A culvert is a covered channel designed to pass water through an embankment. The recognition of the adverse ecological impacts of culverts on upstream fish passage is driving the development of new culvert design guidelines, with a focus on small-bodied fish species seeking low velocity zones to minimise energy expenditure. Herein a hybrid modelling technique was applied, combining physical modelling, one-dimensional theoretical calculation and three-dimensional computational fluid dynamics modelling. The results reveal fundamental turbulent processes that may affect small-body-mass fish navigability and provide new insights for the development of standard box culvert design guidelines. Systematic validations were performed to a wide range of initial conditions and smooth barrel geometries. A physical relationship was derived from numerical and experimental data of past and present studies, correlating the dimensionless flow area with a normalised local velocity V/V_mean.

中文翻译：

---

箱涵低速区的混合建模，以协助上游鱼类通过

涵洞是一个有盖的渠道，旨在使水通过路堤。涵洞对上游鱼类通过的不利生态影响的认识推动了新涵洞设计准则的发展，其重点是寻求低速区域以最小化能源消耗的小型鱼类。本文采用了一种混合建模技术，将物理建模，一维理论计算和三维计算流体动力学建模相结合。结果揭示了可能影响小体量鱼类通航性的基本湍流过程，并为标准箱涵设计指南的开发提供了新见识。对各种初始条件和光滑的机筒几何形状进行了系统验证。_卑鄙的。