Mô hình tính toán dòng chảy và vận tải bùn cát ba chiều trong sông và kênh hở=3D numerical modeling of flow and sediment transport in rivers and open channels

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Ngôn ngữ: vie

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Thông tin xuất bản: Tạp chí Phát triển Khoa học & Công nghệ: Khoa học Trái đất và Môi trường, 2019

Mô tả vật lý: tr.23

Bộ sưu tập: Báo, Tạp chí

ID: 582169

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Mô hình toán là một công cụ hữu ích trong nghiên cứu dòng chảy và vận tải bùn cát, bồi xói lòng dẫn và được xây dựng dựa trên việc giải các phương trình vi phân cơ bản. Mô hình toán có nhiều cấp độ khác nhau và mô hình 3 chiều là cấp độ cao nhất, cho phép mô phỏng chi tiết dòng chảy và quá trình vận tải bùn cát trong không gian 3 chiều. Bài báo này trình bày một sơ đồ tính toán dòng chảy và vận tải bùn cát ba chiều trong kênh hở. Mực nước và vận tốc dòng chảy được giải từ phương trình chuyển động ba chiều với giả thuyết thủy tĩnh. Nồng độ bùn cát lơ lửng, bùn cát đáy và diễn biến đáy được giải từ các phương trình vận tải. Các phương trình vi phân cơ bản được viết trong hệ tọa độ biến đổi ``sigma'' và được giải theo phương pháp thể tích hữu hạn trên lưới phi cấu trúc phần tử tứ giác. Đối với dòng chảy điều kiện biên mực nước hoặc lưu lượng sẽ được áp đặt trên các biên hở. Đối với bùn cát lơ lửng nồng độ bùn cát trên biên được áp đặt trong pha chảy vào và điều kiện thoát tự do được sử dụng trong pha chảy ra. Sơ đồ tính toán được kiểm travới bài toán vận tải bùn cát trong kênh cong được nghiên cứu bằng thực nghiệm bởi Odgaard và Bergs. Kết quả tính toán khá phù hợp với số liệu đo. Nhằm kiểm tra khả năng ứng dụng thực tế, sơ đồ tính toán mới cũng được kiểm tra với bài toán vận tải bùn cát trên sông Đồng Nai tại khu vực Cù lao Phố. Để giải quyết vấn đề điều kiện biên thủy lực của bài toán này, mô hình khu vực Cù Lao Phố được tích hợp vào mô hình hệ thống sông Sài Gòn – Đồng Nai. Kết quả tính diễn biến lòng dẫn khu vực cù lao Phố trên sông Đồng Nai cũng cho thấy phương pháp tính toán này cho kết quả phù hợp với quy luật và hoàn toàn có thể sử dụng trong nghiên cứu thực tếNumerical model is a useful tool in studying the flow and sediment transport, change in river bed and is built on solving governing differential equations. Numerical model has many different levels and three-dimensional model is the highest level, allowing detailed simulation of flow and sediment transport process in 3D space. The paper presents a method calculating three - dimensional flow and sediment transport in the open channel. Water level and flow velocity are solved fromthree-dimensional equations with hydrostatic hypothesis. Concentration of suspended sediment, bottom sediment and bottom evolution is solved from transport equations. The governing differential equations in the "sigma" transform coordinate system are solved by finite volume methodon unstructured grid of quadrilateral elements. Boundary condition of water level or flow will be imposed on open boundary. For suspended sediment concentrations in the injected phase, suspended sediment concentrations are applied and the outflow phase applies free drainage conditions. This method of calculation was tested with the problem of curved channel sediment transport which was studied experimentally by Odgaard and Bergs. Calculation results are quite consistent with the measured data. In order to test the practical applicability, this method is also tested with the problem of sediment transport in Cu lao Pho islet on Dong Nai river. To solve the matter of hydraulic boundary condition of this problem, the model of Cu lao Pho islet is integrated intothe Sai Gon - Dong Nai river system model. Results of the calculation of the river bed evolution of the Cu lao Pho islet on the Dong Nai river also show that this calculation method gives results consistent with the rule and can be used in practical research

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