Inverse Design Of An Indoor Environment Using The Improved CFD-based Adjoint Method

With the improvement of people's living standards,the importance of the building indoor environment has drawn more and more attention.How to solve the problems in the indoor environment such strong air draft,poor indoor air quality,sick building syndrome,disease transmission,and large energy consumption,etc are worthy of in-depth study.Such indoor environments were always caused by unreasonable airflow organization design.The purpose of this research was to create a healthy,comfortable,productive and energy-efficient indoor environment by improving the existing CFD-based adjoint method and then using it to design the airflow in indoor environments.In order to achieve the above purpose,this study conducted the research from the following aspects:1)For the lower accuracy or inaccuracy of the "frozen turbulence" assumption used for calculating the gradient of the objective function over the design variables,this study developed the adjoint RNG k-? turbulence model to improve the accuracy of the CFD-based adjoint method for inversely designing the building indoor environment.2)The constant step size used in the CFD-based adjoint method was usually determined by a time-consuming trial and error process.To solve this problem,this investigation introduced adaptive step size to update design variables which greatly improved the inverse design efficiency.The performance of the CFD-based adjoint method with adaptive step size was further verified by comparing the inverse design results of the same case with constant step size and adaptive step size,respectively.3)In order to design the ideal number,size,location,and shape of the air supply inlets,as well as the air supply parameters(ie,air supply velocity,temperature,and angle),this study combined the area-constrained topology method and the CFD-based adjoint method for the first time.Then,the filter method was used to improve the performance of the topology method which laid the method foundation for indoor environment design.Finally,the improved adjoint method was used to design an optimal indoor environment for a real room and an experiment was also conducted to verify the accuracy of the inverse design results.The following conclusions can be drawn from this investigation: 1 Design process with the adjoint RNG k-? turbulence model led to a near-zero objective function(optimal value),while those with the "frozen turbulence" assumption did not.2 Adaptive step size can automatically determine the optimization step size during the inverse design process,which can be used for inverse design of indoor environment.3The CFD-based adjoint method combined with the area-constrained topology method can find the optimal number,size,location,and shape of air supply inlets,as well as the air supply parameters,which can achieve a healthy,comfortable,productive and energy-efficient indoor environment.At the same time,the filter method was introduced in this study to improve the performance of the topology method.Finally,the measured experimental data in the environmental chamber,which installed the inversely designed optimal inlets,matched the CFD simulation results very closely.Thus,the performance of the improved CFD-based adjoint method was verified.