The Effect Of Periodic Heating On The Convective Structure Of Inclined Cavity

Convection refers to the relative flow in the fluid due to the different temperature of each part.There are two forms of convection:natural convection and forced convection.Natural convection is caused by density change caused by concentration difference or temperature difference,and forced convection is caused by external force.The heat island effect in the city,the circulation of sea water in the ocean and the movement form of pollutants are all related to the convection movement.Since convection was found,researchers have done a lot of research on convection.In this paper,the main research is thermal convcction.On the basis of the traditional horizontal rectangular convection cavity,increase the tilt angle and flow through,Periodic heating is used to analyze the convection characteristics of water,air and mercury.In this paper,three kinds of fluids(Pr=6.99,Pr=0.72,Pr=0.0272)are simulated in a rectangular cavity with a length to height ratio by using the fluid dynamics equations and fluent software.The spatio-temporal evolution,partition and convection characteristics of the three kinds of fluids are analyzed under different relative Rayleigh number,Reynolds number and tilt angle.The results are as follows:(1)The spatio-temporal evolution of three fluids can be roughly divided into three stages:the initial development stage,the transitional development stage and the relatively stable stage;the convective pattern structures of the upstream and downstream regions of the fluids with Pr=6.99 and 0.72 are different;the convective pattern structures of the upstream and downstream regions of the fluids with Pr=0.0272 are periodically symmetric.(2)The special convection structure of the local traveling wave in three kinds of fluids is affected by the relative Rayleigh number and Reynolds number.It is found that the local traveling wave corresponding to different relative Rayleigh number is transformed into the critical Reynolds number passing through the flow.The curve fitting of the two data points shows that r and Reu are power function relations.The critical Reynolds number increa ses with the increase of the tilt angle large.(3)There are four zones for Pr=6.99 fluid with different relative Rayleigh numbers:local single convection zone,local uniform convection zone,local non-uniform convection zone,and through flow zone.The fluid with Pr=0.72and0.0272 has four zones:local uniform convection zone,local mixed convection zone,transitional convection zone and flowing zone.With the increase of relative Rayleigh number,the stable value,maximum velocity and maximum amplitude of Nusselt number increase.(4)The length of the convective zone increases with the increase of the relative Rayleigh number,but the influence occurs in a certain range;the length of the convective zone increases with the increase of the tilt angle,but the influence occurs in a certain range;the length of the convective zone decreases with the increase of the Reynolds number,which shows that the Reynolds number is the main factor affecting the length of the convective zone in the cavity.