The influence of surface roughness on overlying turbulence is represented by a drag layer, with a quadratic drag law. The drag coefficient is considered to be a function of effective sandgrain roughness. The challenge to hybrid modeling is posed as being to calibrate that drag law, such that the calibration be nearly the same for either RANS or LES. To that end the coefficient is first calibrated for LES. With roughness represented by the drag formula, the RANS model and boundary condition are adjusted to provide consistency in the log layer. Then, it is found that RANS and LES calibrations become nearly the same. The model is validated by simulations of a rough wall boundary layer, of rough to smooth junction flow, of a rough ramp, and of streamwise roughness strips.

表面粗糙度对上覆湍流的影响由阻力层表示，具有二次阻力定律。阻力系数被认为是有效砂粒粗糙度的函数。混合建模的挑战在于校准该阻力定律，以使 RANS 或 LES 的校准几乎相同。为此，首先针对 LES 校准系数。使用阻力公式表示的粗糙度，调整 RANS 模型和边界条件以提供测井层的一致性。然后，发现 RANS 和 LES 校准变得几乎相同。该模型通过对粗糙壁边界层、粗糙到光滑的交界流、粗糙坡道和流向粗糙带的模拟得到验证。