| In order to cool the power plant of the underwater submerged body,seawater is continuously used as cooling water.A thermal wake will be formed when the cooling water is discharged at a certain speed and mixes with the surrounding background seawater.Since the temperature of the heated seawater is relatively high,its density is correspondingly small,so it will gradually rise upward during the diffusion process,and if it rises to the sea surface,a thermal wake will be formed.In addition,due to the sunlight,the temperature of seawater generally has a stable vertical stratification.When the submerged body moves underwater,it will disturb the stable stratification of the seawater and stimulate the internal wave,and the lower temperature seawater which in lower layer will spread to the sea surface to form a cold wake.The infrared detector has extremely high sensitivity and precision for temperature difference capture,and underwater submersible detection can be performed by real-time imaging of thermal and cold wakes.In this paper,the following researches are carried out on the floating diffusion of the thermal wake and the temperature change of the flow field:Firstly,the simplified fairing Suboff hull model is taken as the research object.Under the condition of controlling the heat of the cooling water discharged per unit time,combined working conditions of the arrangement of drainage port,the cross-sectional area of drainage port,the temperature of cooling water,and the discharge rate of cooling water are divided.The diffusion of thermal wake in uniform flow was simulated by using CFD technology and RANS turbulence calculation method.Results have shown that the higher temperature thermal wake will make heat conduction and heat convection with the surrounding seawater during the diffusion process,and its temperature will gradually drop with time.And the temperature difference of the cooling water has a greater influence on the diffusion and temperature attenuation of thermal wake than the flow.Secondly,on the basis of the above research,reference is made to the physical hydrological data of the Chinese sea and the world oceans.By analyzing the time,spatial distribution and morphological characteristics of the thermocline,the mathematical models of continuous linear stratification,mixed stratification and strong stratification of the ocean were constructed to study the effect of stratification modes and the presence or absence of stratification on the rise and diffusion of thermal wakes.Results have shown that compared with the uniform flow,due to the non-uniformity of the temperature distribution of the stratified seawater,when the submerged body is located in the middle of the thermocline or below the thermocline,the stratification of the seawater will promote the attenuation of the temperature and suppress the floating height of the thermal wake.When the submerged body is above the thermocline,the effect of seawater stratification on the thermal wake is not obvious.In addition,the movement of the submerged body in the stratified seawater disturbs the stable stratification of the seawater,causing a huge change in the temperature distribution of the flow field.Finally,the speed and depth of the submerged body are changed,and the effects of the speed and depth in the uniform flow and the mixed stratified flow on the thermal wake floating and temperature attenuation are studied.The results show that the higher the speed of the submerged body in the uniform flow,the stronger the cooling water is diluted by the surrounding seawater,and the more severe the temperature attenuation of the thermal wake is.The lower the depth of the submerged body in the uniform flow,the higher the floating height,and the larger the vertical diffusion range of the thermal wake.The greater the latent depth of the submerged body in the mixed stratified flow,the faster the heat transfer,the more severe the temperature attenuation,and the smaller the floating height and amplitude of the thermal wake. |
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