# Influence of flow confinement on the drag force on a static cylinder - Physics > Fluid Dynamics

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Abstract: The influence of confinement on the drag force $F$ on a static cylinder in aviscous flow inside a rectangular slit of aperture $h 0$ has been investigatedfrom experimental measurements and numerical simulations. At low enoughReynolds numbers, $F$ varies linearly with the mean velocity and the viscosity,allowing for the precise determination of drag coefficients $\lambda {||}$ and$\lambda {\bot}$ corresponding respectively to a mean flow parallel andperpendicular to the cylinder length $L$. In the parallel configuration, thevariation of $\lambda {||}$ with the normalized diameter $\beta = d-h 0$ of thecylinder is close to that for a 2D flow invariant in the direction of thecylinder axis and does not diverge when $\beta = 1$. The variation of$\lambda {||}$ with the distance from the midplane of the model reflects theparabolic Poiseuille profile between the plates for $\beta \ll 1$ while itremains almost constant for $\beta \sim 1$. In the perpendicular configuration,the value of $\lambda {\bot}$ is close to that corresponding to a 2D systemonly if $\beta \ll 1$ and-or if the clearance between the ends of the cylinderand the side walls is very small: in that latter case, $\lambda {\bot}$diverges as $\beta \to 1$ due to the blockage of the flow. In other cases, theside flow between the ends of the cylinder and the side walls plays animportant part to reduce $\lambda {\bot}$: a full 3D description of the flow isneeded to account for these effects.

Author: ** Benoît Semin FAST, Jean-Pierre Hulin FAST, Harold Auradou FAST**

Source: https://arxiv.org/