Internal And External Flow Coupled Simulation Research Of The Aerodynamic Characteristics Of A Bus

In modern transportation, bus is being used more and more widely. And driving with windowsopen is a common working condition, in which there is an exchange of air between the inside andoutside of the carriage, leading to a coupled flowfield. Therefore, the flowfield both inside andoutside of the carriage will change a lot. On one hand, The airflow circled in the bus is sure toincrease the drag coefficient of the whole vehicle, and the opening windows will also haveinfluence on the wake flow. On the other hand, the airflow will impact on the passengers directlydue to that the carriage is no longer air-proof, at which time, the comfort of the passengers and theaerodynamic noise of the bus becomes worse. So It is significant to study the aerodynamiccharacteristic in this working condition.At the very first beginning,real CAD model is established in CATIA and Hypermesh, and thengenerate the mesh with Hypermesh and T-GRID, the simulation on six representative workingconditions of the transit bus are carried out in Fluent and the turbulent model that is used isk-ω.These working conditions are:1).Bus that is all closed.2).Bus that is with sidewindows openand full of seated passengers.3).Bus that is with sidewindows open and full of seated passengersand standing passengers.4).Based on working condition3,the sunroofs are opened windward.5).Based on working condition3,the sunroofs are opened parallel.6).Based on working condition3,the sunroofs are opened leeward. Finally, the transient simulation about sunroofs of highway busis carried out in Fluent and the turbulent model is DES.Based on the simulation, the velocity of airflow around passengers in different workingconditions is analyzed and the results provide the reference for the evaluation of thermal comfort ofpassengers when the bus is driving with sidewindows open. With the transient results, sound powerlevel of the monitor point around sunroofs is obtained, and the fact that the noise in this workingcondition is resonance noise is verified.