Abstract: The Tetrahedron Frame Groups (TFG) protection method,a new engineering measure to prevent bank erosion and promote sediment deposition,has been widely adopted in many river engineering practices in China.However,due to the unique geometric forms of TFG,it is difficult to measure the external flow in TFG,which limit further understanding about the mechanism of the TFG protection method.A three dimensional (3-D) hydrodynamic model is developed on the platform of the Computational Fluid Dynamics (CFD) platform fluent to simulate the external flow field and drag around the Tetrahedron Frame (TF) with a single attached wall in clear water environment.The simulation results are compared with the Acoustic Doppler Velocimetry (ADV) experimental measurements.The result shows that the 3-D model can effectively supplement the experimental study of the complex flow fields,which provides valuable information for the mechanism study of the TFG protection method.Giving different values of hydraulic parameters,the diagram of drag coefficient CD vs Reynolds number Re is obtained using the 3-D model.The diagram shows that the drag coefficient in TF with a single attached wall tends to be a constant value of.1.557 when the Reynolds number is larger than 10⁵.