8m and upstream of a 1[sdot ]2m straight section. The experiments were carried out at a Reynolds number, based on the hydraulic diameter and bulk velocity, of 790 (corresponding to a Dean number of 368). Flow visualization was used to identify qualitatively the characteristics of the flow and laser-Doppler anemometry to quantify the velocity field. The results confirm and quantify that the location of maximum velocity moves from the centre of the duct towards the outer wall and, in the 90° plane, is located around 85% of the duct width from the inner wall. Secondary velocities up to 65% of the bulk longitudinal velocity were calculated and small regions of recirculation, close to the outer corners of the duct and in the upstream region, were also observed.The calculated results were obtained by solving the Navier–Stokes equations in cylindrical co-ordinates. They are shown to exhibit the same trends as the experiments and to be in reasonable quantitative agreement even though the number of node points used to discretize the flow for the finite-difference solution of the differential equations was limited by available computer time and storage. The region of recirculation observed experimentally is confirmed by the calculations. The magnitude of the various terms in the equations is examined to determine the extent to which the details of the flow can be represented by reduced forms of the Navier–Stokes equations. The implications of the use of so-called ‘partially parabolic’ equations and of potential- and rotational-flow analysis of an ideal fluid are quantified.

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This study is concerned with the mathematical modelling of the motion of arthropod filiform hairs in general, and of spider trichobothria specifically, in oscillating air flows. Analysis of the behaviour of hair motion is based on numerical calculations of the equation for conservation of hair angular momentum. In this equation the air-induced drag and virtual mass forces driving the hair about the point of attachment to the substrate are both significant and require a correct prescription of the air velocity. Two biologically significant cases are considered. In one the air oscillates parallel to the axis of the cylindrical substrate supporting the hair. In the other the air oscillates normal to that axis. It is shown that the relative orientation between the respective directions of the air motion and the substrate axis has a marked effect on the magnitudes of hair displacement, velocity and acceleration but not on the resonance frequency of the hair. It is also shown that the variation of velocity with distance from the substrate depends on the value of the parameter Re s St s , the product of the Reynolds number and the Strouhal number characterizing the motion of air past the substrate. In the case of air motion parallel to the substrate axis the analytical result derived by Stokes (1851), for a fluid oscillating along a flat surface of infinite extent, applies if Re s St s >10 or, equivalently, if fD 2 / v >20/n where f is the air oscillation frequency, D the substrate diameter and v the kinematic viscosity of the air. In contrast, in the case of air motion perpendicular to the substrate axis Stokes’ (1851) analysis never applies due to a substrate curvature dependence of the velocity profile for all biologically significant values of Re s St s . Present theoretical considerations point to a new method for simultaneously determining R , the damping constant, and S, the torsional restoring constant of a filiform hair from measurements of the phase difference between hair displacement and air velocity as a function of the air oscillation frequency. For the filiform hairs of crickets we find from the data available that S = 0 (10 -11 ) N m rad -1 and R = 0 (10 -13 ) N m rad -1 . All major qualitative aspects of known hair motion in response to air motion are correctly predicted by the numerical model.

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