Experimental Research On The Evolution Law Of Submarine Wake

With the development of submarine shock absorption and noise reduction technology,the most advanced submarines can reduce the noise to the same level as the ocean background noise.It is necessary to develop new submarine detection technology to effectively detect submarines.The detection of the submarine’s hydrodynamic wake information is a new type of submarine detection method.The navigation information of the submarine is obtained by detecting the wake information left by the submarine in the water.Therefore,it is of great significance to study the evolution process of the submarine wake for the development of new submarine exploration technology.This dissertation mainly studies the evolution law of submarine wake.In this experiment,the standard SUBOFF submarine without appendage model in the state of direct sailing at a scale of 1:240 is the research object.Unlike previous studies on submarine wakes,which only focused on 15 times the diameter of the downstream.This experiment was carried out using hot wire anemometers in the wind tunnel at Re=6×10~5,3×10~5and 10~5.Measured the flow field data in the range of 3 to 50times the diameter of the submarine downstream.In this dissertation,the evolution of the maximum velocity deficit and velocity half-width of the submarine wake is analyzed.The results show that the maximum velocity deficit and velocity half-width at three Reynolds numbers both satisfy the development laws of-2/3 and1/3 in the theory.On this basis,the average velocity and fluctuation velocity of the wake field are normalized using the maximum velocity deficit and velocity half-width as characteristic scales.The experimental results show that the distribution of the average velocity of submarine wake in the whole experimental range can be well coincident under three different Reynolds numbers.And the normalized fluctuation velocity,which is the Reynolds stress term,will fluctuate around a constant value when it develops to 30 times the diameter under all Reynolds numbers.It can be considered that the Reynolds stress term has reached a self-similar state at this time.The Reynolds stress has obvious bimodal distribution when the Reynolds number is 3×10~5and 6×10~5.The one-side peak of the support structure will weaken and disappear as the wake develops when the Reynolds number is 10~5.In addition,this dissertation analyzes the power spectrum of the wake axial velocity.It is found that the premultiplied power spectrum at the peak of the Reynolds stress on the unsupported structure side at all downstream positions has a obvious peak at three Reynolds numbers.The corresponding dimensionless frequencies are f~*≈0.3 when the Reynolds number is 6×10~5and 10~5,and f~*≈0.23when the Reynolds number is 3×10~5,which indicates that there is a corresponding coherent structure in the wake.