ANALYSIS OF CROSS VENTILATION AIRFLOW IN AND AROUND SIMPLE HOUSE MODEL CONSIDERING FLOW FLUCTUATION

Natural cross ventilation in house is commonly used as ventilation method in Japan. It is influenced by wind direction, distribution of wind velocity and total pressure on walls. Cross ventilation is not observed with using Reynolds Averaged Navier-Stokes Simulation (RANS), nevertheless occurs in actual phenomena. Flow field in the house varies depending on fluctuating wind. For example, cross ventilation is affected by the wind turbulence around the house, in case of two openings positioned symmetrically on opposite walls parallel to wind direction. Therefore, replicating actual phenomena with using CFD is very important to provide evaluation method for ventilation design. Recently, unsteady fluid flow phenomena are analyzed using Large-Eddy Simulation (LES). In this study, opening conditions and wind direction are calculation variables, five cross ventilated simple house models are calculated using LES. Distributions of instantaneous wind speed ratio and pressure, mean wind speed ratio about cross-ventilated houses are reported. In opening conditions that time-averaged inflow is not observed, instantaneous inflow caused by pressure difference on the walls is generated by turns at each opening. Unsteady cross ventilation is replicated with using LES under opening conditions that obtain no-ventilation in steady-state flow field.