Numerical Computational Of Wind Load Onsemi-submersible Tender Support Platform

As a tall structure in the sea, semi-submerged platform is particularly sensitive to the wind load.If the semi-submerged platform is overthrown by the typhoon or hurricane, this will not only posed a threat on people’s lives and bring about unpredictable economic loss but also cause serious marine environment pollution which will damage the marine ecosystems,so it’s quite significant to accurately predict the wind load for the platform’s security and efficiency.At present, domestic research of the semi-submerged platform’s wind load are still focus on the steady wind and gradient wind but less involved the random wind, so this thesis takes the semi-submersible tender support platform BT-3500 as the researc h object, then calculate the wind loads of BT3500 under the random wind and steady wind by using the numerical wind tunnel and specifications calculation. Also the shadowing effect of the platform is calculated and analyzed in this thesis, at last three optimization schemes about the platform’s superstructure are proposed and their optimization effects are verified.The main research contents of this paper are as follows:(1) The real wind has a certain randomness and fluctuation. So we choose Davenport、API and NPD wind spectrums, and analysis the influences of the different heights and different mean wind speeds on the three wind spectrums. Then the three wind spectrums are transformed into the random fluctuating winds by harmonic superposition method from frequency domain to time domain. The fluctuating regions of the random winds in different mean wind speeds are analyzed.(2) I calculate the wind loads of BT3500 TSV in different working conditions according to the regulations of C CS, ABS and DNV, then analysis and contract the res ults calculated by different regulations,which can provide references for the subsequent calculation results of numerical simulation.(3) Based on Fluent and own compiled UDF, the wind-forces and wind-moments under random fluctuating winds and s teady wind in different working conditions are numerically simulated by using Reynold’s average NS equation and DES numerical model. Then the results of the wind loads under random fluctuating winds and steady wind are compared and analyzed with the specifications calculation results. Also the pressure coefficient distribution of BT3500 is elaborated in this thesis.(4) The shadowing effect is described in detail and the sack_cement_room’s sheltering coefficient is calculated through the existing research results of the shadowing effect, which make the specifications calculation result more close to the actual value.(5) Research the shadowing effects of the tandem square columns and cylinders in different spacing ratios and different height ratios and statistics the covered square column and covered cylinder’s wind forces and sheltering coefficient.(6) Select five typical components from the pl atform’s superstructure and calculate their actual wind forces and single wind forces in no tilt load condition. The sheltering coefficients and obscured rates of this five typical components are given in this thesis which can provide detailed data support for researching the wind loads of the superstructure.(7) Through the force analysis of th e platform’s superstructure and shadowing effect between different components of superstructure, also consulting past experiences in the layout and structural style of both domestic and foreign’s Semi-submersible Tender Support Platforms, I provide 3 optimization schemes of layout and structural style of platform’s super structure. Then I compare the advantage and disadvantage of different optimization schemes in steady wind and unsteady wind through numerical simulation.The research results can provide reference for subsequent design of Semi-submersible Tender Support Platforms.