Abstract A set of wind tunnel experiments was performed to study the average and fluctuating wind loading on an ”infinite” 2D square prism with rounded edges of r / D = 0.16 for different heights of simulated hard marine growth at sub-to transcritical Reynolds numbers. It has already been shown, that a change in surface roughness from ks/D = 4.5 × 10−6 (smooth) to 1 × 10−3 (rough) on a similar prism at α = 0° and 45° had large effects on the widths and the Reynolds numbers marking the boundaries of the various flow states. At α = 45° it furthermore led to a large Reynolds-number independency of the lift and drag forces and of the Strouhal number. For the present wind tunnel tests two additional values of ks/D were selected to obtain smaller increments in surface roughness: 4.5 × 10-4 (slightly rough) and 1.4 × 10−3 (very rough). Mean and fluctuating lift and drag forces, the main vortex shedding frequency, distributions of the mean surface pressures in the mid-span cross-section of the prism and the mean wake profiles were recorded simultaneously. The same two static angles of incidence, α = 0° and 45°, were investigated for R e D = 60,000–12 million. For the prisms with smooth up to rough surfaces strong effects on the behaviour of all aerodynamic parameters with Reynolds number were found, whereas a further increase in ks/D induced hardly any additional effects. The absolute values of the aerodynamic parameters were found to be independent of a change in ks/D for the sub-to supercritical flow states. For the smooth and slightly rough prisms at α = 0° the supercritical flow state was present up to R e D = 12 million, whereas for the rougher prisms the upper transition and the transcritical flow states appeared at high Reynolds numbers. A change to α = 45° induced little variation with ks/D for all aerodynamic coefficients. The overall behaviour of the force coefficients and the Strouhal number with ks/D and R e D were caused by motions of the transition, separation and reattachment locations.

中文翻译：

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圆边方形棱镜上的平均和非稳态载荷：硬海洋生长、入射和雷诺数效应

摘要 进行了一组风洞实验，以研究在亚临界到跨临界雷诺数下模拟硬海洋生长的不同高度的“无限”二维方形棱柱上的平均和波动风载荷，其圆角边缘为 r / D = 0.16。已经表明，在 α = 0° 和 45° 的类似棱镜上，表面粗糙度从 ks/D = 4.5 × 10−6（光滑）到 1 × 10−3（粗糙）的变化对宽度和雷诺数标记了各种流动状态的边界。在 α = 45° 时，它还导致升力和阻力以及斯特劳哈尔数的雷诺数独立性很大。对于当前的风洞测试，选择了两个额外的 ks/D 值以获得更小的表面粗糙度增量：4.5 × 10-4（略粗糙）和 1.4 × 10-3（非常粗糙）。同时记录了平均和波动的升力和阻力、主要涡旋脱落频率、棱镜跨中截面的平均表面压力分布和平均尾流剖面。研究了相同的两个静态入射角，α = 0° 和 45°，R e D = 60,000-1200 万。对于具有光滑到粗糙表面的棱镜，发现对所有具有雷诺数的空气动力学参数的行为有很强的影响，而 ks/D 的进一步增加几乎不会引起任何额外的影响。发现空气动力学参数的绝对值与亚至超临界流动状态的 ks/D 变化无关。对于 α = 0° 的光滑和略微粗糙的棱柱，超临界流动状态最高可达 R e D = 1200 万，而对于较粗糙的棱柱，上部过渡和跨临界流动状态出现在高雷诺数下。对于所有空气动力学系数，α = 45° 的变化几乎不会引起 ks/D 的变化。力系数和具有 ks/D 和 R e D 的 Strouhal 数的整体行为是由过渡、分离和重新附着位置的运动引起的。