Numerical simulation of internal wave propagation in two-layer fluid under two water surface boundary conditions
-
摘要: 基于FLUENT计算流体力学软件及其二次开发功能,采用VOF(Volume of Fluid)多相流模型,在
$k{\text{-}}\varepsilon$ 湍流模型下建立了模拟内波传播的分层数值水槽。设置两层稳定分层,以上下层不同密度差和水深比设置工况,利用平板拍击法造波。在刚盖和自由表面两种上边界条件下进行数值模拟并与各自的理论解进行比较,分析了两者之间的异同。研究发现密度差的改变不会明显影响理论解与数值解之间的一致程度;上下两层流体深度差值的改变会明显影响数值计算结果。上层水深很小时,在自由表面假定下水气交界面处出现了较为明显的垂向速度;在两种假定下,数值模拟的水平速度都体现了非线性的影响。而当下层水深很小时,非线性的影响微弱。鉴于在实际海洋中上层水深远小于下层水深,尤其是当计算运动幅值更大的内孤立波时,采用更为真实的自由表面假定更为合理。Abstract: Based on the FLUENT computational fluid dynamics software and its secondary development function, as well as the VOF (Volume of Fluid) multiphase flow model, a stratified numerical water flume that simulates the propagation of oceanic internal waves is established with the standard$k{\text{-}}\varepsilon$ turbulence model. In the numerical water flume, two-layer density-stratified fluid is set up, and the flapping plate method is used as the wave maker. Different combinations of density differences and water depth ratio between the upper and lower fluid are numerically simulated under two boundary assumptions of rigid lid and free surface at the still water level, and their numerical results are compared to their theoretical ones respectively. It is found that the differences of the densities of upper and lower fluid do not significantly influence the consistency between the numerical results and theoretical ones, and that the differences of the depths of upper and lower fluid significantly influence the numerical results. When the depth of the upper fluid is low, the notable vertical velocity appears at the interface between water and air under the assumption of free surface. Under the two assumptions at the still water level, the calculated horizontal velocities both reflect the nonlinear effect when the depth of the upper fluid is low, but hardly reflect the nonlinear effect when the depth of the lower fluid is low. Considering the fact that the depth of the upper fluid is much lower than that of the lower fluid in the actual ocean circumstance, it is more reasonable to adopt the assumption of free surface at the still water level, especially when the internal solitary waves with a larger amplitude are numerically simulated.-
Key words:
- internal wave /
- numerical simulation /
- free surface assumption /
- rigid lid assumption
-
表 1 上下层不同密度工况设置
Table 1. Cases with different densities for upper and lower layers
工况 $\;{\rho }_{1}\text{/}(\text{kg}\cdot {\text{m} }^{-3})$ $\;{\rho }_{2}\text{/}(\text{kg}\cdot {\text{m} }^{-3})$ $ {b_1}{\text{/m}} $ $ {b_2}{\text{/m}} $ $ k $ 测点坐标/m Case 1 1 020 1 022 50 50 0.028 7 (750, 0), (750, 50) Case 2 1 020 1 024 50 50 0.018 0 (1 200, 0), (1 200, 50) Case 3 1 020 1 026 50 50 0.014 1 (1 500, 0), (1 500, 50) Case 4 1 020 1 028 50 50 0.012 0 (1 750, 0), (1 750, 50) 表 2 上下层不同水深工况设置
Table 2. Cases with different water depths of upper and lower layers
工况 $\; {\rho }_{1}\text{/}(\text{kg}\cdot {\text{m} }^{-3})$ $\; {\rho }_{2}\text{/}(\text{kg}\cdot {\text{m} }^{-3})$ $ {b_1}{\text{/m}} $ $ {b_2}{\text{/m}} $ $ k $ 测点坐标 Case 5 1 020 1 028 10 90 0.019 8 (1 200, 0), (1 200, 10) Case 6 1 020 1 028 20 80 0.014 9 (1 500, 0), (1 500, 20) Case 7 1 020 1 028 80 20 0.014 9 (1 500, 0), (1 500, 80) Case 8 1 020 1 028 90 10 0.019 8 (1 200, 0), (1 200, 90) 表 3 各工况水平和垂向速度的数值解和理论解一致性分析
Table 3. Consistency analysis between the numerical and analytical results for the horizontal and vertical velocities of different cases
d Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7 Case 8 $ d{\left(w峰\right)}_{\text{R}} $ 0.999 8 0.999 8 0.998 7 0.997 3 0.938 9 0.988 4 0.993 2 0.994 2 $ d{\left(w峰\right)}_{\text{F}} $ 0.996 4 0.996 0 0.998 9 0.998 2 0.927 5 0.984 2 0.997 0 0.996 6 $ d{\left(u峰\right)}_{\text{R}} $ 0.992 2 0.994 4 0.997 1 0.997 6 0.971 1 0.995 4 0.992 5 0.968 3 $ d{\left(u峰\right)}_{\text{F}} $ 0.994 1 0.996 0 0.997 1 0.997 0 0.962 8 0.996 2 0.994 4 0.979 8 $ d{\left(w谷\right)}_{\text{R}} $ 0.999 8 0.999 8 0.998 5 0.999 8 0.993 4 0.995 2 0.994 2 0.977 7 $ d{\left(w谷\right)}_{\text{F}} $ 0.994 7 0.995 9 0.997 3 0.998 9 0.979 0 0.997 4 0.992 5 0.978 0 $ d{\left(u谷\right)}_{\text{R}} $ 0.993 8 0.995 5 0.997 8 0.998 2 0.977 4 0.996 0 0.996 8 0.972 6 $ d{\left(u谷\right)}_{\text{F}} $ 0.995 1 0.997 1 0.998 0 0.998 3 0.971 3 0.995 8 0.996 8 0.987 5 注:R代表刚盖,F代表自由表面。 -
[1] 张洪生, 郑应刚, 王有强. 基于VMD对SAR海洋内波参数的自动反演[J]. 海洋工程,2021,39(3):1-10. (ZHANG Hongsheng, ZHENG Yinggang, WANG Youqiang. Automatically extracting parameters of oceanic internal wave from SAR image based on variational mode decomposition[J]. The Ocean Engineering, 2021, 39(3): 1-10. (in Chinese) [2] 王火平, 陈亮, 郭延良, 等. 海洋内孤立波预警监测识别技术及其在流花16-2油田群开发中的应用[J]. 海洋工程,2021,39(2):162-170. (WANG Huoping, CHEN Liang, GUO Yanliang, et al. Observing, identification and early warning technology of internal solitary wave and its application in Liuhua 16-2 oilfield group development project[J]. The Ocean Engineering, 2021, 39(2): 162-170. (in Chinese) [3] ZHANG H S, JIA H Q, GU J B, et al. Numerical simulation of the internal wave propagation in continuously density-stratified ocean[J]. Journal of Hydrodynamics, 2014, 26(5): 770-779. doi: 10.1016/S1001-6058(14)60086-X [4] 李景远, 张庆河, 陈同庆. 密度连续变化水体内孤立波数值模拟研究[J]. 天津大学学报(自然科学与工程技术版),2021,54(2):161-170. (LI Jingyuan, ZHANG Qinghe, CHEN Tongqing. Numerical simulation of internal solitary wave in continuously stratified fluid[J]. Journal of Tianjin University (Science and Technology), 2021, 54(2): 161-170. (in Chinese) [5] 高原雪, 尤云祥, 王旭, 等. 基于MCC理论的内孤立波数值模拟[J]. 海洋工程,2012,30(4):29-36. (GAO Yuanxue, YOU Yunxiang, WANG Xu, et al. Numerical simulation for the internal solitary wave based on MCC theory[J]. The Ocean Engineering, 2012, 30(4): 29-36. (in Chinese) [6] 陈钰, 朱良生. 基于FLUENT的海洋内孤立波数值水槽模拟[J]. 海洋技术,2009,28(4):72-75, 100. (CHEN Yu, ZHU Liangsheng. Numerical wave tank simulation of oceanic internal solitary waves based on FLUENT[J]. Ocean Technology, 2009, 28(4): 72-75, 100. (in Chinese) doi: 10.3969/j.issn.1003-2029.2009.04.021 [7] TEREZ D E, KNIO O M. Numerical simulations of large-amplitude internal solitary waves[J]. Journal of Fluid Mechanics, 1998, 362: 53-82. doi: 10.1017/S0022112098008799 [8] 韩鹏, 钱洪宝, 李宇航, 等. 内波的生成、传播、遥感观测及其与海洋结构物相互作用研究进展[J]. 海洋工程,2020,38(4):148-158. (HAN Peng, QIAN Hongbao, LI Yuhang, et al. Generation, propagation and detection of internal wave and its interaction with ocean structures[J]. The Ocean Engineering, 2020, 38(4): 148-158. (in Chinese) [9] BAIE M A, PIROOZNIA M, AKBARINASAB M. Simulation of the internal wave of a subsurface vehicle in a two-layer stratified fluid[J]. Journal of Ocean University of China, 2020, 19(6): 1255-1264. doi: 10.1007/s11802-020-4223-9 [10] 刘亚男, 郭晓宇, 王本龙, 等. 基于RANS方程的海堤越浪数值模拟[J]. 水动力学研究与进展(A辑),2007,22(6):682-688. (LIU Yanan, GUO Xiaoyu, WANG Benlong, et al. Numerical simulation of wave overtopping over seawalls using the RANS equations[J]. Journal of Hydrodynamics (SerA), 2007, 22(6): 682-688. (in Chinese) [11] 叶安乐, 李凤岐. 物理海洋学[M]. 青岛: 青岛海洋大学出版社, 1992. YE Anle, LI Fengqi. Physical oceanography[M]. Qingdao: Qingdao Ocean University Press, 1992. (in Chinese) [12] 方欣华, 杜涛. 海洋内波基础和中国海内波[M]. 青岛: 中国海洋大学出版社, 2005. FANG Xinhua, DU Tao. Fundamentals of oceanic internal waves and internal waves in the China seas[M]. Qingdao: China Ocean University Press, 2005. (in Chinese) [13] 文圣常, 余宙文. 海浪理论与计算原理[M]. 北京: 科学出版社, 1984. WEN Shengchang, YU Zhouwen. Wave theory and its calculation principle[M]. Beijing: Science Press, 1984. (in Chinese) [14] YEUNG R W, NGUYEN T C. Waves generated by a moving source in a two-layer ocean of finite depth[J]. Journal of Engineering Mathematics, 1999, 35(1): 85-107. [15] 邓成进, 袁秋霜, 侯延华, 等. 基于FLUENT的库区涌浪数值模拟[J]. 水利水运工程学报,2014(3):84-91. (DENG Chengjin, YUAN Qiushuang, HOU Yanhua, et al. Numerical simulation of the surge based on FLUENT software[J]. Hydro-Science and Engineering, 2014(3): 84-91. (in Chinese) doi: 10.3969/j.issn.1009-640X.2014.03.013 [16] 徐鑫哲. 内波生成机理及二维内波数值水槽模型研究[D]. 哈尔滨: 哈尔滨工程大学, 2012. XU Xinzhe. Study on generational mechanism and 2-D numerical flume model of internal waves[D]. Harbin: Harbin Engineering University. (in Chinese) [17] 姜胜超, 滕斌, 勾莹. 两种水面边界条件下的内波解及其比较[J]. 中国海洋平台,2008,23(3):11-16. (JIANG Shengchao, TENG Bin, GOU Ying. The characters and comparison of two internal wave solutions with different surface conditions[J]. China Offshore Platform, 2008, 23(3): 11-16. (in Chinese) doi: 10.3969/j.issn.1001-4500.2008.03.002 [18] WILLMOTT C J. On the validation of models[J]. Physical Geography, 1981, 2(2): 184-194. doi: 10.1080/02723646.1981.10642213 [19] ZHANG H S, ZHU L S, YOU Y X. A numerical model for wave propagation in curvilinear coordinates[J]. Coastal Engineering, 2005, 52(6): 513-533. doi: 10.1016/j.coastaleng.2005.02.004 -