考虑侧壁效应修正的循环水槽船模斜航试验水动力计算

采用计算流体动力学技术,以KVLCC2船模为对象研究速度修正方法对斜航水动力修正的影响及其适用工况,并与循环水槽试验结果对比以验证速度修正方法的有效性;采用Tamura速度修正公式对宽阔水域的试验流速进行修正,将速度修正前后的水动力及流场特征与循环水槽斜航试验的计算结果进行对比.结果表明:Tamura速度修正公式在阻塞比为3.5%~5.0%时有效,阻塞比过大将会加大船体两侧流场流速的变化;循环水槽中船体两侧的压力分布与其在宽阔水域中的差别较大;速度修正方法会同时增大船体两侧的压力,因此,在一定的阻塞比范围内可以减小两者的水动力差异,但当阻塞比继续增大时会增大两者的水动力差异.同时,基于低速风洞试验的阻塞效应修正方法提出了低速肥大型船循环水槽斜航试验的横向水动力修正公式.

Calculation of the Hydrodynamic Forces ofShip Model Oblique Towing Test in Circulating Water Channel by Considering Side Wall Effect Correction

The characteristics and applicable conditions of a velocity correction method to account for the correction of hydrodynamic forces are investigated by applying computational fluid dynamics (CFD) technique to oblique towing tests of a KVLCC2 model. The results of numerical method are verified by comparing with the test results in a circulating water channel (CWC). Tamura’s formula on velocity correction is appied to obtain new velocities for tests in wide flow field. Comparisons between hydrodynamics and flow field of the corrected or non corrected condition and those of CWC test show that Tamura’s formula is applicable to the blockage range of 3.5%－5.0%, while larger blockage leads to drastic changes of flow velocity around the ship. Remarkable difference of the pressure distribution exists along with two sides of the model ship between the tests in CWC and that in wide flow field. The velocity correction increases the pressure of both sides, therefore it reduces the discrepancy within certain blockage ratios and enlarges discrepancy as the ratio continuonsly grows. Meanwhile, correction formula of the lateral hydrodynamic force for low speed full form ships is proposed based on the blockage correction in a low speed wind tunnel.