Study On The Fractal Characteristics Of Air Supply Turbulence In Air Conditioing System

Many of the air flow phenomena in the natural and engineering applications are turbulence,and our common air conditioning air supply is a kind of turbulence movement.The movement of turbulence is quite complex and extremely irregular.For a long time,researchers have analyzed the turbulent motion using the viewpoints and methods of classical physics,and have not made any major breakthroughs.The fundamental reason is that turbulent motion has obvious nonlinear characteristics.The nonlinear fractal theory has found a new research direction for turbulence,and the fractal dimension can directly reflect the "irregular" degree of the fractal.In this paper,fractal theory and statistical theory are used to study the turbulent fractal characteristics of air supply in indoor air conditioning systems.First of all,the turbulent velocity signals are statistically analyzed.The probability distribution of turbulence velocity is non Gauss type.The steepness F of probability density function is greater than 3,which is the reflection of turbulence intermittency.Secondly,in this paper,the fractal dimension of the velocity signal is calculated and analyzed,and the fractal dimension of the velocity time signal in this experiment is between 1.6 and 1.73.The fractal dimension of the velocity time signal at the same point in space does not change with the time.The fractal dimension of the sample velocity at the same height gradually decreases from the middle position to the both sides,indicating that the irregular and fluctuating degree of the sample points in the middle position is larger than the two sides,and the fluctuation degree of the sample speed gradually decreases from the middle to the both sides.Thirdly,the turbulence intensity and turbulent kinetic energy are calculated and analyzed,and compared with the turbulent fractal dimension,we find that the intensity of velocity pulsation at the same height of the tuyere gradually weakened from the middle to the both sides,and the fractal dimension and turbulence intensity decreases,correspondingly,turbulent kinetic energy is gradually decreased.When the turbulent pulsation velocity becomes 0,the fractal dimension of velocity is 1.The kinetic energy of the fluid is mainly consumed by the dissipation of turbulent kinetic energy.The greater the pulsation speed,the more intense the pulsation and the greater the dissipation rate of the turbulent kinetic energy.In addition,the disturbance of the airflow may lead to the increase of the pulsation,which leads to the increase of the turbulent fractal dimension,the turbulence intensity and the turbulence dissipation rate.Finally,This paper also analyzes the turbulent vortex cascade model.By studying the fractal dimension,turbulence intensity,turbulence energy and dissipation of the turbulent velocity time signal,we can see that it is necessary to conduct multiple statistics and calculations using the traditional methods and ideas to study turbulent motion,while the fractal dimension can be more intuitive,reflecting the specific characteristics pulsating turbulent movement.It can be used to describe the mass transfer range of the fluid and provide a certain reference for the calculation of the indoor air distribution.